Subject: RE: [PCE] Inter-AS PCE Path Sequence Autoexplore

From: "Vijayanand C - TLS, Chennai." <[email-masked]>
Date: Wed, 18 Oct 2006 16:32:10 +0530

Mach,

A question about the pce sequence autoexplore I-D.

This method seems to rely on BGP to get the next AS en-route to the
destination. BGP may not give all the possible ASes, since based on its
decision process and policy it may select only one route to pass on. For ex.
If an EBGP speaker gets route for the same prefix from different EBGP peers
from different ASes, it may select one of them and advertise to its IBGP
peers. (The PCE may not have access to all the alternate routes of the EBGP
speaker connecting to all the ASes) But we don't know the TE characteristic
of the link connecting with the speaker whos' route was chosen( it may not
be TE capable ?). Also, the policy configuration on the EBGP speaker itself
may block some inbound routes. So some information is lost here.

Regards,

Vijay

-----Original Message-----
From: Mach Chen [mailto:[email-masked]] 
Sent: Tuesday, October 17, 2006 7:19 AM
To: [email-masked]
Subject: [PCE] Inter-AS PCE Path Sequence Autoexplore

Hi folks,

We have posted a new I-D
<http://www.ietf.org/internet-drafts/draft-chen-pce-interas-pce-sequence-aut
oexplore-00.txt>
http://www.ietf.org/internet-drafts/draft-chen-pce-interas-pce-sequence-auto
explore-00.txt which is about how to explore those PCEs and track their
sequence which are engaged in computing an end-to-end path spanning multiple
ASes.

Any feed-back and comments would be most welcome.

Best regards,

Mach

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A New Internet-Draft is available from the on-line Internet-Drafts 
directories.

  Title                : Inter-AS PCE Path Sequence Autoexplore 
  Author(s)          : M. Chen
  Filename : draft-chen-pce-interas-pce-sequence-autoexplore-00.txt
  Pages              : 16
  Date                : 2006-10-12
  
   In Inter-AS scenario, as usual, multiple Path Computation Elements 
   (PCEs) will take part in path computation. [PCE-DISCO-OSPF], [PCE-
   DISCO-ISIS],PCE-DISCO-BGP] or some other means can be used to 
   discover all underling PCEs, but there is lack of solutions to find 
   out those PCEs and their sequence which are engaged in computing an 
   end-to-end inter-AS TE LSP.  This document proposes a solution to 
   identify these PCEs and their sequence which can be used to compute a 
   TE LSP across multiple ASes.  

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-chen-pce-interas-pce-sequence-auto
explore-00.txt
<http://www.ietf.org/internet-drafts/draft-chen-pce-interas-pce-sequence-aut
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---

From: Mach Chen <[email-masked]>
Date: Thu, 19 Oct 2006 10:21:50 +0800

Vijay,

What you said is that an EBGP speaker(ASBR) connect to multiple different EBGP peers which are in different ASes, respectively? If so, in such a scenario, the EBGP speaker SHOULD have the multiple paths advertisement capability which was proposed in draft-bhatia-bgp-multiple-next-hops-01.txt or draft-walton-bgp-add-paths-05.txt. So the EBGP speaker can advertise multiple paths to the PCE according to a specific situation. And in the really network,  an AS wants to "multi-home" to multiple ASes, there will be multiple ASBRs.

As to the policy configuration on the EBGP speaker as you said, in such scenario, I think there may be two possibility: one is that the AS where the EBGP speaker is in doesn't want to forward any traffic throuth the AS where those filtered routes come from, the other is that the EBGP speaker just wants to use a default route, the EBGP speaker can advertise a default route to its IBGP peers(includes PCE, of cause , the PCE can't use the default route to track the PCE sequence). So, if you want to use this method to track PCE sequence, enough route infomation is desirable.

Thanks,

Mach

----- Original Message ----- 
  From: Vijayanand C - TLS, Chennai. 
  To: Mach Chen 
  Cc: [email-masked] 
  Sent: Wednesday, October 18, 2006 7:02 PM
  Subject: RE: [PCE] Inter-AS PCE Path Sequence Autoexplore

  Mach,

  This method seems to rely on BGP to get the next AS en-route to the destination. BGP may not give all the possible ASes, since based on its decision process and policy it may select only one route to pass on. For ex. If an EBGP speaker gets route for the same prefix from different EBGP peers from different ASes, it may select one of them and advertise to its IBGP peers. (The PCE may not have access to all the alternate routes of the EBGP speaker connecting to all the ASes) But we don't know the TE characteristic of the link connecting with the speaker whos' route was chosen( it may not be TE capable ?). Also, the policy configuration on the EBGP speaker itself may block some inbound routes. So some information is lost here.

  Regards,

  Vijay

  -----Original Message-----
  From: Mach Chen [mailto:[email-masked]] 
  Sent: Tuesday, October 17, 2006 7:19 AM
  To: [email-masked]
  Subject: [PCE] Inter-AS PCE Path Sequence Autoexplore

  Hi folks,

  We have posted a new I-D http://www.ietf.org/internet-drafts/draft-chen-pce-interas-pce-sequence-autoexplore-00.txt which is about how to explore those PCEs and track their sequence which are engaged in computing an end-to-end path spanning multiple ASes.

  Best regards,

  Mach

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A New Internet-Draft is available from the on-line Internet-Drafts directories.    Title                : Inter-AS PCE Path Sequence Autoexplore   Author(s)          : M. Chen  Filename : draft-chen-pce-interas-pce-sequence-autoexplore-00.txt  Pages              : 16  Date                : 2006-10-12     In Inter-AS scenario, as usual, multiple Path Computation Elements    (PCEs) will take part in path computation. [PCE-DISCO-OSPF], [PCE-   DISCO-ISIS],PCE-DISCO-BGP] or some other means can be used to    discover all underling PCEs, but there is lack of solutions to find    out those PCEs and their sequence which are engaged in computing an    end-to-end inter-AS TE LSP.  This document proposes a solution to    identify these PCEs and their sequence which can be used to compute a    TE LSP across multiple ASes.     A URL for this Internet-Draft is:http://www.ietf.org/internet-drafts/draft-chen-pce-interas-pce-sequence-autoexplore-00.txt To remove yourself from the I-D Announcement list, send a message to i-d-announce-request at ietf.org with the word unsubscribe in the body of the message. You can also visit https://www1.ietf.org/mailman/listinfo/I-D-announce to change your subscription settings. Internet-Drafts are also available by anonymous FTP. Login with the username "anonymous" and a password of your e-mail address. After logging in, type "cd internet-drafts" and then "get draft-chen-pce-interas-pce-sequence-autoexplore-00.txt". A list of Internet-Drafts directories can be found inhttp://www.ietf.org/shadow.html or ftp://ftp.ietf.org/ietf/1shadow-sites.txt Internet-Drafts can also be obtained by e-mail. Send a message to:  mailserv at ietf.org.In the body type:  "FILE /internet-drafts/draft-chen-pce-interas-pce-sequence-autoexplore-00.txt".  NOTE:      The mail server at ietf.org can return the document in  MIME-encoded form by using the "mpack" utility.  To use this  feature, insert the command "ENCODING mime" before the "FILE"  command.  To decode the response(s), you will need "munpack" or  a MIME-compliant mail reader.  Different MIME-compliant mail readers  exhibit different behavior, especially when dealing with  "multipart" MIME messages (i.e. documents which have been split  up into multiple messages), so check your local documentation on  how to manipulate these messages. Below is the data which will enable a MIME compliant mail readerimplementation to automatically retrieve the ASCII version of theInternet-Draft.<ftp://ftp.ietf.org/internet-drafts/draft-chen-pce-interas-pce-sequence-autoexplore-00.txt> 

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