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

Hi,

Again I am not sure that I understand the confusion – if the segment of the LSP is in loopback mode then it should be easy for the source LER to detect either of the misconnectivity conditions that you describe –

1. For the case of messages that are lost due to a misconnectivity between the source LER and the MIP that is looping back – the messages that are lost will not be looped-back, which can be detected by the source LER

2. For the case of messages that are leaking into the segment from a different LSP – this message will be looped back by the MIP and the source LER could detect an excessive message in the stream.

However, as was pointed out in a separate thread – it is advisable to only enter loopback on an LSP that there are no suspected misconnectivities!

Hope this helps,

yaacov

From: ext liu.guoman@zte.com.cn [mailto:liu.guoman@zte.com.cn] 
Sent: Friday, May 13, 2011 4:47 AM
To: Sami Boutros
Cc: draft-ietf-mpls-tp-li-lb@tools.ietf.org; Loa Andersson; mpls@ietf.org; Ross Callon; Weingarten, Yaacov (NSN - IL/Hod HaSharon)
Subject: RE: [mpls] working group last call on draft-ietf-mpls-tp-li-lb-01.txt

sami, yaccov,hi 
firstly i say sorry for not clearly describling my question. 
for the first question, maybe yaacov's understanding be right. if a mep is 
on loopback state, it can't check the e2e path for mis-connectivity because 
the mep point loopback everything including any OAM packet(cc&cv etc); 

for the second question, I know loss/delay measurement should use LM/DM fuction to 
implement it. but for loopback function, there are the following two application: 
  1 To verify bidirectional connectivity of a MEP with a MIP or a peer MEP; 
  2 To perform a bidirectional in-service or out-of-service diagnostics test between a pair of peer MEPs. This includes verifying bandwidth throughput, detecting bit errors, etc; 

so for application 1, loopback anything will not affect verify bidirectional connectivity; but it may affect diagnostics test. 
for example, if mis-connectivity or mis-configuration happened on a LSP path, since the mep of the lsp is under loopback state, it can't check mis-connectivity, 
so the mep of the lsp maybe loopback other data packet of another lsp to the peer mep.or the data pkt of the LSP will be leaked to other LSP path, so it must affect the result of diagnostics test including bandwidth throughput, bit errors. 

maybe i miss something important? 

thank sami and yaacov for prompt replying it. 

B.R. 
Liu

Sami Boutros <sboutros@cisco.com> 

2011-05-13 05:05 

收件人

"Weingarten, Yaacov (NSN - IL/Hod HaSharon)" <yaacov.weingarten@nsn.com>, <liu.guoman@zte.com.cn>, "Loa Andersson" <loa@pi.nu> 

抄送

"Ross Callon" <rcallon@juniper.net>, <mpls@ietf.org>, "MPLS-TP ad hoc team" <ahmpls-tp@lists.itu.int>, <draft-ietf-mpls-tp-li-lb@tools.ietf.org> 

主题

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

Agreed Yaacov, during the period of loopback the cc-cv function can't be performed, and yes the main benefit is of loopback is to measure loss/delay on a segment of a path as you stated.

Thanks,

Sami
At 10:36 PM 5/11/2011, Weingarten, Yaacov (NSN - IL/Hod HaSharon) wrote: 
Sami, hi

My understanding is that the question that was asked is how do you use the cc-cv function to check for mis-connectivity if it is being looped-back.

Truth be told that during the period of loopback you apparently cannot check the e2e path for mis-connectivity, and the operator needs to take this into consideration.  But since the path is not transferring data e2e (it is looping everything back) it is by definition not connected e2e.

What is true is what Sami states this functionality should be used to setup a loss/delay measurement on a segment of a path, and it should be used only for limited periods.

Just my 2cents,
yaacov

From: mpls-bounces@ietf.org [ mailto:mpls-bounces@ietf.org <mailto:mpls-bounces@ietf.org> ] On Behalf Of ext Sami Boutros
Sent: Thursday, May 12, 2011 8:03 AM
To: liu.guoman@zte.com.cn; Loa Andersson
Cc: Ross Callon; mpls@ietf.org; MPLS-TP ad hoc team; draft-ietf-mpls-tp-li-lb@tools.ietf.org
Subject: Re: [mpls] working group last call on draft-ietf-mpls-tp-li-lb-01.txt

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 affect performance <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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