i2rs R. White Internet-Draft IETF Intended status: Informational S. Hares Expires: February 28, 2014 ADARA A. Retana Cisco Systems, Inc. August 27, 2013 Protocol Independent Use Cases for an Interface to the Routing System draft-white-i2rs-use-case-01 Abstract Programmatic interfaces to provide control over individual forwarding devices in a network promise to reduce operational costs while improving scaling, control, and visibility into the operation of large scale networks. To this end, several programmatic interfaces have been proposed. OpenFlow, for instance, provides a mechanism to replace the dynamic control plane processes on individual forwarding devices throughout a network with off box processes that interact with the forwarding tables on each device. Another example is NETCONF, which provides a fast and flexible mechanism to interact with device configuration and policy. There is, however, no proposal which provides an interface to all aspects of the routing system as a system. Such a system would not interact with the forwarding system on individual devices, but rather with the control plane processes already used to discover the best path to any given destination through the network, as well as interact with the routing information base (RIB), which feeds the forwarding table the information needed to actually switch traffic at a local level. This document describes a set of use cases such a system could fulfill. It is designed to provide underlying support for the framework, policy, and other drafts describing the Interface to the Routing System (I2RS). Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. White, et al. Expires February 28, 2014 [Page 1] Internet-Draft IRS Use Cases August 2013 Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on February 28, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Distributed Reaction to Network Based Attacks . . . . . . . . 3 3. Remote Service Routing . . . . . . . . . . . . . . . . . . . 4 4. Within Data Center Routing . . . . . . . . . . . . . . . . . 6 5. Temporary Overlays between Data Centers . . . . . . . . . . . 7 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction The Interface to the Routing System Framework [I-D.ward-i2rs-framework] describes a mechanism where the distributed control plane can be augmented by an outside control plane through an open, accessible interface, including the Routing Information Base (RIB), in individual devices. This represents a "halfway point" between completely replacing the traditional distributed control plane and directly configuring devices to distribute policy or modifications to routing through off-board processes. This draft proposes a set of use cases that explain where the work described in [I2RS - should this be a reference to the framework as above, or to the architecture, or the WG charter or ??] will be useful. The goal is to inform not only the community's understanding of where I2RS White, et al. Expires February 28, 2014 [Page 2] Internet-Draft IRS Use Cases August 2013 fits in the larger scheme of SDN proposals, but also to inform the requirements, framework, and specification of I2RS to provide the best fit for the purposes which make the most sense for this type of programmatic interface. Towards this end the authors have searched for a number of different use cases representing not only complex modifications of the control plane, including interaction with applications and network conditions, but also simpler use cases. The array of use cases presented here should provide the reader with a solid understanding of the power of an SDN solution that will augment, rather than replace, traditional distributed control planes. Each use case is presented in its own section. 2. Distributed Reaction to Network Based Attacks Quickly modifying the control plane to reroute traffic for one destination while leaving a standard configuration in place (filters, metrics, and other policy mechanisms) is a challenge --but this is precisely the challenge of a network engineer attempting to deal with a network incursion. The ability to redirect specific flows of information or specific classes of traffic into, through, and back out of traffic analyzers on the fly is crucial in these situations. The following network diagram provides an illustration of the problem. Valid Source---\ /--R2--------------------\ R1 R3---Valid Destination Attack Source--/ \--Monitoring Device-----/ Modifying the cost of the link between R1 and R2 to draw the attack traffic through the monitoring device in the distributed control plane will, of necessity, also draw the valid traffic through the monitoring device. Drawing valid traffic through a monitoring device introduces delay, jitter, and other quality of service issues, as well as posing a problem for the monitoring device itself in terms of traffic load and management. An I2RS controller could stand between the detection of the attack and the control plane to facilitate the rapid modification of control and forwarding planes to either block the traffic or redirect it to analysis devices connected to the network. Summary of IRS Capabilities and Interactions: White, et al. Expires February 28, 2014 [Page 3] Internet-Draft IRS Use Cases August 2013 o The ability to monitor the available routes installed in the RIB of each forwarding device, including near real time notification of route installation and removal. This information must include the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), the metric of the installed route, and an identifier indicating the installing process. o The ability to install source and destination based routes in the local RIB of each forwarding device. This must include the ability to supply the destination prefix (NLRI), the source prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), a route preference, a route metric, a next hop, an outbound interface, and a route process identifier. o The ability to install a route to a null destination, effectively filtering traffic to this destination. o The ability to interact with various policies configured on the forwarding devices, in order to inform the policies implemented by the dynamic routing processes. This interaction should be through existing configuration mechanisms, such as NETCONF, and should be recorded in the configuration of the local device so operators are aware of the full policy implemented in the network from the running configuration. o The ability to interact with traffic flow and other network traffic level measurement protocols and systems, in order to determine path performance, top talkers, and other information required to make an informed path decision based on locally configured policy. 3. Remote Service Routing In hub and spoke overlay networks, there is always an issue with balancing between the information held in the spoke routing table, optimal routing through the network underlying the overlay, and mobility. Most solutions in this space use some form of centralized route server that acts as a directory of all reachable destinations and next hops, a protocol by which spoke devices and this route server communicate, and caches at the remote sites. White, et al. Expires February 28, 2014 [Page 4] Internet-Draft IRS Use Cases August 2013 An I2RS solution would use the same elements, but with a different control plane. Remote sites would register (or advertise through some standard routing protocol, such as BGP), the reachable destinations at each site, along with the address of the router (or other device) used to reach that destination. These would, as always, be stored in a route server (or several redundant route servers) at a central location. When a remote site sends a set of packets to the central location that are eventually destined to some other remote site, the central location can forward this traffic, but at the same time simply directly insert the correct routing information into the remote site's routing table. If the location of the destination changes, the route server can directly modify the routing information at the remote site as needed. An interesting aspect of this solution is that no new and specialized protocols are needed between the remote sites and the centralized route server(s). Normal routing protocols can be used to notify the centralized route server(s) of modifications in reachability information, and the route server(s) can respond as needed, based on local algorithms optimized for a particular application or network. For instance, short lived flows might be allowed to simply pass through the hub site with no reaction, while longer lived flows might warrant a specific route to be installed in the remote router. Algorithms can also be developed that would optimize traffic flow through the overlay, and also to remove routing entries from remote devices when they are no longer needed based on far greater intelligence than simple non-use for some period of time. Summary of IRS Capabilities and Interactions: o The ability to read the local RIB of each forwarding device, including the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), the metric of each installed route, a route preference, and an identifier indicating the installing process. o The ability to monitor the available routes installed in the RIB of each forwarding device, including near real time notification of route installation and removal. This information must include the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), the metric of the installed route, and an identifier indicating the installing process. o The ability to install destination based routes in the local RIB of each forwarding device. This must include the ability to White, et al. Expires February 28, 2014 [Page 5] Internet-Draft IRS Use Cases August 2013 supply the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), a route preference, a route metric, a next hop, an outbound interface, and a route process identifier. 4. Within Data Center Routing Data Centers have evolved into massive topologies with thousands of server racks and millions of hosts. Data Centers use BGP with ECMP, ISIS (with multiple LAGs), or other protocols to tie the data center together. Data centers are currently designed around a three or four tier structure with: server, top-of-rack switches, aggregation switches, and router interfacing the data center to the Internet. [I-D.lapukhov-bgp-routing-large-dc] examines many of these elements of data center design. One element of these Data Center routing infrastructures is the ability to quickly read topology information and execute configuration from a centralized location. Key to this environment is the tight feedback loop between learning about topology changes or loading changes, and instantiating new routing policy. Without I2RS, may Data Centers are using extra physical topologies or logical topologies to work around the features. An I2RS solution would use the same elements, but with a different control plane. The I2RS enabled control plane could provide the Data Center 4 tier infrastructure the quick access to topology and data flow information needed for traffic flow optimization. Changes to the Data Center infrastructure done via I2RS could have a tight feedback loop. Again, this solution would reduce the need for new and specialized protocols while giving the Data Center the control it desire. The I2RS routing interface could be extended to virtual routers. Summary of IRS Capabilities and Interactions: o The ability to read the local RIB of each forwarding device, including the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), the metric of each installed route, a route preference, and an identifier indicating the installing process. o The ability to monitor the available routes installed in the RIB of each forwarding device, including near real time notification of route installation and removal. This information must include the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), the metric White, et al. Expires February 28, 2014 [Page 6] Internet-Draft IRS Use Cases August 2013 of the installed route, and an identifier indicating the installing process. o The ability to install destination based routes in the local RIB of each forwarding device. This must include the ability to supply the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), a route preference, a route metric, a next hop, an outbound interface, and a route process identifier. o The ability to read the tables of other local protocol processes running on the device. This reading action should be supported through an import/export interface which can present the information in a consistent manner across all protocol implementations, rather than using a protocol specific model for each type of available process. o The ability to inject information directly into the local tables of other protocol processes running on the forwarding device. This injection should be supported through an import/export interface which can inject routing information in a consistent manner across all protocol implementations, rather than using a protocol specific model for each type of available process. o The ability to interact with various policies configured on the forwarding devices, in order to inform the policies implemented by the dynamic routing processes. This interaction should be through existing configuration mechanisms, such as NETCONF, and should be recorded in the configuration of the local device so operators are aware of the full policy implemented in the network from the running configuration. o The ability to interact with traffic flow and other network traffic level measurement protocols and systems, in order to determine path performance, top talkers, and other information required to make an informed path decision based on locally configured policy. 5. Temporary Overlays between Data Centers Data Centers within one organization may operate as one single entity even though they may be geographically distributed. Applications are load balanced within Data Centers and between data centers to take advantage of cost economics in power, storage, and server availability for compute resources. Applications are also transfer to alternate data centers in case of failures within a data center. To reduce time during failure, Data Centers often replicate user storage between two or more data centers. During the transfer of White, et al. Expires February 28, 2014 [Page 7] Internet-Draft IRS Use Cases August 2013 stored information prior to a Data Center to Data Center move, the Data Center controllers need to dynamically acquire a large amount of inter-data center bandwidth through an overlay network, often during off hours. I2RS could provide the connection between the overlay network configuration, local policies, and the control plane to dynamically bring a large bandwidth inter-data center overlay or channel into use, and then to remove it from use when the data transfer is completed. Similarly, during a fail-over, a control process within data centers interacts with a group host process and the network to seamless move the processing to another data center. During the fail-over case, additional process state may need to be moved as well to restart the system. The difference between these data-to-data center moves is immediate and urgent need to move systems. If an application (such as medical or banking services) pays to have this type of fail-over, it is likely the service will pay for preemption on network bandwidth. I2RS can allow the Data Center network and the Network connecting the data center to preempt other best-effort traffic to send this priority data flow. After the high priority data flow has finished, networks can return to their previous condition. Summary of IRS Capabilities and Interactions: o The ability to read the local RIB of each forwarding device, including the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), the metric of each installed route, a route preference, and an identifier indicating the installing process. o The ability to monitor the available routes installed in the RIB of each forwarding device, including near real time notification of route installation and removal. This information must include the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), the metric of the installed route, and an identifier indicating the installing process. o The ability to install destination based routes in the local RIB of each forwarding device. This must include the ability to supply the destination prefix (NLRI), a table identifier (if the forwarding device has multiple forwarding instances), a route preference, a route metric, a next hop, an outbound interface, and a route process identifier. White, et al. Expires February 28, 2014 [Page 8] Internet-Draft IRS Use Cases August 2013 o The ability to interact with various policies configured on the forwarding devices, in order to inform the policies implemented by the dynamic routing processes. This interaction should be through existing configuration mechanisms, such as NETCONF, and should be recorded in the configuration of the local device so operators are aware of the full policy implemented in the network from the running configuration. o The ability to interact with policies and configurations on the forwarding devices using time based processing, either through timed auto-rollback or some other mechanism. This interaction should be through existing configuration mechanisms, such as NETCONF, and should be recorded in the configuration of the local device so operators are aware of the full policy implemented in the network from the running configuration. o The ability to interact with traffic flow and other network traffic level measurement protocols and systems, in order to determine path performance, top talkers, and other information required to make an informed path decision based on locally configured policy. 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 6.2. Informative References [I-D.lapukhov-bgp-routing-large-dc] Lapukhov, P., Premji, A., and J. Mitchell, "Use of BGP for routing in large-scale data centers", draft-lapukhov-bgp- routing-large-dc-06 (work in progress), August 2013. [I-D.ward-i2rs-framework] Atlas, A., Nadeau, T., and D. Ward, "Interface to the Routing System Framework", draft-ward-i2rs-framework-00 (work in progress), February 2013. Authors' Addresses Russ White IETF Email: russw@riw.us White, et al. Expires February 28, 2014 [Page 9] Internet-Draft IRS Use Cases August 2013 Susan Hares ADARA Email: shares@ndzh.com Alvaro Retana Cisco Systems, Inc. 7025 Kit Creek Road Research Triangle Park, NC 27617 USA Email: aretana@cisco.com White, et al. Expires February 28, 2014 [Page 10]