Internet Research Task Force T. Li, Ed.
Internet-Draft Cisco Systems, Inc.
Intended status: Informational July 8, 2007
Expires: January 9, 2008
Design Goals for Scalable Internet Routing
draft-irtf-rrg-design-goals-01
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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.
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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 . . . . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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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.
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
using IP addresses as identifiers. The second requires the
deployment of a 'home agent' to keep track of the mobile entity's
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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 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 change providers with
significantly less disruption.
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.
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
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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
If a solution makes use of a mechanism, it is strongly desired that
the mechanism be a first-class element in the architecture
[FirstClass]. 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.
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 of a routing scheme is the ratio of the maximum length
of the routing path, on which a packet is delivered, to the length
of the shortest path from the source to the destination node, over
all source destination pairs.
[Editor's Note: A better definition of stretch, or a better
reference would be much appreciated. This definition is derived
from [PODC06].]
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
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
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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>.
[PODC06] Konjevod, G., Andrea, R., and D. Xia, "Optimal-Stretch
Name-Independent Compact Routing in Doubling Metrics",
<http://www.public.asu.edu/~dxia2/papers/PODC06.pdf>.
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Author's Address
Tony Li (editor)
Cisco Systems, Inc.
425 East Tasman Dr.
San Jose, CA 95134
USA
Phone: +1 408 853 1494
Email: tli@cisco.com
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