Fernando,
Il 2020-02-27 10:07, Fernando Gont ha scritto:
Bruno,
On 27/2/20 05:41, bruno.decra...@orange.com wrote:
Fernando,
-----Original Message-----
From: ipv6 [mailto:ipv6-boun...@ietf.org] On Behalf Of Fernando Gont
Sent: Thursday, February 27, 2020 12:45 AM
Hello, Eric,
On 26/2/20 20:18, Eric Vyncke (evyncke) wrote:
Writing this without any hat,
Please note that on the logical side, it still have to be "proven"
that this idea is strictly forbidden by RFC 8200.
Here's the proof part:
1) Isn't IPv6 end to end?
2) How do core components of IPv6, such as AH and PMTUD work in the
present of intermediate nodes that can add and/or remove arbitrary
extension headers?
It should be clear from the above that EH insertion/deletion is
forbidden.
This draft does not propose that intermediate node add extension header.
- If this is not clear to you, please read the draft.
What is this:????
4.16.1. PSP: Penultimate Segment Pop of the SRH
The SRH processing of the End, End.X and End.T behaviors are
modified: after the instruction "S14. Update IPv6 DA with Segment
List[Segments Left]" is executed, the following instructions must be
executed as well:
S14.1. If (Segments Left == 0) {
S14.2. Update the Next Header field in the preceding header to the
Next Header value of the SRH
S14.3. Decrease the IPv6 header Payload Length by the Hdr Ext Len
value of the SRH
S14.4. Remove the SRH from the IPv6 extension header chain
S14.5. }
Isn't this having the penultimate segment fo a packet removing an
extension header for a packet whose Destination Address is not even it's
own?
no, this is a wrong interpretation
the penultimate segment is removing the extension header for a packet
whose Destination Address *is its own address*
Doesn't this read a bit as "the router was the DA of the packet, after
you change the DA to that of the next waypoint, if you realize Segments
Left == 0, remove the SRH"?
(which does not even comply with the now infamous "interpretation" of
RFC8200 that if you are the DA, you can add/remove EHs.
during the processing, as described in the pseudo code, there is an
intermediate step in which the packet *processed inside the router* has
the destination address of the last segment and the router removes the SRH
it is never suggested/allowed in the draft that a router can remove the
SRH from a received packet that does not have a router address as DA
Stefano
- If it's clear, please let's stick to technical comment on _this_
draft. Bringing irrelevant points to the discussion is really not
helping (both the discussion and the argument).
This draft does not propose that intermediate node add/or remove
arbitrary extension header.
This draft, and more specifically the PSP flavor [1], is about
removing the SRH header by an SR EndPoint.
Seriously?
- with regards to PMTUD, can you clarify how reducing the size of the
packet break PMTUD? And if there is an impact, let's remember that
this is the source of the packet which instruct the SR EndPoint to
remove the SRH.
- with regards to AH, the SRH specification explicitly states that the
use of SRH with AH by an SR source node is _not_ defined [2].
Do you understand that AH should be usable for all IPv6 traffic?
[....]
(that's what Errata's are for, after all... and it should be clear that
the EH processing part, overall, needs improvements).
Again, thank you for that, I believe this is useful.
But while this errata is not reviewed and accepted, RFC 8200 stands as
is.
The errata is a clarification, not a change. Of course RFC8200 stands:
EHs are not deleted or added en route to destination.
Thanks,
--
*******************************************************************
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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