Re: [mpls] I-D Action:draft-ietf-mpls-p2mp-lsp-ping-12.txt

Hi Shivakumar:

I did not put the suggested text after discussions with other authors.
The behavior you suggest does not solve the problem of receiving
multiple responses from various bud and tail nodes during traceroute.

As per your suggestion, when T flag is used in a PHP scenario:
- Bud nodes will never respond, even if it is their turn to do so,
- Tail nodes will keep responding to all echo requests where TTL is
greater than their depth.

I am not sure how this behavior can be helpful to traceroute.

The original problem is that bud and tail nodes keep responding to
traceroute requests, for TTL greater than their depth. The extra
responses can be prevented if the nodes check for label expiry. However
without the label, traceroute packets for various TTL values look the
same. If you have a suggestion on how to solve this problem in a PHP
scenario, I will be willing to put it in the draft.

Regards,
Shaleen

-----Original Message-----
From: Shivakumar Channalli [mailto:shivakumar@juniper.net] 
Sent: Tuesday, October 19, 2010 2:00 AM
To: Shaleen Saxena (ssaxena)
Cc: mpls@ietf.org; Nitin Bahadur
Subject: [mpls] I-D Action:draft-ietf-mpls-p2mp-lsp-ping-12.txt

Shaleen,
Please find the mail thread, where in we had a discussed about PHP
scenario.

$hiv...

-----Original Message-----
From: Shivakumar Channalli 
Sent: Tuesday, June 01, 2010 6:17 PM
To: 'Shaleen Saxena (ssaxena)'; Santiago Alvarez (saalvare); Nitin
Bahadur
Cc: mpls@ietf.org
Subject: RE: [mpls] Last Calls on P2MP LSP Ping and Enhanced DS Map

|I will updated the P2MP OAM draft to reflect the PHP scenario.
|
|So does PHP always happen before bud node? Consider the following
|topology:
|
|  H - M1 - B - M2 - T
|
|Here:
| H: Head
| M1, M2: Two mid-point nodes
| B: Bud
| T: Tail

PHP will happen before tail (T i.e pure egress) also.
In the example T is pure egress, so packet should be processed by T, but
in case of B (bud node) it should be dropped.

That's why it should be clearly specified as 

"In p2mp LSP case, if a node (other than ++pure egress++) receives a
+MPLS
LSP trace packet+, without any label, then it should drop the packet
without processing"

In other words, "if a bud node receives a unlabelled packets , then it
should be dropped"

|
|So will both M1 and M2 send out unlabelled packets? Will the TTL of the
|packet cause any different behavior from M1 and M2?

I guess, there should not be any problems as such.

|Also, your suggestion applies to only packets with T bit turned on,
|correct? If it is for all ping/trace packets, then I foresee some
|issues, where certain nodes will never respond.

That's correct. The packets should be dropped only if T bit is set.
Other wise in ping mode of operation, we may not get reply at all if we
apply this rule to all packets.

...$hiv

|-----Original Message-----
|From: Shaleen Saxena (ssaxena) [mailto:ssaxena@cisco.com]
|Sent: Tuesday, June 01, 2010 5:51 PM
|To: Shivakumar Channalli; Santiago Alvarez (saalvare); Nitin Bahadur
|Cc: mpls@ietf.org; Shaleen Saxena (ssaxena)
|Subject: RE: [mpls] Last Calls on P2MP LSP Ping and Enhanced DS Map
|
|Hi Shiv, Nitin,
|
|I will updated the P2MP OAM draft to reflect the PHP scenario.
|
|So does PHP always happen before bud node? Consider the following
|topology:
|
|  H - M1 - B - M2 - T
|
|Here:
| H: Head
| M1, M2: Two mid-point nodes
| B: Bud
| T: Tail
|
|So will both M1 and M2 send out unlabelled packets? Will the TTL of the
|packet cause any different behavior from M1 and M2?
|
|Also, your suggestion applies to only packets with T bit turned on,
|correct? If it is for all ping/trace packets, then I foresee some
|issues, where certain nodes will never respond.
|
|Thanks,
|Shaleen
|
|
|> -----Original Message-----
|> From: Shivakumar Channalli [mailto:shivakumar@juniper.net]
|> Sent: Saturday, May 29, 2010 11:13 AM
|> To: Santiago Alvarez (saalvare); Nitin Bahadur; Shaleen Saxena
|> (ssaxena)
|> Cc: mpls@ietf.org
|> Subject: RE: [mpls] Last Calls on P2MP LSP Ping and Enhanced DS Map
|>
|>
|> |> 1. precluding bud node support
|> Another way is to try to solve bud node issue in case of PHP
|>
|> |> 2. bud node receiving duplicate traffic (label and unlabeled)
|> |> Cheers.
|> Receiving unlabelled packet in case of PHP can be solved by following
|a
|> simple rule.
|>
|> "In p2mp LSP case, if a node (other than pure egress) receives a
+MPLS
|> LSP trace packet+, without any label, then we should drop the packet
|> without processing"
|>
|> Reason: In trace route mode we want packets to reach control plane
due
|> to TTL expiry, but in PHP p2mp mode packets are also received by bud
|> nodes due the PHP. As a result we can make an assumption that, the
|> packet received by control plane is not due to TTL expiry, and drop
|the
|> packets.
|>
|>
|> ...$hiv
|>
|>
|>
|> |-----Original Message-----
|> |From: Santiago Alvarez (saalvare) [mailto:saalvare@cisco.com]
|> |Sent: Saturday, May 29, 2010 6:03 AM
|> |To: Nitin Bahadur; Shaleen Saxena (ssaxena); Shivakumar Channalli
|> |Cc: mpls@ietf.org; Santiago Alvarez (saalvare)
|> |Subject: RE: [mpls] Last Calls on P2MP LSP Ping and Enhanced DS Map
|> |
|> |It seems to me that, in order to find PHP acceptable for P2MP LSPs,
|> one
|> |the these two need to be acceptable:
|> |1. precluding bud node support
|> |2. bud node receiving duplicate traffic (label and unlabeled)
|> |Cheers.
|> |
|> |SA
|> |--
|> |> -----Original Message-----
|> |> From: mpls-bounces@ietf.org [mailto:mpls-bounces@ietf.org] On
|Behalf
|> |Of
|> |> Nitin Bahadur
|> |> Sent: Friday, May 28, 2010 4:52 PM
|> |> To: Shaleen Saxena (ssaxena); Shivakumar Channalli
|> |> Cc: mpls@ietf.org
|> |> Subject: Re: [mpls] Last Calls on P2MP LSP Ping and Enhanced DS
Map
|> |>
|> |>
|> |> Shaleen,
|> |>
|> |> > I was referring to
|> |> > http://tools.ietf.org/html/draft-ietf-mpls-rsvp-te-no-php-oob-
|> |> > mapping-04
|> |>
|> |> This draft does not say that PHP *must not* be used ever for RSVP
|> |P2MP.
|> |> This draft specifies a requirement for non-PHP behavior and solves
|> |that
|> |> problem.
|> |>
|> |> > . Do you have an application where you use PHP? Is P2MP TE
|> |> > with PHP going to be deployed in service provider networks?
|> |>
|> |> Yes...we have customers (in deployment) using P2MP with PHP.
|> |>
|> |> nitin
|> |> _______________________________________________
|> |> mpls mailing list
|> |> mpls@ietf.org
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