[e2e] IP options inserted in transit

David Borman dab at windriver.com
Thu Aug 7 10:20:16 PDT 2003

> To: Craig Partridge <craig at aland.bbn.com>, end2end-interest at postel.org
> From: "David P. Reed" <dpreed at reed.com>
> Subject: Re: [e2e] IP options inserted in transit
> Date: Thu, 07 Aug 2003 12:16:21 -0400
> and destination addresses).  The options and other fields are not 
> guaranteed to be preserved end-to-end, and shouldn't be expected to remain 
> the same.
> So your proposed idea is consonant with the "spirit" of the IP layer design.
> I do recall a historical argument that encouraged the design where the 
> source created space in the datagram for intermediate processing, because 
> it saved copying and so forth in the intermediate gateways, reducing the 
> performance hit and decreasing the link-level reliability.   It may well be 

Not to mention ensuring that there was enough room in the packet for the
intermediate router to insert the information.  That's what I see as the
biggest issue in Craig's question.  The entire packet could be the
maximum size, not providing any space to insert new options, (or more
rarely, the IP header could already be at the maximum length of 60 bytes)
Other than that, I don't see any problem with IP options being added
and removed by intermediate routers.  I'd view it along the same lines
as encapsulating/decapsulating the packet along the path.

			-David Borman

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