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Re: Aggregate traffic management

  • From: John Todd
  • Date: Tue Jan 28 18:09:49 2003

It can be done several ways, but the question is "how are you differentiating"?

This is an incomplete list of methods for differentiating, each of which is supported by one or more vendors or open-source solutions:

- destination address
- specific prefix matching
- prefix length matching (.../23, /24, etc.)
- destination AS #
- destination AS path length
- destination (fill in the blank for other BGP or IGP specific tricks)
- source address (see "destination address" for list of possible match criteria)
- protocol (UDP, TCP, ICMP)
- port (source or destination)
- ToS bits
- URL for port 80 traffic
- MAC address of source machine
- amount of throughput to a particular source/destination path

There are even some methods that don't differentiate, but do random traffic distribution (for some highly imperfect value of "random", which I won't debate here.)

- round-robin gateway specification
- DNS round-robin (limited use, usually for servers producing traffic)

If you could be more specific on what your distinguishing method would be for choosing one path over the other, some specific examples could be distilled from this group, I'm sure. <sarcasm> Though, of course, we here in North America don't have to worry ourselves about these issues, and we route everything through our most congested peer. </sarcasm>

Is this simply to get a survey of all possible routing decision concepts, or are you looking for answers only at one layer of the OSI model? You do say "router" in your description, but I'm still uncertain if that is a limiting factor in your question.


Dear NANOGers,

I have a very hands-on question:
Suppose I am a network operator for a decent-sized ISP, and I decide
that I want to "divide" aggregate traffic flowing through a router
toward some destination, in order to then send some of it through one
route and the remainder through another route. Thus, I desire to
enforce some traffic engineering decision.

How would I be able to accomplish this "division"? What technologies
(even if vendor-specific) would I use?
I can think of some methods like prefix-matching classification and
ECMP, but I am still not sure exactly how the latter works in practice
(at the router level) and how one may set them up to achieve such

Thank you for your expertise and lore,

Stanislav Rost <>
Laboratory for Computer Science, MIT

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