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Network Working Group M. Little Request for Comments: 1126 SAIC October 1989 Goals and Functional Requirements for Inter-Autonomous System Routing Status of this Memo This document describes the functional requirements for a routing protocol to be used between autonomous systems. This document is intended as a necessary precursor to the design of a new inter- autonomous system routing protocol and specifies requirements for the Internet applicable for use with the current DoD IP, the ISO IP, and future Internet Protocols. It is intended that these requirements will form the basis for the future development of a new inter- autonomous systems routing architecture and protocol. This document is being circulated to the IETF and Internet community for comment. Comments should be sent to: "open-rout-editor@bbn.com". This memo does not specify a standard. Distribution of this memo is unlimited. 1. Introduction The development of an inter-autonomous systems routing protocol proceeds from those goals and functions seen as both desirable and obtainable for the Internet environment. This document describes these goals and functional requirements. The goals and functional requirements addressed by this document are intended to provide a context within which an inter-autonomous system routing architecture can be developed which will meet both current and future Internet routing needs. The goals presented indicate properties and general capabilities desired of the Internet routing environment and what the inter-autonomous system routing architecture is to accomplish as a whole. The goals are followed by functional requirements, which address either detailed objectives or specific functionality to be achieved by the architecture and resulting protocol(s). These functional requirements are enumerated for clarity and grouped so as to map directly to areas of architectural consideration. This is followed by a listing and description of general objectives, such as robustness, which are applicable in a broad sense. Specific functions which are not reasonably attainable or best left to future efforts are identified as non-requirements. The intent of this document is to provide both the goals and functional requirements in a concise fashion. Supporting arguments, Little [Page 1] RFC 1126 Inter-Autonomous System Routing October 1989 tradeoff considerations and the like have been purposefully omitted in support of this. An appendix has been included which addresses this omission to a limited extent and the reader is directed there for a more detailed discussion of the issues involved. The goals and functional requirements contained in this document are the result of work done by the members of the Open Routing Working Group. It is our intention that these goals and requirements reflect not only those foreseen in the Internet community but are also similar to those encountered in environments proposed by ANSI, ECMA and ISO. It is expected that there will be some interaction and relationship between this work and the product of these groups. 2. Overall Goals In order to derive a set functional requirements there must be one or more principals or overall goals for the routing environment to satisfy. These high level goals provide the basis for each of the functional requirements we have derived and will guide the design philosophy for achieving an inter-autonomous system routing solution. The overall goals we are utilizing are described in the following sections. 2.1 Route to Destination The routing architecture will provide for the routing of datagrams from a single source to one or more destinations in a timely manner. The larger goal is to provide datagram delivery to an identifiable destination, one which is not necessarily immediately reachable by the source. In particular, routing is to address the needs of a single source requiring datagram delivery to one or more destinations. The concepts of multi-homed hosts and multicasting routing services are encompassed by this goal. Datagram delivery is to be provided to all interconnected systems when not otherwise constrained by autonomous considerations. 2.2 Routing is Assured Routing services are to be provided with assurance, where the inability to provide a service is communicated under best effort to the requester within an acceptable level of error. This assurance is not to be misconstrued to mean guaranteed datagram delivery nor does it imply error notification for every lost datagram. Instead, attempts to utilize network routing services when such service cannot be provided will result in requester notification within a reasonable period given persistent attempts. Little [Page 2] RFC 1126 Inter-Autonomous System Routing October 1989 2.3 Large System The design of the architecture, and the protocols within this architecture, should accommodate a large number of routing entities. The exact order of magnitude is a relative guess and the best designs would provide for a practical level of unbounded growth. Nevertheless, the routing architecture is expected to accommodate the growth of the Internet environment for the next 10 years. 2.4 Autonomous Operation The routing architecture is to allow for stable operation when significant portions of the internetworking environment are controlled by disjoint entities. The future Internet environment is envisioned as consisting of a large number of internetworking facilities owned and operated by a variety of funding sources and administrative concerns. Although cooperation between these facilities is necessary to provide interconnectivity, it is viewed that both the degree and type of cooperation will vary widely. Additionally, each of these internetworking facilities desires to operate as independently as possible from the concerns and activities of other facilities individually and the interconnection environment as a whole. Those resources used by (and available for) routing are to be allowed autonomous control by those administrative entities which own or operate them. Specifically, each controlling administration should be allowed to establish and maintain policies regarding the use of a given routing resource. 2.5 Distributed System The routing environment developed should not depend upon a data repository or topological entity which is either centralized or ubiquitous. The growth pattern of the Internet, coupled with the need for autonomous operation, dictates an independence from the topological and administrative centralization of both data and control flows. Past experience with a centralized topology has shown that it is both impractical for the needs of the community and restrictive of administrative freedoms. A distributed routing environment should not be restrictive of either redundancy or diversity. Any new routing environment must allow for arbitrary interconnection between internetworks. 2.6 Provide A Credible Environment The routing environment and services should be based upon mechanisms and information that exhibit both integrity and security. The routing mechanisms should operate in a sound and reliable fashion while the routing information base should provide credible data upon Little [Page 3] RFC 1126 Inter-Autonomous System Routing October 1989 which to base routing decisions. The environment can be unreliable to the extent that the resulting effect on routing services is negligible. The architecture and protocol designs should be such that the routing environment is reasonably secure from unwanted modification or influence. 2.7 Be A Managed Entity Provide a manger insight into the operation of the inter-autonomous system routing environment to support resource management, problem solving, and fault isolation. Allow for management control of the routing system and collect useful information for the internetwork management environment. Datagram events as well as the content and distribution characteristics of relevant databases are of particular importance. 2.8 Minimize Required Resources Any feasible design should restrain the demand for resources required to provide inter-autonomous systems routing. Of particular interest are those resources required for data storage, transmission, and processing. The design must be practical in terms of today's technology. Specifically, do not assume significant upgrades to the existing level of technology in use today for data communication systems. 3. Functional Requirements The functional requirements we have identified have been derived from the overall goals and describe the critical features expected of inter-autonomous system routing. To an extent, these functions are vague in terms of detail. We do not, for instance, specify the quantity or types for quality-of-service parameters. This is purposeful, as the functional requirements specified here are intended to define the features required of the inter-autonomous system routing environment rather than the exact nature of this environment. The functional requirements identified have been loosely grouped according to areas of architectural impact. 3.1 Route Synthesis Requirements Route synthesis is that functional area concerned with both route selection and path determination (identification of a sequence of intermediate systems) from a source to a destination. The functional requirements identified here provide for path determination which is adaptive to topology changes, responsive to administrative policy, cognizant of quality-of-service concerns, and sensitive to an interconnected environment of autonomously managed systems. Little [Page 4] RFC 1126 Inter-Autonomous System Routing October 1989 a) Route around failures dynamically Route synthesis will provide a best effort attempt to detect failures in those routing resources which are currently being utilized. Upon detection of a failed resource, route synthesis will provide a best effort to utilize other available routing resources in an attempt to provide the necessary routing service. b) Provide loop free paths The path provided for a datagram, from source to destination, will be free of circuits or loops most of the time. At those times a circuit or loop exists, it occurs with both negligible probability and duration. c) Know when a path or destination is unavailable Route synthesis will be capable of determining when a path cannot be constructed to reach a known destination. Additionally, route synthesis will be capable of determining when a given destination cannot be determined because the requested destination is unknown (or this knowledge is unavailable). d) Provide paths sensitive to administrative policies Route synthesis will accommodate the resource utilization policies of those administrative entities which manage the resources identified by the resulting path. However, it is inconceivable to accommodate all policies which can be defined by a managing administrative entity. Specifically, policies dependent upon volatile events of great celerity or those which are non-deterministic in nature cannot be accommodated. e) Provide paths sensitive to user policies Paths produced by route synthesis must be sensitive to policies expressed by the user. These user policies are expressed in terms relevant to known characteristics of the topology. The path achieved will meet the requirements stated by the user policy. f) Provide paths which characterize user quality-of-service requirements The characteristics of the path provided should match those indicated by the quality-of-service requested. When Little [Page 5] RFC 1126 Inter-Autonomous System Routing October 1989 appropriate, utilize only those resources which can support the desired quality-of-service (e.g., bandwidth). g) Provide autonomy between inter- and intra-autonomous system route synthesis The inter- and intra-autonomous system routing environments should operate independent of one another. The architecture and design should be such that route synthesis of either routing environment does not depend upon information from the other for successful functioning. Specifically, the inter- autonomous system route synthesis design should minimize the constraints on the intra-autonomous system route synthesis decisions when transiting (or delivering to) the autonomous system. 3.2 Forwarding Requirements The following requirements specifically address the functionality of the datagram forwarding process. The forwarding process transfers datagrams to intermediate or final destinations based upon datagram characteristics, environmental characteristics, and route synthesis decisions. a) Decouple inter- and intra-autonomous system forwarding decisions The requirement is to provide a degree of independence between the inter-autonomous system forwarding decision and the intra- autonomous system forwarding decision within the forwarding process. Though the forwarding decisions are to be independent of each other, the inter-autonomous system delivery process may necessarily be dependent upon intra-autonomous system route synthesis and forwarding. b) Do not forward datagrams deemed administratively inappropriate Forward datagrams according to the route synthesis decision if it does not conflict with known policy. Policy sensitive route synthesis will prevent normally routed datagrams from utilizing inappropriate resources. However, a datagram routed abnormally due to unknown events or actions can always occur and the only way to prohibit unwanted traffic from entering or leaving an autonomous system is to provide policy enforcement within the forwarding function. Little [Page 6] RFC 1126 Inter-Autonomous System Routing October 1989 c) Do not forward datagrams to failed resources A datagram is not to be forwarded to a resource known to be unavailable, notably an intermediate system such as a gateway. This implies some ability to detect and react to resource failures. d) Forward datagram according to its characteristics The datagram forwarding function is to be sensitive to the characteristics of the datagram in order to execute the appropriate route synthesis decision. Characteristics to consider are the destination, quality-of-service, precedence, datagram (or user) policy, and security. Note that some characteristics, precedence for example, affect the forwarding service provided whereas others affect the path chosen. 3.3 Information Requirements This functional area addresses the general information requirements of the routing environment. This encompasses both the nature and disbursal of routing information. The characteristics of the routing information and its disbursal are given by the following functional requirements. a) Provide a distributed and descriptive information base The information base must not depend upon either centralization or exact replication. The content of the information base must be sufficient to support all provided routing functionality, specifically that of route synthesis and forwarding. Information of particular importance includes resource characteristics and resource utilization policies. b) Determine resource availability Provide a means of determining the availability of any utilized resource in a timely manner. The timeliness of this determination is dependent upon the routing service(s) to be supported. c) Restrain transmission utilization The dynamics of routing information flow should be such that a significant portion of transmission resources are not consumed. Routing information flow should adjust to the demands of the environment, the capacities of the distribution facilities utilized, and the desires of the resource manager. Little [Page 7] RFC 1126 Inter-Autonomous System Routing October 1989 d) Allow limited information exchange Information distribution is to be sensitive to administrative policies. An administrative policy may affect the content or completeness of the information distributed. Additionally, administrative policy may determine the extent of information distributed. 3.4 Environmental Requirements The following items identify those requirements directly related to the nature of the environment within which routing is to occur. a) Support a packet-switching environment The routing environment should be capable of supporting datagram transfer within a packet-switched oriented networking environment. b) Accommodate a connection-less oriented user transport service The routing environment should be designed such that it accommodates the model for connection-less oriented user transport service. c) Accommodate 10K autonomous systems and 100K networks This requirement identifies the scale of the internetwork environment we view as appearing in the future. A routing design which does not accommodate this order of magnitude is viewed as being inappropriate. d) Allow for arbitrary interconnection of autonomous systems The routing environment should accommodate interconnectivity between autonomous systems which may occur in an arbitrary manner. It is recognized that a practical solution is likely to favor a given structure of interconnectivity for reasons of efficiency. However, a design which does not allow for and utilize interconnectivity of an arbitrary nature would not be considered a feasible design. 3.5 General Objectives The following are overall objectives to be achieved by the inter- autonomous routing architecture and its protocols. a) Provide routing services in a timely manner Little [Page 8] RFC 1126 Inter-Autonomous System Routing October 1989 Those routing services provided, encapsulated by the requirements stated herein, are to be provided in a timely manner. The time scale for this provision must be reasonable to support those services provided by the internetwork environment as a whole. b) Minimize constraints on systems with limited resources Allow autonomous systems, or gateways, of limited resources to participate in the inter-autonomous system routing architecture. This limited participation is not necessarily without cost, either in terms of responsiveness, path optimization, or other factor(s). c) Minimize impact of dissimilarities between autonomous systems Attempt to achieve a design in which the dissimilarities between autonomous systems do not impinge upon the routing services provided to any autonomous system. d) Accommodate the addressing schemes and protocol mechanisms of the autonomous systems The routing environment should accommodate the addressing schemes and protocol mechanisms of autonomous systems, where these schemes and mechanisms may differ among autonomous systems. e) Must be implementable by network vendors This is to say that the algorithms and complexities of the design must be such that they can be understood outside of the research community and implementable by people other than the designers themselves. Any feasible design must be capable of being put into practice. 4. Non-Goals In view of the conflicting nature of many of the stated goals and the careful considerations and tradeoffs necessary to achieve a successful design, it is important to also identify those goals or functions which we are not attempting to achieve. The following items are not considered to be reasonable goals or functional requirements at this time and are best left to future efforts. These are non-goals, or non-requirements, within the context of the goals and requirements previously stated by this document as well as our interpretation of what can be practically achieved. Little [Page 9] RFC 1126 Inter-Autonomous System Routing October 1989 a) Ubiquity It i 15 r (In) s 0 r (ternet) s 14 r 119 c 0 r (orkshop) s 14 r (in) s 15 r (San) s 0 r (ta) s 0 2529 p (Clara,) s 13 r (Jan) s 0 r (uary) s -3 r 44 c 11 r (1989.) s cmr10.1643-34 @sf 0 2678 p (Estrin) s 1669 r ([P) s 0 r (age) s 14 r (5]) s @eop 4 @bop0 cmbx10.2160-55 @sf [<007FFFF8007FFFF8007FFFF80000FF000000FF000000FF000000FF000000FF000000FF000000FF00FFFFFFF8FFFFFFF8FFFF FFF8E0007F0070007F0038007F001C007F000E007F000F007F0007007F0003807F0001C07F0000E07F0000F07F0000707F00 00387F00001C7F00000E7F00000F7F0000077F000003FF000001FF000000FF000000FF0000007F0000003F0000001F000000 0F0000000700> 32 39 -2 0 34.370] 52 @dc [<00000E00000700000000001F00000F80000000001F00000F80000000001F80001F80000000003F80001FC0000000003F8000 1FC0000000003FC0003FC0000000007FC0003FE0000000007FC0003FE000000000FFE0007FF000000000FFE0007FF0000000 00FFF000FFF000000001FFF000FFB800000001FF7000FFB800000001FF7801FFB800000003FE3801FF1C00000003FE3801FF 1C00000007FE1C03FE1E00000007FC1C03FE0E00000007FC1E07FE0E0000000FFC0E07FC070000000FF80E07FC070000001F F80F0FFC078000001FF0070FF8038000001FF0070FF8038000003FF0039FF003C000003FE0039FF001C000003FE003FFF001 C000007FE001FFE000E000007FC001FFE000E00000FFC000FFE000F00000FF8000FFC000700000FF8000FFC000700001FF80 00FF8000780001FF0000FF8000380001FF0001FF8000380003FE0001FF00001C0003FE0001FF00001C00FFFFF87FFFF807FF F0FFFFF87FFFF807FFF0FFFFF87FFFF807FFF0> 72 41 -1 0 71.065] 87 @dc [<7FFF0FFFE3FFF87FFF0FFFE3FFF87FFF0FFFE3FFF807F000FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007 F000FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007F0 00FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007F000FE003F8007F000 FE003F8007F000FE003F8007F000FE003F80FFFFFFFFFFFF80FFFFFFFFFFFF80FFFFFFFFFFFF8007F000FE00000007F000FE 00000007F000FE00000007F000FE00000007F000FE001E0007F001FE003F0007F001FE007F8007F001FE007F8007F001FE00 7F8003F801FF007F8003FC01FF803F8001FE00FFC01F00007FC0FFF03E00001FFFE3FFFC000003FF807FF000> 56 42 -1 0 57.283] 14 @dc cmr8.1500-13 @sf [<0FE01FF83C3C701C700E600EE00EE00EE00EF01EF81CFFF8EFF0E08070007000781C3C1C1E1C0FF803F0> 16 21 -1 0 17.642] 54 @dc [<0E000E000E000E000E000E0006000700070003000380018001C000E00060C070C038E01C7FFE7FFE7FFE6000> 16 22 -2 0 17.642] 55 @dc cmr6.1500-4 @sf [<1F003FC071C060E0C060C060C060E0E0FFC0FFC0C200600071C039C01FC00F80> 16 16 -1 0 15.220] 54 @dc cmr9.1500-18 @sf [<7F8FE3FC0E0380E00E0380E00E0380E00E0380E00E0380E00E0380E00E0380E00E0380E00E0380E00E0380E00E0380E00E03 80E00E0380E00E0380E0FFFFFFE00E0380000E0380000E0380000E0380000E0380C00E0781E0060781E00703C0E001C370C0 007C1F00> 32 26 0 0 31.997] 14 @dc [<00800100020004000C00080018003000300030006000600060006000E000E000E000E000E000E000E000E000E000E0006000 600060006000300030003000180008000C000400020001000080> 16 38 -3 10 14.932] 40 @dc [<8000400020001000180008000C00060006000600030003000300030003800380038003800380038003800380038003800300 0300030003000600060006000C00080018001000200040008000> 16 38 -2 10 14.932] 41 @dc [<FFFFC00F00F00F00780F003C0F001C0F001E0F001E0F001E0F001E0F001C0F003C0F00380F00F00FFFC00F01E00F00700F00 780F003C0F003C0F003C0F003C0F003C0F00380F00700F00E0FFFF80> 24 26 -1 0 27.195] 66 @dc [<FFC0FFC0> 16 2 0 -7 12.799] 45 @dc [ 1500 ] /cmti9.1500-21 @newfont cmti9.1500-21 @sf [<3E3C7FFEF3F7E0F3E073E07BE078E038E038F03C703C781C383C1E7E0FFE03EE> 16 16 -4 0 19.602] 97 @dc [<700F80780FC0781CC0381EE0380E603C0E603C0F001C07001C07001E0700DE0780CF0380CF8380EFC7807EFF003C7E00> 24 16 -3 0 21.562] 110 @dc [<3E3C007FFE00F3F700E0F300E07300E07B00E07800E03800E03800F03C00703C00781C00383C001E7E000FFE0003EE00000E 00000F00000F00000700000700000780000780000380001F80001F80> 24 26 -4 0 19.602] 100 @dc cmr6.1500-4 @sf [<1C001C001C001C001C001C000C000E000E00060007000380C1C0C0E07FE07FE06000> 16 17 -2 0 15.220] 55 @dc cmr9.1500-18 @sf [<FFFFF80F00780F001C0F000C0F00040F00040F00040F00020F00020F02000F02000F02000F06000FFE000F06000F02000F02 000F02000F00040F00040F00040F000C0F00080F00180F0038FFFFF8> 24 26 -1 0 26.128] 69 @dc [<306078F0F9F0B1608100810081004080408020401830> 16 11 -5 -15 19.198] 92 @dc [<C18020401020102008100810081068D0F9F0F1E060C0> 16 11 -1 -15 19.198] 34 @dc [<0F8030E040704038E038F03CF03C703C003C003C00380038207030602FC0200020002000200020003FC03FE03FF03018> 16 24 -2 0 19.198] 53 @dc 4 @bop1 cmsl10.1643-38 @sf 0 -99 p (RF) s 0 r 67 c 14 r (1125) s 518 r 80 c -1 r (olicy) s 14 r (Requiremen) s 0 r (ts) s 517 r (No) s 0 r 118 c -2 r (em) s -1 r 98 c 0 r (er) s 15 r (1989) s cmbx10.2160-55 @sf 0 45 p 52 c 69 r (Wh) s -1 r 121 c 22 r (the) s 23 r (problem) s 23 r (is) s 22 r (di\016cult) s cmr10.1643-34 @sf 0 186 p (Before) s 18 r (pro) s 1 r (ceeding) s 19 r (with) s 18 r (our) s 18 r (description) s 18 r (of) s 18 r (top) s 1 r (ology) s 18 r (and) s 19 r 112 c 1 r (olicy) s 18 r (requiremen) s 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101 c 20 r (assume) s 21 r (no) s 21 r (global) s 22 r (authorit) s -1 r 121 c -3 r 44 c 21 r (and) s 21 r (no) s 22 r (global) s 21 r 112 c 1 r (olicies,) s 23 r 119 c -1 r 101 c 21 r (recognize) s 21 r (that) s 21 r (com-) s 0 733 p (plete) s 18 r (autonom) s -1 r 121 c 17 r (implies) s 18 r (no) s 17 r (dep) s 2 r (endence) s 17 r (and) s 18 r (therefore) s 18 r (no) s 17 r (comm) s 0 r (unication.) s 27 r (The) s 17 r 109 c 0 r (ulti-organization) s 0 789 p (in) s 0 r (ternets) s 12 r (addressed) s 13 r (here) s 14 r (ha) s -1 r 118 c -1 r 101 c 12 r (inheren) s 0 r 116 c 12 r (regions) s 14 r (of) s 13 r (autonom) s 0 r 121 c -4 r 44 c 13 r (as) s 13 r 119 c 0 r (ell) s 12 r (as) s 13 r (requiremen) s 0 r (ts) s 12 r (for) s 13 r (in) s 0 r (terdep) s 0 r (en-) s 0 846 p (dence.) s 20 r (Our) s 14 r (mec) s 0 r (hanisms) s 13 r (should) s 14 r (allo) s 0 r 119 c 13 r (ADs) s 14 r (to) s 14 r (design) s 14 r (their) s 14 r 98 c 1 r (oundaries,) s 15 r (instead) s 14 r (of) s 14 r (requiring) s 14 r (that) s 14 r (the) s 0 902 p 98 c 1 r (oundaries) s 15 r 98 c 2 r 101 c 15 r (either) s 15 r (imp) s 1 r (enetrable) s 15 r (or) s 16 r (eliminated.) s 71 998 p (One) s 17 r (of) s 18 r (the) s 17 r (most) s 18 r (problematic) s 18 r (asp) s 1 r (ects) s 17 r (of) s 18 r (the) s 18 r 112 c 1 r (olicy) s 17 r (routing) s 18 r (requiremen) s 0 r (ts) s 16 r (iden) s 0 r (ti\014ed) s 17 r (here) s 17 r (is) s 18 r (the) s 0 1054 p (need) s 19 r (to) s 18 r (supp) s 1 r (ort) s 19 r 98 c 1 r (oth) s 19 r (net) s 0 r 119 c -2 r (ork) s 18 r (resource) s 19 r (sharing) s 18 r (and) s 19 r (in) s 0 r (terconnection) s 17 r (across) s 19 r (ADs.) s 30 r (An) s 19 r (example) s 19 r (of) s 0 1111 p (resource) s 16 r (sharing) s 16 r (is) s 17 r 116 c -1 r 119 c -1 r 111 c 15 r (ADs) s 17 r (\(e.g.,) s 16 r (agencies,) s 17 r (divisions,) s 16 r (companies\)) s 16 r (sharing) s 17 r (net) s -1 r 119 c -1 r (ork) s 15 r (resources) s 17 r (\(e.g.,) s 0 1167 p (links,) s 19 r (or) s 18 r (gatew) s 0 r 97 c -2 r (ys) s 17 r (and) s 19 r (links\)) s 18 r (to) s 18 r (tak) s 0 r 101 c 17 r (adv) s -2 r (an) s -1 r (tage) s 17 r (of) s 18 r (economies) s 18 r (of) s 18 r (scale.) s 29 r (Pro) s 0 r (viding) s 17 r (transit) s 18 r (services) s 0 1224 p (to) s 22 r (external) s 22 r (ADs) s 22 r (is) s 22 r (another) s 21 r (example) s 22 r (of) s 22 r (net) s 0 r 119 c -1 r (ork) s 21 r (resource) s 22 r (sharing.) s 40 r (In) s 0 r (terconnection) s 21 r (is) s 21 r (the) s 22 r (more) s 0 1280 p (common) s 19 r (example) s 19 r (of) s 19 r (ADs) s 19 r (in) s 0 r (terconnecting) s 18 r (their) s 19 r (indep) s 2 r (enden) s -1 r (tly) s 19 r (used) s 19 r (net) s -1 r 119 c -1 r (ork) s 18 r (resources) s 19 r (to) s 20 r (ac) s -1 r (hiev) s -1 r 101 c 0 1337 p (connectivit) s 0 r 121 c 14 r (across) s 15 r (the) s 15 r (ADs,) s 15 r (i.e.,) s 15 r (to) s 15 r (allo) s 0 r 119 c 14 r 97 c 15 r (user) s 15 r (in) s 15 r (one) s 15 r (AD) s 15 r (to) s 15 r (comm) s 0 r (unicate) s 14 r (with) s 15 r (users) s 15 r (in) s 15 r (another) s 0 1393 p (AD.) s 19 r (In) s 20 r (some) s 19 r (resp) s 1 r (ects,) s 21 r (net) s -1 r 119 c -1 r (ork) s 19 r (resource) s 19 r (con) s 0 r (trol) s 18 r (is) s 19 r (simpler) s 20 r (than) s 19 r (net) s 0 r 119 c -1 r (ork) s 18 r (in) s 0 r (terconnection) s 18 r (con) s 0 r (trol) s 0 1450 p (since) s 17 r (the) s 17 r 112 c 1 r (oten) s 0 r (tial) s 15 r (dangers) s 17 r (are) s 17 r (few) s -1 r (er) s 16 r (\(i.e.,) s 17 r (denial) s 17 r (of) s 17 r (service) s 17 r (and) s 16 r (loss) s 17 r (of) s 17 r (rev) s 0 r (en) s -2 r (ue) s 16 r (as) s 17 r (compared) s 17 r (with) s 0 1506 p 97 c 20 r (wide) s 19 r (range) s 20 r (of) s 20 r (attac) s -1 r (ks) s 19 r (on) s 20 r (end) s 19 r (systems) s 20 r (through) s 20 r (net) s 0 r 119 c -2 r (ork) s 19 r (in) s 0 r (terconnection\).) s 32 r (Ho) s 0 r 119 c -1 r (ev) s -1 r (er,) s 19 r (con) s 0 r (trolled) s 0 1562 p (net) s 0 r 119 c -2 r (ork) s 16 r (resource) s 16 r (sharing) s 16 r (is) s 16 r (more) s 17 r (di\016cult) s 16 r (to) s 16 r (supp) s 1 r (ort.) s 24 r (In) s 16 r (an) s 16 r (in) s 0 r (ternet) s 15 r 97 c 17 r (pac) s -1 r 107 c -1 r (et) s 15 r (ma) s 0 r 121 c 15 r (tra) s 0 r 118 c -1 r (el) s 15 r (through) s 0 1619 p 97 c 14 r 110 c 0 r (um) s -1 r 98 c 0 r (er) s 14 r (of) s 14 r (transit) s 14 r (ADs) s 15 r (on) s 14 r (its) s 14 r 119 c 0 r 97 c -2 r 121 c 14 r (to) s 14 r (the) s 14 r (destination.) s 20 r (Consequen) s 0 r (tly) s -4 r 44 c 13 r 112 c 2 r (olicies) s 14 r (from) s 14 r (all) s 14 r (transit) s 14 r (ADs) s 0 1675 p 109 c 0 r (ust) s 15 r 98 c 2 r 101 c 16 r (considered) s 17 r (when) s 16 r 97 c 17 r (pac) s 0 r 107 c -2 r (et) s 16 r (is) s 16 r 98 c 2 r (eing) s 16 r (sen) s 0 r (t,) s 16 r (whereas) s 16 r (for) s 17 r (stub-AD) s 17 r (con) s -1 r (trol) s 16 r (only) s 16 r (the) s 17 r 112 c 1 r (olicies) s 17 r (of) s 0 1732 p (the) s 15 r 116 c -1 r 119 c -1 r 111 c 14 r (end) s 14 r 112 c 2 r (oin) s -1 r 116 c 14 r (ADs) s 15 r (ha) s -1 r 118 c -1 r 101 c 14 r (to) s 14 r 98 c 2 r 101 c 14 r (considered.) s 20 r (In) s 15 r (other) s 14 r 119 c 0 r (ords,) s 14 r (con) s 0 r (trolled) s 13 r (net) s 0 r 119 c -1 r (ork) s 13 r (resource) s 15 r (sharing) s 0 1788 p (and) s 13 r (transit) s 13 r (require) s 12 r (that) s 13 r 112 c 2 r (olicy) s 12 r (enforcemen) s 0 r 116 c 12 r 98 c 1 r 101 c 13 r (in) s 0 r (tegrated) s 11 r (in) s 0 r (to) s 12 r (the) s 13 r (routing) s 13 r (proto) s 1 r (cols) s 13 r (themselv) s -1 r (es) s 12 r (and) s 0 1845 p (can) s 15 r (not) s 15 r 98 c 2 r 101 c 15 r (left) s 15 r (to) s 15 r (net) s 0 r 119 c -2 r (ork) s 15 r (con) s -1 r (trol) s 15 r (mec) s -1 r (hanisms) s 14 r (at) s 16 r (the) s 15 r (end) s 15 r 112 c 1 r (oin) s 0 r (ts.) s cmr8.1500-13 @sf 1293 1828 p 54 c 22 r 55 c cmr10.1643-34 @sf 71 1940 p (Complications) s 22 r (also) s 22 r (result) s 22 r (from) s 22 r (the) s 22 r (fact) s 22 r (that) s 22 r (legitimate) s 22 r (users) s 22 r (of) s 22 r (an) s 22 r (AD's) s 23 r (resources) s 22 r (are) s 22 r (not) s 0 1997 p (all) s 21 r (lo) s 1 r (cated) s 21 r (in) s 20 r (that) s 21 r (AD.) s 20 r (Man) s 0 r 121 c 20 r (users) s 21 r (\(and) s 20 r (their) s 21 r (computers\)) s 20 r (who) s 21 r (are) s 21 r (funded) s 20 r 98 c 0 r 121 c -4 r 44 c 21 r (or) s 21 r (are) s 21 r (a\016liated) s 0 2053 p (with,) s 25 r 97 c 22 r (particular) s 23 r (agency's) s 23 r (program) s 22 r (reside) s 23 r (within) s 22 r (the) s 23 r (AD) s 23 r (of) s 22 r (the) s 23 r (user's) s 23 r (univ) s -1 r (ersit) s -1 r 121 c 22 r (or) s 23 r (researc) s -1 r 104 c 0 2093 p 780 2 ru cmr6.1500-4 @sf 52 2120 p 54 c cmr9.1500-18 @sf 69 2136 p (Another) s 13 r (di\013erence) s 13 r (is) s 13 r (that) s 13 r (in) s 13 r (the) s 13 r (in) s 0 r (terconnect) s 12 r (case,) s 13 r (tra\016c) s 13 r (tra) s 0 r 118 c -1 r (eling) s 12 r 111 c 0 r 118 c -2 r (er) s 12 r (AD) s 13 r (A's) s 13 r (net) s 0 r 119 c -1 r (ork) s 12 r (resources) s 13 r (alw) s 0 r 97 c -1 r (ys) s 12 r (has) s 13 r 97 c 0 2181 p (mem) s 0 r 98 c (er) s 11 r (of) s 11 r (AD) s 11 r 65 c 10 r (as) s 11 r (its) s 11 r (source) s 11 r (or) s 11 r (destination) s 11 r (\(or) s 11 r 98 c 1 r (oth\).) s 16 r (Under) s 11 r (resource) s 11 r (sharing) s 11 r (arrangemen) s 0 r (ts) s 9 r (mem) s 0 r 98 c 0 r (ers) s 11 r (of) s 11 r 98 c 1 r (oth) s 11 r (AD) s 11 r 65 c 0 2227 p (and) s 13 r 66 c 13 r (are) s 14 r (connected) s 13 r (to) s 13 r (the) s 13 r (same) s 14 r (resources) s 13 r (and) s 13 r (consequen) s 0 r (tly) s 12 r (in) s 0 r (tra-AD) s 13 r (tra\016c) s 13 r (\(i.e.,) s 13 r (pac) s 0 r 107 c -1 r (ets) s 12 r (sourced) s cmti9.1500-21 @sf 13 r (and) s cmr9.1500-18 @sf 14 r (destined) s 13 r (for) s 0 2272 p (mem) s 0 r 98 c (ers) s 14 r (of) s 13 r (the) s 14 r (same) s 14 r (AD\)) s 14 r (tra) s -1 r 118 c -1 r (els) s 13 r 111 c 0 r 118 c -1 r (er) s 13 r (the) s 13 r (resources.) s 20 r (This) s 14 r (distinction) s 14 r (is) s 13 r (relev) s -1 r (an) s -1 r 116 c 13 r (to) s 14 r (the) s 13 r (writing) s 14 r (of) s 14 r 112 c 1 r (olicies) s 13 r (in) s 14 r (terms) s 0 2318 p (of) s 13 r (principal) s 13 r (a\016liation.) s cmr6.1500-4 @sf 52 2348 p 55 c cmr9.1500-18 @sf 69 2364 p (Economies) s 16 r (of) s 16 r (scale) s 15 r (is) s 16 r (one) s 16 r (motiv) s -1 r (ation) s 15 r (for) s 15 r (resource) s 16 r (sharing.) s 26 r 70 c -2 r (or) s 15 r (example,) s 16 r (instead) s 16 r (of) s 16 r (in) s 0 r (terconnecting) s 15 r (separately) s 0 2409 p (to) s 14 r (sev) s 0 r (eral) s 13 r (indep) s 1 r (enden) s 0 r 116 c 13 r (agency) s 14 r (net) s 0 r 119 c -1 r (orks,) s 13 r 97 c 14 r (campus) s 14 r (net) s 0 r 119 c -1 r (ork) s 13 r (ma) s 0 r 121 c 13 r (in) s 0 r (terconnect) s 12 r (to) s 14 r 97 c 14 r (shared) s 14 r (bac) s 0 r (kb) s 0 r (one) s 14 r (facilit) s 0 r 121 c -3 r 46 c 20 r 84 c -3 r 111 c 1 r (da) s -1 r 121 c -3 r 44 c 0 2455 p (in) s 0 r (terconnection) s 13 r (is) s 15 r (ac) s 0 r (hiev) s -1 r (ed) s 13 r (through) s 15 r 97 c 14 r (com) s 0 r (bination) s 14 r (of) s 14 r (AD) s 15 r (sp) s 1 r (eci\014c) s 14 r (and) s 15 r (shared) s 14 r (arrangemen) s 0 r (ts.) s 21 r 87 c -2 r 101 c 14 r (exp) s 1 r (ect) s 14 r (this) s 15 r (mixed) s 0 2501 p (situation) s 12 r (to) s 12 r 112 c 1 r (ersist) s 11 r (for) s 12 r (\\w) s 0 r (ell-connected") s 11 r (campuses) s 12 r (for) s 11 r (reasons) s 12 r (of) s 12 r 112 c 1 r (olitics,) s 12 r (economics,) s 12 r (and) s 12 r (functionalit) s -1 r 121 c 11 r (\(e.g.,) s 12 r (di\013eren) s 0 r 116 c 0 2546 p 99 c 0 r (haracteristics) s 12 r (of) s 13 r (the) s 12 r (di\013eren) s 0 r 116 c 12 r (agency-net) s 0 r 119 c -1 r (orks\).) s 16 r (See) s 13 r (Section) s 13 r 53 c 12 r (for) s 13 r (more) s 13 r (discussion.) s cmr10.1643-34 @sf 0 2678 p (Estrin) s 1669 r ([P) s 0 r (age) s 14 r (4]) s @eop 3 @bop0 cmbx12.1500-48 @sf [<FFFF800FF8FFFF807FFC07F000FF1E07F001FE0E07F001FC0607F001FC0007F001FC0007F001FC0007F001FC0007F001FC00 07F001FC0007F001FC0007F003FC0007F003F80007F007F80007F01FF00007FFFFC00007FFFFC00007F007F00007F001F800 07F000FC0007F0007E0007F0007F0007F0007F0007F0007F0007F0007F0007F0007F0007F0007F0007F0007E0007F000FC00 07F001F80007F007F000FFFFFFC000FFFFFE0000> 40 34 -2 0 41.798] 82 @dc [<03FC7FC00FFF7FC00FC3FE001F81FE001F80FE001F80FE001F807E001F807E001F807E001F807E001F807E001F807E001F80 7E001F807E001F807E001F807E001F807E001F807E001F807E001F807E00FF83FE00FF83FE00> 32 22 -2 0 31.133] 117 @dc cmr8.1500-13 @sf [<03FE03FE0070007000700070FFFEFFFEE0707070307018701C700E700670077003F001F000F000F00070> 16 21 -1 0 17.642] 52 @dc [<1F807FE0F0F0E070E038E038003800380038607078F07FE06FC060006000600060007FC07FE07FF07030> 16 21 -2 0 17.642] 53 @dc cmr6.1500-4 @sf [<1FE01FE0030003000300FFE0FFE0E300630033003B001B001F000F0007000700> 16 16 -1 0 15.220] 52 @dc [<3F00FFC0E1C0E0E0E0E000E070E079E07FC06F80600060007C007F007F806180> 16 16 -1 0 15.220] 53 @dc cmr9.1500-18 @sf [<C000C000E000600060007000300030003800180018001C000C000C000E00060006000700030003800180018001C000C000C0 00E000600060007000300030003800180018001C000C000C> 16 37 -2 9 19.198] 47 @dc 3 @bop1 cmsl10.1643-38 @sf 0 -99 p (RF) s 0 r 67 c 14 r (1125) s 518 r 80 c -1 r (olicy) s 14 r (Requiremen) s 0 r (ts) s 517 r (No) s 0 r 118 c -2 r (em) s -1 r 98 c 0 r (er) s 15 r (1989) s cmbx12.1500-48 @sf 0 45 p (3.1) s 56 r 80 c -1 r (olicy) s 18 r (Routing) s cmr10.1643-34 @sf 0 170 p (Previous) s 20 r (proto) s 1 r (cols) s 20 r (suc) s 0 r 104 c 19 r (as) s 20 r (the) s 21 r (Exterior) s 20 r (Gatew) s -1 r 97 c -1 r 121 c 19 r (Proto) s 1 r (col) s 21 r (\(EGP\)[) s 0 r 51 c 0 r 93 c 20 r (em) s -1 r 98 c 1 r 111 c 1 r (died) s 20 r 97 c 20 r (limited) s 20 r (notion) s 0 227 p (of) s 17 r 112 c 1 r (olicy) s 17 r (and) s 17 r (ADs.) s 26 r (In) s 17 r (particular,) s 17 r (autonomous) s 17 r (system) s 17 r 98 c 2 r (oundaries) s 17 r (constrained) s 17 r (the) s 17 r (\015o) s -1 r 119 c 16 r (of) s 17 r (routing) s 0 283 p (database) s 20 r (information,) s 21 r (and) s 21 r (only) s 20 r (indirectly) s 20 r (a\013ected) s 20 r (the) s 20 r (\015o) s 0 r 119 c 19 r (of) s 20 r (pac) s 0 r 107 c -1 r (ets) s 19 r (themselv) s -1 r (es.) s 35 r 87 c -3 r 101 c 19 r (consider) s 0 339 p (an) s 15 r (Administrativ) s 0 r 101 c 14 r (Domain) s 15 r (\(AD\)) s 15 r (to) s 16 r 98 c 1 r 101 c 15 r 97 c 15 r (set) s 15 r (of) s 16 r (hosts) s 15 r (and) s 15 r (net) s 0 r 119 c -2 r (ork) s 15 r (resources) s 15 r (\(gatew) s 0 r 97 c -2 r (ys,) s 15 r (links,) s 15 r (etc.\)) s 0 396 p (that) s 12 r (is) s 12 r (go) s 0 r 118 c -1 r (erned) s 11 r 98 c 0 r 121 c 11 r (common) s 12 r 112 c 1 r (olicies.) s 20 r (In) s 12 r (large) s 12 r (in) s 0 r (ternets) s 11 r (that) s 12 r (cross) s 12 r (organization) s 12 r 98 c 2 r (oundaries,) s 12 r (e.g.,) s 13 r (the) s 0 452 p (Researc) s 0 r 104 c 17 r (In) s -1 r (ternet,) s 18 r (in) s 0 r (ter-AD) s 17 r (routes) s 17 r 109 c 0 r (ust) s 17 r 98 c 1 r 101 c 18 r (selected) s 18 r (according) s 18 r (to) s 18 r 112 c 1 r (olicy-related) s 18 r (parameters) s 18 r (suc) s 0 r 104 c 0 509 p (as) s 15 r (cost) s 14 r (and) s 15 r (access) s 15 r (righ) s 0 r (ts,) s 14 r (in) s 14 r (addition) s 15 r (to) s 15 r (the) s 15 r (traditional) s 14 r (parameters) s 15 r (of) s 15 r (connectivit) s 0 r 121 c 13 r (and) s 15 r (congestion.) s 0 565 p (In) s 20 r (other) s 21 r 119 c -1 r (ords,) s 21 r 80 c 0 r (olicy) s 19 r (Routing) s 20 r (\(PR\)) s 21 r (is) s 20 r (needed) s 21 r (to) s 20 r (na) s 0 r (vigate) s 19 r (through) s 20 r (the) s 21 r (complex) s 20 r 119 c 0 r (eb) s 19 r (of) s 20 r 112 c 2 r (olicy) s 0 622 p 98 c 1 r (oundaries) s 18 r (created) s 19 r 98 c -1 r 121 c 17 r 110 c 0 r (umerous) s 17 r (in) s 0 r (terconnected) s 17 r (ADs.) s 29 r (Moreo) s 0 r 118 c -1 r (er,) s 18 r (eac) s -1 r 104 c 17 r (AD) s 18 r (has) s 19 r (its) s 18 r 111 c -1 r (wn) s 18 r (privileges) s 0 678 p (and) s 16 r 112 c 1 r (ersp) s 1 r (ectiv) s 0 r 101 c 15 r (and) s 15 r (therefore) s 16 r 109 c 0 r (ust) s 15 r (mak) s -1 r 101 c 15 r (its) s 16 r 111 c -1 r (wn) s 15 r (ev) s -1 r (aluation) s 14 r (of) s 16 r (legal) s 16 r (and) s 15 r (preferred) s 16 r (routes.) s 22 r (E\013orts) s 0 735 p (are) s 20 r (no) s 0 r 119 c 19 r (underw) s 0 r 97 c -1 r 121 c 19 r (to) s 20 r (dev) s 0 r (elop) s 20 r 97 c 20 r (new) s 20 r (generation) s 20 r (of) s 21 r (routing) s 20 r (proto) s 1 r (col) s 21 r (that) s 20 r (will) s 20 r (allo) s 0 r 119 c 19 r (eac) s 0 r 104 c 19 r (AD) s 21 r (to) s 0 791 p (indep) s 1 r (enden) s 0 r (tly) s 15 r (express) s 15 r (and) s 16 r (enforce) s 16 r 112 c 1 r (olicies) s 16 r (regarding) s 16 r (the) s 15 r (\015o) s 0 r 119 c 15 r (of) s 16 r (pac) s -1 r 107 c -1 r (ets) s 15 r (to,) s 16 r (from,) s 16 r (and) s 15 r (through) s 16 r (its) s 0 847 p (resources[) s 52 c (].) s cmr8.1500-13 @sf 241 831 p 52 c cmr10.1643-34 @sf 71 943 p (The) s 14 r (purp) s 2 r (ose) s 15 r (of) s 14 r (this) s 15 r (pap) s 2 r (er) s 14 r (is) s 15 r (to) s 15 r (articulate) s 15 r (the) s 15 r (requiremen) s 0 r (ts) s 13 r (for) s 15 r (suc) s 0 r 104 c 14 r 112 c 1 r (olicy) s 15 r (based) s 15 r (routing.) s 20 r (Tw) s 0 r 111 c 0 1000 p (critical) s 15 r (assumptions) s 15 r (will) s 15 r (shap) s 2 r 101 c 15 r (the) s 15 r 116 c 0 r (yp) s 0 r 101 c 15 r (of) s 15 r (routing) s 15 r (mec) s 0 r (hanism) s 14 r (that) s 16 r (is) s 15 r (devised:) s cmsy10.1643-36 @sf 68 1132 p 15 c cmr10.1643-34 @sf 23 r (The) s 15 r (top) s 1 r (ological) s 15 r (organization) s 16 r (of) s 15 r (ADs,) s 15 r (and) s cmsy10.1643-36 @sf 68 1226 p 15 c cmr10.1643-34 @sf 23 r (The) s 15 r 116 c 0 r (yp) s 0 r 101 c 15 r (and) s 15 r 118 c -1 r (ariabilit) s -1 r 121 c 14 r (of) s 15 r 112 c 1 r (olicies) s 15 r (expressed) s 15 r 98 c 0 r 121 c 14 r (ADs.) s 0 1359 p 87 c -3 r 101 c 12 r (mak) s 0 r 101 c 12 r (use) s 13 r (of) s 13 r (the) s 13 r 112 c 2 r (olicies) s 13 r (expressed) s 13 r 98 c 0 r 121 c 12 r 111 c -1 r (wners) s 12 r (of) s 13 r (curren) s 0 r 116 c 12 r (Researc) s 0 r 104 c 12 r (In) s 0 r (ternet) s 12 r (resources) s 13 r (and) s 13 r (priv) s -1 r (ate) s 0 1416 p (net) s 0 r 119 c -2 r (orks) s 12 r (connected) s 13 r (to) s 12 r (the) s 13 r (Researc) s 0 r 104 c 11 r (In) s 0 r (ternet) s 12 r (to) s 12 r (generalize) s 13 r 116 c 0 r (yp) s 0 r (es) s 13 r (of) s 12 r 112 c 2 r (olicies) s 12 r (that) s 13 r 109 c 0 r (ust) s 11 r 98 c 2 r 101 c 12 r (supp) s 1 r (orted.) s 0 1472 p (This) s 14 r (top) s 15 r (do) s 0 r (wn) s 13 r (e\013ort) s 14 r 109 c 0 r (ust) s 13 r 98 c 2 r 101 c 14 r (done) s 15 r (with) s 14 r (atten) s 0 r (tion) s 13 r (to) s 14 r (the) s 15 r (tec) s 0 r (hnical) s 13 r (implications) s 14 r (of) s 15 r (the) s 14 r 112 c 1 r (olicy) s 15 r (state-) s 0 1529 p (men) s 0 r (ts) s 11 r (if) s 13 r (the) s 12 r (result) s 12 r (is) s 13 r (to) s 12 r 98 c 2 r 101 c 12 r (useful) s 13 r (in) s 12 r (guiding) s 12 r (tec) s 0 r (hnical) s 12 r (dev) s -1 r (elopmen) s -1 r (t.) s 18 r 70 c -2 r (or) s 11 r (example,) s 13 r (some) s 12 r (ADs) s 13 r (express) s 0 1585 p (the) s 15 r (desire) s 15 r (to) s 16 r (enforce) s 15 r (lo) s 1 r (cal) s 15 r (constrain) s 0 r (ts) s 14 r 111 c 0 r 118 c -1 r (er) s 14 r (ho) s 0 r 119 c 14 r (pac) s 0 r 107 c -2 r (ets) s 15 r (tra) s -1 r 118 c -1 r (el) s 14 r (to) s 16 r (their) s 15 r (destination.) s 20 r (Other) s 15 r (ADs) s 16 r (are) s 0 1642 p (only) s 12 r (concerned) s 13 r (with) s 12 r (prev) s 0 r (en) s -1 r (ting) s 11 r (use) s 13 r (of) s 12 r (their) s 13 r 111 c -1 r (wn) s 12 r (net) s -1 r 119 c -1 r (ork) s 12 r (resources) s 12 r 98 c 0 r 121 c 11 r (restricting) s 13 r (transit.) s 19 r (Still) s 12 r (other) s 0 1698 p (ADs) s 13 r (are) s 13 r (concerned) s 13 r (primarily) s 13 r (with) s 13 r (reco) s 0 r 118 c -2 r (ering) s 12 r (the) s 13 r (exp) s 1 r (ense) s 13 r (of) s 13 r (carrying) s 13 r (tra\016c) s 13 r (and) s 13 r (pro) s 0 r (viding) s 12 r (feedbac) s 0 r 107 c 0 1754 p (to) s 13 r (users) s 13 r (so) s 14 r (that) s 13 r (users) s 13 r (will) s 13 r (limit) s 14 r (their) s 13 r 111 c 0 r (wn) s 12 r (data) s 13 r (\015o) s 0 r (ws;) s 13 r (in) s 13 r (other) s 13 r 119 c 0 r (ords) s 12 r (they) s 13 r (are) s 14 r (concerned) s 13 r (with) s 13 r 99 c 0 r (harg-) s 0 1811 p (ing.) s 20 r 87 c -3 r 101 c 14 r (refer) s 15 r (to) s 14 r (ADs) s 15 r (whose) s 14 r (primary) s 15 r (concern) s 15 r (is) s 14 r (comm) s 0 r (unication) s 14 r (to) s 14 r (and) s 15 r (from) s 15 r (hosts) s 14 r (within) s 15 r (their) s 14 r (AD) s 0 1867 p (as) s cmti10.1643-37 @sf 17 r (stub) s cmr10.1643-34 @sf 16 r (and) s 17 r (to) s 17 r (ADs) s 17 r (whose) s 16 r (primary) s 17 r (concern) s 17 r (is) s 16 r (carrying) s 17 r (pac) s 0 r 107 c -1 r (ets) s 15 r (to) s 17 r (and) s 17 r (from) s 17 r (other) s 16 r (ADs) s 17 r (as) s cmti10.1643-37 @sf 17 r (tr) s -2 r (ansit) s cmr10.1643-34 @sf 0 r 46 c 0 1924 p (If) s 18 r 119 c -1 r 101 c 17 r (address) s 18 r (con) s 0 r (trol) s 16 r (of) s 18 r (transit) s 18 r (alone,) s 18 r (for) s 18 r (example,) s 18 r (the) s 18 r (resulting) s 17 r (mec) s 0 r (hanisms) s 17 r (will) s 18 r (not) s 17 r (necessarily) s 0 1980 p (allo) s 0 r 119 c 14 r (an) s 15 r (AD) s 16 r (to) s 15 r (con) s 0 r (trol) s 14 r (the) s 16 r (\015o) s -1 r 119 c 15 r (of) s 15 r (its) s 15 r (pac) s 0 r 107 c -1 r (ets) s 14 r (from) s 16 r (source) s 15 r (to) s 15 r (destination,) s 16 r (or) s 15 r (to) s 15 r (implemen) s 0 r 116 c 14 r (\015exible) s 0 2037 p 99 c 0 r (harging) s 18 r (sc) s -1 r (hemes.) s cmr8.1500-13 @sf 358 2020 p 53 c cmr10.1643-34 @sf 409 2037 p (Our) s 19 r (purp) s 2 r (ose) s 19 r (is) s 19 r (to) s 18 r (articulate) s 19 r 97 c 19 r (comprehensiv) s 0 r 101 c 18 r (set) s 19 r (of) s 19 r (requiremen) s 0 r (ts) s 18 r (for) s 19 r (PR) s 19 r (as) s 0 2093 p (input) s 15 r (to) s 15 r (the) s 15 r (functional) s 16 r (sp) s 1 r (eci\014cation,) s 15 r (and) s 15 r (ev) s -1 r (aluation,) s 14 r (of) s 15 r (prop) s 1 r (osed) s 15 r (proto) s 2 r (cols.) s 0 2133 p 780 2 ru cmr6.1500-4 @sf 52 2160 p 52 c cmr9.1500-18 @sf 69 2175 p (These) s 18 r (issues) s 17 r (are) s 18 r (under) s 18 r (in) s -1 r 118 c -1 r (estigation) s 17 r 98 c 0 r 121 c 17 r (the) s 17 r (IAB) s 18 r (Autonomous) s 17 r (Net) s 0 r 119 c -1 r (orks) s 17 r (Researc) s 0 r 104 c 16 r (Group) s 18 r (and) s 18 r (the) s 17 r (IAB) s 18 r (Op) s 1 r (en) s 0 2221 p (Routing) s 13 r 87 c -2 r (orking) s 11 r (Group.) s 17 r 70 c -2 r (or) s 12 r (further) s 13 r (information) s 13 r (con) s 0 r (tact) s 11 r (the) s 13 r (author.) s cmr6.1500-4 @sf 52 2251 p 53 c cmr9.1500-18 @sf 69 2267 p (Gene) s 15 r (Tsudik) s 14 r (uses) s 14 r (the) s 15 r (analogy) s 14 r (of) s 15 r (in) s 0 r (ternational) s 13 r (tra) s 0 r 118 c -1 r (el) s 13 r (to) s 15 r (express) s 14 r (the) s 15 r (need) s 14 r (for) s 15 r (source) s 14 r (and) s 15 r (transit) s 14 r (con) s 0 r (trols.) s 21 r (Eac) s 0 r 104 c 0 2312 p (coun) s 0 r (try) s 16 r (expresses) s 16 r (its) s 17 r 111 c 0 r (wn) s 15 r 112 c 1 r (olicies) s 17 r (ab) s 1 r (out) s 17 r (tra) s 0 r 118 c -2 r (el) s 16 r (to) s 17 r (and) s 16 r (through) s 17 r (its) s 16 r (land.) s 29 r 84 c -2 r (ra) s -1 r 118 c -1 r (el) s 15 r (through) s 17 r (one) s 16 r (coun) s 0 r (try) s 16 r (en) s 17 r (route) s 16 r (to) s 0 2358 p (another) s 14 r (is) s 14 r (analogous) s 14 r (to) s 14 r (transit) s 13 r (tra\016c) s 14 r (in) s 14 r (the) s 14 r (net) s 0 r 119 c -1 r (ork) s 13 r 119 c 0 r (orld.) s 19 r 65 c 14 r (tra) s 0 r 118 c -1 r (eler) s 13 r (collects) s 14 r 112 c 1 r (olicy) s 14 r (information) s 14 r (from) s 14 r (eac) s 0 r 104 c 12 r (of) s 14 r (the) s 0 2404 p (coun) s 0 r (tries) s 13 r (of) s 13 r (in) s 0 r (terest) s 13 r (and) s 14 r (plans) s 13 r (an) s 14 r (itinerary) s 14 r (that) s 13 r (conforms) s 14 r (to) s 14 r (those) s 13 r 112 c 1 r (olicies) s 14 r (as) s 14 r 119 c 0 r (ell) s 12 r (as) s 14 r (the) s 14 r (preferences) s 13 r (of) s 14 r (the) s 14 r (tra) s 0 r 118 c -2 r (eler) s 0 2449 p (and) s 13 r (his/her) s 13 r (home) s 12 r (nation.) s 17 r (Th) s 0 r (us) s 12 r (there) s 13 r (is) s 13 r 98 c 1 r (oth) s 13 r (source) s 12 r (and) s 13 r (transit) s 13 r (region) s 13 r (con) s 0 r (trol) s 12 r (of) s 12 r (routing.) s cmr10.1643-34 @sf 0 2678 p (Estrin) s 1669 r ([P) s 0 r (age) s 14 r (3]) s @eop 2 @bop0 cmbx10.2160-55 @sf [<00FFC00007FFF8001FFFFC003F81FF007F00FF807F807F80FFC07FC0FFC03FC0FFC03FE0FFC03FE0FFC03FE07F803FE07F80 3FE01E003FE000003FE000003FC000007FC000007F800000FF000001FE0000FFF80000FFC0000007F0000003FC000001FE00 0000FF000F80FF001FC0FF803FE07F803FE07F803FE07F803FE07F803FE07F803FC0FF001F80FF000FC1FE0007FFFC0003FF F000007FC000> 32 39 -3 0 34.370] 51 @dc [<FFFFFFFE0000FFFFFFFFC000FFFFFFFFF00003FC000FFC0003FC0007FE0003FC0003FE0003FC0001FF0003FC0000FF0003FC 0000FF8003FC0000FF8003FC0000FF8003FC0000FF8003FC0000FF8003FC0000FF8003FC0000FF0003FC0000FF0003FC0001 FE0003FC0001FE0003FC0003FC0003FC0007F00003FFFFFFE00003FFFFFF000003FC007FC00003FC001FE00003FC000FF000 03FC0007F80003FC0003FC0003FC0003FC0003FC0003FE0003FC0001FE0003FC0001FE0003FC0001FE0003FC0003FE0003FC 0003FC0003FC0003FC0003FC0007FC0003FC0007F80003FC001FF000FFFFFFFFE000FFFFFFFF8000FFFFFFFC0000> 48 41 -3 0 48.898] 66 @dc cmr9.1500-18 @sf [<FFF0000F00000F00000F00000F00000F00000F00000F00000F00000F00000F00000F00000FFF800F01E00F00700F00380F00 380F003C0F003C0F003C0F003C0F00380F00380F00700F01E0FFFF80> 24 26 -1 0 26.128] 80 @dc 2 @bop1 cmsl10.1643-38 @sf 0 -99 p (RF) s 0 r 67 c 14 r (1125) s 518 r 80 c -1 r (olicy) s 14 r (Requiremen) s 0 r (ts) s 517 r (No) s 0 r 118 c -2 r (em) s -1 r 98 c 0 r (er) s 15 r (1989) s cmbx10.2160-55 @sf 0 45 p 51 c 69 r (Bac) s -1 r (kground) s cmr10.1643-34 @sf 0 186 p (The) s cmti10.1643-37 @sf 12 r 82 c -1 r (ese) s -3 r (ar) s -2 r (ch) s 12 r (Internet) s cmr8.1500-13 @sf 436 169 p 50 c cmr10.1643-34 @sf 468 186 p (has) s 12 r (ev) s 0 r (olv) s -1 r (ed) s 10 r (from) s 12 r 97 c 12 r (single) s 12 r (bac) s 0 r (kb) s 0 r (one) s 12 r (wide) s 12 r (area) s 12 r (net) s 0 r 119 c -1 r (ork) s 10 r (with) s 12 r (man) s 0 r 121 c 11 r (connected) s 0 242 p (campus) s 16 r (net) s -1 r 119 c -1 r (orks,) s 15 r (to) s 16 r (an) s 16 r (in) s -1 r (ternet) s 15 r (with) s 16 r 109 c -1 r (ultiple) s 15 r (cross-coun) s 0 r (try) s 15 r (bac) s -1 r (kb) s 1 r (ones,) s 15 r (regional) s 16 r (access) s 16 r (net) s 0 r 119 c -2 r (orks,) s 0 299 p (and) s 23 r 97 c 22 r (profusion) s 23 r (of) s 23 r (campus) s 22 r (net) s 0 r 119 c -1 r (orks.) s 41 r 65 c 0 r 116 c 22 r (times) s 23 r (during) s 22 r (its) s 23 r (dev) s 0 r (elopmen) s -2 r 116 c 22 r (the) s 23 r (Researc) s -1 r 104 c 22 r (In) s 0 r (ternet) s 0 355 p (top) s 1 r (ology) s 12 r (app) s 1 r (eared) s 12 r (somewhat) s 12 r 99 c -1 r (haotic.) s 19 r (Ov) s -1 r (erlapping) s 11 r (facilities) s 12 r (and) s 12 r (lateral) s 11 r (\(as) s 12 r (opp) s 1 r (osed) s 12 r (to) s 12 r (hierarc) s -1 r (hical\)) s 0 412 p (connections) s 12 r (seemed) s 13 r (to) s 12 r 98 c 2 r 101 c 12 r (the) s 13 r (rule) s 12 r (rather) s 13 r (than) s 12 r (the) s 13 r (exception.) s 19 r 84 c -3 r 111 c 0 r (da) s 0 r 121 c 12 r (the) s 12 r (Researc) s 0 r 104 c 11 r (In) s 0 r (ternet) s 12 r (top) s 1 r (ology) s 0 468 p (is) s 16 r 98 c 2 r (ecoming) s 16 r (more) s 16 r (regular) s 16 r (through) s 17 r (co) s 1 r (ordination) s 16 r (of) s 16 r (agency) s 17 r (in) s -1 r 118 c -1 r (estmen) s -1 r 116 c 15 r (and) s 16 r (adoption) s 16 r (of) s 17 r 97 c 16 r (hierarc) s 0 r 104 c -2 r 121 c 0 524 p (similar) s 17 r (to) s 16 r (that) s 17 r (of) s 16 r (the) s 17 r (telephone) s 17 r (net) s -1 r 119 c -1 r (orks'.) s 24 r (The) s 16 r (result) s 17 r (is) s 17 r (sev) s -1 r (eral) s 16 r 111 c 0 r 118 c -2 r (erlapping) s 16 r (wide) s 17 r (area) s 16 r (bac) s 0 r (kb) s 0 r (ones) s 0 581 p (connected) s 13 r (to) s 14 r (regional) s 13 r (net) s 0 r 119 c -1 r (orks,) s 12 r (whic) s 0 r 104 c 13 r (in) s 13 r (turn) s 13 r (connect) s 14 r (to) s 13 r (campus) s 14 r (net) s -1 r 119 c -1 r (orks) s 12 r (at) s 14 r (univ) s 0 r (ersities,) s 12 r (researc) s 0 r 104 c 0 637 p (lab) s 1 r (oratories,) s 16 r (and) s 15 r (priv) s -1 r (ate) s 14 r (companies.) s 22 r (Ho) s -1 r 119 c -1 r (ev) s -1 r (er,) s 15 r (the) s 15 r (telephone) s 16 r (net) s -1 r 119 c -1 r (ork) s 15 r (has) s 15 r (lateral) s 16 r (connections) s 15 r (only) s 0 694 p (at) s 18 r (the) s 18 r (highest) s 18 r (lev) s 0 r (el,) s 18 r (i.e.,) s 19 r 98 c 1 r (et) s 0 r 119 c -2 r (een) s 17 r (long) s 18 r (haul) s 18 r (carriers.) s 29 r (In) s 18 r (the) s 19 r (Researc) s -1 r 104 c 17 r (In) s 0 r (ternet) s 17 r (there) s 18 r (exist) s 18 r (lateral) s 0 750 p (connections) s 15 r (at) s 15 r (eac) s 0 r 104 c 14 r (lev) s 0 r (el) s 14 r (of) s 15 r (the) s 15 r (hierarc) s 0 r 104 c -1 r 121 c -4 r 44 c 14 r (i.e.,) s 15 r 98 c 2 r (et) s -1 r 119 c -1 r (een) s 14 r (campus) s 15 r (\(and) s 16 r (regional\)) s 15 r (net) s -1 r 119 c -1 r (orks) s 14 r (as) s 15 r 119 c 0 r (ell.) s 71 846 p (Additional) s 12 r (complexit) s 0 r 121 c 11 r (is) s 13 r (in) s 0 r (tro) s 0 r (duced) s 12 r (in) s 13 r (the) s 12 r (Researc) s 0 r 104 c 12 r (In) s -1 r (ternet) s 12 r 98 c 0 r 121 c 11 r (virtue) s 13 r (of) s 12 r (connections) s 13 r (to) s 12 r (priv) s -1 r (ate) s 0 902 p (net) s 0 r 119 c -2 r (orks.) s 19 r (Man) s 0 r 121 c 13 r (priv) s -2 r (ate) s 13 r (companies) s 13 r (are) s 14 r (connected) s 14 r (to) s 14 r (the) s 13 r (Researc) s 0 r 104 c 13 r (In) s -1 r (ternet) s 13 r (for) s 14 r (purp) s 1 r (oses) s 14 r (of) s 14 r (researc) s -1 r 104 c 0 959 p (or) s 19 r (supp) s 1 r (ort) s 20 r (activities.) s 32 r (These) s 19 r (priv) s -1 r (ate) s 18 r (companies) s 19 r (connect) s 19 r (in) s 20 r (the) s 19 r (same) s 19 r (manner) s 19 r (as) s 20 r (campuses,) s 20 r (via) s 19 r 97 c 0 1015 p (regional) s 15 r (net) s 0 r 119 c -1 r (ork) s 14 r (or) s 15 r (via) s 15 r (lateral) s 15 r (links) s 15 r (to) s 15 r (other) s 15 r (campuses.) s 20 r (Ho) s 0 r 119 c -2 r (ev) s -1 r (er,) s 14 r (man) s 0 r 121 c 14 r (companies) s 15 r (ha) s 0 r 118 c -1 r 101 c 14 r (their) s 15 r 111 c -1 r (wn) s 0 1072 p (priv) s -2 r (ate) s 12 r (wide) s 13 r (area) s 12 r (net) s 0 r 119 c -1 r (orks) s 11 r (whic) s 0 r 104 c 12 r (ph) s 0 r (ysically) s 11 r 111 c 0 r 118 c -1 r (erlap) s 11 r (with) s 13 r (bac) s 0 r (kb) s 0 r (one) s 13 r (and/or) s 12 r (regional) s 13 r (net) s 0 r 119 c -2 r (orks) s 12 r (in) s 13 r (the) s 0 1128 p (researc) s 0 r 104 c 14 r (in) s 0 r (ternet,) s 14 r (i.e.,) s 15 r (priv) s -2 r (ate) s 15 r 118 c -1 r (ertical) s 14 r 98 c 0 r (ypass) s 14 r (links.) s 71 1224 p (Implicit) s 16 r (in) s 16 r (this) s 16 r (complex) s 16 r (top) s 1 r (ology) s 17 r (are) s 16 r (organizational) s 16 r 98 c 1 r (oundaries.) s 23 r (These) s 17 r 98 c 1 r (oundaries) s 16 r (de\014ne) s 16 r (Ad-) s 0 1280 p (ministrativ) s 0 r 101 c 16 r (Domains) s 18 r (\(ADs\)) s 17 r (whic) s 0 r 104 c 16 r (preclude) s 18 r (the) s 18 r (imp) s 1 r (osition) s 17 r (of) s 18 r 97 c 17 r (single,) s 18 r (cen) s 0 r (tralized) s 17 r (set) s 17 r (of) s 18 r 112 c 1 r (olicies) s 0 1337 p (on) s 15 r (all) s 15 r (resources.) s 21 r (The) s 15 r (sub) s 3 r (ject) s 15 r (of) s 15 r (this) s 15 r (pap) s 1 r (er) s 16 r (is) s 15 r (the) s 15 r 112 c 1 r (olicy) s 16 r (requiremen) s -1 r (ts) s 15 r (for) s 15 r (resource) s 15 r (usage) s 15 r (con) s 0 r (trol) s 14 r (in) s 0 1393 p (the) s 15 r (Researc) s 0 r 104 c 14 r (In) s 0 r (ternet.) s 71 1489 p (In) s 16 r (the) s 16 r (remainder) s 16 r (of) s 16 r (this) s 15 r (section) s 16 r 119 c 0 r 101 c 15 r (describ) s 1 r 101 c 16 r (the) s 16 r 112 c 2 ticularly difficult to achieve stability in multi-vendor environments, in large internets, and in environments characterized by a large variation in network characteristics. For these reasons, we believe that it would be a mistake to attempt to achieve effective load-based routing in an Inter-AS Routing scheme. A.6.5 Non-Interference Policies There are policies which are in effect, or desired to be in effect, which are based upon the concept of non-interference. These policies state that the utilization of a given resource is permissible by one party as long as that utilization does not disrupt the current or future utilization of another party. These policies are often of the kind "you may use the excess capacity of my link" without guaranteeing any capacity will be available. The expectation is to be able to utilize the link as needed, perhaps to the exclusion of the other party. The problem with supporting such a policy is the need to be cognizant of highly dynamic state information and the implicit requirement to adapt to these changes. Rapid, persistent, and non-deterministic state changes would lead to routing oscillations and looping. We do not believe it is feasible to support policies based on these considerations in a large internetworking environment based on the current design of IP. Security Considerations Security issues are not addressed in this memo. Little [Page 24] RFC 1126 Inter-Autonomous System Routing October 1989 Author's Address Mike Little Science Applications International Corporation (SAIC) 8619 Westwood Center Drive Vienna, Virginia 22182 Phone: 703-734-9000 EMail: little@SAIC.COM Little [Page 25]