< draft-ietf-issll-diffserv-rsvp-04.txt   draft-ietf-issll-diffserv-rsvp-05.txt >
Y. Bernet, Microsoft Y. Bernet, Microsoft
R. Yavatkar, Intel R. Yavatkar, Intel
P. Ford, Microsoft P. Ford, Microsoft
F. Baker, Cisco F. Baker, Cisco
L. Zhang, UCLA L. Zhang, UCLA
M. Speer, Sun Microsystems M. Speer, Sun Microsystems
R. Braden, ISI R. Braden, ISI
B. Davie, Cisco B. Davie, Cisco
John Wroclawski, MIT LCS J. Wroclawski, MIT LCS
E. Felstaine, Allot Communications E. Felstaine, Technion
Internet Draft Internet Draft
Expires: September, 2000 Expires: November, 2000
Document: draft-ietf-issll-diffserv-rsvp-04.txt March, 2000 Document: draft-ietf-issll-diffserv-rsvp-05.txt May, 2000
A Framework For Integrated Services Operation Over Diffserv Networks A Framework For Integrated Services Operation Over Diffserv Networks
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are all provisions of Section 10 of RFC2026. Internet-Drafts are
Working documents of the Internet Engineering Task Force (IETF), its Working documents of the Internet Engineering Task Force (IETF), its
areas, and its working groups. Note that other groups may also areas, and its working groups. Note that other groups may also
distribute working documents as Internet-Drafts. distribute working documents as Internet-Drafts.
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The Integrated Services architecture provides a means for the The Integrated Services architecture provides a means for the
delivery of end-to-end QoS to applications over heterogeneous delivery of end-to-end QoS to applications over heterogeneous
networks. To support this end-to-end model, the Intserv architecture networks. To support this end-to-end model, the Intserv architecture
must be supported over a wide variety of different types of network must be supported over a wide variety of different types of network
elements. In this context, a network that supports Differentiated elements. In this context, a network that supports Differentiated
Services (Diffserv) may be viewed as a network element in the total Services (Diffserv) may be viewed as a network element in the total
end-to-end path. This document describes a framework by which end-to-end path. This document describes a framework by which
Integrated Services may be supported over Diffserv networks. Integrated Services may be supported over Diffserv networks.
Bernet, ed. et al. 1 Bernet, ed. et al. 1
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2. Introduction 2. Introduction
Work on QoS-enabled IP networks has led to two distinct approaches: Work on QoS-enabled IP networks has led to two distinct approaches:
the Integrated Services architecture (Intserv)[10] and its the Integrated Services architecture (Intserv)[10] and its
accompanying signaling protocol, RSVP [1], and the Differentiated accompanying signaling protocol, RSVP [1], and the Differentiated
Services architecture (Diffserv)[8]. This document describes ways in Services architecture (Diffserv)[8]. This document describes ways in
which a Diffserv network can be used in the context of the Intserv which a Diffserv network can be used in the context of the Intserv
architecture to support the delivery of end-to-end QOS. architecture to support the delivery of end-to-end QOS.
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mechanism, the Intserv architecture is designed to accommodate other mechanism, the Intserv architecture is designed to accommodate other
mechanisms. mechanisms.
Intserv services are implemented by "network elements". While it is Intserv services are implemented by "network elements". While it is
common for network elements to be individual nodes such as routers common for network elements to be individual nodes such as routers
or links, more complex entities, such as ATM "clouds" or 802.3 or links, more complex entities, such as ATM "clouds" or 802.3
networks may also function as network elements. As discussed in more networks may also function as network elements. As discussed in more
detail below, a Diffserv network (or "cloud") may be viewed as a detail below, a Diffserv network (or "cloud") may be viewed as a
network element within a larger Intserv network. network element within a larger Intserv network.
2.3 RSVP 2.2 RSVP
RSVP is a signaling protocol that applications may use to request RSVP is a signaling protocol that applications may use to request
resources from the network. The network responds by explicitly resources from the network. The network responds by explicitly
admitting or rejecting RSVP requests. Certain applications that have admitting or rejecting RSVP requests. Certain applications that have
quantifiable resource requirements express these requirements using quantifiable resource requirements express these requirements using
Intserv parameters as defined in the appropriate Intserv service Intserv parameters as defined in the appropriate Intserv service
specification. As noted above, RSVP and Intserv are separable. RSVP specification. As noted above, RSVP and Intserv are separable. RSVP
is a signaling protocol which may carry Intserv information. Intserv is a signaling protocol which may carry Intserv information. Intserv
defines the models for expressing service types, quantifying defines the models for expressing service types, quantifying
resource requirements and for determining the availability of the resource requirements and for determining the availability of the
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The current prevailing model of RSVP usage is based on a combined The current prevailing model of RSVP usage is based on a combined
RSVP/Intserv architecture. In this model, RSVP signals per-flow RSVP/Intserv architecture. In this model, RSVP signals per-flow
resource requirements to network elements, using Intserv parameters. resource requirements to network elements, using Intserv parameters.
These network elements apply Intserv admission control to signaled These network elements apply Intserv admission control to signaled
requests. In addition, traffic control mechanisms on the network requests. In addition, traffic control mechanisms on the network
element are configured to ensure that each admitted flow receives element are configured to ensure that each admitted flow receives
the service requested in strict isolation from other traffic. To the service requested in strict isolation from other traffic. To
Bernet, ed. et al. 2 Bernet, ed. et al. 2
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this end, RSVP signaling configures microflow (MF) [8] packet this end, RSVP signaling configures microflow (MF) [8] packet
classifiers in Intserv capable routers along the path of the traffic classifiers in Intserv capable routers along the path of the traffic
flow. These classifiers enable per-flow classification of packets flow. These classifiers enable per-flow classification of packets
based on IP addresses and port numbers. based on IP addresses and port numbers.
The following factors have impeded deployment of RSVP (and the The following factors have impeded deployment of RSVP (and the
Intserv architecture) in the Internet at large: Intserv architecture) in the Internet at large:
1. The use of per-flow state and per-flow processing raises 1. The use of per-flow state and per-flow processing raises
scalability concerns for large networks. scalability concerns for large networks.
2. Only a small number of hosts currently generate RSVP signaling. 2. Only a small number of hosts currently generate RSVP signaling.
While this number is expected to grow dramatically, many While this number is expected to grow dramatically, many
applications may never generate RSVP signaling. applications may never generate RSVP signaling.
3. The necessary policy control mechanisms -- access control, 3. The necessary policy control mechanisms -- access control,
authentication, and accounting -- have only recently become authentication, and accounting -- have only recently become
available [17]. available [17].
2.4 Diffserv 2.3 Diffserv
In contrast to the per-flow orientation of RSVP, Diffserv networks In contrast to the per-flow orientation of RSVP, Diffserv networks
classify packets into one of a small number of aggregated flows or classify packets into one of a small number of aggregated flows or
"classes", based on the Diffserv codepoint (DSCP) in the packet's IP "classes", based on the Diffserv codepoint (DSCP) in the packet's IP
header. This is known as behavior aggregate (BA) classification header. This is known as behavior aggregate (BA) classification
[8]. At each Diffserv router, packets are subjected to a "per-hop [8]. At each Diffserv router, packets are subjected to a "per-hop
behavior" (PHB), which is invoked by the DSCP. The primary benefit behavior" (PHB), which is invoked by the DSCP. The primary benefit
of Diffserv is its scalability. Diffserv eliminates the need for of Diffserv is its scalability. Diffserv eliminates the need for
per-flow state and per-flow processing and therefore scales well to per-flow state and per-flow processing and therefore scales well to
large networks. large networks.
2.5 Roles of Intserv, RSVP and Diffserv 2.4 Roles of Intserv, RSVP and Diffserv
We view Intserv, RSVP and Diffserv as complementary technologies in We view Intserv, RSVP and Diffserv as complementary technologies in
the pursuit of end-to-end QoS. Together, these mechanisms can the pursuit of end-to-end QoS. Together, these mechanisms can
facilitate deployment of applications such as IP-telephony, video- facilitate deployment of applications such as IP-telephony, video-
on-demand, and various non-multimedia mission-critical applications. on-demand, and various non-multimedia mission-critical applications.
Intserv enables hosts to request per-flow, quantifiable resources, Intserv enables hosts to request per-flow, quantifiable resources,
along end-to-end data paths and to obtain feedback regarding along end-to-end data paths and to obtain feedback regarding
admissibility of these requests. Diffserv enables scalability across admissibility of these requests. Diffserv enables scalability across
large networks. large networks.
2.6 Components of Intserv, RSVP and Diffserv 2.5 Components of Intserv, RSVP and Diffserv
Before proceeding, it is helpful to identify the following Before proceeding, it is helpful to identify the following
components of the QoS technologies described: components of the QoS technologies described:
RSVP signaling - This term refers to the standard RSVP signaling RSVP signaling - This term refers to the standard RSVP signaling
protocol. RSVP signaling is used by hosts to signal application protocol. RSVP signaling is used by hosts to signal application
resource requirements to the network (and to each other). Network resource requirements to the network (and to each other). Network
elements use RSVP signaling to return an admission control decision elements use RSVP signaling to return an admission control decision
to hosts. RSVP signaling may or may not carry Intserv parameters. to hosts. RSVP signaling may or may not carry Intserv parameters.
Bernet, ed. et al. 3 Bernet, ed. et al. 3
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Admission control at a network element may or may not be based on Admission control at a network element may or may not be based on
the Intserv model. the Intserv model.
MF traffic control - This term refers to traffic control which is MF traffic control - This term refers to traffic control which is
applied independently to individual traffic flows and therefore applied independently to individual traffic flows and therefore
requires recognizing individual traffic flows via MF classification. requires recognizing individual traffic flows via MF classification.
Aggregate traffic control - This term refers to traffic control Aggregate traffic control - This term refers to traffic control
which is applied collectively to sets of traffic flows. These sets which is applied collectively to sets of traffic flows. These sets
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Note that, for the purposes of this document, the defining features Note that, for the purposes of this document, the defining features
of a Diffserv region is the type of classification and traffic of a Diffserv region is the type of classification and traffic
control that is used for the delivery of end-to-end QOS for a control that is used for the delivery of end-to-end QOS for a
particular application. Thus, while it may not be possible to particular application. Thus, while it may not be possible to
identify a certain region as "purely Diffserv" with respect to all identify a certain region as "purely Diffserv" with respect to all
traffic flowing through the region, it is possible to define it in traffic flowing through the region, it is possible to define it in
this way from the perspective of the treatment of traffic from a this way from the perspective of the treatment of traffic from a
single application. single application.
2.7 The Framework 2.6 The Framework
In the framework we present, end-to-end, quantitative QoS is In the framework we present, end-to-end, quantitative QoS is
provided by applying the Intserv model end-to-end across a network provided by applying the Intserv model end-to-end across a network
Bernet, ed. et al. 4 Bernet, ed. et al. 4
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containing one or more Diffserv regions. The Diffserv regions may, containing one or more Diffserv regions. The Diffserv regions may,
but are not required to, participate in end-to-end RSVP signaling but are not required to, participate in end-to-end RSVP signaling
for the purpose of optimizing resource allocation and supporting for the purpose of optimizing resource allocation and supporting
admission control. admission control.
From the perspective of Intserv, Diffserv regions of the network are From the perspective of Intserv, Diffserv regions of the network are
treated as virtual links connecting Intserv capable routers or hosts treated as virtual links connecting Intserv capable routers or hosts
(much as an 802.1p network region is treated as a virtual link in (much as an 802.1p network region is treated as a virtual link in
[5]). Within the Diffserv regions of the network routers implement [5]). Within the Diffserv regions of the network routers implement
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support the Intserv style services requested from the periphery. support the Intserv style services requested from the periphery.
In our framework, we address the support of end-to-end Integrated In our framework, we address the support of end-to-end Integrated
Services over the Diffserv regions of the network. Our goal is to Services over the Diffserv regions of the network. Our goal is to
enable seamless inter-operation. As a result, the network enable seamless inter-operation. As a result, the network
administrator is free to choose which regions of the network act as administrator is free to choose which regions of the network act as
Diffserv regions. In one extreme the Diffserv region is pushed all Diffserv regions. In one extreme the Diffserv region is pushed all
the way to the periphery, with hosts alone having full Intserv the way to the periphery, with hosts alone having full Intserv
capability. In the other extreme, Intserv is pushed all the way to capability. In the other extreme, Intserv is pushed all the way to
the core, with no Diffserv region. the core, with no Diffserv region.
2.8 Contents 2.7 Contents
In section 3 we discuss the benefits that can be realized by using In section 3 we discuss the benefits that can be realized by using
the aggregate traffic control provided by Diffserv network regions the aggregate traffic control provided by Diffserv network regions
in the broader context of the Intserv architecture. In section 4, we in the broader context of the Intserv architecture. In section 4, we
present the framework and the reference network. Section 5 details present the framework and the reference network. Section 5 details
two possible realizations of the framework. Section 6 discusses the two possible realizations of the framework. Section 6 discusses the
implications of the framework for Diffserv. Section 7 presents some implications of the framework for Diffserv. Section 7 presents some
issues specific to multicast flows. issues specific to multicast flows.
3. Benefits of Using Intserv with Diffserv 3. Benefits of Using Intserv with Diffserv
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Note that this discussion is in the context of servicing Note that this discussion is in the context of servicing
quantitative QoS applications specifically. By this we mean those quantitative QoS applications specifically. By this we mean those
applications that are able to quantify their traffic and QoS applications that are able to quantify their traffic and QoS
requirements. requirements.
3.1 Resource Based Admission Control 3.1 Resource Based Admission Control
In Intserv networks, quantitative QoS applications use an explicit In Intserv networks, quantitative QoS applications use an explicit
setup mechanism (e.g. RSVP) to request resources from the network. setup mechanism (e.g. RSVP) to request resources from the network.
The network may accept or reject these requests in response. This is The network may accept or reject these requests in response. This is
"explicit admission control". Explicit admission control helps to "explicit admission control". Explicit and dynamic admission control
assure that network resources are optimally used. To further helps to assure that network resources are optimally used. To
understand this issue, consider a Diffserv network region providing further understand this issue, consider a Diffserv network region
only aggregate traffic control with no signaling. In the Diffserv providing only aggregate traffic control with no signaling. In the
Bernet, ed. et al. 5 Bernet, ed. et al. 5
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Integrated Services Operation Over Diffserv Networks March, 2000 Diffserv network region, admission control is applied in a
relatively static way by provisioning policing parameters at network
network region, admission control is applied implicitly by elements. For example, a network element at the ingress to a
provisioning policing parameters at network elements. For example, a Diffserv network region could be provisioned to accept only 50 Kbps
network element at the ingress to a Diffserv network region could be of traffic for the EF DSCP.
provisioned to accept only 50 Kbps of traffic for the EF DSCP.
While such implicit admission control does protect the network to While such static forms of admission control do protect the network
some degree, it can be quite ineffective. For example, consider that to some degree, they can be quite ineffective. For example, consider
there may be 10 IP telephony sessions originating outside the that there may be 10 IP telephony sessions originating outside the
Diffserv network region, each requiring 10 Kbps of EF service from Diffserv network region, each requiring 10 Kbps of EF service from
the Diffserv network region. Since the network element protecting the Diffserv network region. Since the network element protecting
the Diffserv network region is provisioned to accept only 50 Kbps of the Diffserv network region is provisioned to accept only 50 Kbps of
traffic for the EF DSCP, it will discard half the offered traffic. traffic for the EF DSCP, it will discard half the offered traffic.
This traffic will be discarded from the aggregation of traffic This traffic will be discarded from the aggregation of traffic
marked EF, with no regard to the microflow from which it originated. marked EF, with no regard to the microflow from which it originated.
As a result, it is likely that of the ten IP telephony sessions, As a result, it is likely that of the ten IP telephony sessions,
none will obtain satisfactory service when in fact, there are none will obtain satisfactory service when in fact, there are
sufficient resources available in the Diffserv network region to sufficient resources available in the Diffserv network region to
satisfy five sessions. satisfy five sessions.
In the case of explicit admission control, the network will signal In the case of explicitly signalled, dynamic admission control, the
rejection in response to requests for resources that would exceed network will signal rejection in response to requests for resources
the 50 Kbps limit. As a result, upstream network elements (including that would exceed the 50 Kbps limit. As a result, upstream network
originating hosts) and applications will have the information they elements (including originating hosts) and applications will have
require to take corrective action. The application might respond by the information they require to take corrective action. The
refraining from transmitting, or by requesting admission for a application might respond by refraining from transmitting, or by
lesser traffic profile. The host operating system might respond by requesting admission for a lesser traffic profile. The host
marking the application's traffic for the DSCP that corresponds to operating system might respond by marking the application's traffic
best-effort service. Upstream network elements might respond by re- for the DSCP that corresponds to best-effort service. Upstream
marking packets on the rejected flow to a lower service level. In network elements might respond by re-marking packets on the rejected
some cases, it may be possible to reroute traffic over alternate flow to a lower service level. In some cases, it may be possible to
paths or even alternate networks (e.g. the PSTN for voice calls). In reroute traffic over alternate paths or even alternate networks
any case, the integrity of those flows that were admitted would be (e.g. the PSTN for voice calls). In any case, the integrity of those
preserved, at the expense of the flows that were not admitted. Thus, flows that were admitted would be preserved, at the expense of the
by appointing an Intserv-conversant admission control agent for the flows that were not admitted. Thus, by appointing an Intserv-
Diffserv region of the network it is possible to enhance the service conversant admission control agent for the Diffserv region of the
that the network can provide to quantitative QoS applications. network it is possible to enhance the service that the network can
provide to quantitative QoS applications.
3.2 Policy Based Admission Control 3.2 Policy Based Admission Control
In network regions where RSVP is used, resource requests can be In network regions where RSVP is used, resource requests can be
intercepted by RSVP-aware network elements and can be reviewed intercepted by RSVP-aware network elements and can be reviewed
against policies stored in policy databases. These resource requests against policies stored in policy databases. These resource requests
securely identify the user and the application for which the securely identify the user and the application for which the
resources are requested. Consequently, the network element is able resources are requested. Consequently, the network element is able
to consider per-user and/or per-application policy when deciding to consider per-user and/or per-application policy when deciding
whether or not to admit a resource request. So, in addition to whether or not to admit a resource request. So, in addition to
optimizing the use of resources in a Diffserv network region (as optimizing the use of resources in a Diffserv network region (as
discussed in 3.1) RSVP conversant admission control agents can be discussed in 3.1) RSVP conversant admission control agents can be
used to apply specific customer policies in determining the specific used to apply specific customer policies in determining the specific
customer traffic flows entitled to use the Diffserv network region's customer traffic flows entitled to use the Diffserv network region's
resources. Customer policies can be used to allocate resources to
specific users and/or applications.
Bernet, ed. et al. 6 Bernet, ed. et al. 6
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Integrated Services Operation Over Diffserv Networks March, 2000 resources. Customer policies can be used to allocate resources to
specific users and/or applications.
By comparison, in Diffserv network regions without RSVP signaling, By comparison, in Diffserv network regions without RSVP signaling,
policies are typically applied based on the Diffserv customer policies are typically applied based on the Diffserv customer
network from which traffic originates, not on the originating user network from which traffic originates, not on the originating user
or application within the customer network. or application within the customer network.
3.3 Assistance in Traffic Identification/Classification 3.3 Assistance in Traffic Identification/Classification
Within Diffserv network regions, traffic is allotted service based Within Diffserv network regions, traffic is allotted service based
on the DSCP marked in each packet's IP header. Thus, in order to on the DSCP marked in each packet's IP header. Thus, in order to
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In the case of host marking, the host operating system marks the In the case of host marking, the host operating system marks the
DSCP in transmitted packets. This approach has the benefit of DSCP in transmitted packets. This approach has the benefit of
shifting per-flow classification and marking to the source of the shifting per-flow classification and marking to the source of the
traffic, where it scales best. It also enables the host to make traffic, where it scales best. It also enables the host to make
decisions regarding the mark that is appropriate for each decisions regarding the mark that is appropriate for each
transmitted packet and hence the relative importance attached to transmitted packet and hence the relative importance attached to
each packet. The host is generally better equipped to make this each packet. The host is generally better equipped to make this
decision than the network. Furthermore, if IPSEC encryption is used, decision than the network. Furthermore, if IPSEC encryption is used,
the host may be the only device in the network that is able to make the host may be the only device in the network that is able to make
a meaningful determination of the appropriate marking for each a meaningful determination of the appropriate marking for each
packet. packet, since various fields such as port numbers would be
unavailable to routers for MF classification.
Host marking requires that the host be aware of the interpretation Host marking requires that the host be aware of the interpretation
of DSCPs by the network. This information can be configured into of DSCPs by the network. This information can be configured into
each host. However, such configuration imposes a management burden. each host. However, such configuration imposes a management burden.
Alternatively, hosts can use an explicit signaling protocol such as Alternatively, hosts can use an explicit signaling protocol such as
RSVP to query the network to obtain a suitable DSCP or set of DSCPs RSVP to query the network to obtain a suitable DSCP or set of DSCPs
to apply to packets for which a certain Intserv service has been to apply to packets for which a certain Intserv service has been
requested. An example of how this can be achieved is described in requested. An example of how this can be achieved is described in
[14]. [14].
3.3.2 Router Marking 3.3.2 Router Marking
In the case of router marking, MF classification criteria must be In the case of router marking, MF classification criteria must be
configured in the router. This may be done dynamically, by request configured in the router in some way. This may be done dynamically
from the host operating system, or statically via manual (e.g., using COPS provisioning), by request from the host operating
configuration or via automated scripts.
Bernet, ed. et al. 7 Bernet, ed. et al. 7
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Integrated Services Operation Over Diffserv Networks March, 2000 system, or statically via manual configuration or via automated
scripts.
There are significant difficulties in doing so statically. There are significant difficulties in doing so statically. In many
Typically, it is desirable to allot service to traffic based on the cases, it is desirable to allot service to traffic based on the
application and/or user originating the traffic. At times it is application and/or user originating the traffic. At times it is
possible to identify packets associated with a specific application possible to identify packets associated with a specific application
by the IP port numbers in the headers. It may also be possible to by the IP port numbers in the headers. It may also be possible to
identify packets originating from a specific user by the source IP identify packets originating from a specific user by the source IP
address. However, such classification criteria may change address. However, such classification criteria may change
frequently. Users may be assigned different IP addresses by DHCP. frequently. Users may be assigned different IP addresses by DHCP.
Applications may use transient ports. To further complicate matters, Applications may use transient ports. To further complicate matters,
multiple users may share an IP address. These factors make it very multiple users may share an IP address. These factors make it very
difficult to manage static configuration of the classification difficult to manage static configuration of the classification
information required to mark traffic in routers. information required to mark traffic in routers.
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control is applied). Individual routers may or may not participate control is applied). Individual routers may or may not participate
in RSVP signaling regardless of where in the network they reside. in RSVP signaling regardless of where in the network they reside.
We will consider two specific realizations of the framework. In the We will consider two specific realizations of the framework. In the
first, resources within the Diffserv regions of the network are first, resources within the Diffserv regions of the network are
statically provisioned and these regions include no RSVP aware statically provisioned and these regions include no RSVP aware
devices. In the second, resources within the Diffserv region of the devices. In the second, resources within the Diffserv region of the
network are dynamically provisioned and select devices within the network are dynamically provisioned and select devices within the
Diffserv network regions participate in RSVP signaling. Diffserv network regions participate in RSVP signaling.
4.1 Reference Network
Bernet, ed. et al. 8 Bernet, ed. et al. 8
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The two realizations of the framework will be discussed in the The two realizations of the framework will be discussed in the
context of the following reference network: context of the following reference network:
________ ______________ ________ ________ ______________ ________
/ \ / \ / \ / \ / \ / \
/ \ / \ / \ / \ / \ / \
|---| | |---| |---| |---| |---| | |---| |---| | |---| |---| |---| |---| | |---|
|Tx |-| |ER1|---|BR1| |BR2|---|ER2| |-|Rx | |Tx |-| |ER1|---|BR1| |BR2|---|ER2| |-|Rx |
|---| | |-- | |---| |---| |---| | |---| |---| | |-- | |---| |---| |---| | |---|
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We now define the major components of the reference network. We now define the major components of the reference network.
4.1.1 Hosts 4.1.1 Hosts
We assume that both sending and receiving hosts use RSVP to We assume that both sending and receiving hosts use RSVP to
communicate the quantitative QoS requirements of QoS-aware communicate the quantitative QoS requirements of QoS-aware
applications running on the host. In principle, other mechanisms may applications running on the host. In principle, other mechanisms may
be used to establish resource reservations in Intserv-capable nodes, be used to establish resource reservations in Intserv-capable nodes,
but RSVP is clearly the prevalent mechanism for this purpose. but RSVP is clearly the prevalent mechanism for this purpose.
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Typically, a QoS process within the host operating system generates Typically, a QoS process within the host operating system generates
RSVP signaling on behalf of applications. This process may also RSVP signaling on behalf of applications. This process may also
invoke local traffic control. invoke local traffic control.
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As discussed above, traffic control in the host may mark the DSCP in As discussed above, traffic control in the host may mark the DSCP in
transmitted packets, and shape transmitted traffic to the transmitted packets, and shape transmitted traffic to the
requirements of the Intserv service in use. Alternatively, the first requirements of the Intserv service in use. Alternatively, the first
Intserv-capable router downstream from the host may provide these Intserv-capable router downstream from the host may provide these
traffic control functions. traffic control functions.
4.1.2 End-to-End RSVP Signaling 4.1.2 End-to-End RSVP Signaling
We assume that RSVP signaling messages travel end-to-end between We assume that RSVP signaling messages travel end-to-end between
hosts Tx and Rx to support RSVP/Intserv reservations outside the hosts Tx and Rx to support RSVP/Intserv reservations outside the
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region. The functionality of the border routers varies depending on region. The functionality of the border routers varies depending on
the specific realization of the framework. In the case in which the the specific realization of the framework. In the case in which the
Diffserv network region is RSVP-unaware, these routers act as pure Diffserv network region is RSVP-unaware, these routers act as pure
Diffserv routers. As such, their sole responsibility is to police Diffserv routers. As such, their sole responsibility is to police
submitted traffic based on the service level specified in the DSCP submitted traffic based on the service level specified in the DSCP
and the agreement negotiated with the customer (aggregate traffic and the agreement negotiated with the customer (aggregate traffic
control). In the case in which the Diffserv network region is RSVP- control). In the case in which the Diffserv network region is RSVP-
aware, the border routers participate in RSVP signaling and act as aware, the border routers participate in RSVP signaling and act as
admission control agents for the Diffserv network region. admission control agents for the Diffserv network region.
We will later describe the functionality of the border routers in
greater depth for each of the two realizations of the framework.
Bernet, ed. et al. 10 Bernet, ed. et al. 10
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Integrated Services Operation Over Diffserv Networks March, 2000 We will later describe the functionality of the border routers in
greater depth for each of the two realizations of the framework.
4.1.5 Diffserv Network Region 4.1.5 Diffserv Network Region
The Diffserv network region supports aggregate traffic control and The Diffserv network region supports aggregate traffic control and
is assumed not to be capable of MF classification. Depending on the is assumed not to be capable of MF classification. Depending on the
specific realization of the framework, some number of routers within specific realization of the framework, some number of routers within
the Diffserv region may be RSVP aware and therefore capable of per- the Diffserv region may be RSVP aware and therefore capable of per-
flow signaling and admission control. If devices in the Diffserv flow signaling and admission control. If devices in the Diffserv
region are not RSVP aware, they will pass RSVP messages region are not RSVP aware, they will pass RSVP messages
transparently with negligible performance impact (see [6]). transparently with negligible performance impact (see [6]).
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the 802.1p capable switched segments described in [5]. Requests for the 802.1p capable switched segments described in [5]. Requests for
Intserv services must be mapped onto the underlying capabilities of Intserv services must be mapped onto the underlying capabilities of
the Diffserv network region. Aspects of the mapping include: the Diffserv network region. Aspects of the mapping include:
- selecting an appropriate PHB, or set of PHBs, for the requested - selecting an appropriate PHB, or set of PHBs, for the requested
service; service;
- performing appropriate policing (including, perhaps, shaping or - performing appropriate policing (including, perhaps, shaping or
remarking) at the edges of the Diffserv region; remarking) at the edges of the Diffserv region;
- exporting Intserv parameters from the Diffserv region (e.g. for - exporting Intserv parameters from the Diffserv region (e.g. for
the updating of ADSPECs); the updating of ADSPECs);
- performing admission control on the Intserv requests that takes
into account the resource availability in the Diffserv region.
Bernet, ed. et al. 11 Bernet, ed. et al. 11
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 - performing admission control on the Intserv requests that takes
into account the resource availability in the Diffserv region.
Exactly how these functions are performed will be a function of the Exactly how these functions are performed will be a function of the
way bandwidth is managed inside the Diffserv network region, which way bandwidth is managed inside the Diffserv network region, which
is a topic we discuss in Section 4.3. is a topic we discuss in Section 4.3.
When the PHB (or set of PHBs) has been selected for a particular When the PHB (or set of PHBs) has been selected for a particular
Intserv flow, it may be necessary to communicate the choice of DSCP Intserv flow, it may be necessary to communicate the choice of DSCP
for the flow to other network elements. Two schemes may be used to for the flow to other network elements. Two schemes may be used to
achieve this end, as discussed below. achieve this end, as discussed below.
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it is possible for a misbehaving microflow to claim more than its it is possible for a misbehaving microflow to claim more than its
fair share of resources within the aggregate, thereby degrading the fair share of resources within the aggregate, thereby degrading the
service provided to other microflows. This problem may be addressed service provided to other microflows. This problem may be addressed
by: by:
1. Providing per microflow policing at the edge routers - this is 1. Providing per microflow policing at the edge routers - this is
generally the most appropriate location for microflow policing, generally the most appropriate location for microflow policing,
since it pushes per-flow work to the edges of the network, where it since it pushes per-flow work to the edges of the network, where it
scales better. In addition, since Intserv-capable routers outside scales better. In addition, since Intserv-capable routers outside
the Diffserv region are responsible for providing microflow service the Diffserv region are responsible for providing microflow service
to their customers and the Diffserv region is responsible for
providing aggregate service to its customers, this distribution of
functionality mirrors the distribution of responsibility.
Bernet, ed. et al. 12 Bernet, ed. et al. 12
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 to their customers and the Diffserv region is responsible for
providing aggregate service to its customers, this distribution of
functionality mirrors the distribution of responsibility.
2. Providing per microflow policing at the border routers - this 2. Providing per microflow policing at the border routers - this
approach tends to be less scalable than the previous approach. It approach tends to be less scalable than the previous approach. It
also imposes a management burden on the Diffserv region of the also imposes a management burden on the Diffserv region of the
network. However, it may be appropriate in certain cases, for the network. However, it may be appropriate in certain cases, for the
Diffserv boundary routers to offer per microflow policing as a Diffserv boundary routers to offer per microflow policing as a
value-add to its Intserv customers. value-add to its Intserv customers.
3. Relying on upstream shaping and policing - in certain cases, the 3. Relying on upstream shaping and policing - in certain cases, the
customer may trust the shaping of certain groups of hosts customer may trust the shaping of certain groups of hosts
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action. We discuss two examples, one in which the Diffserv network action. We discuss two examples, one in which the Diffserv network
region is RSVP unaware, the other in which the Diffserv network region is RSVP unaware, the other in which the Diffserv network
region is RSVP aware. region is RSVP aware.
5.1 Statically Provisioned Diffserv Network Region 5.1 Statically Provisioned Diffserv Network Region
In this example, no devices in the Diffserv network region are RSVP In this example, no devices in the Diffserv network region are RSVP
aware. The Diffserv network region is statically provisioned. The aware. The Diffserv network region is statically provisioned. The
customer(s) of the Diffserv network regions and the owner of the customer(s) of the Diffserv network regions and the owner of the
Diffserv network region have negotiated a static contract (service Diffserv network region have negotiated a static contract (service
level specification, or SLS) for the transmit capacity to be
provided to the customer at each of a number of standard Diffserv
service levels. The "transmit capacity" may be simply an amount of
Bernet, ed. et al. 13 Bernet, ed. et al. 13
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 level specification, or SLS) for the transmit capacity to be
provided to the customer at each of a number of standard Diffserv
service levels. The "transmit capacity" may be simply an amount of
bandwidth or it could be a more complex "profile" involving a number bandwidth or it could be a more complex "profile" involving a number
of factors such as burst size, peak rate, time of day etc. of factors such as burst size, peak rate, time of day etc.
It is helpful to consider each edge router in the customer network It is helpful to consider each edge router in the customer network
as consisting of two halves, a standard Intserv half, which as consisting of two halves, a standard Intserv half, which
interfaces to the customer's network regions and a Diffserv half interfaces to the customer's network regions and a Diffserv half
which interfaces to the Diffserv network region. The Intserv half is which interfaces to the Diffserv network region. The Intserv half is
able to identify and process traffic on per-flow granularity. able to identify and process traffic on per-flow granularity.
The Diffserv half of the router can be considered to consist of a The Diffserv half of the router can be considered to consist of a
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operating system generates an RSVP RESV message, indicating interest operating system generates an RSVP RESV message, indicating interest
in offered traffic of a certain Intserv service type. in offered traffic of a certain Intserv service type.
6. The RESV message is carried back towards the Diffserv network 6. The RESV message is carried back towards the Diffserv network
region and the sending host. Consistent with standard RSVP/Intserv region and the sending host. Consistent with standard RSVP/Intserv
processing, it may be rejected at any RSVP-capable node in the path processing, it may be rejected at any RSVP-capable node in the path
if resources are deemed insufficient to carry the traffic requested. if resources are deemed insufficient to carry the traffic requested.
7. At ER2, the RESV message is subjected to standard RSVP/Intserv 7. At ER2, the RESV message is subjected to standard RSVP/Intserv
processing. It may be rejected if resources on the downstream processing. It may be rejected if resources on the downstream
interface of ER2 are deemed insufficient to carry the resources
requested. If it is not rejected, it will be carried transparently
through the Diffserv network region, arriving at ER1.
Bernet, ed. et al. 14 Bernet, ed. et al. 14
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 interface of ER2 are deemed insufficient to carry the resources
requested. If it is not rejected, it will be carried transparently
through the Diffserv network region, arriving at ER1.
8. In ER1, the RESV message triggers admission control processing. 8. In ER1, the RESV message triggers admission control processing.
ER1 compares the resources requested in the RSVP/Intserv request to ER1 compares the resources requested in the RSVP/Intserv request to
the resources available in the Diffserv network region at the the resources available in the Diffserv network region at the
corresponding Diffserv service level. The corresponding service corresponding Diffserv service level. The corresponding service
level is determined by the Intserv to Diffserv mapping discussed level is determined by the Intserv to Diffserv mapping discussed
previously. The availability of resources is determined by the previously. The availability of resources is determined by the
capacity provisioned in the SLS. ER1 may also apply a policy capacity provisioned in the SLS. ER1 may also apply a policy
decision such that the resource request may be rejected based on the decision such that the resource request may be rejected based on the
customer's specific policy criteria, even though the aggregate customer's specific policy criteria, even though the aggregate
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networks that support RSVP/Intserv and networks that support networks that support RSVP/Intserv and networks that support
Diffserv. Diffserv.
5.2 RSVP-Aware Diffserv Network Region 5.2 RSVP-Aware Diffserv Network Region
In this example, the customer's edge routers are standard RSVP In this example, the customer's edge routers are standard RSVP
routers. The border router, BR1 is RSVP aware. In addition, there routers. The border router, BR1 is RSVP aware. In addition, there
may be other routers within the Diffserv network region which are may be other routers within the Diffserv network region which are
RSVP aware. Note that although these routers are able to participate RSVP aware. Note that although these routers are able to participate
in some form of RSVP signaling, they classify and schedule traffic in some form of RSVP signaling, they classify and schedule traffic
in aggregate, based on DSCP, not on the per-flow classification
criteria used by standard RSVP/Intserv routers. It can be said that
their control-plane is RSVP while their data-plane is Diffserv. This
Bernet, ed. et al. 15 Bernet, ed. et al. 15
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 in aggregate, based on DSCP, not on the per-flow classification
criteria used by standard RSVP/Intserv routers. It can be said that
their control-plane is RSVP while their data-plane is Diffserv. This
approach exploits the benefits of RSVP signaling while maintaining approach exploits the benefits of RSVP signaling while maintaining
much of the scalability associated with Diffserv. much of the scalability associated with Diffserv.
In the preceding example, there is no signaling between the Diffserv In the preceding example, there is no signaling between the Diffserv
network region and network elements outside it. The negotiation of network region and network elements outside it. The negotiation of
an SLS is the only explicit exchange of resource availability an SLS is the only explicit exchange of resource availability
information between the two network regions. ER1 is configured with information between the two network regions. ER1 is configured with
the information represented by the SLS and as such, is able to act the information represented by the SLS and as such, is able to act
as an admission control agent for the Diffserv network region. Such as an admission control agent for the Diffserv network region. Such
configuration does not readily support dynamically changing SLSs, configuration does not readily support dynamically changing SLSs,
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5.2.1 Aggregated or Tunneled RSVP 5.2.1 Aggregated or Tunneled RSVP
A number of drafts [3,6,15, 16] propose mechanisms for extending A number of drafts [3,6,15, 16] propose mechanisms for extending
RSVP to reserve resources for an aggregation of flows between edges RSVP to reserve resources for an aggregation of flows between edges
of a network. Border routers may interact with core routers and of a network. Border routers may interact with core routers and
other border routers using aggregated RSVP to reserve resources other border routers using aggregated RSVP to reserve resources
between edges of the Diffserv network region. Initial reservation between edges of the Diffserv network region. Initial reservation
levels for each service level may be established between major levels for each service level may be established between major
border routers, based on anticipated traffic patterns. Border border routers, based on anticipated traffic patterns. Border
routers could trigger changes in reservation levels as a result of
the cumulative per-flow RSVP requests from the non-Diffserv regions
reaching high or low-water marks.
Bernet, ed. et al. 16 Bernet, ed. et al. 16
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 routers could trigger changes in reservation levels as a result of
the cumulative per-flow RSVP requests from the non-Diffserv regions
reaching high or low-water marks.
In this approach, admission of per-flow RSVP requests from nodes In this approach, admission of per-flow RSVP requests from nodes
outside the Diffserv region would be counted against the appropriate outside the Diffserv region would be counted against the appropriate
aggregate reservations for the corresponding service level. The size aggregate reservations for the corresponding service level. The size
of the aggregate reservations may or may not be dynamically adjusted of the aggregate reservations may or may not be dynamically adjusted
to deal with the changes in per-flow reservations. to deal with the changes in per-flow reservations.
The advantage of this approach is that it offers dynamic, topology The advantage of this approach is that it offers dynamic, topology
aware admission control to the Diffserv network region without aware admission control to the Diffserv network region without
requiring the level of RSVP signaling processing that would be requiring the level of RSVP signaling processing that would be
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aggregated as opposed to per-flow). The relative number of routers aggregated as opposed to per-flow). The relative number of routers
in the core that participate in RSVP signaling is a provisioning in the core that participate in RSVP signaling is a provisioning
decision that must be made by the network administrator. decision that must be made by the network administrator.
In one extreme case, only the border routers participate in RSVP In one extreme case, only the border routers participate in RSVP
signaling. In this case, either the Diffserv network region must be signaling. In this case, either the Diffserv network region must be
extremely over-provisioned and therefore, inefficiently used, or extremely over-provisioned and therefore, inefficiently used, or
else it must be carefully and statically provisioned for limited else it must be carefully and statically provisioned for limited
traffic patterns. The border routers must enforce these patterns. traffic patterns. The border routers must enforce these patterns.
Bernet, ed. et al. 17
Integrated Services Operation Over Diffserv Networks May, 2000
In the other extreme case, each router in the Diffserv network In the other extreme case, each router in the Diffserv network
region might participate in RSVP signaling. In this case, resources region might participate in RSVP signaling. In this case, resources
can be used with optimal efficiency, but signaling processing can be used with optimal efficiency, but signaling processing
requirements and associated overhead increase. As noted above, RSVP requirements and associated overhead increase. As noted above, RSVP
Bernet, ed. et al. 17
Integrated Services Operation Over Diffserv Networks March, 2000
aggregation is one way to limit the signaling overhead at the cost aggregation is one way to limit the signaling overhead at the cost
of some loss of optimality in resource utilization. of some loss of optimality in resource utilization.
It is likely that some network administrators will compromise by It is likely that some network administrators will compromise by
enabling RSVP signaling on some subset of routers in the Diffserv enabling RSVP signaling on some subset of routers in the Diffserv
network region. These routers will likely represent major traffic network region. These routers will likely represent major traffic
switching points with over-provisioned or statically provisioned switching points with over-provisioned or statically provisioned
regions of RSVP unaware routers between them. regions of RSVP unaware routers between them.
5.3 Dynamically Provisioned, Non-RSVP-aware Diffserv Region 5.3 Dynamically Provisioned, Non-RSVP-aware Diffserv Region
Border routers might not use any form of RSVP signaling within the Border routers might not use any form of RSVP signaling within the
Diffserv network region but might instead use custom protocols to Diffserv network region but might instead use custom protocols to
interact with an "oracle". The oracle is a hypothetical agent that interact with an "oracle". The oracle is an agent that has
has sufficient knowledge of resource availability and network sufficient knowledge of resource availability and network topology
topology to make admission control decisions. The set of RSVP aware to make admission control decisions. The set of RSVP aware routers
routers in the previous two examples can be considered collectively in the previous two examples can be considered collectively as a
as a form of distributed oracle. In various definitions of the form of distributed oracle. In various definitions of the "bandwidth
"bandwidth broker" [4], it is able to act as a centralized oracle. broker" [4], it is able to act as a centralized oracle.
6. Implications of the Framework for Diffserv Network Regions 6. Implications of the Framework for Diffserv Network Regions
We have described a framework in which RSVP/Intserv style QoS can be We have described a framework in which RSVP/Intserv style QoS can be
provided across end-to-end paths that include Diffserv network provided across end-to-end paths that include Diffserv network
regions. This section discusses some of the implications of this regions. This section discusses some of the implications of this
framework for the Diffserv network region. framework for the Diffserv network region.
6.1 Requirements from Diffserv Network Regions 6.1 Requirements from Diffserv Network Regions
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2. Diffserv network regions must provide admission control 2. Diffserv network regions must provide admission control
information to their "customer" (non-Diffserv) network regions. information to their "customer" (non-Diffserv) network regions.
This information can be provided by a dynamic protocol or through This information can be provided by a dynamic protocol or through
static service level agreements enforced at the edges of the static service level agreements enforced at the edges of the
Diffserv region. Diffserv region.
3. Diffserv network regions must be able to pass RSVP messages, in 3. Diffserv network regions must be able to pass RSVP messages, in
such a manner that they can be recovered at the egress of the such a manner that they can be recovered at the egress of the
Diffserv network region. The Diffserv network region may, but is not Diffserv network region. The Diffserv network region may, but is not
required to, process these messages. Mechanisms for transparently
carrying RSVP messages across a transit network are described in
[3,6,15, 16].
Bernet, ed. et al. 18 Bernet, ed. et al. 18
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 required to, process these messages. Mechanisms for transparently
carrying RSVP messages across a transit network are described in
[3,6,15, 16].
To meet these requirements, additional work is required in the areas To meet these requirements, additional work is required in the areas
of: of:
1. Mapping Intserv style service specifications to services that can 1. Mapping Intserv style service specifications to services that can
be provided by Diffserv network regions. be provided by Diffserv network regions.
2. Definition of the functionality required in network elements to 2. Definition of the functionality required in network elements to
support RSVP signaling with aggregate traffic control (for network support RSVP signaling with aggregate traffic control (for network
elements residing in the Diffserv network region). elements residing in the Diffserv network region).
3. Definition of mechanisms to efficiently and dynamically provision 3. Definition of mechanisms to efficiently and dynamically provision
resources in a Diffserv network region (e.g. aggregated RSVP, resources in a Diffserv network region (e.g. aggregated RSVP,
tunneling, MPLS, etc.). This might include protocols by which an tunneling, MPLS, etc.). This might include protocols by which an
"oracle" (e.g., a centralized server) conveys information about "oracle" conveys information about resource availability within a
resource availability within a Diffserv region to border routers. Diffserv region to border routers. One example of such a mechanism
One example of such a mechanism is the so-called "bandwidth broker" is the so-called "bandwidth broker" proposed in [19, 20, 21].
proposed in [19, 20, 21].
6.2 Protection of Intserv Traffic from Other Traffic 6.2 Protection of Intserv Traffic from Other Traffic
Network administrators must be able to share resources in the Network administrators must be able to share resources in the
Diffserv network region between three types of traffic: Diffserv network region between three types of traffic:
a. End-to-end Intserv traffic - this is typically traffic a. End-to-end Intserv traffic - this is typically traffic
associated with quantitative QoS applications. It requires a associated with quantitative QoS applications. It requires a
specific quantity of resources with a high degree of assurance. specific quantity of resources with a high degree of assurance.
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c. All other (best-effort) traffic c. All other (best-effort) traffic
These three classes of traffic must be isolated from each other by These three classes of traffic must be isolated from each other by
the appropriate configuration of policers and classifiers at ingress the appropriate configuration of policers and classifiers at ingress
points to the Diffserv network region, and by appropriate points to the Diffserv network region, and by appropriate
provisioning within the Diffserv network region. To provide provisioning within the Diffserv network region. To provide
protection for Intserv traffic in Diffserv regions of the network, protection for Intserv traffic in Diffserv regions of the network,
we suggest that the DSCPs assigned to such traffic not overlap with we suggest that the DSCPs assigned to such traffic not overlap with
the DSCPs assigned to other traffic. the DSCPs assigned to other traffic.
7. Multicast 7. Multicast
The use of integrated services over Diffserv networks is The use of integrated services over Diffserv networks is
significantly more complex for multicast sessions than for unicast significantly more complex for multicast sessions than for unicast
sessions. With respect to a multicast connection, each participating sessions. With respect to a multicast connection, each participating
region has a single ingress router and zero, one or several egress region has a single ingress router and zero, one or several egress
routers. The difficulties of multicast are associated with Diffserv routers. The difficulties of multicast are associated with Diffserv
regions that contain several egress routers. (Support of multicast
functionality outside the Diffserv region is relatively
Bernet, ed. et al. 19 Bernet, ed. et al. 19
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 regions that contain several egress routers. (Support of multicast
functionality outside the Diffserv region is relatively
straightforward since every Intserv-capable router along the straightforward since every Intserv-capable router along the
multicast tree stores state for each flow.) multicast tree stores state for each flow.)
Consider the following reference network: Consider the following reference network:
Non-Diffserv region 2 Non-Diffserv region 2
________ ________
/ \ / \
| | |---| | | |---|
________ _____________ | |-|Rx1| ________ _____________ | |-|Rx1|
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BR1, or perhaps an upstream node such as ER1, marks packets entering BR1, or perhaps an upstream node such as ER1, marks packets entering
the Diffserv region with the appropriate DSCP. The packets are the Diffserv region with the appropriate DSCP. The packets are
routed to the egresses of the Diffserv domain using the original routed to the egresses of the Diffserv domain using the original
multicast address. multicast address.
The two major problems, explained in the following, are associated The two major problems, explained in the following, are associated
with heterogeneous multicast trees containing branch points within with heterogeneous multicast trees containing branch points within
the Diffserv region, i.e. multicast trees where the level of the Diffserv region, i.e. multicast trees where the level of
resource requirement is not uniform among all receivers. An example resource requirement is not uniform among all receivers. An example
of such a scenario in the network of Figure 2 is the case where both of such a scenario in the network of Figure 2 is the case where both
Rx1 and Rx2 need to receive multicast data from Tx1 but only one of
Bernet, ed. et al. 20 Bernet, ed. et al. 20
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 Rx1 and Rx2 need to receive multicast data from Tx1 but only one of
the receivers has requested a level of service above best effort. We the receivers has requested a level of service above best effort. We
consider such scenarios in the following paragraphs. consider such scenarios in the following paragraphs.
7.1 Remarking of packets in branch point routers 7.1 Remarking of packets in branch point routers
In the above scenario, the packets that arrive at BR1 are marked In the above scenario, the packets that arrive at BR1 are marked
with an appropriate DSCP for the requested Intserv service and are with an appropriate DSCP for the requested Intserv service and are
sent to RR. Packets arriving at the branch point must be sent sent to RR. Packets arriving at the branch point must be sent
towards BR2 with the same DSCP otherwise the service to Rx1 is towards BR2 with the same DSCP otherwise the service to Rx1 is
degraded. However, the packets going from RR towards BR3 need not degraded. However, the packets going from RR towards BR3 need not
maintain the high assurance level anymore. They may be demoted to maintain the high assurance level anymore. They may be demoted to
best effort so that the QoS provided to other packets along this best effort so that the QoS provided to other packets along this
branch of the tree is not disrupted. Several problems can be branch of the tree is not disrupted. Several problems can be
observed in the given scenario: observed in the given scenario:
- In the Diffserv region, DSCP marking is done at edge routers - In the Diffserv region, DSCP marking is done at edge routers
(ingress), whereas a branch point router might be a core (ingress), whereas a branch point router might be a core
router, which does not mark packets. router, which does not mark packets.
- Being a core Diffserv router, RR classifies based on - Being a core Diffserv router, RR classifies based on
aggregate traffic streams (BA), as opposed to per flow (MF) aggregate traffic streams (BA), as opposed to per flow (MF)
classification. Hence, it does not necessarily have the classification. Hence, it does not necessarily have the
capability to distinguish those packets which belong to a capability to distinguish those packets which belong to a
specific multicast tree and require demotion from the other specific multicast tree and require demotion from the other
packets in the behavior aggregate, which carry the same DSCP. packets in the behavior aggregate, which carry the same DSCP.
- Since RR may be RSVP-unaware, it may not participate in the - Since RR may be RSVP-unaware, it may not participate in the
admission control process, and would thus not store any per- admission control process, and would thus not store any per-
flow state about the reservations for the multicast tree. flow state about the reservations for the multicast tree.
Hence, even if RR were able to perform MF classification and Hence, even if RR were able to perform MF classification and
DSCP remarking, it would not know enough about downstream DSCP remarking, it would not know enough about downstream
reservations to remark the DSCP intelligently. reservations to remark the DSCP intelligently.
These problems can be tackled by the following mechanisms: These problems could be addressed by a variety of mechanisms. We list
some below, while noting that none is ideal in all cases and that
further mechanisms may be developed in the future:
1. If some Intserv-capable routers are placed within the Diffserv 1. If some Intserv-capable routers are placed within the Diffserv
region, it might be possible to administer the network topology and region, it might be possible to administer the network topology and
routing parameters so as to ensure that branch points occur only routing parameters so as to ensure that branch points occur only
within such routers. These routers would support MF classification within such routers. These routers would support MF classification
and remarking and hold per-flow state for the heterogeneous and remarking and hold per-flow state for the heterogeneous
reservations for which they are the branch point. Note that in this reservations for which they are the branch point. Note that in this
case, branch point routers would have essentially the same case, branch point routers would have essentially the same
functionality as ingress routers of an RSVP-aware Diffserv domain. functionality as ingress routers of an RSVP-aware Diffserv domain.
2. Packets sent on the "non-reserved" branch (from RR towards BR3) 2. Packets sent on the "non-reserved" branch (from RR towards BR3)
are marked with the "wrong" DSCP; that is, they are not demoted to are marked with the "wrong" DSCP; that is, they are not demoted to
best effort but retain their DSCP. This in turn requires over best effort but retain their DSCP. This in turn requires over
reservation of resources along that link or runs the risk of reservation of resources along that link or runs the risk of
degrading service to packets that legitimately bear the same DSCP degrading service to packets that legitimately bear the same DSCP
along this path. However, it allows the Diffserv routers to remain along this path. However, it allows the Diffserv routers to remain
free of per-flow state. free of per-flow state.
Bernet, ed. et al. 21 Bernet, ed. et al. 21
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000
3. A combination of mechanism 1 and 2 may be an effective 3. A combination of mechanism 1 and 2 may be an effective
compromise. In this case, there are some Intserv-capable routers in compromise. In this case, there are some Intserv-capable routers in
the core of the network, but the network cannot be administered so the core of the network, but the network cannot be administered so
that ALL branch points fall at such routers. that ALL branch points fall at such routers.
4. Administrators of Diffserv regions may decide not to enable 4. Administrators of Diffserv regions may decide not to enable
heterogeneous sub-trees in their domains. In the case of different heterogeneous sub-trees in their domains. In the case of different
downstream reservations, a ResvErr message would be sent according downstream reservations, a ResvErr message would be sent according
to the RSVP rules. This is similar to the approach taken for Intserv to the RSVP rules. This is similar to the approach taken for Intserv
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approach the goal of allocating appropriate resources only where approach the goal of allocating appropriate resources only where
they are needed rather than overprovisioning or underprovisioning they are needed rather than overprovisioning or underprovisioning
along certain branches of a tree. This is essentially the approach along certain branches of a tree. This is essentially the approach
described in [15]. described in [15].
8. Security Considerations 8. Security Considerations
8.1 General RSVP Security 8.1 General RSVP Security
Bernet, ed. et al. 22 Bernet, ed. et al. 22
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Integrated Services Operation Over Diffserv Networks March, 2000
We are proposing that RSVP signaling be used to obtain resources in We are proposing that RSVP signaling be used to obtain resources in
both Diffserv and non-Diffserv regions of a network. Therefore, all both Diffserv and non-Diffserv regions of a network. Therefore, all
RSVP security considerations apply [9]. In addition, network RSVP security considerations apply [9]. In addition, network
administrators are expected to protect network resources by administrators are expected to protect network resources by
configuring secure policers at interfaces with untrusted customers. configuring secure policers at interfaces with untrusted customers.
8.2 Host Marking 8.2 Host Marking
Though it does not mandate host marking of the DSCP, our proposal Though it does not mandate host marking of the DSCP, our proposal
skipping to change at line 1276 skipping to change at line 1265
task of shaping and policing their own traffic to be in compliance task of shaping and policing their own traffic to be in compliance
with their negotiated Intserv parameters. with their negotiated Intserv parameters.
9. Acknowledgments 9. Acknowledgments
Authors thank the following individuals for their comments that led Authors thank the following individuals for their comments that led
to improvements to the previous version(s) of this document: David to improvements to the previous version(s) of this document: David
Oran, Andy Veitch, Curtis Villamizer, Walter Weiss, Francois le Oran, Andy Veitch, Curtis Villamizer, Walter Weiss, Francois le
Faucheur and Russell White. Faucheur and Russell White.
Many of the ideas in this document have been previously discussed in
the original Intserv architecture document [10].
Bernet, ed. et al. 23 Bernet, ed. et al. 23
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 Many of the ideas in this document have been previously discussed in
the original Intserv architecture document [10].
10. References 10. References
[1] Braden, R., Zhang, L., Berson, S., Herzog, S. and Jamin, S., [1] Braden, R., Zhang, L., Berson, S., Herzog, S. and Jamin, S.,
"Resource Reservation Protocol (RSVP) Version 1 Functional "Resource Reservation Protocol (RSVP) Version 1 Functional
Specification", RFC 2205, Proposed Standard, September 1997 Specification", RFC 2205, Proposed Standard, September 1997
[2] Yavatkar, R., Hoffman, D., Bernet, Y., Baker, F. and Speer, M., [2] Yavatkar, R., Hoffman, D., Bernet, Y., Baker, F. and Speer, M.,
"SBM (Subnet Bandwidth Manager): A Protocol For RSVP-based "SBM (Subnet Bandwidth Manager): A Protocol For RSVP-based
Admission Control Over IEEE 802 Style Networks", Internet Draft, Admission Control Over IEEE 802 Style Networks", Internet Draft,
skipping to change at line 1330 skipping to change at line 1318
[10] Braden, R., Clark, D. and Shenker, S., "Integrated Services in [10] Braden, R., Clark, D. and Shenker, S., "Integrated Services in
the Internet Architecture: an Overview", Internet RFC 1633, the Internet Architecture: an Overview", Internet RFC 1633,
June 1994 June 1994
[11] Garrett, M. W., and Borden, M., "Interoperation of Controlled- [11] Garrett, M. W., and Borden, M., "Interoperation of Controlled-
Load Service and Guaranteed Service with ATM", RFC2381, August Load Service and Guaranteed Service with ATM", RFC2381, August
1998. 1998.
[12] Weiss, Walter, Private communication, November 1998. [12] Weiss, Walter, Private communication, November 1998.
[13] Kent, S., Atkinson, R., "Security Architecture for the Internet
Protocol", RFC 2401, November 1998.
Bernet, ed. et al. 24 Bernet, ed. et al. 24
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 [13] Kent, S., Atkinson, R., "Security Architecture for the Internet
Protocol", RFC 2401, November 1998.
[14] Bernet, Y., "Usage and Format of the DCLASS Object with RSVP [14] Bernet, Y., "Usage and Format of the DCLASS Object with RSVP
Signaling", Internet Draft, draft-issll-dclass-00.txt, August Signaling", Internet Draft, draft-issll-dclass-01.txt, October
1999. 1999.
[15] Baker, F., Iturralde, C., le Faucheur, F., and Davie, B. "RSVP [15] Baker, F., Iturralde, C., le Faucheur, F., and Davie, B. "RSVP
Reservation Aggregation", Internet Draft, draft-ietf-issll- Reservation Aggregation", Internet Draft, draft-ietf-issll-
aggregation-00.txt, September 1999. aggregation-02.txt, March 2000.
[16] Terzis, A., Krawczyk, J., Wroclawski, J., Zhang, L., "RSVP [16] Terzis, A., Krawczyk, J., Wroclawski, J., Zhang, L., "RSVP
Operation Over IP Tunnels", Internet Draft, draft-ietf-rsvp- Operation Over IP Tunnels", RFC 2746, January 2000.
tunnel-04.txt, May 1999.
[17] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, D., and [17] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, D., and
Sastry, A., "COPS Usage for RSVP", Internet Draft, draft-ietf- Sastry, A., "COPS Usage for RSVP", RFC 2749, January 2000.
rap-cops-rsvp-05.txt, June 1999.
[18] Bernet, Y., et al., "A Framework for Differentiated Services", [18] Bernet, Y., et al., "A Framework for Differentiated Services",
Internet draft, draft-ietf-diffserv-framework-02.txt, February Internet draft, draft-ietf-diffserv-framework-02.txt, February
1999. 1999.
[19] Jacobson Van, "Differentiated Services Architecture", talk in [19] Jacobson Van, "Differentiated Services Architecture", talk in
the Int-Serv WG at the Munich IETF, August 1997. the Int-Serv WG at the Munich IETF, August 1997.
[20] Jacobson, V., Nichols K., and Zhang, L. "A Two-bit [20] Jacobson, V., Nichols K., and Zhang, L. "A Two-bit
Differentiated Services Architecture for the Internet", Differentiated Services Architecture for the Internet",
skipping to change at line 1373 skipping to change at line 1358
[21] First Internet2 bandwidth broker operability event [21] First Internet2 bandwidth broker operability event
http://www.merit.edu/internet/working.groups/i2-qbone-bb/ http://www.merit.edu/internet/working.groups/i2-qbone-bb/
inter-op/index.htm inter-op/index.htm
11. Author's Addresses: 11. Author's Addresses:
Yoram Bernet Yoram Bernet
Microsoft Microsoft
One Microsoft Way, Redmond, WA 98052 One Microsoft Way, Redmond, WA 98052
Phone: (425) 936-9568 Phone: +1 425-936-9568
Email: yoramb@microsoft.com Email: yoramb@microsoft.com
Raj Yavatkar Raj Yavatkar
Intel Corporation Intel Corporation
JF3-448 2111 NE 25th. Avenue, Hillsboro, OR 97124 JF3-206 2111 NE 25th. Avenue, Hillsboro, OR 97124
Phone: (503) 264-9077 Phone: +1 503-264-9077
Email: raj.yavatkar@intel.com Email: raj.yavatkar@intel.com
Peter Ford Peter Ford
Microsoft Microsoft
One Microsoft Way, Redmond, WA 98052 One Microsoft Way, Redmond, WA 98052
Phone: (425) 703-2032 Phone: +1 425-703-2032
Email: peterf@microsoft.com Email: peterf@microsoft.com
Fred Baker Fred Baker
Bernet, ed. et al. 25 Bernet, ed. et al. 25
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000
Cisco Systems Cisco Systems
519 Lado Drive, Santa Barbara, CA 93111 519 Lado Drive, Santa Barbara, CA 93111
Phone: (408) 526-4257 Phone: +1 408-526-4257
Email: fred@cisco.com Email: fred@cisco.com
Lixia Zhang Lixia Zhang
UCLA UCLA
4531G Boelter Hall Los Angeles, CA 90095 4531G Boelter Hall Los Angeles, CA 90095
Phone: (310) 825-2695 Phone: +1 310-825-2695
Email: lixia@cs.ucla.edu Email: lixia@cs.ucla.edu
Michael Speer Michael Speer
Sun Microsystems Sun Microsystems
901 San Antonio Road UMPK15-215 Palo Alto, CA 94303 901 San Antonio Road UMPK15-215 Palo Alto, CA 94303
Phone: (650)786-6368 Phone: +1 650-786-6368
Email: speer@Eng.Sun.COM Email: speer@Eng.Sun.COM
Bob Braden Bob Braden
USC Information Sciences Institute USC Information Sciences Institute
4676 Admiralty Way Marina del Rey, CA 90292-6695 4676 Admiralty Way Marina del Rey, CA 90292-6695
Phone: (310) 822-1511 Phone: +1 310-822-1511
Email: braden@isi.edu Email: braden@isi.edu
Bruce Davie Bruce Davie
Cisco Systems Cisco Systems
250 Apollo Drive, Chelmsford, MA 01824 250 Apollo Drive, Chelmsford, MA 01824
Phone: (978) 244-8000 Phone: +1 978-244-8000
Email: bsd@cisco.com Email: bsd@cisco.com
Eyal Felstaine Eyal Felstaine
Dept. of Computer Science Dept. of Computer Science
Technion, IIT Technion, IIT
32000 Haifa, Israel 32000 Haifa, Israel
Phone: +972-50-747672 Phone: +972-50-747672
Email: eyalfe@cs.technion.ac.il Email: eyalfe@cs.technion.ac.il
John Wroclawski John Wroclawski
MIT Laboratory for Computer Science MIT Laboratory for Computer Science
545 Technology Sq. 545 Technology Sq.
Cambridge, MA 02139 Cambridge, MA 02139
Phone: (617) 253-7885 Phone: +1 617-253-7885
E-mail: jtw@lcs.mit.edu E-mail: jtw@lcs.mit.edu
12. Full Copyright Statement 12. Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
Bernet, ed. et al. 26 Bernet, ed. et al. 26
Integrated Services Operation Over Diffserv Networks May, 2000
Integrated Services Operation Over Diffserv Networks March, 2000 or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than followed, or as required to translate it into languages other than
English. English.
The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns. revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
This draft expires September, 2000 This draft expires November, 2000
Bernet, ed. et al. 27 Bernet, ed. et al. 27
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