Re: [mpls] working group last call on draft-ietf-mpls-tp-li-lb-01.txt

Stewart Bryant <stbryant@cisco.com> Thu, 12 May 2011 08:01 UTC

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Date: Thu, 12 May 2011 09:01:31 +0100
From: Stewart Bryant <stbryant@cisco.com>
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Subject: Re: [mpls] working group last call on draft-ietf-mpls-tp-li-lb-01.txt
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What is the test that needs to be made and exactly when?

Let's talk MEPs first.

You could get a cc-cv pkt to the remote end by sending it with the right 
TTL, and you can receive any cc-cv pkt from the remote end by examining 
all received pkts.

To do cc-cv during a LB any diagnostics you run in LB need to take that 
into account and that will complicate the diagnostics.

I do not see how you could ever do it with MIPs.

I would think that most users would be content to verify the LSP using 
traceroute/ping/cc-cv then to set LB and run the tests then clear LB and 
re-verify as above.

The above procedure is an applications issue and not a protocol issue, 
and thus does not belong in this document.

The only case that does not seem to be covered is a problem that occurs 
during the LB, but that is a low probability event, and since there is 
no user data being carried  on the LSP under LB user service will not be 
disrupted. In the case of data in the LSP under LB leaking as a result 
of a problem, that is the responsibility of the other LSP to police.

Note that by examining the data received during a LB text the initiator 
of the LB is able to verify that it is their data that is being looped 
back which is equivalent to running a cc-cv.

Thus I do not think that there is any practical problem that needs to be 
addressed in the protocol.

- Stewart


On 12/05/2011 06:03, Sami Boutros wrote:
> To check for mis-connectivity/mis-configuration, you need a cc-cv 
> function not a loopback function.
>
> The loopback function can be used for loss/delay measurements, and 
> this will be addressed in the delay/loss draft.
>
> Thanks,
>
> Sami
> At 07:11 PM 5/10/2011, liu.guoman@zte.com.cn wrote:
>
>> hi, all
>> for this draft, I have a question for Loopback function.
>> in last ietf meeting, IMO, the author sami said this
>> Loopback function is to loopback anything. for MEP point of
>> a LSP, if it is set to Loopback state, it will loopback all received
>> packets including any OAM packet. if so, how to detect 
>> mis-connectivity or
>> mis-configuration for the LSP?
>> in addtion, if it happen mis-connectivity, maybe other LSP packet be 
>> transported to
>> the MEP , and the mep point will still Loopback the wrong packet to 
>> peer mep point,
>> can it affectperformance <app:ds:performance>statistics 
>> <app:ds:statistics> or measurement on the peer mep point?
>>
>> B.R.
>> liu
>>
>>
>>
>>
>>
>>
>> *Loa Andersson <loa@pi.nu>*
>> ·¢¼þÈË:  mpls-bounces@ietf.org
>>
>> 2011-05-10 23:43
>> ÊÕ¼þÈË
>> "mpls@ietf.org" <mpls@ietf.org>
>> ³­ËÍ
>> Ross Callon <rcallon@juniper.net>, MPLS-TP ad hoc team 
>> <ahmpls-tp@lists.itu.int>, draft-ietf-mpls-tp-li-lb@tools.ietf.org
>> Ö÷Ìâ
>> [mpls] working group last call on draft-ietf-mpls-tp-li-lb-01.txt
>>
>>
>>
>>
>> Working Group,
>>
>> this is to start a two week working group last call on
>>
>> draft-ietf-mpls-tp-li-lb-01.txt
>>
>> Please send your comments to the mpls@ietf.org mailing list.
>>
>> This working group last call ends on May 25th.
>>
>> /Loa
>>
>> for the mpls wg co-chairs
>>
>> -- 
>>
>>
>> Loa Andersson                         email: loa.andersson@ericsson.com
>> Sr Strategy and Standards Manager            loa@pi.nu
>> Ericsson Inc                          phone: +46 10 717 52 13
>>                                              +46 767 72 92 13
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