Subject: [PWE3] fragmentation and MTU

From: "Yaakov Stein" <[email-masked]>
Date: Mon, 26 Jun 2006 11:38:15 +0200

Andy, 
 
I just noticed something that is possibly missing in the 
MPLS control protocol extension section of the fragmentation draft.
 
The PW Interface Parameter sub-TLV parameter 0x09
indicates whether a PE supports fragmentation (i.e. can process
the FRG field in the CW, has memory for storage of intermediate packets,
etc)
but there is no indication of the MTU of the AC.

Thus, for an Ethernet PW, we don't know whether a PE specifying
that it can handle fragmentation means that it can swallow a jumbo
frame,
or just reconstruct a regular 1500 byte frame that had to be fragmented
due to the PSN overhead. 

The L2TPv3 section has MRU and MRRU AVPs, but they focus on the PW
packet
(i.e. includes some or all of the L2TP + PSN overheads), rather than the
AC
limitations. Of course for the L2TPv3 case an AC limitation can be
uniquely translated.

Y(J)S

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