Network Working Group D. Trossen
Internet-Draft Huawei Technologies
Intended status: Standards Track LM. Contreras
Expires: 7 August 2023 Telefonica
J. Finkhaeuser
Interpeer gUG
P. Mendes
Airbus
3 February 2023
Routing on Service Addresses
draft-trossen-rtgwg-rosa-02
Abstract
This document proposes a novel communication approach which reasons
about WHAT is being communicated (and invoked) instead of WHO is
communicating. Such approach is meant to transition away from
locator-based addressing (and thus routing and forwarding) to an
addressing scheme where the address semantics relate to services
being invoked (e.g., for computational processes, and their generated
information requests and responses).
The document introduces Routing on Service Addresses (ROSA), as a
realization of what is referred to as 'service-based routing' (SBR),
to replace the usual DNS+IP sequence, i.e., the off-path discovery of
a service name to an IP locator mapping, through an on-path discovery
with in-band data transfer to a suitable service instance location
for a selected set of services, not all Internet-based services.
SBR is designed to be constrained by service-specific parameters that
go beyond load and latency, as in today's best effort or traffic
engineering based routing, leading to an approach to steer traffic in
a service-specific constraint-based manner.
Particularly, this document outlines sample ROSA use case scenarios,
requirements for its design, and the ROSA system design itself.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Backdrop . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Design Goals . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Summary of Contribution . . . . . . . . . . . . . . . . . 5
1.4. Overview of Draft . . . . . . . . . . . . . . . . . . . . 7
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Deployment and Use Case Scenarios . . . . . . . . . . . . . . 8
3.1. CDN Interconnect and Distribution . . . . . . . . . . . . 9
3.2. Distributed user planes for mobile and fixed access . . . 10
3.3. Multi-homed and multi-domain services . . . . . . . . . . 11
3.4. Micro-service Based Mobile Applications . . . . . . . . . 11
3.5. Constrained Video Delivery . . . . . . . . . . . . . . . 13
3.6. AR/VR through Replicated Storage . . . . . . . . . . . . 13
3.7. Cloud-to-Thing Serverless Computing . . . . . . . . . . . 14
3.8. Metaverse . . . . . . . . . . . . . . . . . . . . . . . . 15
3.9. Popularity-based Services . . . . . . . . . . . . . . . . 16
4. Analysis of Use Cases . . . . . . . . . . . . . . . . . . . . 16
4.1. Observations from Use Cases . . . . . . . . . . . . . . . 16
4.2. Suitability of Existing Internet Technologies . . . . . . 18
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Expected Benefits . . . . . . . . . . . . . . . . . . . . . . 24
7. ROSA Design . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.1. System Overview . . . . . . . . . . . . . . . . . . . . . 25
7.2. Message Types . . . . . . . . . . . . . . . . . . . . . . 28
7.3. Changes to Clients to Support ROSA . . . . . . . . . . . 30
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7.4. SAR Forwarding Engine . . . . . . . . . . . . . . . . . . 31
7.5. Traffic Steering . . . . . . . . . . . . . . . . . . . . 35
7.5.1. Ingress Request Scheduling . . . . . . . . . . . . . 36
7.5.2. Routing Across Multiple SARs . . . . . . . . . . . . 37
7.6. Interconnection . . . . . . . . . . . . . . . . . . . . . 39
8. Extensions to Base ROSA Capabilities . . . . . . . . . . . . 40
8.1. Supporting Different Namespace Encodings . . . . . . . . 40
8.2. Supporting Multi-Homing of Service Instances . . . . . . 41
8.3. Supporting 0-RTT TLS . . . . . . . . . . . . . . . . . . 41
8.4. Supporting Transaction Mobility . . . . . . . . . . . . . 42
8.5. Supporting Service Function Chaining . . . . . . . . . . 42
8.6. Supporting Privacy-Compliant Communication . . . . . . . 42
9. Prototype-based Insights . . . . . . . . . . . . . . . . . . 43
10. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 43
11. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 43
12. Security Considerations . . . . . . . . . . . . . . . . . . . 44
13. Privacy Considerations . . . . . . . . . . . . . . . . . . . 45
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45
15. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 45
16. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 46
17. Informative References . . . . . . . . . . . . . . . . . . . 46
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52
1. Introduction
The centralization of Internet services has been well observed, not
just in IETF discussions [Huston2021]
[I-D.nottingham-avoiding-internet-centralization], but also in other
efforts that aim to quantify the centralization, using methods such
as the Herfindahl-Hirschman Index [HHI] or the Gini coefficient
[Gini]. Dashboards of the Internet Society [ISOC2022] confirm the
dominant role of CDNs in service delivery beyond just streaming
services, both in centralization as well as resulting market
inequality, which has been compounded through the global CV19
pandemic [CV19].
The impact on routing can be seen in, e.g., [TIES2021], which goes as
far as centralizing service requests into a single IP address behind
which data centre (DC) internal mechanisms take over.
Thus, ROSA is being motivated by the requirements stemming from use
cases where the distribution of compute, storage, and networking
resources associated with a service brings not just benefits but also
its distributed, runtime utilization may yield in better performance,
such as improved service completion latency, utilization, and others.
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At the same time, it is important to recognize that we do not aim for
replacing existing service routing capabilities, most notably the DNS
as the main form of resolving a service name into routing locator; we
see those capabilities working perfectly well for many Internet
services. Instead, we argue in the following that some more
challenging service scenarios, such as multi-access edge computing
and cloud-to-thing, as well as more dynamic networking scenarios such
as LEO constellations, may require service routing capabilities
embedded in the networking stack, without relying on application
layer translations or resolution services.
1.1. Backdrop
Providing the backdrop to this draft, [EI2021] addresses the
challenge of overcoming the architectural stagnation of the Internet
while supporting an increasing divergence of services, by means of an
extensible Internet architecture able to support in-network services
that go beyond best-effort packet delivery. Within this extended
Internet, novel network services are executed in Service Nodes (SNs)
interconnected by networks running IP. Deployment of SNs depends
upon the use-case, but in general may be placed within Last Mile
Providers (LMPs) or within Cloud Providers (CPs). The proposed ROSA
framework follows a similar architectural view.
Evolving the IPv6 network layer has been part of its design from the
very start. Key enabler here are Extension headers (EHs), which are
part of the IPv6 specifications [RFC8200], with some observed
problems, e.g., firewall traversal, in real-world deployments
[SHIM2014]. Recent solutions, such as Segment routing (SR)
[RFC8402], specifically SRv6 [RFC8986] build on this capability by
establishing a shim layer overlay (of SR-enabled routers), utilizing
an extension header to carry needed information for realizing the
source routing capabilities. ROSA follows a similar approach, by
using EHs to build a shim overlay above the IP layer.
1.2. Design Goals
The key problem in service routing is that of determining the routing
locator for a network endpoint that realizes a specific service. For
this, explicit resolution steps are usually implemented at the
application level, through mechanisms such as DNS, GSLB, and Alto.
The result of the explicit resolution is then used to establish a
suitable communication at the application level, including transport
sessions, to invoke a particular service, possibly followed by
subsequent data transfer to the endpoint chosen in the resolution
step (called 'affinity' in the following).
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This additional resolution does cost time in the form of the
resolution latency, including the latency to access the resolver, but
also requires for the resolver to have available the relevant (and
up-to-date) mappings for any incoming resolution request.
Furthermore, updating the mappings is a difficult problem, either
requiring to push such updates to the resolver or pull suitable
updates from elsewhere. As outlined in [OnOff2022], both aspects
lead to problems when wanting (or needing) to support shorter
interactions with service instances, while interactions may be served
by different service instances.
Moreover, services that rely on application specific resolvers (e.g.
DNS servers) may fail when facing intermittent connectivity to those
resolvers, as can happen in moving networks (e.g. vehicle networks).
This puts three goals in the foreground that are important for use
cases for ROSA, namely (i) need for 'dynamicity' and (ii)
'efficiency' as well as (iii) the 'service specificity' of the
steering decision, i.e., the selection of the suitable service
instance to send traffic to. The first is about the support for fast
changing relations with service endpoints, while the second aims to
reduce any potential latency in doing so. The third caters to the
situation that the selection of one of the possibly many choices for
a service endpoint is often defined through service-specific
policies, including runtime decisions that may change from one
transaction to another.
1.3. Summary of Contribution
The main contribution of Routing on Service Addresses (ROSA) is to
replace the usual DNS+IP sequence, i.e., the off-path discovery of
service name to IP locator mapping, through an on-path discovery with
in-band data transfer to a suitable service instance location for a
selected set of services, not all Internet-based services.
The basic functionality of ROSA can be described as follows:
1 A client sends an initial IP packet, 'directed' to service address
S, to a special shim (ROSA) overlay.
2 The shim overlay routes the packet based on the service address to
one of the possibly many service instances for S over an existing
IP network. For this, mappings between S and the known service
instance locators are used by the ROSA overlay, replacing the role
of DNS records, while the selection of the 'suitable' service
instance locator may use service-specific policies (and
parameters).
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3 The chosen service instance delivers its network locator SI in the
response to the initial packet back to the client.
4 The client will now continue to use SI in native IPv6 packets to
direct any subsequent packets to the chosen service instance.
This is to support possible ephemeral state created at service
instance as a consequence of previous exchanges.
Steps 1 through 4 are repeated for every new service transaction,
allowing those transactions now to be served at any of the available
service instances albeit keeping one transaction at one chosen
service instance! Steps 1 through 4 may also be repeated in case of
mobility. For stateless services, only steps 1, 2, and 3 are
executed.
In order to react to system, e.g., network but more importantly
service changes, ROSA achieves dynamicity, as mentioned in the
previous section, by including a routing-based approach able to map
service addresses to routing locators, where mappings of service
addresses to routing locators are pushed to the (shim overlay)
elements, enabling to perform the translation from a service
addressed packet to an IP-addressed packet on the data path. When
using, e.g., eBPF-based techniques in SW-based routers, such approach
can achieve 100s of thousands of resolution steps per ingress node,
as discussed in Section 9.
When it comes to efficiency, our design is positioned at L3.5, using
an extension header based approach. With this, the initial packet,
realizing an in-band resolution step, can include upper layer, i.e.,
transport and/or application-level, in-band data within the normal
payload of the IP packet, further reducing the latency for completing
a transaction, even opening the possibility for single packet
transactions being completed in a single round trip.
Additionally, similar to application-level solutions, the positioning
as a (L3.5) shim overlay faciliates the exposure of service-specific
selection policies from the service to a ROSA provider through
explicit commercial relations, separate from those defining the
routing policies in the underlay network.
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Unlike name-based routing solutions at the underlay, routing
scalability is achieved by limiting the resolution to those services
explicitly announced to the service routing (i.e., ROSA) overlay.
Thus, ROSA does not aim to replace ALL service routing through the
above proposed steps, but focus on those services explicitly
announcing their desire for a ROSA-based resolution to an appropriate
ROSA provider. The assumed explicit (often commercial) relationship
between the service provider and the ROSA provider is what allows for
controlling the scalability requirements of the elements realizing
the ROSA overlay.
1.4. Overview of Draft
In the remainder of this document, we first introduce in Section 2 a
terminology that provides the common language used throughout the
remainder of the document. We then introduce use cases in Section 3
that drive the need for a routing on service address solution. Our
analysis in Section 4 then leads us to outline in Section 5 the
requirements for ROSA and the expected benefits of ROSA in Section 6.
The main part of the document focusses on introducing the ROSA design
in Section 7, elaborating on the main idea presented above in more
detail, followed by possible extensions to the design in Section 8.
2. Terminology
The following terminology is used throughout the remainder of this
document:
Service: A monolithic functionality that is provided according to
the specification for said service. A composite service can be
built by orchestrating a combination of monolithic services.
Service Instance: A running environment (e.g., a node, a virtual
instance) that provides the expected service. One service can
involve several instances running within the same ROSA network at
different network locations, thus providing service equivalence
between those instances.
Service Address: An identifier for a specific service.
Service Instance Address: A locator for a specific service instance.
Service Request: A request for a specific service, addressed to a
specific service address, which is directed to at least one of
possibly many service instances.
Affinity Request: A request to a specific service, following an
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initial service request, requiring steering to the same service
instance chosen for the initial service request.
Service Transaction: A sequence of higher-layer requests for a
specific service, consisting of at least one service request,
addressed to the service address, and zero or more affinity
requests.
Service Affinity: Preservation of a relationship between a client
and one service instance, with the initial service request
creating said affinity and following affinity requests utilizing
said affinity.
ROSA Provider: Realizing the ROSA-based traffic steering
capabilities over at least one infrastructure provider by
deploying and operating the ROSA components within its defining
ROSA domain.
ROSA Domain: Domain of reachability for services supported by a
single ROSA provider.
ROSA Endpoint: A node accessing or providing one or more services
through one or more ROSA providers.
ROSA Client: A ROSA endpoint accessing one or more services through
one or more ROSA providers, thus issuing services requests
directed to one of possible many service instances that have
previously announced the service address provided by the ROSA
client in the service request.
Service Address Router (SAR): A node supporting the operations for
steering service requests to one of possibly many service
instances, following the procedures outlined in Section 7.5.
Service Address Gateway (SAG): A node supporting the operations for
steering service requests to service addresses not announced to
SARs of the same ROSA domain to suitable endpoints in the Internet
or within other ROSA domains.
3. Deployment and Use Case Scenarios
In the following, we outline examples for use cases that exhibit the
degrees of distribution in which relationship management (through
explicit mapping and/or gatewaying) may become complex and a possible
hindrance for service performance. The following sections only serve
as illustrating examples with other work, such as the BBF Metro
Compute Networking (MCN) [MCN], among others, having developed
similar but also additional use cases.
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3.1. CDN Interconnect and Distribution
Video streaming has been revealed nowadays as the main contributing
service to the traffic observed in operators' networks. Multiple
stakeholders, including operators and third party content providers,
have been deploying Content Distribution Networks (CDNs), formed by a
number of cache nodes spread across the network with the purpose of
serving certain regions or coverage areas with the proper quality
levels. In such a deployment, protection schemas are defined in
order to ensure the delivery continuity even in the case of outages
or starvation in cache nodes.
In addition to that, novel schemes of CDN interconnection [RFC6770]
[SVA] are being defined allowing a given CDN to leverage the
installed base of another CDN to complement its overall footprint.
As result, several caches are deployed in different Points of
Presence in the network. Then for a given content requested by an
end user, several of those caches could be candidate nodes for
delivery. Currently, the choice of the cache node to serve the
customer relies solely on the content provider logic, considering
only a limited set of conditions to apply.
For instance, the usage of cache-control [RFC7234] allows data
origins to indicate caching rules downstream. Since the original
intent was quite limited, to operate between the data source and the
data consumer (browser), Targeted Cache Control (TCC) [RFC9213]
defines a convention for HTTP response header fields that allow cache
directives to be targeted at specific caches or classes of caches.
The performance can be improved by the consideration of further
conditions in the decision on what cache node to be selected. Thus,
the decision can depend of course on the requested content and the
operational conditions of the cache itself, but also on the network
status or any other valuable, often service-specific, semantic for
reaching those nodes, such data validity, end to end delays, or even
video analytics. The latter is relevant since as the number of video
files grows, so does the need to easily and accurately search and
retrieve specific content found within them.
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Furthermore, those decision points may be dynamic and could even
change during the lifetime of the overall service, thus requiring to
revisit decisions and therefore assignments to the most appropriate
CDN node. An example encompasses the usage of satellites to enhance
the content distribution efficiency in cooperation with the
terrestrial network. Combining satellites with CDNs may leverage LEO
(low earth orbit) satellite mobility characteristics to cache and
deliver content among different static caches in the terrestrial CDN,
but may also include mobile satellites serving as couriers.
3.2. Distributed user planes for mobile and fixed access
5G networks natively facilitate the decoupling of control and user
plane. The 5G User Plane Function (UPF) connects the actual data
coming over the Radio Area Network (RAN) to the Internet. Being able
to quickly and accurately route packets to the correct destination on
the internet is key to improving efficiency and user satisfaction.
For this, the UPF terminates the tunnel set carrying end user traffic
permitting to route the end user traffic in the network towards its
destination, e.g., providing reachability to edge computing
facilities.
Currently, UPF is planned to appear in two places, namely in the Core
Network and at the Edge inside a Multi-Access Edge Controller (MEC).
However, in a future 6G network, it is envisioned that several UPFs
can be deployed in a distributed manner, not only for covering
different access areas, but UPFs can also be distributed with the
attempt of providing access to different services, linked with the
idea of network slicing as means for tailored service
differentiation. For instance, some UPFs could be deployed very
close to the access for services requiring either low latency or very
high bandwidth, while others could be deployed in a more centralized
manner for requiring less service flows. Furthermore, multiple
instances can be deployed for scaling purposes depending on the
demand in a specific moment.
Similarly, to what happens in mobile access, fixed access solutions
are proposing schemas of separation of control and user plane for BNG
elements [I-D.wadhwa-rtgwg-bng-cups] [BBF]. From the deployment
point of view, different instances can be deployed based on the
coverage, the temporary demand, etc, as before.
As a complement to both mobile and fixed access scenarios, edge
computing capabilities are expected to complement the deployments for
hosting service and applications of different purposes, for both
services internal to the operator or hosting of services from third
parties.
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In this situation, either for both selection of the specific user
plane termination instance, or from that point on, selection of the
service endpoint after the user plane function, it makes sense the
introduction of mechanisms enabling selection choices based on
service-specific semantics.
3.3. Multi-homed and multi-domain services
Corporate services usually define requirements in terms of
availability and resiliency. This is why multi-homing is common in
order to diversify the access to services external to the premises of
the corporation, or for providing interconnectivity of corporate
sites (and access to internal services such as databases, etc).
A similar scenario in which external services need to be reached from
within a specific location, is the Connecter Aircraft. Exploiting
solutions that allow for the exploitation of multi-connected
aircrafts (e.g., several satellite connections, plus air-to-ground
connectivity) are important to improve passenger experience, while
helping make the crew more productive with networking solutions that
enable seamless, high-speed broadband. Managing a multi-connected
Aircraft would benefit from mechanisms that would enable the
selection of the best connection points based on service-specific
semantics, besides the traffic related parameters considered by
solutions such as SD-WAN, which aims to automate traffic steering in
an application-driven manner, based on the equivalent of a VPN
service between well defined points.
The diversity of providers implies to consider service situations in
a multi-domain environment, because of the interaction with multiple
administrative domains.
From the service perspective, it seems necessary to ensure a common
understanding of the service expectations and objectives
independently of the domain traversed or the domain providing such a
service. Common semantics can facilitate the assurance of the
service delivery and a quick adaptation to changing conditions in the
internal of a domain, or even across different domains.
3.4. Micro-service Based Mobile Applications
Mobile applications, installed on mobile devices such as smartphones
and deployed through 'marketplace' platforms, usually install a
monolithic implementation of the device-specific functionality, where
this functionality may explicitly utilize remote service
capabilities, e.g., provided through cloud-based services.
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Application functionality may also be realized as micro-services
themselves. When such micro-services are jointly deployed (i.e.,
installed) at the mobile device, its overall functionality resembles
that of existing applications.
Micro-services architectures are usually best suited to larger, more
complex applications built for scalability and agile iteration. In
this scenario, a monolithic architecture can be a problem for
applications as the codebase becomes unwieldy and difficult to
manage.
However, micro-services may also be invoked on network devices other
than the mobile device itself, utilizing service routing capabilities
to forward the micro-service request (and its response) to the remote
entity, effectively implementing an 'off-loading' capability.
Efforts such as the BBF MCN work capture this aspect as 'edge-to-edge
collaboration', where in our case here the edge does include the end
user devices themselves.
A distributed system like microservices inevitably introduces
additional complexity as multiple moving parts need to be
synchronized in a way that allows them to work as a unified software
system. If services are split across servers you will have to
provision that multi-faceted infrastructure. This is where a
service-centric network solution able to coordinate the chain of such
micro-services could plan an important role.
The work in [I-D.sarathchandra-coin-appcentres] proposes such
approach, positioning compute capabilities as forming a distributed
(app-centric) data centre. The simple example in
[I-D.sarathchandra-coin-appcentres] outlines the distribution of
video reception, processing, and displaying capabilities as
individual micro-services. With this, remote (edge computing)
capabilities may be used for complex processing beyond those of the
mobile device. This includes, for instance, to utilize hardware,
such as displays, other than the device's built-in one.
Interaction may be one driver for dynamicity in those scenarios. For
instance, the aforementioned display indirection may take place at
high frequency, triggered by sensory input (e.g., gaze control) to
decide which instance is best to direct the video stream to. This
may be beneficial for new, e.g., gaming experiences that utilize
immersive device capabilities. Other examples may include the
offloading of processing capabilities (in case of 'better', i.e.,
more capable, processing being available elsewhere).
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As briefly discussed in [I-D.sarathchandra-coin-appcentres], such
micro-service design may well be integrated into today's application
development frameworks, where a device-internal service registry
would allow for utilizing device-local service instances first before
directing the service invocation to the network to route the service
request.
In conclusiom, this concept of application-centric microservices,
deployed within other edge devices, including end user devices
themselves, extends the concept of 'edge computing', also captured in
use cases of the BBF MCN initiative [MCN], by foreseeing more focus
on the device applications, aiming at higher dynamicity in relations
being realized.
3.5. Constrained Video Delivery
Chunk-based video delivery is often constrained to, e.g., latency or
playout requirements, while the content itself may be distributed as
well as replicated across several network locations. Thus, it is
required to steer client requests for specific content under specific
constraints to one of the possibly many network locations at which
the respective content may reside.
The work in [I-D.jennings-moq-quicr-arch] proposes a publish-
subscribe metaphor that connects clients to suitable relays for
delivering the desired content under the specific constraint. Within
our context of service routing, the relays realize the service
instances for a video delivery service, where the selection of the
'right' instance is being constrained by the requirements for the
video's delivery to the client.
Instead, we suggest to complement QUICr by largely realizing the
explicit publish/subscribe architecture in
[I-D.jennings-moq-quicr-arch] through the traffic steering
capabilities within a routing on service addresses infrastructure,
specifically replace the explicit lookup for a suitable relay in
[I-D.jennings-moq-quicr-arch] through a service routing operation
with the aim to not just reduce any lookup latencies involved in the
relay selection but also to enable a high dynamicity in the selection
constraints.
3.6. AR/VR through Replicated Storage
One aspect of dynamicity in selecting content storages in the
previous use case has been investigated in [OnOff2022] through the
example of an AR/VR service that underlies a tight delay budget but
would like to benefit from any replication of content chunks across
more than one network location.
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Here, a system of N clients is suggested to be retrieving content
chunks from k service instances, where each chunk request is directed
to any of the possible k instances; given the stateless nature of
this service, any of the k instances is able to serve the chunk
without knowledge of any previous one.
As shown in [OnOff2022], a retrieval that utilizes any of the k
replicas significantly reduces the variance of the retrieval latency
experienced by any of the N clients. Such reduced variance
positively impacts the user experience through less buffering applied
at the client side but also better adhering to the overall latency
budget (often in the range of 100ms in AR/VR scenarios with pre-
emptive chunk retrieval). Although pre-emptive retrieval is also
possible in systems with explicit lookup operations, the involved
latencies for such resolution may make it difficult to adhere to the
latency budget for an E2E operation (see [I-D.liu-can-ps-usecases]
for example latency budgets).
3.7. Cloud-to-Thing Serverless Computing
The computing continuum is a crucial enabler of 5G and 6G networks as
it supports the requirements of new services, such as latency and
bandwidth critical ones, using the available infrastructure. With
the advent of new networks deployed beyond the edge, such as
vehicular and satellite networks, researchers have begun
investigating solutions to support the cloud-to-thing continuum, in
which services distribute logic across the network, and storage is
decentralized between cloud, the edge (most liked MEC) and the adhoc
network of moving devices, such as aircraft and satellites.
In this scenario, a serverless-based service architecture may be
beneficial for the deployment and management of interdependent
distributed computing functions, whose behavior can be redefined in
real-time. Serverless architecture is closely related to micro-
services. The latter is a way to design an application and the
former a way to run all or part of an application. That is the key
to their compatibility. It is possible to code a micro-service and
run it as a serverless function.
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The consideration of serverless architectures is important for the
Cloud-to-Thing continuum, since resources beyond the edge, in the
adhoc part of the continuum, may be constraint and intermittently
available. Hence it makes sense to leverage a serverless
architecture that consists of a set of functions rather than
services. The difference is that a service is permanently available
whereas a function has a lifecycle as it is triggered, called,
executed, runs and is then removed as soon as it is no longer needed.
Serverless functions only run when they are needed, potentially
saving significant resources.
In this scenario, the combination of a service oriented data plan
with a model capable of delegating and adapting serverless functions
in a cloud-to-thing continuum is important. The former need to be
aware of the presence of different functions in order to be able to
execute services based on the correct selection and invocation of
different functions, within their lifetime. Most importantly, this
awareness of the functions is likely to be highly dynamic in the
nature of its distribution across network-connected nodes.
3.8. Metaverse
Large-scale interactive and networked real-time rendered tree
dimension XR spaces, such as the Metaverse, follow the assumption
that applications will be hosted on platforms, similarly to current
web and social media applications. However, the Metaverse is
supposed to be more than the participation in isolated three
dimension XR spaces. The Metaverse is supposed to allow the
internetworking among a large number of XR spaces, although some
problems have been observed such as lock-in effects, centralization,
and cost overheads.
In spite of the general understanding about potential internetworking
limitations, current technical discussions are ignoring the
networking challenges altogether. From a networking perspective, it
is expected that the Metaverse will challenge traditional client-
server inspired web models, centralized security trust anchors and
server-style distributed computing, due to the need to take into
account interoperability among a large number of XR spaces, low
latency and the envisioned Metaverse pervasiveness.
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In this context, an open and decentralized Metaverse, able to allow
the internetworking of a large number of XR spaces, may be supported
by intertwining distributed computing and networking. Hence it is
expected that Metaverse applications may gain from a network able to
support the execution of services while taking advantage of storage,
networking, and computing resources located as close as possible from
users, with a dynamic assignment of client requests to those
resources.
3.9. Popularity-based Services
The BBF MCN use case report [MCN] outlines 'popularity' as a criteria
to move from current explicit indirection-based approaches (such as
DNS, GSLB, or Alto) to active service routing approaches.
Here, popularity, e.g., measured in service usage over a period of
time, is being used as a trigger to announce a popular service to an
active service routing platform, while less popular service continue
to be served via existing (e.g., DNS-based) methods. Equally,
services may be unannounced, thus retracted, from the service routing
overlay to better control the overall cost for the provisioning of
the service routing overlay.
With this, one could foresee the provisioning of a service routing
overlay, such as ROSA, as an optimization for a CDN platform
provider, either through commercially interfacing to a separate ROSA
provider or providing the ROSA domain itself.
4. Analysis of Use Cases
We now discuss observations and suitability of existing technologies
for realizing the use cases in the previous section, leading to the
requirements outlined in Section 5. We then list the expected
benefits for utilizing the ROSA design, presented in more detail in
Section 7.
4.1. Observations from Use Cases
Several observations can be drawn from the use case examples in the
previous section in what concerns their technical needs:
1 The namespace for services and applications is separate from that
of routable identifiers used to reach the implementing endpoints,
i.e., the service instances. Resolution and gateway services are
often required to map between those namespace, adding management
and thus complexity overhead, an observation also made in
[Namespaces2022].
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2 Service instances for a specific service may exist in more than
one network location, e.g., for replication purposes to serve
localized demand, while reducing latency, as well as to increase
service resilience.
3 While the deployment of service instances may follow a longer term
planning cycle, e.g., based on demand/supply patterns of content
usage, it may also have an ephemeral nature, e.g., scaling in and
out dynamically to cope with temporary load situations as well as
with the temporary nature of serverless functions.
4 Knowing which are the best locations to deploy a service instance
is crucial and may depend on service-specific demands, realizing a
specific service level agreement (with an underlying decision
policy) that is tailored to the service and agreed upon between
the service platform provider and the communication service
provider.
5 Decisions for selecting the 'right' or 'best' service instance may
be highly dynamic under the given service-specific decision policy
and thus may change frequently with demand patterns driven by the
use case. For instance, in our examples of Section 3.4 or
Section 3.8, human interaction may drive the requirement for
selecting a suitable service instance down to few tens of
milliseconds only, thus creating a need for high frequency updates
on the to-be-chosen service instance. As a consequence, traffic
following a specific network path from a client to one service
instance, may need to follow another network path or even utilize
an entirely different service instance as a result of re-applying
the decision policy.
6 Minimizing the latency from the initiating client request to the
actual service response arriving back at the client is crucial in
many of our scenarios. Any improvement on utilizing the best
service instance as quickly as possible, thus taking into account
any 'better' alternative to the currently used one, is crucial for
reducing latency.
7 A specific service may require the execution of more than one
service instance, in an intertwining way, which in turn requires
the coordination of the right service instances, each of which can
have more than one replica in the network.
We can conclude from our observations above that (i) distribution (of
service instances), (ii) dynamicity in the availability of and
chosing the the 'best' service instance, and (iii) efficiency in
utilizing the best possible service instance are crucial for our use
cases.
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4.2. Suitability of Existing Internet Technologies
There exist a number of L4 through L7 based solutions that could be
leveraged to fulfil the technical needs of the aforementioned use
cases, with [I-D.liu-can-gap-reqs] providing an initial overview into
the gaps that those solutions experience in the light of the
observations above.
A key takeaway from this analysis is that the explicit indirection
for service discovery, realized for instance through DNS, GSLB, or
other solutions, poses a challenge to the dynamicity also observed in
our use cases here due to the additional latency incurred but also
due to the relatively static mapping of service name onto network
locator that is maintained in most of those solutions. The work in
[OnOff2022] investigates the impact of such off-path vs possible on-
path decision making onto service performance and user experience.
The identifier/locator split provided by LISP
[I-D.ietf-lisp-introduction] provides a similar separation of (an
endpoint) identifier from its routable locator. In a way, a service
address could be seen as an anycast EID in LISP. However, the
reliance in LISP on a federated mapping service also positions LISP
as an off-path solution with explicit resolution latency being
incurred; this is due to the desired scale of LISP in which a
routing-based solution (in contrast to the pull-based mapping
service) is not tractable in terms of scalability, while for most
services, a pull-based mapping service suffices. ROSA is based on
the recognition that an explicit pull model (and its associated
latency) may not be suitable for certain use cases (see Section 3),
while still allowing for the traditional, e.g., DNS-based resolution
methods being used for the wide range of services for which
dynamicity and efficiency impact are not an issue.
Furthermore, the inherent anycast nature of service routing, when
applied to replicated service instances, requires the use of anycast
IP addresses, in turn often relying on centralized anycast routing
architectures for delivering the service to the 'best' instance under
the given anycast address. Lastly, communication over LISP does not
see a difference between initial (service) requests and following
(affinity) requests but instead realizes all communication through
the EID abstraction.
Service instances or network service functions can be used by network
operators to provide a better quality of service and manage their
networks more efficiently. In this context, there is a growing
interest in Service Function Chaining (SFC) [RFC7665], an ordered set
of service functions that are applied to end-to-end traffic. It is
expected for mobile network operators or Internet service providers
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to deploy SFCs in a geographically centralized manner, such as a data
center where service function chains can be easily managed and
configured. However, in a Cloud-to-thing scenario, the configuration
and management of the service function chain is significantly more
complex, because careful orchestration strategies are required to
discover proper service instances and connect them across multiple
networks operated with different resource management and network
policies.
The deployment of SFC in a cloud-to-thing scenario is even more
complex if service instances are developed following a serverless
architecture, in which case orchestration strategies to discover
proper service instances need to consider the network function
semantics, namely its intermittent availability in the network.
In the next section, we outline requirements for a solution that
would realize those use cases and address some of the gaps outlined
in [I-D.liu-can-gap-reqs], with Section 7 presenting our initial
design on how to address those requirements through a shim layer atop
IPv6.
5. Requirements
The following requirements for a routing on service addresses (ROSA)
solution (referred to as 'solution' for short) have been identified
from our use cases in the previous section
One commonality of all use cases is the communication with a
'service', realized at one or more network locations as equivalent
'service instances'. Associating the service to an 'owner' is key to
avoid services being announced by fake entities, thus misdirecting
the client's traffic, while obfuscating the purpose of communication
(e.g., leaked through the specific name of a service) but also any
possible policy to select one over another service instance may want
to be kept private; this is likely the case across all of our use
cases. Hence, any solution
REQ1: MUST provide means to associate service instances with a
single service address.
(a) MUST provide secure association of service address to
service owner.
(b) SHOULD provide means to obfuscate the purpose of
communication to intermediary network elements.
(c) MAY provide means to obfuscate the constraint parameters
used for selecting specific service instances.
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Across all our use cases, the knowledge of where service instances
(realizing specific services) reside within the network, i.e.,
possibly at different network locations, is crucial for the
communication to happen, at least for the ROSA domain with which the
service has an association with. Such knowledge may be created by a
service management platform, e.g., as part of the overall service
deployment, and thus may not be initiated by the deployed service
instance itself, such as in the example of Section 3.4. Furthermore,
service deployment may be delegated to service or CDN platforms,
e.g., in the CDN, AR/VR and video distribution examples of
Section 3.1, Section 3.6 or Section 3.5, respectively, albeit with
linkages needed to the service routing capabilities of ROSA.
Crucially, however, is that a solution ought to use proactive pushing
of suitable reachability information to service instances into the
ROSA system, i.e., pursuing a routing-based approach, allowing for
faster availability of information to make suitable decisions on
which service instance to choose among those available. Hence, any
solution
REQ2: MUST provide means to announce route(s) to specific instances
realizing a specific service address, thus enabling service
equivalence for this set of service instances.
(a) MUST provide scalable means to route announcements.
(b) MUST announce routes within a ROSA domain.
(c) SHOULD provide means to delegate route announcement.
(d) SHOULD provide means to announce routes at other than the
network attachment point realizing the announced service
address.
(e) MUST allow for removing service instances that are
intermittently availab,e, i.e., revoking their service
announcement after a defined timeframe.
A client application may not just invoke services within a single
ROSA domain. While associating with different ROSA domain may be
possible, clients may simply invoke services through their existing
ROSA domain, e.g., for utilizing helper services in examples like
Section 3.4, expecting the service transaction to be realized
regardless. The same goes for invoking services that may reside in
the public Internet, without requiring an explicit awareness of the
client to which ROSA domain (or the public Internet) to direct the
invocation. Thus, any solution
REQ3: MUST provide means to interconnect ROSA islands.
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(a) MUST allow for announcing services across ROSA domains.
(b) MUST allow for announcing services outside ROSA domains.
Use cases like Section 3.4 but also video delivery ones such as
Section 3.5 and Section 3.6 or the selection of an appropriate UPF
(user plane functions) within a cellular sub-system in Section 3.2,
may want to constrain the selection of 'suitable' service instances
through service-specific constraints, such as the computing load (on
the deployed service instances or their host platforms), service-
level latency, but also, e.g., HW or SW, capabilities. This may also
be the case for multi-homed deployments (see Section 3.3), where
constraints on the multi-connectivity of the service instance may
constrain the suitability for specific clients. Thus any solution
REQ4: Solution MUST provide constraint-based routing capability.
(a) MUST provide means to announce routing constraints
associated with specific service instances and their
realizing networking, computing and storaged resources.
(b) SHOULD allow for providing constraints in the service
(address) announcement.
The work in [OnOff2022] has shown the potential gains in making
runtime decisions for every incoming service transaction, where
transaction lenths may be as small as single (application-level)
requests. For use cases such as Section 3.5 or Section 3.6, this may
lead to significant smoothening of the request completition latency,
i.e., reducing the latency variance, thus enabling a better, smoother
experience at the client. However, the specific mechanism may vary
and, more importantly, may be highly service-specific, with solutions
such as [CArDS2022] providing a simple weighted round robin, while
other methods may rely on regular (service) metric reporting. Thus
any solution
REQ5: MUST provide an instance selection at ROSA domain ingress
nodes only.
(a) MUST allow for signalling selection mechanism and
necessary input parameters for selection to the ROSA
domain ingress nodes.
Explicit resolution steps, such as those in DNS, GSLB, or Alto,
suffer from the need for an explicit control plane exchange. This
causes additional latency before the data transfer to the chosen
service instance may start. In-band data, i.e., the inclusion of
application-level data in the control messages, is not supported due
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to the layering of such solutions at the application level itself.
It is desirable, however, to already allow for the exchange of
application data, including that needed for establishing secure
connections, in the process that determines the most suitable service
instance to further reduce any latency for completing a given
application-level service transaction. Thus any solution
REQ6: MUST provide an in-band data transfer capability in the
process of determining the suitable service instance for any
following data transfer within the same service transaction.
While video delivery use cases like Section 3.5 or Section 3.6 may
exhibit short lived transactions of just one (service-level) request,
due to the replicated nature of the video content in each service
instance, service transactions may last many requests after the
initial one has been sent. Ephemeral state may be created during
this transaction, which would require that a change of the (initial)
service instance during a transaction would share such ephemeral
state with any new service instance being used. While service
platforms, like K8S, provide such ability through 'shared data layer'
capabilities, those are often limited to single site deployments.
Any support across sites would incur additional costs or even
possibly latencies for such state sharing, thus often leading to
completing an ongoing service transaction with the service instance
that has been originally been used (note that a service instance in
ROSA may use internal methods for serving incoming requests across
which state sharing would be applied - from a ROSA perspective,
however, only one service instance is being used). We call the
capability to retain an initial selection of a service instance for
the length of a service transaction 'affinity'. Thus, any solution
REQ7: MUST adhere to the affinity towards the service instance
chosen in the initial service request of the service
transaction, thus directing all subsequent service transaction
requests to the same instance.
All of our use cases are likely being deployed over existing network
infrastructure, which makes a consideration to use its existing
solutions in any realization of ROSA very important. Specifically,
any solution
REQ8: Solution SHOULD use IPv6 for the routing and forwarding of
service and affinity requests.
(a) Solution MAY use IPv4 for the routing and forwarding of
service and affinity requests.
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Most of our use cases, specifically Section 3.4 but also our video
delivery examples, may be realized in inherently mobile settings with
clients moving about for their experience. While mobile IP solutions
exist, the service initialization in ROSA needs to be equally
supported in order to allow for invoking ROSA services on the move.
Thus, any solution
REQ9: SHOULD support in-request mobility for a ROSA client.
Mobility of clients, but also varying loads in scenarios of no client
mobility, may also lead to situations where moving on ongoing service
transaction to another service instance may be beneficial, termed
'transaction mobility'. In other words, service instances may be
replaced mid-transaction, in order to ensure the service level
agreement. This may happen if, for instance, the local node where
the service instance was initially installed is running out of
resources, or its accessibility is reduced (which be periodically).
Thus, any solution
REQ10: SHOULD support transaction mobility, i.e., changing service
instances during an ongoing service transaction.
With most service transactions likely being encrypted for privacy and
security reasons, supporting the appropriate transport layer methods
is crucial in all our scenarios in Section 3, which is achieved by
ROSA being positioned as a L3.5 solution, as presented in Section 7.
While work in [OnOff2022] has shown that small service transactions
in scenarios like Section 3.5 or Section 3.6 may be beneficial for
significantly reducing the service-level latency, the challenge lies
in initiating suitable transport layer security associations with
frequently changing service instances. Pre-shared certificates may
address this to allow for 0-RTT handshakes being realized but come
with well-known forward secrecy problems. Thus, any solution
REQ11: SHOULD support TLS 0-RTT handshakes without the need for pre-
shared certificates.
We envision the ROSA layer in ROSA endpoints to be transparently
integrated in the operation of transport protocols, and thus
applications, by provuding suitable interfaces to accessing the ROSA
services of a specific ROSA domain. Thus, any solution
REQ12: SHOULD be transparent to applications in order to ensure a
smooth deployment.
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6. Expected Benefits
We expect the following benefits to be realized through the ROSA
design, discussed in the next section. We here refer to
investigations in several research works by reference for more detail
on the findings:
* Dynamicity: Decisions to select one out of possibly many service
instance can be highly dynamic, done per service transactions,
including for single packet ones. This is enabled by the move
from an explicit off-path resolution step to an in-band, on-path
mapping of a service address to its realizing service instance.
Such dynamicity aims at improving transaction completion latency
and variance, balancing load across service instances, as well as
possibly deal with temporary network conditions. The work in
[OnOff2022] evaluates the impact of performing traffic steering
decisions at the level of ROSA rather than at application level.
* Service-specifity: The constraints for selecting a suitable
service instance should not be limited to network metrics like
delay or bandwidth. Instead, services should be able to define
service-specific constraints, allowing for either multi-optimality
routing or realising request-level and possibly compute-aware
request scheduling for selecting one of possibly several service
endpoints. The mechanism in [CArDS2022] outlines an example for
such steering decisions, taking into account service-specific
compute information. However, to avoid embedding full path
information into the service routing itself, the consideration of
service-specific constraints should be limited to the selection of
service instances, while the forwarding of transaction data (in
the form of subsequent affinity requests) solely follows the
routing policies defined by the underlay network.
* Reduce dependency on DNS: Current service routing utilises a DNS-
based approach, thereby requiring explicit off-path operations
before being able to utilise a specific service. We aim at
reducing this dependency on the DNS. The work in [OnOff2022]
outlines the possible impact of reducing the use of the DNS, while
also evaluating the capabilities enabled in flexible (small
affinity) traffic steering under the constraint of a given latency
budget.
* Efficiently support higher degree of service distribution: Typical
application or also L4-level solutions, such as GSLB, QUIC-based
indirection, and others, lead effectively to egress hopping when
performed in a multi-site deployment scenario in that the client
request will be routed first to an egress as defined either
through the DNS resolution or the indirection through a central
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server, from which the request is now resolved or redirected to
the most appropriate DC site. In deployments with a high degree
of distribution across many (e.g., smaller edge computing) sites,
this leads to inefficiencies through path stretch and additional
signalling that will increase the request completion time.
Instead, direct or on-path solutions such as ROSA are expected to
lead to a more direct traffic towards the site where the service
will eventually be executed, while also allowing for application
data to be already carried as part of the service instance
selection process, thus keeping the request completion time close
to its optimum in respect to the best site being used for
execution of the request.
* Bring application namespace closer to communication relations:
Reid et al [Namespaces2022] outline insights into the aspects and
pain points experienced when deploying existing intra-DC service
platforms in multi-site settings, i.e., networked over the
Internet. The main takeaway in is the lacking protocol support
for routing requests of microservices that would allow for mapping
application onto network address spaces without the need for
explicitly managed mapping and gateway services. While this
results in management overhead and thus costs, efficiency of such
additional mapping and gateway services is also seen as a
hinderance in scenarios with highly dynamic relationships between
distributed microservices, an observation aligned with the
findings in [OnOff2022]. The use cases presented in Section 3,
among others, exhibit the degrees of distribution in which
relationship management (through explicit mapping and/or
gatewaying) may become complex and a possible hinderance for
service deployment and suitable performance.
7. ROSA Design
This section outlines the design of a shim layer relying upon IPv6 to
provide routing on service addresses (ROSA). It first outlines the
system overview, before outlining the interfaces to the IP layer
(Section 7.2 and applications in ROSA endpoints (Section 7.3),
followed with the various operational methods of ROSA in terms of
forwarding operations (Section 7.4), traffic steering methods
(Section 7.5), and interconnection (Section 7.6).
7.1. System Overview
Figure 1 illustrates a ROSA domain, interconnected to other ROSA-
supporting domains via the public Internet through the Service
Address Gateway (SAG), where a ROSA domain may span one or more IPv6
underlay domain. Section 7.6 provides more detail on how to achieve
interconnection between ROSA domains.
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ROSA is positioned as a shim overlay atop IPv6, using Extension
headers that carry the suitable information for routing and
forwarding the ROSA service requests, unlike [I-D.eip-arch] which
proposes to include extension processing directly into the transport
network.
+-----------+ +-----------+ +-------+
+service.org+ +service.org+ +foo.com|
+----+------+ +-------+---+ +----+--+
| | |
+-----------+ +----+-+ +----+-----------+--+
+service.org+---+DC Net| | DC Net |
+-----------+ +---+--+ +-------------+-----+
| |
+-+--+ +-+--+
+-----+SAR4| |SAR5|
| +-+--+ +-+--+
+------+ +-+--+ +----+ |
+Client+--------+SAR1+-------------+ +SAR6+ |
+------+ +----+ | +-+--+ |
| | |
+------+ +----+ ++-----+----+ |
+Client+--------+SAR2+------------+IPv6 Net(s)+---------+
+------+ +----+ +---+--+----+ (----)
| | ( )
+------------------+ +----+ | | +----+ ( Other )
+MyMobile.org/video+--------+SAR3+----+ +----+SAG1+----( Domains )
+------------------+ +----+ +----+ ( )
(------)
SAR: Service Address Router
SAG: Service Address Gateway
Figure 1: ROSA System Overview
ROSA endpoints start with discovering their ingress Service Address
Router (SAR), e.g., through DHCP extensions or through utilizing the
Session Management Function (SMF) in 5G networks [TS23501]. An
endpoint may discover several ingress SARs for different categories
of services, each SAR being part of, e.g., a category-specific ROSA
overlay, which in turn may be governed by different routing policies
and differ in deployment (size and capacity). The category discovery
mechanism may be subject to specific deployments of ROSA and thus is
likely outside the scope of this document at this point.
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Services are realized by service instances, possibly at different
network locations. Those instances expose their availability to
serve requests through announcing the service address of their
service to their ingress SAR, which in turn distributes suitable ROSA
routing state across the SARs in its domain. The lacking tie of
service addresses to the network topology, and thus the lacking
possibility to aggregate relationships of service addresses to
routing locators, poses a scalability challenge (specifically to
address Req 2.a in Section 7.4) However, the routing tables in ROSA
are bounded by the number of services explicitly announcing their
service to ingress SARs, while utilizing explicit interconnection
(see Section 7.6) to other ROSA domains or the Internet for any
service requested in the domain that has not previously been
announced.
To invoke a service, a ROSA client sends an initial request,
addressed to a service, to its ingress SAR, which in turn steers the
request (possibly via other SARs) to one of possibly many service
instances. See Section 7.4 for the required SAR-local forwarding
operations and end-to-end message exchange and Section 7.3 for the
needed changes to ROSA clients. Conversely, non-ROSA services may
continue to be invoked using existing means for service routing, such
as DNS, GSLB, Alto and others.
We refer to initial requests as 'service requests'. If an overall
service transaction creates ephemeral state, the client may send
additional requests to the service instance chosen in the (preceding)
service request; we refer to those as 'affinity requests'. With
this, routing service requests (over the ROSA network) can be
positioned as on-path service discovery (winth in-band data),
contrasted against explicit, often off-path solutions such as the
DNS.
In order to support transactions across different service instances,
e.g., within a single DC, a sessionID may be used, as suggested in
[SOI2020]. Unlike [SOI2020], discovery does not include mapping
abstract service classes onto specific service addresses, avoiding
semantic knowledge to exist in the ROSA shim layer for doing so.
With the above, we can outline the following design principles that
guide the development for the solutions described next:
* Service addresses have unique meaning only in the overlay network.
* Service instance IP addresses have meaning only in the underlay
networks, over which the ROSA domain operates.
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* SARs map service addresses to the IP addresses for the next hop to
send the service request to, finally directed to the service
instance IP address.
* Within the underlay network, service instance IP addresses have
both locator and identifier semantics.
* A service address within a ROSA domain carries both identifier and
locator semantics to other nodes within that domain but also other
ROSA domains (through the interconnection methods shown in
Section 7.6).
* Affinity requests directly utilize the underlay networks, based on
the relationships build during the service request handling phase.
We can recognize similarities of these principles with those outlined
for the Locator Identifier Separation Protocol (LISP) in
[I-D.ietf-lisp-introduction] albeit extended with using direct IP
communication for longer service transactions.
7.2. Message Types
Apart from affinity requests, which utilize standard IPv6 packet
exchange between the client and the service instance selected through
the initial service request, ROSA introduces three new message types,
shown in Figure 2.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Instance=IP |
| Service=ID |
| Constraint=txt |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Service Announcement
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Client=IP |
| Ingress=IP |
| Service=ID |
| Port=port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Service Request
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Client=IP |
| Ingress=IP |
| Service=ID |
| Port=port |
| Instance=IP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Service Response
Figure 2: ROSA message types
Given the overlay nature of ROSA, clients, SARs, and service
instances are destinations in the IPv6 underlay of the network
domains that the overlay spans across. This is unlike approaches
such as [I-D.huang-service-aware-network-framework], which place the
service address into the destination address of the respective IPv6
header field, although [I-D.ma-intarea-encapsulation-of-san-header]
also foresees the encapsulation into the IPv6 EH, as suggested here.
Istead, we propose to use the destination option EH [RFC8200], where
Figure 2 shows the options carried, proposed here as using a TLV
format for the extension header with Concise Binary Object
Representation (CBOR) [RFC8949] being studied as an alternative. The
EH entries shown are populated at the client and service instance,
while read at traversing SARs.
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A service address is encoded through a hierarchical naming scheme,
e.g., using [RFC8609]. Here, service addresses consist of
components, mapping existing naming hierarchies in the Internet onto
those over which to forward packets, illustrated in the forwarding
information base (FIB) of Figure 3 as illustrative URLs. With
components treated as binary objects, the hierarchical structure
allows for prefix-based grouping of addresses, reducing routing table
size, while the explicit structure allows for efficient hash-based
lookup during forwarding operations, unlike IP addresses which
require either log(n) radix tree search software or expensive TCAM
hardware solutions.
Note that other encoding approaches could be used, such as hashing
the service name at the ROSA endpoint or assigning a service address
through a mapping system, such as the DNS, but this would require
either additional methods, e.g., for hash conflict management or
name-address mapping management, which lead to more complexity.
With the service announcement message, a service instance signals
towards its ingress SAR its ability to serve requests for a specific
service address. Section 7.5 outlines the use of this message in
routing or scheduling-based traffic steering methods.
The service request message is originally sent by a client to its
ingress SAR, which in turn uses the service address provided in the
extension header to forward the request, while the selected service
instance provides its own IP locator as an extension header entry in
the service response. In addition to the service address, suitable
port information is being provided (through upper layer protocols),
allowing to associate future affinity requests with their initial
service requests.
The next section describes the SAR-local forwarding operations and
the end-to-end message exchange that uses the extension header
information for traversing the ROSA network, while Section 7.6
outlines the handling of service addresses that have not been
previously announced within the client-local ROSA domain.
7.3. Changes to Clients to Support ROSA
Within endpoints, the ROSA functionality is realized as a shim layer
atop IPv6 and below transport protocols. For this, endpoints need
the following adjustments to support ROSA:
* Adapting network layer interface: Introducing service addresses
requires changes to the current network interface for discovering
the ingress SAR and issuing service requests as well as
maintaining affinity to a particular service instance, i.e.
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mapping a service instance IP address to the initial service
address. As one possible choice, a new address type (e.g.,
ADDR_SA) could be introduced at the socket interface, provided
during socket creation and assigning the service address to the
returned handle, while utilizing socket options to assign
constraints to receiving sockets, utilized in the announcement of
the service address. Alternatively, supporting service addresses
could be integrated with efforts such as [POSTSOCK2017] to
redefine the transport interface towards applications. Any OS-
level client changes, as required by introducing new sockets,
could be avoided by relying on, e.g., UDP-based, encapsulation of
client traffic to the ingress SAR albeit with the drawback of
needing to maintain client-state at the ingress SAR.
* Transport protocol integration: We see our design aligned with
existing transport protocols, like TCP or QUIC, albeit with
changes required to utilize the aforementioned new address type.
For the application (protocol), the opening and closing of a
transport connection would then signal the affinity to a specific
instance, where the semantic of the 'connection' changes from an
IP locator to a service address associated to that specific
service instance. With this, a new service transaction is
started, akin to a fresh DNS resolution with IP-level exchange.
* Changes to application protocols: The most notable change for
application protocols, like HTTP, would be in bypassing the DNS
for resolving service names, using instead the aforementioned
different (service) socket type. These adaptions are, however,
entirely internal to the protocol implementation. Given the ROSA
deployment alongside existing IP protocols, those changes to
clients can happen gradually or driven through (e.g., edge SW)
platforms.
7.4. SAR Forwarding Engine
The SAR operations are typical for an EH-based IPv6 forwarding node:
an incoming service request or response is delivered to the SAR
forwarding engine, parsing the EH for relevant information for the
forwarding decision, followed by a lookup on previously announced
service addresses, and ending with the forwarding action.
Figure 3 shows a schematic overview of the forwarding engine with the
forwarding information base (FIB) and the next hop information base
(NHIB) as main data structures. The NHIB is managed through a
routing protocol, see Section 7.5, with entries leading to announced
services.
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incoming service request/response
-------------------------------------|| Next Hop
\/ Information Base
Forwarding Information Base +----------+ +-+--------+----+
+------------------+--------+ |EH parsing| |#|Next Hop|Cost|
|Service address |Next Hop| +----||----+ |#| IP |Cost|
+------------------+--------+ \/ +-+--------+----+
| service.org | 4, 5, 0| +----------+ |0| SAR5 | 2 |
+------------------+--------+ | SAR | +-+--------+----+
| foo.com | 1 |-->|Forwarding| |1| SAR6 | 1 |
+------------------+--------+ | Decision | +-+--------+----+
|MyMobile.org/video| 2 | +----||----+ |2| SAR2 | 4 |
+------------------+--------+ \/ +-+--------+----+
| * | 3 | +----------+ |3| SAR1 | 2 |
+------------------+--------+ | SA/DA | +-+--------+----+
|Adjustment|<--|4| SI1 | - |
+----||----+ +-+--------+----+
\/ |5| SI2 | - |
+----------+ +-+--------+----+
|IP packet |
|forwarding| Outgoing service
| engine | request/response
+----------+------------------->
Figure 3: SAR forwarding engine model
The FIB is dynamically populated by service announcements via the
intyer-SAR routing protocol, with the FIB including only one (ROSA
next hop) entry into the NHIB when using routing-based methods (rows
0 to 3 in Figure 3), described in Section 7.5.2. Scheduling-based
solutions (see Section 7.5.1), however, may yield several dynamically
created entries into the NHIB (items 0, 4 and 5 in Figure 3, where
SI1 and SI2 represent the IPv6 address announced by the respective
service instances) as well as additional information needed for the
scheduling decision; those dynamic NHIB entries directly identify
service instances locations (or their egress as in item 0) and only
exist at ingress SARs towards ROSA clients.
As stated in Section 1.2, we expect the number of forwarding entries
to be limited by the explicit relations service providers may have
with their ROSA provider. In other words, we do not expect the FIB
to include ALL possible service names but those explicitly announcing
their service (and being authorized by the ROSA provider doing so).
In our use cases of Section 3, those services may be very limited in
numbers, particularly if we foresee dedicated ROSA providers to aim
at realizing those use cases.
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For a service request, a hash-based service address lookup (using the
Service EH entry) is performed, leading to next hop (NH) information
for the IPv6 destination address to forward to (the final destination
address at the last hop SAR will be the instance serving the service
request).
Forwarding the response utilizes the Client and Ingress EH fields,
where the latter is used by the service instance's ingress SAR to
forward the response to the client ingress SAR, while the former is
used to eventually deliver the response to the client by the client's
ingress SAR, ensuring proper firewall traversal of the response back
to the client. We have shown in prototype realizations of ROSA that
the operations in Figure 3 can be performed using eBPF [eBPF]
extensions to Linux SW routers, while [SarNet2021] showed the
possibility a realizing a similar design using P4-based platforms.
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Client Ingress Service Service
SAR Instance Instance
(CIP) (SAR IP) (SI1 IP) (SI2 IP)
---------------------------------------------------------------------
ServiceRequest
(ClientIP,SAR IP)
(CIP, SAR IP, ServiceID)
--------------------->
\ Determine ROSA
/ and, ultimately, IP Next Hop
ServiceRequest
(SAR IP, SI1 IP)
(CIP, SAR IP, ServiceID)
--------------------->
\ Generate
/ Response
ServiceResponse
(SI1 IP, SAR IP)
(CIP, SAR IP, ServiceID, SI1 IP)
<---------------------
ServiceResponse
(SAR IP, CIP)
(CIP, SAR IP, ServiceID, SI1 IP)
<---------------------
AffinityRequest
(CIP, SI1 IP)
------------------------------------------->
\ Generate
/ Response
<-------------------------------------------
Figure 4: ROSA message exchanges
Figure 4 shows the resulting end-to-end message exchange, using the
aforementioned SAR-local forwarding decisions. We here show the IP
source and destination addresses in the first brackets and the
extension header information in the second bracket.
We can recognize two key aspects. First, the SA/DA re-writing
happens at the SARs, using the EH-provided information on service
address, initial ingress SAR and client IP locators, as described
above. Second, the selection of the service instance is signalled
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back to the client through the additional Instance EH field, which is
used for sending subsequent (affinity) requests via the IPv6 network.
As noted in the figure, when using transport layer security, the
service request and response will relate to the security handshake,
thereby being rather small in size, while the likely larger HTTP
transaction is sent in affinity requests. As discussed in
Section 12, 0-RTT handshakes may result in transactions being
performed in service request/response exchanges only.
7.5. Traffic Steering
Traffic steering in ROSA is applied to service requests for selecting
the service instance that may serve the request, while affinity
requests use existing IPv6 routing and any policies constraining
traffic steering in this part of the overall system. At receiving
service endpoints, service provisioning platforms may use additional
methods to schedule incoming service requests to suitable resources
with the ingress point to the service provisioning platform being the
service endpoint for ROSA.
In the following, we outline two approaches for traffic steering.
The first uses ingress-based scheduling decisions to steer traffic to
one of the possible service instances for a given service address.
The second follows a routing-based model, determining a single
destination for a given service address using a routing protocol,
similar to what is suggested in
[I-D.huang-service-aware-network-framework].
We envision that some services may be steered through scheduling
methods, while others use routing approaches. The indication which
one to apply may be derived from the number of next hop entries for a
service address. In Figure 3, service.org uses a scheduling method
(with instances connected to SAR5 being exposed as a single instance
to ROSA, using DC-internal methods for scheduling incoming requests),
while the other services are routed via SARs.
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We furthermore envision an interface to exist between the ROSA
provider and the underlying network provider, exchanging routing
policy relation information. The richness of this interface depends
on the specific business relation between both providers, i.e., the
ROSA and the network provider. In integrated settings, where ROSA
and network provider may belong to the same commercial entity, this
interface may provide rich routing policy relation information, such
as network latency and bandwidth information, which in turn may be
used in the ROSA traffic steering decisions. In other, more
disintegrated deployments, the information may entirely be limited to
SLA-level information with no specific runtime information exchanged
between both providers. The exact nature of this interface remains
for further study.
Important here is that traffic steering is limited to a single ROSA
domain, i.e., traffic steering is not provided across instances of
the same service in different ROSA domains; traffic will always be
steered to (ROSA) domain-local instances only.
7.5.1. Ingress Request Scheduling
Traffic steering through explicit request scheduling follows an
approach similar to application- or transport-level solutions, such
as GSLB [GSLB], DNS over HTTPS [RFC8484], HTTP indirection [RFC7231]
or QUIC-LB [I-D.ietf-quic-load-balancers]: Traffic is routed to an
indirection point which directs the traffic towards one of several
possible destinations.
In ROSA, this indirection point is the client's ingress SAR.
However, unlike application or transport methods, scheduling is
realized in-band when forwarding service requests in the ingress SAR,
i.e., the original request is forwarded directly (not returned with
indirection information upon which the client will act), while
adhering to the affinity of a transaction by routing subsequent
requests in a transaction using the instance's IP address.
Scheduling commences to a possibly different instance with the start
of a new transaction.
For this, the ingress SAR's NHIB needs to hold information to ALL
announced service instances for a service address. Furthermore, any
required information, e.g., capabilities or metric information, that
is used for the scheduling decision is signalled via the service
announcement, with (frequent) updates to existing announcements
possible. Announcements for services following a scheduling- rather
than a routing-based steering approach carry suitably encoded
information in the Constraint field of the announcement's EH, leading
to announcements forwarded to client-facing ingress SARs without NHIB
entries stored in intermediary SARs.
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In addition, a scheduling decision needs to be realized in the SAR
forwarding decision step of Figure 3. This may require additional
information to be maintained, such as instance-specific state,
further increasing the additional NHIB data to be maintained.
Examples for scheduling decisions are:
* Random selection of one of the service instances for a given
service address, not requiring any additional state information
per service address. Announcing the service instance is required
once.
* Round robin, i.e., cycling through service instance choices with
every incoming service request, requiring to keep an internal
counter for the current position in the NHIB for the service
address. Announcing the service instance is only required once.
* Capability-based round robin: Cycle through service instances in
weighted round robin fashion with the weight (as additional
information in each NHIB entry) representing a capability, e.g.,
number of (normalized) compute resources committed to a service
instance. Announcing the service instance requires an update when
capabilities change (e.g., during re-orchestration). Weights
could be expressed as numerals, limiting the needed semantic
exposure of service provider knowledge and thereby supporting the
possible separation of service and communication network provider.
The solution in [CArDS2022] realises a compute-aware selection
through such decision.
* Metric-based selection: Select service instance with lowest or
highest reported metric, such as load, requiring to keep
additional metric information per service instance entry in the
NHIB. Frequent signalling of the metric is required to keep this
information updated.
Although each method yields specific performance benefits, e.g.,
reduced latency or smooth load distribution, [OnOff2022] outlines
simulation-based insights into benefits for realising the compute-
aware solution of [CArDS2022] in ROSA.
7.5.2. Routing Across Multiple SARs
In order to send a service request to the `best' service instance
(among all announced ones) using a routing-based approach, we build
NHIB routing entries by disseminating a service instance's
announcement for a given service address S, arriving at its ingress
SAR. This distribution may be realized via a routing protocol or a
central routing controller or a hybrid solution.
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If no particular constraint is given in the announcement's EH
Constraint field, shortest path will be realized as a default policy
for selecting the `best' instance, routing any client's request to S
the nearest service instance available.
Alternatively, selecting a service instance may use service-specific
policies (encoded in the Constraint field of the EH, with the
specific encoding details being left for future work). Here,
multiple constraints may be used, with [Multi2020] providing a
framework to determine optimal paths for such cases, while also
conventional traffic engineering methods may be used.
Through utilizing the work in [Multi2020], a number of multi-criteria
examples can be modelled through a dominant path model, relying on a
partial order only, as long as isotonicity is observed. Typical
examples here are widest-shortest path or shortest-widest routing
(see [Multi2020]), which allow for performance metrics such as
capacity, load, rate of requests, and others. However, metrics such
as failure rate or request completion time cannot directly be
captured and need formulation as a max metric. Furthermore, metrics
may not be isotonic, with Section 3.4 of [Multi2020] supporting those
cases through computing a set of dominant attributes according to the
largest reduction. [Multi2020] furthermore shows that non-restarting
or restarting vectoring protocols may be used to compute dominant
paths and to distribute the routing state throughout the network.
However, the framework in [Multi2020] is limited to unicast vectoring
protocols, while the routing problem in ROSA requires selecting the
'best' path to the 'best' instance, i.e., as an anycast routing
problem. To capture this, [Multi2020] could be extended through
introducing a (anycast) virtual node, placed at the end of a logical
path that extends from each service instance to the virtual node.
Selecting the best path (over the announced attributes of each
service instance) to the virtual node will now select the best
service instance (over which to reach the virtual node in the
logically extended topology).
Alternatively, ROSA routing may rely on methods for anycast routing,
but formulated for service instead of anycast addresses. For
instance, AnyOpt [AnyOpt2021] uses a measurement-based approach to
predict the best (in terms of latency) anycast (i.e. service)
instance for a particular client. Alternatively, approaches using
regular expressions may be extended towards spanning a set of
destinations rather than a single one. Realizations in a routing
controller would likely improve on convergence time compared to a
distributed vector protocol; an aspect for further work to explore.
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7.6. Interconnection
There are two cases for interconnection: access to (i) non-ROSA
services in the public Internet and (ii) ROSA services not domain-
locally announced but existing in other domains.
For both cases, we utilize a reserved wildcard service address '*'
that points to a default route for any service address that is not
being advertised in the local domain. This default route is the
service address gateway (see Figure 1), ultimately receiving the
service request to the locally unknown service.
Upon arriving at the SAG, it searches its local routing table for any
information. If none is found, it consults the DNS to retrieve an IP
address where the service is hosted; those mappings could be cached
for improving future requests or being pre-populated for popular
services.
For case (i), the resolution returns a server's IP address to which
the SAG sends the service request with its own IP address as source
address. The service response is routed back via the SAG, which in
turn uses the Ingress EH information to return the response to the
client via its ingress SAR.
For case (ii), the IP address would be that of the SAG of the ROSA
domain in which the service is hosted. For this, a domain-local
service instance would have exposed its service, e.g., Mobile.com/
video Figure 1, by registering its domain-local SAG IP address with
the mapping service. To suitably forward the request, the SAG adds
its own IP address as the value to an additional SAG label into the
extension header. At the destination SAG, the service address
information, extracted from the extension header, is used to forward
the service request based on ROSA mechanisms. For the service
response, the destination SAG uses the SAG entry in the EH to return
the response to the originating ROSA domain's SAG, which in turn uses
the Ingress information of the EH to return the response via the
ingress to the client.
Given the EH deployment issues pointed out in [SHIM2014], a UDP-based
encapsulation may overcome the observed issues, not relying on the EH
being properly observed during the traversal over the public
Internet. Furthermore, while Figure 1 shows the SAG as an
independent component, we foresee deployments in existing PoPs. This
would allow combining provisioning through frontloaded PoP-based
services and ROSA services. Any service not explicitly announced in
the ROSA system would lead to being routed to the PoP-based SAG,
which may use any locally deployed services before forwarding the
request to the public Internet.
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8. Extensions to Base ROSA Capabilities
ROSA, as defined in Section 7, can be extended to address various
capabilities useful for specific or across a number of use cases.
The following provides a list of those possible extended
capabilities. At this stage, we would expect those capabilities to
be defined in more detail in separate drafts, complementing the ROSA
'base' specification, as defined in this current draft.
8.1. Supporting Different Namespace Encodings
Although most of our examples assume the use of URL-based service
addresses, encoded using [RFC8609], supporting other, e.g., corporate
service, namespaces may be desired. [RFC8609] generally supports
this and could thus be used.
As briefly alluded to in Section 7.2, other encodings to that
following [RFC8609] may be used, focussing on different ways to
represent a service address differently, including linking it to the
service name used at the application level.
One such encoding may be that of a unique service address per service
name, with the linkage between both provided through the DNS. Here,
the client sends an initial DNS query with the URL of the purported
service or application. Instead of requesting a resolution to a
locator, however, is the request for mapping between the URL and the
service address of ROSA, where the service address has been assigned
as part of the domain name registration (which may be done after
initial registration of the domain name for backward compatibility).
Service addresses here may be simply encoded as numerals, where
uniqueness is achieved through linking to the domain name
registration and thus DNS mapping. Encoding in the respective EH
header field (see Section 7.2) would be shorter and thus more
efficient, still achieving the desired uniqueness in the SAR
forwarding process to avoid ambiguity in forwarding decisions. The
drawback is the need for the additional DNS mapping step (albeit only
required once per application, where the service address could be
stored persistently for later use), while also the additional DNS
mapping will need standardization (likely in the form of a new DNS
record).
Another possible encoding, without the aforementioned explicit DNS
mapping step, could be to explicitly hash the service name into a
service address at the ROSA endpoint, operating on those hash values
for service announcement and requests. Due to the large service
namespace, hash conflicts may, however, occur, which needs resolving
at the SAR (which may operate on a service address for a service
request for a different, but same hashed, service address of an
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announcement service). Further study is needed into the probability
for such hash conflicts and possible mitigation methods for such
conflicts.
If the use of different encoding methods beyond [RFC8609] was to be
considered, appropriate modifications to the EH fields need to be
done to signal the used encoding method for the service address.
8.2. Supporting Multi-Homing of Service Instances
Multi-homed service instances may benefit from path-aware routing
decisions after mapping service addresses to service instance
addresses. To that end, service instances would need to advertise
multiple instance IPs as part of their service announcement.
The optimal path may differ while a client communicates with a
service instance; this is in particular likely for mobile clients.
This provides some complication for affinity requests; in such a
case, the service instance IP is no longer sufficient to identify a
service instance, merely to locate a particular path.
Multi-homing issues in connection with aircrafts also extend to
Unmanned Aerial Systems (UAS). Rather than focusing on passenger
experience, multi-homing over commercial off-the-shelf (COTS)
communications modules such as 5G or IEEE 802.11 provides command,
control and communications (C3) capabilities to Unmanned Aerial
Vehicles (UAV; drones). Despite the difference in focus, the
technical challenges in maintaining connection quality are largely
equivalent.
Multi-homing thus either requires an undesirable further resolution
step from a service instance identifier to a (optimal path) locator.
Alternatively, ROSA message types may be extended to include a
distinct service instance identifier and service instance locator
identifiers, i.e., IP addresses, which provides sufficient
information for SARs to map to specific and changing locators, while
retaining the affinity to the service instance by identifier.
8.3. Supporting 0-RTT TLS
TBD Dirk
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8.4. Supporting Transaction Mobility
When it comes to the transaction mobility in which the serving
service instance needs to be shifted to another selected alternative
instance, the ROSA service address could provide a good starting as
an location-independent ID. Other than TCP for which the client and
server have to maintain strict machine state, UDP-based protocol
could be extended with the service address to be treated as the
connection ID rather than the traditional 4-tuple including the host
destination address when the server does not have to maintain session
state. The chief gain here is the service connection could remain
intact when the serving service instance has been switched over at
ROSA level (routing plane).
As part of the ability to switch over from one service instance, ROSA
may explicitly support that mobility in that the choice of the (new)
service instance is explicitly made within the service-specific
traffic steering method. For this, ROSA may introduce a separate
message alongside the service request message (see see Section 7.2),
which not only allows for the ingress SAR to perform the same routing
policy as if it was sent through a new service request message, but
may also include application-specific context data to facilitate the
needed application state transfer from the original service instance
to the new one. Here, the in-band capability of a ROSA request is
being used to carry this context data as part of the new ROSA
message.
8.5. Supporting Service Function Chaining
Service Function Chaining (SFC) [RFC7665] allows for chaining the
execution of services at L2 or L3 level, targeting scenarios such as
carrier-grade NAT and others. The work in [RFC8677] extends the
chaining onto the name level, using service names to identify the
individual services of the chain, even allowing combinations of name
and L2/L3-based chains.
Although [RFC8677] is tied into a realization of the SFF (service
function forwarder) using a path-based forwarding approach, the
concept of name-based SFCs can equally be realized utilizing ROSA.
8.6. Supporting Privacy-Compliant Communication
The exposure of service-related information in the ROSA EHs may be
seen as a privacy issue, particularly when utilizing the service name
as the basis for the service address formulation. Although
Section 12 outlines the possible use of service categories (instead
of finer-grained service names) as input into the service address
formulation, it is also desirable to protect the privacy of fine-
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grained service address information, should the specific ROSA
deployment make use of them.
Beyond using encryption methods to protect the ROSA EH information,
such privacy methods could also include the obfuscation of client and
transit information as well, thus moving into the space of routing
privacy, as outlined for instance in
[I-D.ip-address-privacy-considerations]
9. Prototype-based Insights
To come before IETF116 with description of planned demo to
demonstrate some of the benefits outlined in Section 6.
10. Open Issues
There are a number of open issues with the following list providing a
non-exhaustive list of examples:
1 A ROSA control plane is required for handling aspects of ingress
SAR discovery and signalling of service instance announcements to
the ROSA network, either to ingress SARs only (for services
utilizing traffic scheduling mode) or across all domain-internal
SARs. Here, the signalling for achieving interconnections, based
on the methods outlined in Section 7.6, is also required to be
specified.
2 Possible segmentation of ROSA service request and responses need
handling.
3 Prototypical but also possibly simulation-based insights into
benefits are desirable to motivate the adoption of ROSA.
11. Conclusions
This draft outlined a methods for service-specific traffic steering
through an IPv6 EH-based shim overlay, allowing for routing on
service addresses as either ingress-based instance selection or
through multi-SAR routing methods.
As next steps, we plan on extending various aspects of the ROSA
operations, specifically to address the open issues listed in the
previous section, e.g., control plane aspects such as SAR discovery
and routing protocol, support for service request segmentation, and
others. We expect that aspects for a ROSA control plane, e.g., to
signal suitable traffic steering parameters to the ingress SARs or to
establish multi-SAR routing state, are captured in separate works.
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We furthermore have plans on bringing an eBPF-based prototypical
realization of the forwarding behaviour in Section 7.4 to future IETF
events, e.g., for a hackathon participation to showcase ROSA-based
applications in a test setup.
12. Security Considerations
Aligned with security considerations in existing service provisioning
systems, we address aspects related to authenticity, i.e., preventing
fake service announcements, confidentiality, both in securing
relationship as well as payload information, and operational
integrity.
* Announcement security: A key exchange between service and network
provider may be used to secure the service announcement for
ensuring an authorized announcement of services. Self-certifying
identifiers could be used for this purpose
* Relationship security: Using service addresses at the routing
layer poses not just a privacy but possibly also a net neutrality
problem, allowing for non-ROSA elements to discriminate against
specific service addresses. Similar to
[I-D.per-app-networking-considerations], service addresses could
reflect service categories, not services themselves. Service
endpoints to those category-level services can use information in
the secured payload (e.g., the URL in an HTTP-based service
invocation) to direct the traffic accordingly. The downside of
such model is a possible convergence towards a PoP-like model of
service provisioning, since exposing an entire service category
naturally requires provisioning many possible services under that
category, likely favouring large-scale providers over smaller
ones; an imbalance that ROSA intends to change, not favour. Work
on identity privacy in ILNP [ILNP2021] has shown that ephemeral
identifiers may increase the private nature of the communication
relation; a direction that needs further exploration in the
context of our work. Also, the service address in the extension
header could be encrypted, based on a key exchange during the SAR
discovery. However, the impact of such mechanism would need
further study.
* Transport-level security: Given the often sensitive nature of
service requests, payload security is key. We adopt techniques
used in TLSV1.3 [RFC8446], providing a 1-RTT handshake for
communication between formerly untrusted parties. While the
initial 'Client Hello' is sent as a service request, the
subsequent communication uses the topological address of the
responding server in an affinity request. Using pre-shared keys
may allow for communication between trusted client and service
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instances, e.g., where the client is provided by the service
authority and preconfigured with a pre-shared key. This results
in a 0-RTT handshake with the 'Client Hello' including the initial
service data, encrypted with the pre-shared key. This comes with
known forward-secrecy issues and should be avoided in networks
with untrusted intermediary nodes. Alternatively, the service's
public key could encrypt the initial security handshake, akin to
the solutions proposed for Encrypted Client Hello (ECH), using the
DNS for obtaining the public key.
* Bandwidth DoS: We assume network provider level mechanisms to
restrict traffic injected both by the service provider and client,
including for the number of service advertisements in order to
control the routing traffic.
* Denying routing service: A SAR could maliciously deny forwarding
of client requests, which is no different from denying IP packet
forwarding. In both cases, we assume an existing commercial
relationship that avoids such situation.
13. Privacy Considerations
The exposure of service-related information in the ROSA EHs may be
seen as a privacy issue, particularly when utilizing the service name
as the basis for the service address formulation. As discussed in
Section 8.6, extensions to the base ROSA capabilities may address
this issue to ensure the privacy of the clients' communication
relations in ROSA deployments, where needed.
14. IANA Considerations
This draft does not request any IANA action.
15. Change Log
1 Restructured introduction to improve readability and
argumentation for this draft
2 Addressing IETF115 comments in various parts of the draft, e.g.,
introduction, analysis (relation to other technologies), traffic
steering (relation to anycast) etc
3 Added six new use cases (mobile applications - Section 3.4, chunk
retrieval - Section 3.5, AR/VR - Section 3.6, Cloud-to-Thing -
Section 3.7, Metaverse - Section 3.8, and popularity-based
services - Section 3.9)
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4 Added separate analysis section, as derived from use cases
(Section 4)
5 Revised and linked requirements to use cases through additional
text (Section 5)
6 Discussed possible benefits from applying ROSA in identified use
cases (Section 6)
7 Revised ROSA messages figure (Figure 2)
8 Added section on possible extended capabilities to 'base' ROSA
(Section 8), including multi-homing support, namespace support.
9 Added and maintaining open issues (Section 10)
10 Added missing sections, like conclusions (Section 11) and privacy
considerations (Section 13)
11 Added Jens Finkhaeuser, Daniel Huang, and Paulo Mendes as co-
authors.
16. Acknowledgements
Many thanks go to Mohamed Boucadair, Tommy Pauly, Joel Halpern,
Daniel Huang, and Russ White for their comments to the text to
clarify several aspects of the motiviation for and technical details
of ROSA.
17. Informative References
[AnyOpt2021]
Zhang, Z., April, T., Chandrasekaran, B., Choffnes, D.,
Maggs, B. M., Shen, H., Sitaraman, R. K., Yang, X., Zhang,
X., and T. Sen, "AnyOpt: predicting and optimizing IP
Anycast performance", Paper ACM SIGCOMM, 2021.
[BBF] ""Control and User Plane Separation for a disaggregated
BNG"", Technical Report-459 Broadband Forum (BBF), 2020.
[CArDS2022]
Khandaker, K., Trossen, D., Khalili, R., Despotovic, Z.,
Hecker, A., and G. Carle, "CArDS:Dealing a New Hand in
Reducing Service Request Completion Times", Paper IFIP
Networking, 2022.
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[CV19] Feldmann, A., Gasser, O., Lichtblau, F., Pujol, E., Poese,
I., Dietzel, C., Wagner, D., Wichtlhuber, M., Tapiador,
J., Vallina-Rodriguez, N., Hohlfeld, O., and G.
Smaragdakis, "A Year in Lockdown: How the Waves of
COVID-19 Impact Internet Traffic", Paper Communications of
ACM 64, 7 (2021), 101-108, 2021.
[eBPF] "What is eBPF?", Technical Report eBPF Foundation, 2022,
.
[EI2021] Cidon, I., Culler, D., Estrin, D., Katz-Bassett, E.,
Krishnamurthy, A., McCauley, M., McKeown, N., Panda, A.,
Ratnasamy, S., Rexford, J., Schapira, M., Shenker, S.,
Stoica, I., Tennenhouse, D., Vahdat, A., Zegura, E.,
Balakrishnan, H., and S. Banerjee, "Revitalizing the
public internet by making it extensible", Paper ACM
Computer Communication Review, Vol. 51. 18-24. Issue 2,
2021.
[Gini] "Gini Coefficient", Technical Report Wikipedia, 2022,
.
[GSLB] "What is GSLB?", Technical Report Efficient IP, 2022,
.
[HHI] "Herfindahl-Hirschman index", Technical Report Wikipedia,
2022, .
[Huston2021]
Huston, G., "Internet Centrality and its Impact on
Routing", Technical Report IETF side meeting on 'service
routing and addressing', 2021,
.
[I-D.eip-arch]
Salsano, S., ElBakoury, H., and D. Lopez, "Extensible In-
band Processing (EIP) Architecture and Framework", Work in
Progress, Internet-Draft, draft-eip-arch-01, 16 December
2022,
.
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[I-D.huang-service-aware-network-framework]
Huang, D., Tan, B., and D. Yang, "Service Aware Network
Framework", Work in Progress, Internet-Draft, draft-huang-
service-aware-network-framework-01, 22 November 2022,
.
[I-D.ietf-lisp-introduction]
Cabellos-Aparicio, A. and D. Saucez, "An Architectural
Introduction to the Locator/ID Separation Protocol
(LISP)", Work in Progress, Internet-Draft, draft-ietf-
lisp-introduction-15, 20 September 2021,
.
[I-D.ietf-quic-load-balancers]
Duke, M., Banks, N., and C. Huitema, "QUIC-LB: Generating
Routable QUIC Connection IDs", Work in Progress, Internet-
Draft, draft-ietf-quic-load-balancers-15, 24 October 2022,
.
[I-D.ip-address-privacy-considerations]
Finkel, M., Lassey, B., Iannone, L., and B. Chen, "IP
Address Privacy Considerations", Work in Progress,
Internet-Draft, draft-ip-address-privacy-considerations-
03, 10 January 2022, .
[I-D.jennings-moq-quicr-arch]
Jennings, C. and S. Nandakumar, "QuicR - Media Delivery
Protocol over QUIC", Work in Progress, Internet-Draft,
draft-jennings-moq-quicr-arch-01, 11 July 2022,
.
[I-D.liu-can-gap-reqs]
Liu, P., Jiang, T., Eardley, P., Trossen, D., Li, C., and
D. Huang, "Computing-Aware Networking (CAN) Gap Analysis
and Requirements", Work in Progress, Internet-Draft,
draft-liu-can-gap-reqs-00, 23 October 2022,
.
[I-D.liu-can-ps-usecases]
Liu, P., Eardley, P., Trossen, D., Boucadair, M.,
Contreras, L. M., Li, C., and Y. Li, "Computing-Aware
Networking (CAN) Problem Statement and Use Cases", Work in
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Progress, Internet-Draft, draft-liu-can-ps-usecases-00, 23
October 2022, .
[I-D.ma-intarea-encapsulation-of-san-header]
Ma, L., Zhao, D., Zhou, F., and D. Yang, "Encapsulation of
SAN Header", Work in Progress, Internet-Draft, draft-ma-
intarea-encapsulation-of-san-header-00, 23 October 2022,
.
[I-D.nottingham-avoiding-internet-centralization]
Nottingham, M., "Internet Consolidation: What can
Standards Efforts Do?", Work in Progress, Internet-Draft,
draft-nottingham-avoiding-internet-centralization-07, 17
January 2023, .
[I-D.per-app-networking-considerations]
Colitti, L. and T. Pauly, "Per-Application Networking
Considerations", Work in Progress, Internet-Draft, draft-
per-app-networking-considerations-00, 15 November 2020,
.
[I-D.sarathchandra-coin-appcentres]
Trossen, D., Sarathchandra, C., and M. Boniface, "In-
Network Computing for App-Centric Micro-Services", Work in
Progress, Internet-Draft, draft-sarathchandra-coin-
appcentres-04, 26 January 2021,
.
[I-D.wadhwa-rtgwg-bng-cups]
Wadhwa, S., Shinde, R., Newton, J., Hoffman, R., Muley,
P., and S. Pani, "Architecture for Control and User Plane
Separation on BNG", Work in Progress, Internet-Draft,
draft-wadhwa-rtgwg-bng-cups-03, 11 March 2019,
.
[ILNP2021] Yanagida, R., Bhatti, S., and G. Haywood, "End-to-end
privacy for identity and location with IP", Paper 2nd
Workshop on New Internetworking Protocols, Architecture
and Algorithms, 29th IEEE International Conference on
Network Protocols, 2021.
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[ISOC2022] "Internet Centralization", Technical Report ISOC
Dashboard, 2022,
.
[MCN] ""Metro Compute Networking: Use Cases and High Level
Requirements"", Technical Report-466 Broadband Forum
(BBF), 2021.
[Multi2020]
Ferreira, M. A. and J. L. Sobrinho, "Routing on Multi
Optimality Criteria", Paper ACM SIGCOMM, 2020.
[Namespaces2022]
Reid, A., Eardley, P., and D. Kutscher, "Namespaces,
Security, and Network Addresses", Paper ACM SIGCOMM
workshop on Future of Internet Routing and Addressing
(FIRA), 2022.
[OnOff2022]
Khandaker, K., Trossen, D., Yang, J., Despotovic, Z., and
G. Carle, "On-path vs Off-path Traffic Steering, That Is
The Question", Paper ACM SIGCOMM workshop on Future of
Internet Routing and Addressing (FIRA), 2022.
[POSTSOCK2017]
Kuehlewind, M., Trammell, B., and C. Perkins, "Post
sockets: Towards an evolvable network transport
interface", Paper IFIP Networking Conference (IFIP
Networking) and Workshops, 2017.
[RFC6770] Bertrand, G., Ed., Stephan, E., Burbridge, T., Eardley,
P., Ma, K., and G. Watson, "Use Cases for Content Delivery
Network Interconnection", RFC 6770, DOI 10.17487/RFC6770,
November 2012, .
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, DOI 10.17487/RFC7234, June 2014,
.
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[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, .
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
.
[RFC8609] Mosko, M., Solis, I., and C. Wood, "Content-Centric
Networking (CCNx) Messages in TLV Format", RFC 8609,
DOI 10.17487/RFC8609, July 2019,
.
[RFC8677] Trossen, D., Purkayastha, D., and A. Rahman, "Name-Based
Service Function Forwarder (nSFF) Component within a
Service Function Chaining (SFC) Framework", RFC 8677,
DOI 10.17487/RFC8677, November 2019,
.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
.
[RFC9213] Ludin, S., Nottingham, M., and Y. Wu, "Targeted HTTP Cache
Control", RFC 9213, DOI 10.17487/RFC9213, June 2022,
.
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[SarNet2021]
Glebke, R., Trossen, D., Kunze, I., Lou, Z., Rueth, J.,
Stoffers, M., and K. Wehrle, "Service-based Forwarding via
Programmable Dataplanes", Paper 1st Intl Workshop on
Semantic Addressing and Routing for Future Networks, 2021.
[SHIM2014] Naderi, H. and B. Carpenter, "Putting SHIM6 into
practice", Paper 2014 Australasian Telecommunication
Networks and Applications Conference (ATNAC), 2014.
[SOI2020] Jiang, S., Li, G., and B. Carpenter, "A New Approach to a
Service Oriented Internet Protocol", Paper IEEE INFOCOM
2020 - IEEE Conference on Computer Communications
Workshops (INFOCOM WKSHPS), 2020.
[SVA] ""Optimizing Video Delivery With The Open Caching
Network"", Technical Report Streaming Video Alliance,
2018.
[TIES2021] Giotsas, V., Kerola, S., Majkowski, M., Odinstov, P.,
Sitnicki, J., Chung, T., Levin, D., Mislove, A., Wood, C.
A., Sullivan, N., Fayed, M., and L. Bauer, "The Ties that
un-Bind: Decoupling IP from web services and sockets for
robust addressing agility at CDN-scale", Paper ACM
SIGCOMM, 2021.
[TS23501] "System architecture for the 5G System (5GS); Stage 2
(Release 16)", Technical Report 3GPP TS 23.501 V16.11.0
(2021-12), 2021,
.
Authors' Addresses
Dirk Trossen
Huawei Technologies
80992 Munich
Germany
Email: dirk.trossen@huawei.com
URI: https://www.dirk-trossen.de
Luis M. Contreras
Telefonica
Ronda de la Comunicacion, s/n
Sur-3 building, 1st floor
28050 Madrid
Spain
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Email: luismiguel.contrerasmurillo@telefonica.com
URI: http://lmcontreras.com/
Jens Finkhaeuser
Interpeer gUG
86926 Greifenberg
Germany
Email: ietf@interpeer.io
URI: https://interpeer.io/
Paulo Mendes
Airbus
82024 Taufkirchen
Germany
Email: paulo.mendes@airbus.com
URI: http://www.airbus.com
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