[e2e] TCP fragmentation and reassembly

David Borman david.borman at windriver.com
Fri Dec 9 08:21:02 PST 2005

On Dec 8, 2005, at 1:11 PM, Joe Touch wrote:

> (i.e., it doesn't require 'equal to') I'm suggesting that an
> _additional_ requirement is that TCP be able to support the  
> reassembled
> payload. There's nothing in 1122 that precludes that, and 793  
> implies it.

That already exists.  It's called the receive window.  Or are you  
suggesting that there are TCPs that can't handle packets that fit  
within their receive window?

>> Provided you know for sure which is the incoming interface.  You can
>> always know what interface you are using to send packets, but in many
>> multi-homed situations you can't guarantee on which interface the
>> traffic will arrive.
> You know which ones were used; it might be sufficient to use the lower
> bound of the incoming interfaces that were actually used as a limit
> (lower bound of all interfaces if you haven't received anything).

Not necessarily.  For an outbound connection, you have to put the MSS  
in the initial SYN, so you haven't received any packets yet for that  
connection.  For an inbound connection, yes, you can look at what  
interface the SYN arrived on and use that in determining the MSS  
value to put in the SYN/ACK.

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