Subject: Question regarding UDP and IPV6

From: "Vimal Vikrant Vardhan" <[email-masked]>
Date: Sat, 23 Jun 2001 17:44:35 +0500

Hello,

 Would be thanxful if I can get an answer to the following question.

In IPV6, only the source node fragments the packet, and the assembly 
happens at the destination. The fragment size is determined by a 
finding out the MTU on the path - implying that the source now knows 
the route that the packet has to take to reach the destination. My 
doubt is this: Will a datagram in UDP have to traverse a path that is 
discovered before it is sent out (since the source may have to fragment 
the packet)or will it work just like in IPV4 where its route is 
determined by routers between the source & destination? 

In essence, will datagrams exhibit the same behaviour as in the 
previous version of IP?

Regards,
Vimal

---

From: [email-masked]
Date: Sat, 23 Jun 2001 22:47:00 +0900

>In essence, will datagrams exhibit the same behaviour as in the 

	IPv6 UDP works just like IPv4 UDP with DF bit set.

	- first (or a couple of) packets can get dropped due to PMTUD,
	  if you throw packet larger than minimum path MTU.
	- if you would like to avoid PMTUD, you can try sending packet
	  fragmented into minimum link MTU (1280).  there's an API defined for
	  this (see draft-ietf-ipngwg-2292bis-02, section 11.1 and 11.2)

itojun