A Framework for QoS-based Routing in the Internet
RFC 2386
Document | Type | RFC - Informational (August 1998) | |
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Authors | Eric S. Crawley , Raj Nair , Dr. Bala Rajagopalan , Hal J. Sandick | ||
Last updated | 2013-03-02 | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
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IESG | Responsible AD | (None) | |
Send notices to | (None) |
RFC 2386
RFC 2386 A Framework for QoS-based Routing August 1998 RSVP has been designed to operate independent of the underlying routing scheme. Under this model, RSVP PATH messages establish the reverse path for RESV messages. In essence, this model is not compatible with QoS-based routing schemes that compute paths after receiver reservations are received. While this incompatibility can be resolved in a simple manner for unicast flows, multicast with heterogeneous receiver requirements is a more difficult case. For this, reconciliation between RSVP and QoS-based routing models is necessary. Such a reconciliation, however, may require some changes to the RSVP model depending on the QoS-based routing model [ZES97, ZSSC97, GOA97]. On the other hand, QoS-based routing schemes may be designed with RSVP compatibility as a necessary goal. How this affects scalability and other performance measures must be considered. 8. SECURITY CONSIDERATIONS Security issues that arise with routing in general are about maintaining the integrity of the routing protocol in the presence of unintentional or malicious introduction of information that may lead to protocol failure [P88]. QoS-based routing requires additional security measures both to validate QoS requests for flows and to prevent resource-depletion type of threats that can arise when flows are allowed to make arbitratry resource requests along various paths in the network. Excessive resource consumption by an errant flow results in denial of resources to legitimate flows. While these situations may be prevented by setting up proper policy constraints, charging models and policing at various points in the network, the formalization of such protection requires work [BCCH94]. 9. RELATED WORK "Adaptive" routing, based on network state, has a long history, especially in circuit-switched networks. Such routing has also been implemented in early datagram and virtual circuit packet networks. More recently, this type of routing has been the subject of study in the context of ATM networks, where the traffic characteristics and topology are substantially different from those of circuit-switched networks [MMR96]. It is instructive to review the adaptive routing methodologies, both to understand the problems encountered and possible solutions. Fundamentally, there are two aspects to adaptive, network state- dependent routing: 1. Measuring and gathering network state information, and 2. Computing routes based on the available information. Crawley, et. al. Informational [Page 24] RFC 2386 A Framework for QoS-based Routing August 1998 Depending on how these two steps are implemented, a variety of routing techniques are possible. These differ in the following respects: - what state information is used - whether local or global state is used - what triggers the propagation of state information - whether routes are computed in a distributed or centralized manner - whether routes are computed on-demand, pre-computed, or in a hybrid manner - what optimization criteria, if any, are used in computing routes - whether source routing or hop by hop routing is used, and - how alternate route choices are explored It should be noted that most of the adaptive routing work has focused on unicast routing. Multicast routing is one of the areas that would be prominent with Internet QoS-based routing. We treat this separately, and the following review considers only unicast routing. This review is not exhaustive, but gives a brief overview of some of the approaches. 9.1 Optimization Criteria The most common optimization criteria used in adaptive routing is throughput maximization or delay minimization. A general formulation of the optimization problem is the one in which the network revenue is maximized, given that there is a cost associated with routing a flow over a given path [MMR96, K88]. In general, global optimization solutions are difficult to implement, and they rely on a number of assumptions on the characteristics of the traffic being routed [MMR96]. Thus, the practical approach has been to treat the routing of each flow (VC, circuit or packet stream to a given destination) independently of the routing of other flows. Many such routing schemes have been implemented. 9.2 Circuit Switched Networks Many adaptive routing concepts have been proposed for circuit- switched networks. An example of a simple adaptive routing scheme is sequential alternate routing [T88]. This is a hop-by-hop destination-based routing scheme where only local state information is utilized. Under this scheme, a routing table is computed for each node, which lists multiple output link choices for each destination. When a call set-up request is received by a node, it tries each output link choice in sequence, until it finds one that can accommodate the call. Resources are reserved on this link, and the call set-up is forwarded to the next node. The set-up either reaches the destination, or is blocked at some node. In the latter case, the Crawley, et. al. Informational [Page 25] RFC 2386 A Framework for QoS-based Routing August 1998 set-up can be cranked back to the previous node or a failure declared. Crankback allows the previous node to try an alternate path. The routing table under this scheme can be computed in a centralized or distributed manner, based only on the topology of the network. For instance, a k-shortest-path algorithm can be used to determine k alternate paths from a node with distinct initial links [T88]. Some mechanism must be implemented during path computation or call set-up to prevent looping. Performance studies of this scheme illustrate some of the pitfalls of alternate routing in general, and crankback in particular [A84, M86, YS87]. Specifically, alternate routing improves the throughput when traffic load is relatively light, but adversely affects the performance when traffic load is heavy. Crankback could further degrade the performance under these conditions. In general, uncontrolled alternate routing (with or without crankback) can be harmful in a heavily utilized network, since circuits tend to be routed along longer paths thereby utilizing more capacity. This is an obvious, but important result that applies to QoS-based Internet routing also. The problem with alternate routing is that both direct routed (i.e., over shortest paths) and alternate routed calls compete for the same resource. At higher loads, allocating these resources to alternate routed calls result in the displacement of direct routed calls and hence the alternate routing of these calls. Therefore, many approaches have been proposed to limit the flow of alternate routed calls under high traffic loads. These schemes are designed for the fully-connected logical topology of long distance telephone networks (i.e., there is a logical link between every pair of nodes). In this topology, direct routed calls always traverse a 1-hop path to the destination and alternate routed calls traverse at most a 2-hop path. "Trunk reservation" is a scheme whereby on each link a certain bandwidth is reserved for direct routed calls [MS91]. Alternate routed calls are allowed on a trunk as long as the remaining trunk bandwidth is greater than the reserved capacity. Thus, alternate routed calls cannot totally displace direct routed calls on a trunk. This strategy has been shown to be very effective in preventing the adverse effects of alternate routing. "Dynamic alternate routing" (DAR) is a strategy whereby alternate routing is controlled by limiting the number of choices, in addition to trunk reservation [MS91]. Under DAR, the source first attempts to use the direct link to the destination. When blocked, the source attempts to alternate route the call via a pre-selected neighbor. If the call is still blocked, a different neighbor is selected for alternate routing to this destination in the future. The present call Crawley, et. al. Informational [Page 26] RFC 2386 A Framework for QoS-based Routing August 1998 is dropped. DAR thus requires only local state information. Also, it "learns" of good alternate paths by random sampling and sticks to them as long as possible. More recent circuit-switched routing schemes utilize global state to select routes for calls. An example is AT&T's Real-Time Network Routing (RTNR) scheme [ACFH92]. Unlike schemes like DAR, RTNR handles multiple classes of service, including voice and data at fixed rates. RTNR utilizes a sophisticated per-class trunk reservation mechanism with dynamic bandwidth sharing between classes. Also, when alternate routing a call, RTNR utilizes the loading on all trunks in the network to select a path. Because of the fully-connected topology, disseminating status information is simple under RTNR; each node simply exchanges status information directly with all others. From the point of view of designing QoS-based Internet routing schemes, there is much to be learned from circuit-switched routing. For example, alternate routing and its control, and dynamic resource sharing among different classes of traffic. It is, however, not simple to apply some of the results to a general topology network with heterogeneous multirate traffic. Work in the area of ATM network routing described next illustrates this. 9.3 ATM Networks The VC routing problem in ATM networks presents issues similar to that encountered in circuit-switched networks. Not surprisingly, some extensions of circuit-switched routing have been proposed. The goal of these routing schemes is to achieve higher throughput as compared to traditional shortest-path routing. The flows considered usually have a single QoS requirement, i.e., bandwidth. The first idea is to extend alternate routing with trunk reservation to general topologies [SD95]. Under this scheme, a distance vector routing protocol is used to build routing tables at each node with multiple choices of increasing hop count to each destination. A VC set-up is first routed along the primary ("direct") path. If sufficient resources are not available along this path, alternate paths are tried in the order of increasing hop count. A flag in the VC set-up message indicates primary or alternate routing, and bandwidth on links along an alternate path is allocated subject to trunk reservation. The trunk reservation values are determined based on some assumptions on traffic characteristics. Because the scheme works only for a single data rate, the practical utility of it is limited. The next idea is to import the notion of controlled alternate routing into traditional link state QoS-based routing [GKR96]. To do this, Crawley, et. al. Informational [Page 27] RFC 2386 A Framework for QoS-based Routing August 1998 first each VC is associated with a maximum permissible routing cost. This cost can be set based on expected revenues in carrying the VC or simply based on the length of the shortest path to the destination. Each link is associated with a metric that increases exponentially with its utilization. A switch computing a path for a VC simply determines a least-cost feasible path based on the link metric and the VC's QoS requirement. The VC is admitted if the cost of the path is less than or equal to the maximum permissible routing cost. This routing scheme thus limits the extent of "detour" a VC experiences, thus preventing excessive resource consumption. This is a practical scheme and the basic idea can be extended to hierarchical routing. But the performance of this scheme has not been analyzed thoroughly. A similar notion of admission control based on the connection route was also incorporated in a routing scheme presented in [ACG92]. Considering the ATM Forum PNNI protocol [PNNI96], a partial list of its stated characteristics are as follows: o Scales to very large networks o Supports hierarchical routing o Supports QoS o Uses source routed connection setup o Supports multiple metrics and attributes o Provides dynamic routing The PNNI specification is sub-divided into two protocols: a signaling and a routing protocol. The PNNI signaling protocol is used to establish point-to-point and point to multipoint connections and supports source routing, crankback and alternate routing. PNNI source routing allows loop free paths. Also, it allows each implementation to use its own path computation algorithm. Furthermore, source routing is expected to support incremental deployment of future enhancements such as policy routing. The PNNI routing protocol is a dynamic, hierarchical link state protocol that propagates topology information by flooding it through the network. The topology information is the set of resources (e.g., nodes, links and addresses) which define the network. Resources are qualified by defined sets of metrics and attributes (delay, available bandwidth, jitter, etc.) which are grouped by supported traffic class. Since some of the metrics used will change frequently, e.g., available bandwidth, threshold algorithms are used to determine if the change in a metric or attribute is significant enough to require propagation of updated information. Other features include, auto configuration of the routing hierarchy, connection admission control (as part of path calculation) and aggregation and summarization of topology and reachability information. Crawley, et. al. Informational [Page 28] RFC 2386 A Framework for QoS-based Routing August 1998 Despite its functionality, the PNNI routing protocol does not address the issues of multicast routing, policy routing and control of alternate routing. A problem in general with link state QoS-based routing is that of efficient broadcasting of state information. While flooding is a reasonable choice with static link metrics it may impact the performance adversely with dynamic metrics. Finally, Integrated PNNI [I-PNNI] has been designed from the start to take advantage of the QoS Routing capabilities that are available in PNNI and integrate them with routing for layer 3. This would provide an integrated layer 2 and layer 3 routing protocol for networks that include PNNI in the ATM core. The I-PNNI specification has been under development in the ATM Forum and, at this time, has not yet incorporated QoS routing mechanisms for layer 3. 9.4 Packet Networks Early attempts at adaptive routing in packet networks had the objective of delay minimization by dynamically adapting to network congestion. Alternate routing based on k-shortest path tables, with route selection based on some local measure (e.g., shortest output queue) has been described [R76, YS81]. The original ARPAnet routing scheme was a distance vector protocol with delay-based cost metric [MW77]. Such a scheme was shown to be prone to route oscillations [B82]. For this and other reasons, a link state delay-based routing scheme was later developed for the ARPAnet [MRR80]. This scheme demonstrated a number of techniques such as triggered updates, flooding, etc., which are being used in OSPF and PNNI routing today. Although none of these schemes can be called QoS-based routing schemes, they had features that are relevant to QoS-based routing. IBM's System Network Architecture (SNA) introduced the concept of Class of Service (COS)-based routing [A79, GM79]. There were several classes of service: interactive, batch, and network control. In addition, users could define other classes. When starting a data session an application or device would request a COS. Routing would then map the COS into a statically configured route which marked a path across the physical network. Since SNA is connection oriented, a session was set up along this path and the application's or device's data would traverse this path for the life of the session. Initially, the service delivered to a session was based on the network engineering and current state of network congestion. Later, transmission priority was added to subarea SNA. Transmission priority allowed more important traffic (e.g. interactive) to proceed before less time-critical traffic (e.g. batch) and improved link and network utilization. Transmission priority of a session was based on its COS. Crawley, et. al. Informational [Page 29] RFC 2386 A Framework for QoS-based Routing August 1998 SNA later evolved to support multiple or alternate paths between nodes. But, although assisted by network design tools, the network administrator still had to statically configure routes. IBM later introduced SNA's Advanced Peer to Peer Networking (APPN) [B85]. APPN added new features to SNA including dynamic routing based on a link state database. An application would use COS to indicate it traffic requirements and APPN would calculate a path capable of meeting these requirements. Each COS was mapped to a table of acceptable metrics and parameters that qualified the nodes and links contained in the APPN topology Database. Metrics and parameters used as part of the APPN route calculation include, but are not limited to: delay, cost per minute, node congestion and security. The dynamic nature of APPN allowed it to route around failures and reduce network configuration. The service delivered by APPN was still based on the network engineering, transmission priority and network congestion. IBM later introduced an extension to APPN, High Performance Routing (HPR)[IBM97]. HPR uses a congestion avoidance algorithm called adaptive rate based (ARB) congestion control. Using predictive feedback methods, the ARB algorithm prevents congestion and improves network utilization. Most recently, an extension to the COS table has been defined so that HPR routing could recognize and take advantage of ATM QoS capabilities. Considering IP routing, both IDRP [R92] and OSPF support type of service (TOS)-based routing. While the IP header has a TOS field, there is no standardized way of utilizing it for TOS specification and routing. It seems possible to make use of the IP TOS feature, along with TOS-based routing and proper network engineering, to do QoS-based routing. The emerging differentiated services model is generating renewed interest in TOS support. Among the newer schemes, Source Demand Routing (SDR) [ELRV96] allows on-demand path computation by routers and the implementation of strict and loose source routing. The Nimrod architecture [CCM96] has a number of concepts built in to handle scalability and specialized path computation. Recently, some work has been done on QoS-based routing schemes for the integrated services Internet. For example, in [M98], heuristic schemes for efficient routing of flows with bandwidth and/or delay constraints is described and evaluated. 9. SUMMARY AND CONCLUSIONS In this document, a framework for QoS-based Internet routing was defined. This framework adopts the traditional separation between intra and interdomain routing. This approach is especially meaningful in the case of QoS-based routing, since there are many views on how QoS-based routing should be accomplished and many different needs. The objective of this document was to encourage the development of Crawley, et. al. Informational [Page 30] RFC 2386 A Framework for QoS-based Routing August 1998 different solution approaches for intradomain routing, subject to some broad requirements, while consensus on interdomain routing is achieved. To this end, the QoS-based routing issues were described, and some broad intradomain routing requirements and an interdomain routing model were defined. In addition, QoS-based multicast routing was discussed and a detailed review of related work was presented. The deployment of QoS-based routing across multiple administrative domains requires both the development of intradomain routing schemes and a standard way for them to interact via a well-defined interdomain routing mechanism. This document, while outlining the issues that must be addressed, did not engage in the specification of the actual features of the interdomain routing scheme. This would be the next step in the evolution of wide-area, multidomain QoS-based routing. REFERENCES [A79] V. Ahuja, "Routing and Flow Control in SNA", IBM Systems Journal, 18 No. 2, pp. 298-314, 1979. [A84] J. M. Akinpelu, "The Overload Performance of Engineered Networks with Non-Hierarchical Routing", AT&T Technical Journal, Vol. 63, pp. 1261-1281, 1984. [ACFH92] G. R. Ash, J. S. Chen, A. E. Frey and B. D. Huang, "RealTime Network Routing in a Dynamic Class-of-Service Network", Proceedings of ITC 13, 1992. [ACG92] H. Ahmadi, J. Chen, and R. Guerin, "Dynamic Routing and Call Control in High-Speed Integrated Networks", Proceedings of ITC-13, pp. 397-403, 1992. [B82] D. P. Bertsekas, "Dynamic Behavior of Shortest Path Routing Algorithms for Communication Networks", IEEE Trans. Auto. Control, pp. 60-74, 1982. [B85] A. E. Baratz, "SNA Networks of Small Systems", IEEE JSAC, May, 1985. [BBCD98] Black, D., Blake, S., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An Architecture for Differentiated Services", Work in Progress. [BCCH94] Braden, R., Clark, D., Crocker, D., and C. Huitema, "Report of IAB Workshop on Security in the Internet Architecture", RFC 1636, June 1994. Crawley, et. al. Informational [Page 31] RFC 2386 A Framework for QoS-based Routing August 1998 [BCF94] A. Ballardie, J. Crowcroft and P. Francis, "Core-Based Trees: A Scalable Multicast Routing Protocol", Proceedings of SIGCOMM `94. [BCS94] Braden, R., Clark, D., and S. Shenker, "Integrated Services in the Internet Architecture: An Overview", RFC 1633, July 1994. [BZ92] S. Bahk and M. El Zarki, "Dynamic Multi-Path Routing and How it Compares with Other Dynamic Routing Algorithms for High Speed Wide Area Networks", Proc. SIGCOMM `92, pp. 53-64, 1992. [BZBH97] Braden, R., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Spec", RFC 2205, September 1997. [C91] C-H. Chow, "On Multicast Path Finding Algorithms", Proceedings of the IEEE INFOCOM `91, pp. 1274-1283, 1991. [CCM96] Castineyra, I., Chiappa, J., and M. Steenstrup, "The Nimrod Routing Architecture", RFC 1992, August 1996. [DEFV94] S. E. Deering, D. Estrin, D. Farinnacci, V. Jacobson, C-G. Liu, and L. Wei, "An Architecture for Wide-Area Multicast Routing", Technical Report, 94-565, ISI, University of Southern California, 1994. [ELRV96] Estrin, D., Li, T., Rekhter, Y., Varadhan, K., and D. Zappala, "Source Demand Routing: Packet Format and Forwarding Specification (Version 1)", RFC 1940, May 1996. [GKR96] R. Gawlick, C. R. Kalmanek, and K. G. Ramakrishnan, "On-Line Routing of Permanent Virtual Circuits", Computer Communications, March, 1996. [GPSS98] A. Ghanwani, J. W. Pace, V. Srinivasan, A. Smith and M. Seaman, "A Framework for Providing Integrated Services over Shared and Switched IEEE 802 LAN Technologies", Work in Progress. [GM79] J. P. Gray, T. B. McNeil, "SNA Multi-System Networking", IBM Systems Journal, 18 No. 2, pp. 263-297, 1979. [GOA97] Y. Goto, M. Ohta and K. Araki, "Path QoS Collection for Stable Hop-by-Hop QoS Routing", Proc. INET '97, June, 1997. Crawley, et. al. Informational [Page 32] RFC 2386 A Framework for QoS-based Routing August 1998 [GKOP98] R. Guerin, S. Kamat, A. Orda, T. Przygienda, and D. Williams, "QoS Routing Mechanisms and OSPF extensions", work in progress, March, 1998. [IBM97] IBM Corp, SNA APPN - High Performance Routing Architecture Reference, Version 2.0, SV40-1018, February 1997. [IPNNI] ATM Forum Technical Committee. Integrated PNNI (I-PNNI) v1.0 Specification. af-96-0987r1, September 1996. [ISI81] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [JMW83] J. M. Jaffe, F. H. Moss, R. A. Weingarten, "SNA Routing: Past, Present, and Possible Future", IBM Systems Journal, pp. 417-435, 1983. [K88] F.P. Kelly, "Routing in Circuit-Switched Networks: Optimization, Shadow Prices and Decentralization", Adv. Applied Prob., pp. 112-144, March, 1988. [L95] W. C. Lee, "Topology Aggregation for Hierarchical Routing in ATM Networks", ACM SIGCOMM Computer Communication Review, 1995. [M86] L. G. Mason, "On the Stability of Circuit-Switched Networks with Non-hierarchical Routing", Proc. 25th Conf. On Decision and Control, pp. 1345-1347, 1986. [M98] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [M94] Moy, J., "MOSPF: Analysis and Experience", RFC 1585, March 1994. [M98] Q. Ma, "Quality-of-Service Routing in Integrated Services Networks", PhD thesis, Computer Science Department, Carnegie Mellon University, 1998. [MMR96] D. Mitra, J. Morrison, and K. G. Ramakrishnan, "ATM Network Design and Optimization: A Multirate Loss Network Framework", Proceedings of IEEE INFOCOM `96, 1996. [MRR80] J. M. McQuillan, I. Richer and E. C. Rosen, "The New Routing Algorithm for the ARPANET", IEEE Trans. Communications, pp. 711-719, May, 1980. Crawley, et. al. Informational [Page 33] RFC 2386 A Framework for QoS-based Routing August 1998 [MS91] D. Mitra and J. B. Seery, "Comparative Evaluations of Randomized and Dynamic Routing Strategies for Circuit Switched Networks", IEEE Trans. on Communications, pp. 102- 116, January, 1991. [MW77] J. M. McQuillan and D. C. Walden, "The ARPANET Design Decisions", Computer Networks, August, 1977. [NC94] Nair, R. and Clemmensen, D. : "Routing in Integrated Services Networks", Proc. 2nd International Conference on Telecom. Systems Modeling and Analysis, March 1994. [P88] R. Perlman, "Network Layer Protocol with Byzantine Robustness", Ph.D. Thesis, Dept. of EE and CS, MIT, August, 1988. [PNNI96] ATM Forum PNNI subworking group, "Private Network-Network Interface Spec. v1.0 (PNNI 1.0)", afpnni-0055.00, March 1996. [R76] H. Rudin, "On Routing and "Delta Routing": A Taxonomy and Performance Comparison of Techniques for Packet-Switched Networks", IEEE Trans. Communications, pp. 43-59, January, 1996. [R92] Y. Rekhter, "IDRP Protocol Analysis: Storage Overhead", ACM Comp. Comm. Review, April, 1992. [R96] B. Rajagopalan, "Efficient Link State Routing", Work in Progress, available from braja@ccrl.nj.nec.com. [RN98] B. Rajagopalan and R. Nair, "Multicast Routing with Resource Reservation", to appear in J. of High Speed Networks, 1998. [SD95] S. Sibal and A. Desimone, "Controlling Alternate Routing in General-Mesh Packet Flow Networks", Proceedings of ACM SIGCOMM, 1995. [SPG97] Shenker, S., Partridge, C., and R. Guerin, "Specification of Guaranteed Quality of Service", RFC 2212, September 1997. [T88] D. M. Topkis, "A k-Shortest-Path Algorithm for Adaptive Routing in Communications Networks", IEEE Trans. Communications, pp. 855-859, July, 1988. [W88] B. M. Waxman, "Routing of Multipoint Connections", IEEE JSAC, pp. 1617-1622, December, 1988. Crawley, et. al. Informational [Page 34] RFC 2386 A Framework for QoS-based Routing August 1998 [W97] Wroclawski, J., "Specification of the Controlled-Load Network Element Service", RFC 2211, September 1997. [WC96] Z. Wang and J. Crowcroft, "QoS Routing for Supporting Resource Reservation", IEEE JSAC, September, 1996. [YS81] T. P. Yum and M. Schwartz, "The Join-Based Queue Rule and its Application to Routing in Computer Communications Networks", IEEE Trans. Communications, pp. 505-511, 1981. [YS87] T. G. Yum and M. Schwartz, "Comparison of Routing Procedures for Circuit-Switched Traffic in Nonhierarchical Networks", IEEE Trans. Communications, pp. 535-544, May, 1987. [ZES97] Zappala, D., Estrin, D., and S. Shenker, "Alternate Path Routing and Pinning for Interdomain Multicast Routing", USC Computer Science Technical Report #97-655, USC, 1997. [ZSSC97] Zhang, Z., Sanchez, C., Salkewicz, B., and E. Crawley, "QoS Extensions to OSPF", Work in Progress. Crawley, et. al. Informational [Page 35] RFC 2386 A Framework for QoS-based Routing August 1998 AUTHORS' ADDRESSES Bala Rajagopalan NEC USA, C&C Research Labs 4 Independence Way Princeton, NJ 08540 U.S.A Phone: +1-609-951-2969 EMail: braja@ccrl.nj.nec.com Raj Nair Arrowpoint 235 Littleton Rd. Westford, MA 01886 U.S.A Phone: +1-508-692-5875, x29 EMail: nair@arrowpoint.com Hal Sandick Bay Networks, Inc. 1009 Slater Rd., Suite 220 Durham, NC 27703 U.S.A Phone: +1-919-941-1739 EMail: Hsandick@baynetworks.com Eric S. Crawley Argon Networks, Inc. 25 Porter Rd. Littelton, MA 01460 U.S.A Phone: +1-508-486-0665 EMail: esc@argon.com Crawley, et. al. Informational [Page 36] RFC 2386 A Framework for QoS-based Routing August 1998 Full Copyright Statement Copyright (C) The Internet Society (1998). All Rights Reserved. This document and translations of it may be copied and furnished to 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 kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. 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