Re: [mpls] Requesting WG LC for draft-ietf-mpls-rsvp-shared-labels

[Matt Hartley <[e-mail]>]

Pavan,

The problem with lists like this (in general) is that it's not clear what
the status is for anything that isn't on the list, and most lists will
probably manage to omit *something*. I think there's three reasonable
options:

1. State unequivocally that everything works
2. List the functionalities that definitely don't work, and make it clear
that everything else does
3. List the functionalities that definitely work, and explicitly make no
guarantees about anything that isn't listed.

It isn't really clear what you're trying to do here.

Note that in this case option 1 isn't on the table because we've already
established that nnhop FRR requires further extensions.

Cheers

Matt

On Wed, Sep 26, 2018 at 10:17 AM Vishnu Pavan Beeram <[e-mail]>
wrote:

> Alexander Hi!
>
>
>
> The intent of the following statement in Section 1 is certainly not to be
> evasive (slightly or otherwise).
>
>    Functionalities such as bandwidth admission control, LSP
>
>    priorities, preemption, auto-bandwidth and Fast Reroute
>
>    continue to work with this forwarding plane.
>
>
>
> We (the authors) still don’t see any problem with the above statement. But
> we’ll go ahead and make a slight adjustment (see below) to address your
> concern.
>
>    Key functionalities such as bandwidth admission control, LSP
>
>    priorities, preemption, auto-bandwidth and Fast Reroute via
>
>    facility backup protection continue to work with this
>
>    forwarding plane.
>
>
>
> Regards,
>
> -Pavan
>
>
> On Tue, Sep 25, 2018 at 11:34 AM Alexander Okonnikov <
> [e-mail]> wrote:
>
>> Hi Panav,
>>
>> Ok, 1:1 is not to be supported by this approach. In general, 1:1 has its
>> own benefits  - for example, it is more attractive versus N:1 in ring
>> topologies. After all, it is FRR too, as N:1 one. My point was that
>> description in section 1 is slightly evasive regarding FRR and other
>> RSVP-TE properties (PMTUD).
>>
>> Thank you.
>>
>>
>> 16 сент. 2018 г., в 4:38, Vishnu Pavan Beeram <[e-mail]>
>> написал(а):
>>
>> Alexander, Hi!
>>
>>
>> Please see inline for responses (prefixed VPB).
>>
>>
>> Regards,
>> -Pavan
>>
>> On Thu, Sep 13, 2018 at 1:37 PM Alexander Okonnikov <
>> [e-mail]> wrote:
>>
>>> Hi Panav,
>>>
>>> From section 7:
>>>
>>>
>>> "If the label type is a delegation label, then the stacking procedure
>>> stops at that delegation hop."
>>> It is OK for "Stack to Reach Delegation Hop" approach, but it doesn't
>>> work for "Stack to Reach Egress", isn't it?
>>>
>>
>> [VPB] The logic specified in Section 7 could be used by any node
>> constructing the label stack (this could be the ingress or a delegation
>> hop). The sentence immediately following the above quoted sentence in
>> Section 7 is important. It currently reads –
>> Approaches in Section 5.1
>> <https://tools.ietf.org/html/draft-ietf-mpls-rsvp-shared-labels-03#section-5.1>
>> SHOULD be used to determine how the delegation labels are pushed in the
>> label stack.
>>
>>
>> The intent here is to say that if you encounter a delegation label, use
>> the procedures outlined in Section 5.1 to determine how the delegation
>> labels are pushed in the label stack. The following change to the text
>> should address this comment:
>>
>> OLD:
>>
>> If the label type is a delegation label, then the stacking procedure stops at that delegation hop.
>> Approaches in Section 5.1 <https://tools.ietf.org/html/draft-ietf-mpls-rsvp-shared-labels-03#section-5.1> SHOULD be used to determine how the delegation labels are pushed in the label stack.
>>
>>
>> NEW:
>> If the label type is a delegation label, then the type of stacking
>> approach chosen by the ingress for this LSP (Section 5.1) MUST be used to
>> determine how the delegation labels are pushed in the label stack.
>>
>>
>>
>>>
>>> Also, regarding FRR support. Section 1 says:
>>>
>>> "Functionalities such as bandwidth admission control, LSP priorities,
>>> preemption,
>>> auto-bandwidth and Fast Reroute continue to work with this forwarding
>>> plane."
>>> It seems that shared labels approach supports only facility bypass
>>> link-protection. It doesn't support one-to-one link- and node-protection,
>>> per my understanding. Facility bypass node-protection is not supported as
>>> well (as mentioned in Section 8). Hence, FRR support is very limited, and
>>> section 1 needs correction.
>>>
>>
>> [VPB] I don’t see anything wrong with the quoted text. Fast Reroute for
>> MPLS-TE LSPs can be realized by either the 1-to-1 protection mechanism
>> (detours) or the facility bypass mechanism. The authors don’t intend to add
>> procedures for 1-to-1 link/node protection (who needs it?).  The
>> facility bypass link-protection procedure is discussed in this draft. The
>> facility bypass node-protection procedure is discussed in
>> https://tools.ietf.org/html/draft-chandra-mpls-rsvp-shared-labels-np-00
>> (this was presented at the last IETF).
>>
>>
>>>
>>> Thank you.
>>>
>>> 13 сент. 2018 г., в 20:28, Alexander Okonnikov <
>>> [e-mail]> написал(а):
>>>
>>> Hi Panav,
>>>
>>> Questions regarding ETLD:
>>>
>>> The draft is not clear about signaling of ETLD attribute. It says that
>>> ETLD is conveyed as per-hop attribute. Is my understanding correct that it
>>> is conveyed as RRO Hop attribute? Probably it could be cleaned to avoid
>>> confusion whether ERO or RRO Hop attribute mechanism is used.
>>>
>>> Next, the draft says that:
>>>
>>> "... If a node is reached where the ETLD set from the previous hop is 1,
>>> then that
>>> node MUST select itself as the delegation hop.  If a node is reached and
>>> it is
>>> determined that this hop cannot receive more than one transport label,
>>> then that node
>>> MUST select itself as the delegation hop. ..."
>>>
>>> What is purpose of the second sentence/rule?
>>>
>>> Next:
>>>
>>> "If there is a node or a sequence of nodes along the path of the LSP
>>> that do not
>>> support ETLD, then the immediate hop that supports ETLD MUST select
>>> itself as the
>>> delegation hop."
>>>
>>> If some node (consecutive nodes) doesn't support ETLD then it doesn't
>>> support TE labels. Hence, that node (regular RSVP-TE LSR) will do SWAP and
>>> not POP. As a result non-decremented ETLD is OK and immediate hop that
>>> supports ETLD not necessary should become delegation hop?
>>>
>>> Also, from Section 9.7:
>>>
>>> "The ETLD field specifies the maximum number of transport labels that
>>> this hop can potentially send to its downstream hop.  It MUST be set to a
>>> non-zero value."
>>>
>>> Strictly speaking it is not correct. ETLD reflects decrementing counter
>>> and not capability of some transit node. I.e. if we consider LSP R1-R2-R3,
>>> R1 puts value 5 in ETLD,and R2 supports imposing of 2 labels, it doesn't
>>> mean that R2 should rewrite ETLD with value 2. It just should decrement
>>> value 5. Correct?
>>>
>>> Also, per my understanding it is supposed that in fact ETLD value will
>>> not be just decremented, but it will be copied from previous RRO Hop
>>> attributes subobject into being inserted RRO Hop attributes subobject with
>>> decrementing. May be it would be better to signal ETLD value in LSP
>>> Attributes object (and each capable node decrements ETLD value there),
>>> while signaling support of ETLD itself in RRO Hop attributes subobject?
>>>
>>> Thank you.
>>>
>>> 13 сент. 2018 г., в 20:22, Alexander Okonnikov <
>>> [e-mail]> написал(а):
>>>
>>> Hi Pavan,
>>>
>>> I'm sorry for delay with answer.
>>>
>>> If ingress uses regular Path MTU discovery mechanism, it could produce
>>> value of MTU lower than actual one. This is because ingress doesn't know
>>> MTU per each hop. Let's consider case with four routers: R1 - R2 - R3 - R4.
>>> MTU for R1-R2 link is 2000, MTU for R2-R3 is 1600 and MTU for R3-R4 is
>>> 2000. By virtue of regular Path MTU discovery mechanism R1 will derive from
>>> FLOWSPEC that path MTU is 1600. As soon as R1 doesn't know how many labels
>>> in the stack will be on the lowest MTU hop, it can only set LSP MTU to most
>>> conservative value (1600 - 4 - 4 = 1592, provided that R4 has advertised
>>> implicit null label). In fact actual path MTU is 1596 (1600 - 4 on R2-R3
>>> hop). Of course, it could be acceptable, but calculated LSP MTU as more
>>> lower than actual as longer LSP path. For correct path MTU discovery
>>> ingress needs to know MTU per each hop.
>>>
>>> Thank you.
>>>
>>> 6 сент. 2018 г., в 18:27, Vishnu Pavan Beeram <[e-mail]>
>>> написал(а):
>>>
>>> Alexander, Hi!
>>>
>>> I apologize for the delayed response.
>>>
>>> This draft does not propose any changes to the standard RSVP MTU
>>> signaling procedures (Int Serv object specific signaling procedures). After
>>> the initial signaling sequence is complete, an ingress implementation
>>> (RFC3209) would typically take the path MTU learnt via signaling, run it
>>> through some local logic and then arrive at an MTU value that can be
>>> assigned to the LSP. This local logic typically involves deducting the
>>> number of bytes in the label stack used for the LSP from the path MTU
>>> learnt via signaling. The ingress implementation supporting this draft will
>>> rely on the Resv RRO to accurately determine the max-number of labels
>>> pushed along the path of the LSP (note that with delegation, downstream
>>> hops can impose label stacks) and account for it in the local logic used to
>>> arrive at the MTU value assigned to the LSP.
>>>
>>> I hope this addresses your question..
>>>
>>> Regards,
>>> -Pavan
>>>
>>> On Tue, Aug 7, 2018 at 12:22 PM Alexander Okonnikov <
>>> [e-mail]> wrote:
>>>
>>>> Hi Pavan,
>>>>
>>>>
>>>> Regular RSVP-TE LSPs use standard RSVP path MTU discovery mechanism.
>>>> That one cannot be used "as is" for approach described in the draft, and
>>>> the draft doesn't address path MTU identification. Is it to be considered?
>>>>
>>>>
>>>> Thank you.
>>>>
>>>> 26.07.2018 06:07, Vishnu Pavan Beeram пишет:
>>>>
>>>> Chairs, Hi!
>>>>
>>>> As mentioned (in our presentation) in last week's WG session, we
>>>> believe that the draft is sufficiently baked and ready to progress to the
>>>> next stage. We would like to formally request this draft to be considered
>>>> for WG LC.
>>>>
>>>> Regards,
>>>> - Pavan (on behalf of the authors)
>>>>
>>>>
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>>>>
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>>>
>>>
>>>
>>>
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