Il 2021-10-21 12:02, Nick Hilliard ha scritto:
Hi Stefano,
[spring@ re-added to cc:]
Stefano Salsano wrote on 20/10/2021 22:36:
I can anticipate that it is possible to use wireshark to dissect CSID
packets, by providing very simple configuration information.
This is exactly the problem though - operators will need to manually
instruct a dissector how to interpret the packet contents and that
defeats the purpose of a debugging tool because the tool is supposed to
be able to objectively tell you what's going on, without the operator
having to tell it what's going on.
In particular, if you're attempt to debug a problem relating to C-SID
length, it would be completely useless.
For example, how would you dissect the following sequence of compressed
SIDs of different lengths?
0x53b7e4f4d23b
The short answer is you can't objectively, yet this could be a valid SID
argument.
Hi Nick,
the draft recommends to use a single CSID length (16 bits for NEXT, 32
bits for REPLACE), and if an operator also chooses a single block length
it's very easy to provide the wireshark extensions to dissect all CSID
containers in your domain
if an operator wants to combine CSIDs of different length, building the
debug tools becomes more complex, but this actually depends on the
specific choices and configurations
SRv6 is confined to an operator's domain, so an operator will have to
debug SRv6 packets that have been created by nodes under the control of
the operator and following the configuration choices of the operator
Stefano
There's an opportunity at this point to ensure that whatever compressed
SID mechanism is implemented, that it's done in such a way if difference
lengths of compressed SIDs are allowed, that the SID length is included
in the encoding.
If this isn't done, it will create a mess which operations and support
people will be stuck with for the lifetime of SRv6. Note that this
devalues SRv6 as an infrastructure component.
Nick
--
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Stefano Salsano
Professore Associato
Dipartimento Ingegneria Elettronica
Universita' di Roma Tor Vergata
Viale Politecnico, 1 - 00133 Roma - ITALY
http://netgroup.uniroma2.it/Stefano_Salsano/
E-mail : stefano.sals...@uniroma2.it
Cell. : +39 320 4307310
Office : (Tel.) +39 06 72597770 (Fax.) +39 06 72597435
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