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

[Shivakumar Channalli <[e-mail]>]

Shaleen,

For tail nodes we don't get 2 copies of the same packet unlike bud
nodes.
Its just a particular case of bud nodes that we have to solve here.



$hiv...



|-----Original Message-----
|From: Shaleen Saxena (ssaxena) [mailto:[e-mail]]
|Sent: Wednesday, October 20, 2010 9:59 PM
|To: Shivakumar Channalli
|Cc: [e-mail]; Nitin Bahadur; Shaleen Saxena (ssaxena)
|Subject: RE: [mpls] I-D Action:draft-ietf-mpls-p2mp-lsp-ping-12.txt
|
|Hi,
|
|I understand your PHP usage better now. However changing the behavior
of
|T bit will not prevent multiple responses from tail nodes. If you plan
|to use Responder Identifier TLV to limit that, then it will work for
bud
|nodes as well (unless bud node itself is the target). So changing the
|behavior of the T bit for PHP is only a partial solution to the
problem.
|
|Shaleen
|
|
|-----Original Message-----
|From: Shivakumar Channalli [mailto:[e-mail]]
|Sent: Tuesday, October 19, 2010 8:41 AM
|To: Shaleen Saxena (ssaxena)
|Cc: [e-mail]; Nitin Bahadur
|Subject: RE: [mpls] I-D Action:draft-ietf-mpls-p2mp-lsp-ping-12.txt
|
|Shaleen,
|
|||  H - M1 - B - M2 - T
|||
|||Here:
||| H: Head
||| M1, M2: Two mid-point nodes
||| B: Bud
||| T: Tail
|
||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,
|
|Let me explain it again. If a packet is sent with TTL 2
|Bud node B receives 2 packets:
|1) Labeled packet, due to TTL expiry (for which it would normally
|perform a  swap and send it to M2)
|2) unlabelled packet, which arrives due to PHP done at M1
|
|The suggestion is to drop the unlabelled packet(2) at bud, if "TTL
|expiry flag" is set, because it landed in B due to PHP done at M1, not
|due to label TTL expiry.
|
|
||- 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.
|
|Tail nodes will always get a single copy of the packet unlike bud
nodes.
|
|More ever, if the responder-id tlv is present a node would never
respond
|back, unless the criterions for responder-id tlv are met correctly.
|
|
||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.
|
|
|This problem can be solved by dropping +unlabelled packets+ at +bud
|node+, if TTL expiry flag is set in the request.
|
|
|
|
|$hiv...
|
|
|
||-----Original Message-----
||From: Shaleen Saxena (ssaxena) [mailto:[e-mail]]
||Sent: Tuesday, October 19, 2010 5:08 PM
||To: Shivakumar Channalli
||Cc: [e-mail]; Nitin Bahadur; Shaleen Saxena (ssaxena)
||Subject: RE: [mpls] I-D Action:draft-ietf-mpls-p2mp-lsp-ping-12.txt
||
||Hi Shivakumar:
||
||I did not put the suggested text after discussions with other authors.
||The behavior you suggest does not solve the problem of receiving
||multiple responses from various bud and tail nodes during traceroute.
||
||As per your suggestion, when T flag is used in a PHP scenario:
||- Bud nodes will never respond, even if it is their turn to do so,
||- Tail nodes will keep responding to all echo requests where TTL is
||greater than their depth.
||
||I am not sure how this behavior can be helpful to traceroute.
||
||The original problem is that bud and tail nodes keep responding to
||traceroute requests, for TTL greater than their depth. The extra
||responses can be prevented if the nodes check for label expiry.
However
||without the label, traceroute packets for various TTL values look the
||same. If you have a suggestion on how to solve this problem in a PHP
||scenario, I will be willing to put it in the draft.
||
||Regards,
||Shaleen
||
||-----Original Message-----
||From: Shivakumar Channalli [mailto:[e-mail]]
||Sent: Tuesday, October 19, 2010 2:00 AM
||To: Shaleen Saxena (ssaxena)
||Cc: [e-mail]; Nitin Bahadur
||Subject: [mpls] I-D Action:draft-ietf-mpls-p2mp-lsp-ping-12.txt
||
||Shaleen,
||Please find the mail thread, where in we had a discussed about PHP
||scenario.
||
||
||
||$hiv...
||
||
||
||-----Original Message-----
||From: Shivakumar Channalli
||Sent: Tuesday, June 01, 2010 6:17 PM
||To: 'Shaleen Saxena (ssaxena)'; Santiago Alvarez (saalvare); Nitin
||Bahadur
||Cc: [e-mail]
||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:[e-mail]]
|||Sent: Tuesday, June 01, 2010 5:51 PM
|||To: Shivakumar Channalli; Santiago Alvarez (saalvare); Nitin Bahadur
|||Cc: [e-mail]; 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:[e-mail]]
|||> Sent: Saturday, May 29, 2010 11:13 AM
|||> To: Santiago Alvarez (saalvare); Nitin Bahadur; Shaleen Saxena
|||> (ssaxena)
|||> Cc: [e-mail]
|||> 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:[e-mail]]
|||> |Sent: Saturday, May 29, 2010 6:03 AM
|||> |To: Nitin Bahadur; Shaleen Saxena (ssaxena); Shivakumar Channalli
|||> |Cc: [e-mail]; 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: [e-mail] [mailto:[e-mail]] On
|||Behalf
|||> |Of
|||> |> Nitin Bahadur
|||> |> Sent: Friday, May 28, 2010 4:52 PM
|||> |> To: Shaleen Saxena (ssaxena); Shivakumar Channalli
|||> |> Cc: [e-mail]
|||> |> 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
|||> |> [e-mail]
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