Subject: Fragmentation and reassembly of MPLS packets

From: [email-masked]
Date: Tue, 15 May 2001 13:43:59 +0530

Hi all,

Section 3 of RFC 3032 discusses the procedure for fragmenting the labeled as
well as unlabeled MPLS packet. In IP there are fields in the datagram header
(IDENTIFICATION, FLAGS, and FRAGMENT OFFSET) which control fragmentation and
reassembely of datagrams. But in MPLS header there are no such fields defined.
So how does reassembly of the fragmented MPLS packets happens at the destination
host.

Thanks in advance
Mohit

---

From: "Alok! Tripathi" <[email-masked]>
Date: Tue, 15 May 2001 15:57:44 +0530

> So how does reassembly of the fragmented MPLS packets happens at the destination

Mohit,

As per RFC3032, in case a LSR needs to fragment an IP packet before forwarding,
it strips of its MPLS label stack entries to obtain an IP datagram.
Then the IP fragmentation is done as usual.

Each fragment is then  labelled again with the same header as the orginal one would
have got. This takes
care that all these fragments are forwarded in the same way in the network till
they reach
the destination. At the destination, IP layer shall assemble the packets in the
normal way after all  label
stack entries are popped.

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