Hi Sasha,
Thanks again for your comments and suggestions.
As requested we have added a section indicating that the workings of this draft
can be extended to VRRPv2 as well. We have updated a new version of the draft
as well.
Also for the below point:
“I also think that lack of clarity regarding re-evaluation of the Critical Path
BFD session is both problematic and pretty trivial to resolve before adoption
(at least, we seem to agree that such clarification is necessary).”
[nitisgup] I believe that we have already pointed this out earlier and I would
like to reiterate my point, we have already explained the VRRP state machine
and the changes required in the state machine for VRRP to interface with BFD.
For instance, what you are asking us to put is already there:
(1015) - If a BACKUP ADVERTISEMENT is received, then:
(1020) + If the Priority in the BACKUP ADVERTISEMENT is
zero, then:
(1025) * Remove the Peer from peer table.
(1030) + else: // priority non-zero
(1035) * Update the Peer info in peer table.
(1040) * Recompute the Backup_Down_Interval
(1045) * Reset the Backup_Down_Timer to
Backup_Down_Interval
(1050) + endif // priority in backup advert zero
(1055) + Calculate the Critical_Backup
Thanks,
Nitish
From: Alexander Vainshtein <[email protected]>
Date: Tuesday, January 16, 2018 at 2:03 AM
To: "[email protected]" <[email protected]>
Cc: "[email protected]" <[email protected]>, "[email protected]"
<[email protected]>, "[email protected]" <[email protected]>, "Aditya Dogra
(addogra)" <[email protected]>, "[email protected]"
<[email protected]>, "Nitish Gupta (nitisgup)"
<[email protected]>, "[email protected]" <[email protected]>
Subject: RE: WG adoption poll for draft-nitish-vrrp-bfd-p2p
Colin,
I do not see that VRRPv2 is really abandoned in IPv4 deployments that I see (of
course, my exposure is limited).
I also do not see that VRRPv3 has really added much to VRRPv2 for IPv4.
I also have not seen any vendors announcing end of life/end of support of
VRRPv2 in their implementations. Or did I miss something?
The bottom line: We can “agree to disagree” about this point, and see what
other WG members have to say on this issue.
I also think that lack of clarity regarding re-evaluation of the Critical Path
BFD session is both problematic and pretty trivial to resolve before adoption
(at least, we seem to agree that such clarification is necessary).
My 2c,
Sasha
Office: +972-39266302
Cell: +972-549266302
Email: [email protected]
From: Colin Docherty [mailto:[email protected]] On Behalf Of Colin
Docherty
Sent: Tuesday, January 16, 2018 11:32 AM
To: Alexander Vainshtein <[email protected]>; Nitish Gupta (nitisgup)
<[email protected]>
Cc: [email protected]; [email protected]; [email protected]; Aditya Dogra
(addogra) <[email protected]>; Alexander Vainshtein
<[email protected]>; [email protected]
Subject: Re: WG adoption poll for draft-nitish-vrrp-bfd-p2p
Hi Alexander/Group,
Some replies,
On 16/01/18 08:54, Alexander Vainshtein wrote:
Nitish and all,
Lots of thanks for a prompt and detailed response.
Based on your response I think that some changes to the draft should be made
prior to its adoption by the WG. Some other changes can be safely handled once
the draft becomes a WG document. The details can be found in my comments to
your responses.
I would also like to discuss one more issue that I did not mention in my
original set of comments.
The last statement in Section 5 says:
<quote>
This Draft does not preclude the possibility of the peer table being
populated by means of manual configuration, instead of using the
BACKUP ADVERTISEMENT as defined by the Draft.
<end quote>
I wonder if this statement is sufficient of and by itself for the implementers
of such an option.
If the peer table is populated by manual configuration, and if, say, object
tracking is used to modify priorities of different members of the VRRP group,
priority-based selection of the CRITICAL PATH member becomes more or less
meaningless (because priorities become dynamic). As a consequence, all BACKUP
members of the group would have to monitor their BFD sessions with teh Master
and would treat failure of these sessions as the Master Down event. Once this
happens, they would all sent VRRP Advertisement messages and resolve the
mastership in teh usual VRRP way. I do not see any serious issues with this
approach but it is different from the approach defined in the draft. I wonder
if clarification of this behavior should not be added to the draft. In any
case, this is not a stopper for adopting the draft as a WG document.
If we leave the statement as is then it is open to further expansion in the
future, however I think it would be good to just to focus on the core
functionality, and I don't think its a stopper at this stage.
Hopefully my comments will help.
Here begin my comments to your responses:
-----
1. The draft seems to deal just with VRRPv3 (RFC 5798) while completely
ignoring VRRPv2 (RFC 3768). I wonder if this omission is due to some technical
issue; if not, do the authors plan to extend the draft to cover also VRRPv2 in
future? (The context for this question is that, AFAIK, VRRPv2 is more widely
deployed for IPv4)
[nitisgup] Since VRRPv3 covers First Hop redundancy for both ipv4 and ipv6, We
have taken VRRPv3 as the base for this RFC and the same can be extended to
VRRPv2. We can cover that in future version of the draft.
[Sasha] Taking into account that VRRPv2 is much more widely used with IPv4 than
VRRPv3, I think that at least a declaration of intention to include also VRRPv2
should be done before the draft is adopted.
I strongly disagree with this. Around 2013 when I was developing the initial
BFD/VRRPv3 design, VRRPv2 was been actively deprecated with our team for our
new VRRPv3 implementation. VRRPv2 at that point had already been deprecated
since 2010. I really think it is time to move forward, there is nothing in the
VRRPv2 specification that isn't improved on in VRRPv3. If anything this draft
should serve as an incentive for widespread adoption of VRRPv3 over its
deprecated predecessor. Most implementations have relatively straightforward
upgrade paths for the VRRPv2->VRRPv3 transition.
2. Neither RFC 3768 nor RFC 5798 do not mention a “Master Down event”;
rather they speak about “expiration of the Master_Down_Timer”. However, the
draft uses the term “Master Down event” several times. Can I safely assume that
it is the same as “expiration of the Master_Down_Timer”?
[nitisgup] We have already covered in the Draft, that Master down event is
triggered by either “expiration of the Master_Down_Timer” or
“Critical_BFD_Session going down”. But We will also define it in the section
3.6 of the Draft.
[Sasha] OK with me, can be done after adoption.
Agreed.
3. While neither RFC 3768 nor RFC 5798 mention it, most VRRP
implementations support tracking mechanisms that result in dynamic change of
priorities of VRRP group members. The draft does not discuss what happens when
priority of one of the group members changes. E.g.:
a. Do the backup member that experiences such a change immediately send a
new Backup Advertisement?
[nitisgup] When the VRRP Router Enters the Backup State
it will send a BACKUP ADVERTISEMENT.
b. Is the “Critical Path” re-estimated each time this happens etc.
[nitisgup] Ciritical Path is determined every time an Advert(MASTER/BACKUP) is
received from the PEER, as it will be updated in the PEER table.
[Sasha] From my POV this should be explicitly stated in teh draft before
adoption.
I don't think this needs to be explicitly stated before adoption.
4. Both VRRPv2 and VRRPv3 support no-preemption mode. Please explain what
happens if this mode is set in a VRRP group member whose priority becomes (due
to dynamic changes) higher than that of the current Master?
[nitisgup] We have not changed the Behavior of VRRPv3 with this Draft the, We
have already captured the updated State machine in section 3.6.3, which takes
care of Preempt_Mode of the VRRP router.
[Sasha] My point was that, with preemption mode enabled, some of the BACKUP
members could have higher priority of the current Master. Clarifying that this
does not affect determination of the CRITICAL BFD session would be useful -
could be done after teh draft is adopted.
5. Suppose that the draft is used with VRRPv3 for IPv6. Is the Source
IPv6 address of the Backup Advertisement packet a link-local address of the
interface via which this message is transmitted? (This is explicitly specified
in RFC 5798 for the VRRP Advertisement message, but not specified in the draft)
[nitisgup] We can take care of this in next version of the Draft. [Sasha] OK -
could be done after adoption
Agreed.
6. In the scenario above, will the 1-hop IPv6 BFD session use link-local
IPv6 addresses of the VRRP Master and its primary Backup? (I assume that the
answer is positive, but it would be nice to see this in the draft and not to
leave it for the implementers to guess).
[nitisgup] Same as above we will explicitly mention it. [Sasha] Sams as above
for me too[mage removed by sender. *:) happy]
Agreed.
Regards,
Colin.
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