Wireshark-dev: Re: [Wireshark-dev] UDP Reassembly issue
From: Guy Harris <[email protected]>
Date: Mon, 20 Nov 2006 12:27:12 -0800
prashanth joshi wrote:

We have written TCP Reasembly code for our GCDR (Prime) parsing.
Do we need to write a UDP Reassembly code also?
The ethereal seems to do a GTP packet parsing when ever it receives data on UDP port. Is not reassembly needed in case of UDP packets?
As Jeff Morriss noted, there's no such thing as UDP reassembly; it's IP 
fragment reassembly.
The IP dissector handles reassembly for you.  TCP is a special case, 
because TCP does not have any notion of packet boundaries - it provides 
a byte-stream service, not a packet service.  Thus, reassembly of PDUs 
sent over TCP requires information from the dissector for the protocol 
being carried atop TCP in order to know how much data is in a PDU.  IP 
is a datagram protocol, and has the notion of packets, so the IP 
dissector can do all the reassembly work itself.