Hi all authors of segment routing,
This is the seventh commens. The issues proposed here are for both SR-TE path
and SR-BE path.
1 1 1 1
S11-----------S12----------S13---------S14---------S15
| | | | |
1| 1| 1| 1| 1|
| | | | |
S21-----------S22----------S23---------S24---------S25
4 4 4 4
Still take the topology in the comment 6 as the example. No matter the loose
explicit path or
the strict explicit path for the loose hop, assume the MTU of the interface is
the same,
since the depth of the label stacks for the primary path and the backup path
are different.
There is the risk that the effetive payload may transmit through the primary
path, but may be
fragmented or dropped in the backup path. As the difference between the label
stacks of the
primary path and the backup path increase, the risk will increase.
From the case, we can deduce that the risk may exists for any scenarios in
which the same traffic
may switch from one SR path to the other SR path. The SR path includes SR-TE
path such as MPLS TE
hotstandby/reoptimization and SR-BE path such as TI-FRR.
Besides above issues, LDP/RSVP-TE can support the path MTU to track the MTU
informaiton along the
LSP through signalling. Then the reasonable MTU info will be adopted in the
ingress node. For both
SR-TE path (if PCE is not used) and SR-BE path, since there is no signalling
to advertise
the information. How to implement the feature? Or there maybe the risk that the
packet may be
dropped by the nodes along the LSP.
Regards,
Robin
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