[e2e] IP options

Fred Baker fred at cisco.com
Thu May 3 12:59:56 PDT 2001

At 08:51 PM 5/3/2001 +0200, Stefaan De Cnodder wrote:
>Does someone know whether IP options are used a lot today? Does there
>exist measurements showing the fraction of packets carying IP options in
>the Internet.

options are not heavily used today. Note I did not say "not used", I said 
"not heavily used".

Reason: much equipment that constitutes parts of the backbone today is 
Cisco 7500, 7200, 7000, and lower equipment. This equipment kicks all 
traffic having IP options out of its fast path and into the slowest 
processing path in the system. This is also how packet fragmentation is 
handled, and anything else more complicated than "pick a next hop, put the 
appropriate link layer header on it, and pitch it out."

The Cisco GSR and (I understand) the Juniper M40 are a bit more 
enlightened. They retain the capability of pitching things to the process 
path, but they do attempt to handle known options that require 
straightforward processing in the fast path.

If you plan to propose a new option that would require hardware or firmware 
support, though, think in terms of product managers saying "show me the 
business case" before starting a hardware spin.

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