Note as an observer of this discussion:
If we consider that the need for configuration of observer nodes is an
issue, I am pretty sure we need to remember that it is not just the SID
block that needs to be known. The compressed SID length and flavor also
need to be known.
Yours,
Joel
On 4/8/2024 2:36 PM, Robert Raszuk wrote:
Hi Ketan,
a) SR Source Node: the node originating the packet - it may have
an SRH or may skip it (section 4.1)
b) Transit Node: node doing IPv6 forwarding
c) (Ultimate) Destination Node (from RFC8200): the final node to
which the packet is destined
All you said seems true valid, but the above three node categories do
miss a fourth one - randomly plugged sniffer, or any other way to
selectively capture subset of packets for troubleshooting.
I do think this is a bit of an obstacle to require that before such an
analyzer is connected to process live or offline traffic captures it
needs to be configured with given's network's SRv6 dedicated
locator(s) and/or SID blocks.
We clearly do not have such a requirement today for any other
transport protocol.
Maybe this is a good topic for SRv6OPS WG ? I said maybe as there
clearly seems to be a group of folks who say do not care about SRv6 or
CSIDs and would like to continue using same operational tools for
troubleshooting bare IPv6 protocol. Well in the network where both are
running in parallel lacking a clear demux flag seems to make it a bit
of a challenge ... especially if any endpoints talking native SRv6
with uSIDs would also talk native IPv6.
Can you kindly share your perspective on this ?
Cheers,
Robert
The CSID document in section 6.5 does not change or update the
text in RFC8200 sec 8.1. It is simply stating what the "final
destination" is going to be when CSID is used because RFC8200 does
not talk about RHs in sec 8.1. RFC8754 covered this aspect by
specifying that the last segment is the "final destination" but
this needs to be specified when using C-SID (with or without SRH)
and for all C-SID flavors/behaviors.
I find the current text in section 6.5 to be necessary and
sufficient for implementations that claim (or need to) support SR
Source Node behavior for C-SIDs.
The CSID document does not change any behavior at the Transit Node
or for the (Ultimate) Destination Node. Therefore, the discussion
of Transit Nodes is outside the scope of this document - just as
it was outside the scope for RFC8754.
Now, if some "Special Transit Node" wants to go beyond RFC8200 and
do things like upper layer checksum validation enroute then they
can refer to the same text in section 6.5 to first understand CSID
processing and to do what is necessary for their packet processing
enroute. This requires such "Special Transit Nodes" to be aware of
first SRv6 and now C-SID - this is the same for any new packet
encoding technology.
It seems like we are putting the cart before the horse when
raising concerns about existing implementations that are not SRv6
and C-SID aware of not being able to do their processing. Let us
publish the C-SID document so implementers of those "Special
Transit Nodes" (also being referred to as middleboxes on some
threads) have a reference to upgrade for C-SID support.
Finally, I’ve not heard of issues related to these "Special
Transit Nodes" from operators that have deployed SRv6. That may be
a good discussion to have (again outside the scope of this
document and perhaps in srv6ops?) - so operators who have SRv6
deployment experience can share their learnings and best practices.
Thanks,
Ketan
On Thu, Mar 28, 2024 at 5:34 PM Alvaro Retana
<aretana.i...@gmail.com> wrote:
Section 6.5 of draft-ietf-spring-srv6-srh-compression
describes the
behavior when an originating node inside an SRv6 domain creates a
packet with a C-SID as the final destination. This description
differs
from the text in Section 8.1 of RFC8200.
We plan to send the draft to the 6man WG for review and explicitly
highlight this difference.
Please comment on the text in Section 6.5. Does anything need
to be
added, deleted, changed, or clarified?
We want to ask for feedback soon; please send comments on this
topic
by April 5th.
Thanks!
Alvaro.
-- for spring-chairs
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