Aggregate traffic management

Tue Jan 28 23:04:38 UTC 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.

JT

>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
>load-sharing.
>
>Thank you for your expertise and lore,
>
>--
>Stanislav Rost <stanrost at lcs.mit.edu>
>Laboratory for Computer Science, MIT