Subject: About "extra traffic" and "seperate LSP" in Y.1720

From: lidefeng <[email-masked]>
Date: Tue, 26 Aug 2003 17:16:27 +0800

In section 7.1.4("Switch initiation criteria") of TD25R1(plen) at the ITU-T
SG13 meeting of Geneva,21 July - 1 August 2003(Draft Revised Recommendation
Y.1720 (Protection
switching for MPLS networks)), it notes that "NOTE 1 - A forced switch for
working LSP should not be overridden by a Signal Fail on the protection LSP.
Since unidirectional protection switching is being performed and no APS
protocol is supported over the protection LSP, Signal Fail on the protection
LSP does not interfere with the ability to perform a forced switch for
working LSP."

But if there is a Signal Fail on the protection LSP,how can the protection
LSP work normally,after the traffic on the working LSP is "Forced Switched"
to the protection LSP,then the traffic may be in outage,is there any
detection action or any alarm signal sent before the forced switch?

What is your consideration?

Defeng Li
Huawei Technologies

---

From: "Qureshi, Muhammad A (Akber)" <[email-masked]>
Date: Tue, 26 Aug 2003 11:45:58 -0400

Hi Defeng,

See my comments inline:

Regards,
Akber.

-----Original Message-----
From: lidefeng [mailto:[email-masked]]
Sent: Tuesday, August 26, 2003 5:16 AM
To: [email-masked]
Cc: [email-masked]
Subject: About "extra traffic" and "seperate LSP" in Y.1720

In section 7.1.4("Switch initiation criteria") of TD25R1(plen) at the ITU-T
SG13 meeting of Geneva,21 July - 1 August 2003(Draft Revised Recommendation
Y.1720 (Protection
switching for MPLS networks)), it notes that "NOTE 1 - A forced switch for
working LSP should not be overridden by a Signal Fail on the protection LSP.
Since unidirectional protection switching is being performed and no APS
protocol is supported over the protection LSP, Signal Fail on the protection
LSP does not interfere with the ability to perform a forced switch for
working LSP."
[Akber] This means that when a forced switch is in place (either at the
egress side for 1+1 or ingress side for 1:1) the signal fail condition
on the protection LSP cannot make a switch from the protection to the
working LSP. Further, the note is ellaborating that since there is really no
APS supported on the protection LSP, Signal Fail on the protection
LSP will not any way interfere with forced switch from working to 
protection LSP.

But if there is a Signal Fail on the protection LSP,how can the protection
LSP work normally,after the traffic on the working LSP is "Forced Switched"
to the protection LSP,then the traffic may be in outage,is there any
detection action or any alarm signal sent before the forced switch?
[Akber] When there is a failure on the protection LSP it will be detected
at the sink of the protection LSP (note that the protection LSP is
being monitored independent of the working LSP). Forced switch is a manual
operation and can be avoided when the protection LSP is in fail state.

Defeng Li
Huawei Technologies

---

From: "Qureshi, Muhammad A (Akber)" <[email-masked]>
Date: Tue, 26 Aug 2003 11:05:01 -0400

Hi Defeng,

See my comments inline:

Regards,
Akber.

-----Original Message-----
From: lidefeng [mailto:[email-masked]]
Sent: Tuesday, August 26, 2003 3:48 AM
To: [email-masked]
Cc: [email-masked]
Subject: Re: About "extra traffic" and "seperate LSP" in Y.1720

What traffic belongs to "extra traffic"?
[Akber] Extra traffic can be any traffic with the understanding
that it is using the capacity reserved for protection and in case 
of protection switching will be preempted.

----- Original Message -----
From: "lidefeng" <[email-masked]>
To: <[email-masked]>
Cc: <[email-masked]>
Sent: Tuesday, August 26, 2003 3:44 PM
Subject: About "extra traffic" and "seperate LSP" in Y.1720

> I have some confusion about Y.1720,
>
> 1. What's the relation between "working traffic" and "extra traffic"?
[Akber] In context of 1:1 protection, extra traffic is utilizing the
capacity reserved for protection of the working traffic and in case 
of a failure along the working path will be preempted.
>
> 2. There is a concept "seperate LSP" in Y.1720,is it another LSP different
> from "working LSP" and "protection LSP",as shown in Figure5 and Figure6,if
> that is true,why the extra traffic need to be disconnected to make way for
> the protected traffic from the failed working connection when the working
> traffic is switched over to the protection LSP, as it is stated in section
> 7.1.1.2("Extra traffic" part)?
[Akber] Extra traffic is being carried on a separate LSP as you stated and
is using the reserved protection capacity. After the failure, working traffic
gets switched onto the protection LSP. If extra traffic is not disconnected
then the switched traffic on the protection LSP and the extra traffic on the
separate LSP will compete for the same resources. Therefore, it is recommended 
to disconnect the extra traffic.
>
> Could you please clarify it for me?
>
> Thanks
>
> Defeng Li
> Huawei Technologies
>