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Internet Research Task Force                                  T. Li, Ed.
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Informational                          October 21, 2010
Expires: April 24, 2011


               Design Goals for Scalable Internet Routing
                     draft-irtf-rrg-design-goals-03

Abstract

   It is commonly recognized that the Internet routing and addressing
   architecture is facing challenges in scalability, mobility, multi-
   homing, and inter-domain traffic engineering.  The RRG is designing
   an alternate architecture to meet these challenges.  This document
   consists of a prioritized list of design goals for the architecture.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on April 24, 2011.

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   Copyright (c) 2010 IETF Trust and the persons identified as the
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . . . 3
     1.2.  Priorities  . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  General Design Goals Collected from Past  . . . . . . . . . . . 3
   3.  Design Goals for A New Routing Architecture . . . . . . . . . . 4
     3.1.  Improved routing scalability  . . . . . . . . . . . . . . . 4
     3.2.  Scalable support for traffic engineering  . . . . . . . . . 4
     3.3.  Scalable support for multi-homing . . . . . . . . . . . . . 4
     3.4.  Scalable support for mobility . . . . . . . . . . . . . . . 4
     3.5.  Simplified renumbering  . . . . . . . . . . . . . . . . . . 5
     3.6.  Decoupling location and identification  . . . . . . . . . . 5
     3.7.  First-class elements  . . . . . . . . . . . . . . . . . . . 6
     3.8.  Routing quality . . . . . . . . . . . . . . . . . . . . . . 6
     3.9.  Routing security  . . . . . . . . . . . . . . . . . . . . . 6
     3.10. Deployability . . . . . . . . . . . . . . . . . . . . . . . 7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8




























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1.  Introduction

   It is commonly recognized that the Internet routing and addressing
   architecture is facing challenges in scalability, mobility, multi-
   homing, and inter-domain traffic engineering.  The Routing Research
   Group aims to design an alternate architecture to meet these
   challenges.  This document presents a prioritized list of design
   goals for the architecture.

   These goals should be taken as guidelines for evaluating possible
   architectural solutions.  The expectation is that these goals will be
   applied with good judgment.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

1.2.  Priorities

   Each design goal in this document has been assigned a priority, which
   is one of 'required', 'strongly desired', 'desired', and 'optional'.

   Required:  The solution is REQUIRED to support this goal.

   Strongly desired:  The solution SHOULD support this goal unless there
           exist compelling reasons showing it is unachievable,
           extremely inefficient, or impractical.

   Desired:  The solution SHOULD support this goal.

   Optional:  The solution MAY support this goal.

   It is possible that two design goals at the same priority level may
   be found to be in conflict with one another.  If and when this
   happens, one of them may be subsequently re-prioritized to have the
   two in different priority levels.


2.  General Design Goals Collected from Past

   RFC 1958 [RFC1958] provides an excellent list of the original
   architectural principles of the Internet.  We incorporate them here
   by reference, as part of our desired design goals.






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3.  Design Goals for A New Routing Architecture

3.1.  Improved routing scalability

   Long experience with inter-domain routing has shown us that the
   global BGP routing table is continuing to grow rapidly [BGPGrowth].
   Carrying this large amount of state in the control plane is expensive
   and places undue cost burdens on network participants that do not
   necessarily get value from the increases in the routing table size.
   Thus, the first required goal is to provide significant improvement
   to the scalability of the control plane.  It is strongly desired to
   make the control plane scale independently from the growth of the
   Internet user population.  If a solution includes support for
   alternative routes to support faster convergence, the alternative
   routes should also factor into control plane scalability.

3.2.  Scalable support for traffic engineering

   Traffic engineering is the capability of directing traffic along
   paths other than those that would be computed by normal IGP/EGP
   routing.  Inter-domain traffic engineering today is frequently
   accomplished by injecting more-specific prefixes into the global
   routing table, which results in a negative impact on routing
   scalability.  A scalable solution for inter-domain traffic
   engineering is strongly desired.

3.3.  Scalable support for multi-homing

   Multi-homing is the capability of an organization to be connected to
   the Internet via more than one other organization.  The current
   mechanism for supporting multi-homing is to let the organization
   advertise one or multiple prefixes into the global routing system,
   again resulting in a negative impact on routing scalability.  More
   scalable solutions for multi-homing are strongly desired.

3.4.  Scalable support for mobility

   Mobility is the capability of a host, network, or organization to
   change its topological connectivity with respect to the remainder of
   the Internet, while continuing to receive packets from the Internet.
   Existing mechanisms to provide mobility support include (1)
   renumbering the mobile entity as it changes its topological
   attachment point(s) to the Internet; (2) renumbering and creating a
   tunnel from the entity's new topological location back to its
   original location; and (3) letting the mobile entity announce its
   prefixes from its new attachment point(s).  The first approach alone
   is considered unsatisfactory as the change of IP address may break
   existing transport or higher level connections for those protocols



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   using IP addresses as identifiers.  The second requires the
   deployment of a 'home agent' to keep track of the mobile entity's
   current location and adds overhead to the routers involved, as well
   as adding stretch to the path of inbound packet.  Neither of the
   first two approaches impacts the routing scalability.  The third
   approach, however, injects dynamic updates into the global routing
   system as the mobile entity moves.  Mechanisms that help to provide
   more efficient and scalable mobility support are desired, especially
   when they can be coupled with security, especially privacy, and
   support topological changes at a high-rate.

3.5.  Simplified renumbering

   Today many of the end-sites receive their IP address assignments from
   their Internet Service Providers (ISP).  When such a site changes
   providers, for routing to scale, the site must renumber into a new
   address block assigned by its new ISP.  This can be costly, error-
   prone and painful.  Automated tools, once developed, are expected to
   provide significant help in reducing the renumbering pain.  It is not
   expected that renumbering will be wholly automated, as some manual
   reconfiguration is likely to be necessary for changing the last-mile
   link.  However, the overall cost of this transition should be
   drastically lowered.

   In addition to being configured into hosts and routers, where
   automated renumbering tools can help, IP addresses are also often
   used for other purposes such as access control lists.  They are also
   sometimes hard-coded into applications used in environments where
   failure of the DNS could be catastrophic (e.g. certain remote
   monitoring applications).  Although renumbering may be considered a
   mild inconvenience for some sites, and guidelines have been developed
   for renumbering a network without a flag day [RFC4192], for others,
   the necessary changes are sufficiently difficult so as to make
   renumbering effectively impossible.  It is strongly desired that a
   new architecture allow end-sites to renumber their network with
   significantly less disruption, or, if renumbering can be eliminated,
   the new architecture must demonstrate how the topology can be
   economically morphed to fit the addressing.

3.6.  Decoupling location and identification

   Numerous sources have noted that an IPv4 address embodies both host
   attachment point information and identification information.  This
   overloading has caused numerous semantic collisions that have limited
   the flexibility of the Internet architecture.  Therefore, it is
   desired that a solution separate the host location information
   namespace from the identification namespace.




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   Caution must be taken here to clearly distinguish the decoupling of
   host location and identification information, and the decoupling of
   end-site addresses from globally routable prefixes; the latter has
   been proposed as one of the approaches to a scalable routing
   architecture.  Solutions to both problems, i.e. (1) the decoupling of
   host location and identification information and (2) a scalable
   global routing system (whose solution may, or may not, depend on the
   second decoupling) are required and it is required that their
   solutions are compatible with each other.

3.7.  First-class elements

   In the branch of computer science that is devoted to programming
   language design, there is an explicit notion of a "first-class
   element" in the design.  These are language elements that are fully
   integrated into the language, with clear, consistent, logical and
   natural semantics and obvious interactions with all of the other
   elements in the language [FirstClass].

   For our architectural purposes, it is strongly desired that the
   primary mechanisms in an architecture all be first-class elements.
   More specifically, if a tunneling mechanism is used to provide
   network layering, connectivity virtualization, or a connection-
   oriented mode, then it is strongly desired that the tunneling
   mechanism be a first-class element in the architecture.  This
   requires that the issues of path MTU, reachability, and recursion be
   addressed.

3.8.  Routing quality

   The routing subsystem is responsible for computing a path from any
   point on the Internet to any other point in the Internet.  The
   quality of the routes that are computed can be measured by a number
   of metrics, such as convergence, stability, and stretch.

      The stretch factor is the maximum ratio between the length of a
      route computed by the scheme and that of a shortest path
      connecting the same pair of nodes.  [JACM89]

   A solution is strongly desired to provide routing quality equivalent
   to what is available today or better.

3.9.  Routing security

   Currently, the routing subsystem is secured through a number of
   protocol specific mechanisms of varying strength and applicability.
   Any new architecture is required to provide at least the same level
   of security as is deployed as of when the new architecture is



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   deployed.

3.10.  Deployability

   Since solutions that are not deployable are simply academic
   exercises, solutions are required to be deployable from a technical
   perspective.  Furthermore, given the extensive deployed base of
   today's Internet, a solution is required to be incrementally
   deployable.


4.  IANA Considerations

   This memo includes no requests to IANA.


5.  Security Considerations

   All solutions are required to provide security that is at least as
   strong as the existing Internet routing and addressing architecture.


6.  References

6.1.  Normative References

   [RFC1958]  Carpenter, B., "Architectural Principles of the Internet",
              RFC 1958, June 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4192]  Baker, F., Lear, E., and R. Droms, "Procedures for
              Renumbering an IPv6 Network without a Flag Day", RFC 4192,
              September 2005.

6.2.  Informative References

   [BGPGrowth]
              Huston, G., "BGP Routing Table Analysis Reports",
              <http://bgp.potaroo.net/>.

   [FirstClass]
              "First-class object",
              <http://en.wikipedia.org/wiki/First-class_object>.

   [JACM89]   Peleg, D. and E. Upfal, "A trade-off between space and
              efficiency for routing tables", Journal of the ACM Volume



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              36, Issue 3, July 1989,
              <http://portal.acm.org/citation.cfm?id=65953>.


Author's Address

   Tony Li (editor)
   Cisco Systems, Inc.
   170 W. Tasman Dr.
   San Jose, CA  95134
   USA

   Phone: +1 408 853 9317
   Email: tli@cisco.com





































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