Subject: [Roll] Issue with MPL Option in IPv6 fragments

From: rabi narayan sahoo <[email-masked]>
Date: Sat, 25 May 2019 16:30:34 +0530

Deal All
As per RFC 7731 MPL Option is carried in MPL Data Messages in an IPv6
Hop-by-Hop Options header, immediately following the IPv6 header.
This option carries sequence number and seed id that will be used by MPL
forwarders in the MPL domain to determine if the received data message
is new or duplicate one.

If an UDP based application sends multicast packet whose payload size is >
1280 bytes (Minimum IPv6 MTU) it will result into of fragmentation of the
IPv6 packet.
As per RFC 8200 hop-by-hop header is part of the Per-fragment-header and
will be same for all the fragments. In this case the fragments of multicast
IPv6 packet will have the same sequence number in the MPL option. Once MPL
forwarder receives any of these fragments it will consider the rest of the
fragments as duplicate
one and drop. This will lead to the loss of the multicast message.

Thanks
Rabi