Subject: questions about draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt

From: Terry Lee <[email-masked]>
Date: Mon, 14 Jul 2003 14:12:58 +0800

1.       DETOUR object’s Class is TBD, Why? 

2.       should DETOUR object be contained in the head-end LSR in
one-by-one technique? I think the answer is yes.

3.       in facility technique, a backup tunnel can protected many LSP.
Say LSP1and LSP2 in different SESSION. What 

the FRR backup tunnel’s SESSION should be? 

In draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt:

Thus, the only field in the SESSION and SENDER_TEMPLATE objects which
could be varied between 

a backup path and a protected LSP is the "IPv4 (or IPv6) tunnel sender
address" in the SENDER_TEMPLATE.

---

From: "Prabakaran T Sampath" <[email-masked]>
Date: Mon, 14 Jul 2003 22:02:46 +0530

Hi Terry Lee,

Please find my in lined comments [PrabakarTS].

Thanks and regards,
Prabakaran T.S.
Future Software Limited,
480-481, Anna Salai,
Chennai - 600035, India.
email : [email-masked]
Off Phone: +91-44-24330550 - Extn: 319
-----------------------------------------------------------
  -----Original Message-----
  From: [email-masked] [mailto:[email-masked]]On Behalf Of Terry Lee
  Sent: Monday, 14 July 2003 11:43 AM
  To: [email-masked]'
  Cc: Terry Lee
  Subject: questions about draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt

  [PrabakarTS]  In section 4.2 of the draft, the class value is specified to
be of

  Class = TBD  (to conform 0bbbbbbb format for compatibility)  It meant that
the Class value

  is not yet assigned and time being we can use the "0bbbbbbb" format as
specified in

  RFC 2205 section 3.10 for backward compatibility.  So that,

  The high-order bit of the C-Class is zero; LSRs that do not support

  the DETOUR objects MUST reject any Path message containing a DETOUR

  object and send a PathErr to notify the PLR.  This PathErr SHOULD

  be generated as specified in [RSVP] for unknown objects with a

  class-num of the form "0bbbbbbb".

  So, time being(until draft finalizes the Class value) it is upto the
implementation specific to

  assign some unique Class value of the form "0bbbbbbb" for this DETOUR
Object Class.

  The similar answer is applicable for FAST_REROUTE Object

  of its Class = TBD  (use form 11bbbbbb for compatibility)

  2.       should DETOUR object be contained in the head-end LSR in
one-by-one technique? I think the answer is yes.
  [PrabakarTS]  Yes, you are correct.

  a backup path and a protected LSP is the "IPv4 (or IPv6) tunnel sender
address" in the SENDER_TEMPLATE.
  [PrabakarTS] IPv4 tunnel Sender address in SENDER_TEMPLATE will be used to
identify the Backup path

  in the Sender-Template-Specific Backup path Identification approach at the
PLR.  The PLR should put its

  IPv4 tunnel Sender address in SENDER_TEMPLATE. Whereas in Path-Specific -
Backup path Identification

  approach the DETOUR object, is used to distinguish between PATH messages
for a backup path and the
  protected LSP.

---

From: Alia Atlas <[email-masked]>
Date: Mon, 14 Jul 2003 14:42:59 -0400

At 02:12 AM 7/14/2003, Terry Lee wrote:

1.
DETOUR object s Class is TBD, Why?

I believe that we're awaiting a number to be assigned by IANA.

2.
should DETOUR object be contained in the
head-end LSR in one-by-one technique? I think the answer is
yes.

No, it's not necessary.

3.
in facility technique, a backup tunnel
can protected many LSP. Say LSP1and LSP2 in different SESSION. What

the FRR backup tunnel s SESSION should be?

The bypass tunnel used in the facility method can have whatever SESSION,
SENDER_TEMPLATE, etc., objects.  The bypass tunnel's LSP is set up
exactly the same as any other primary LSP; the only difference is how the
ingress chooses to use it.

In
draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt:

Thus, the only field in the SESSION and
SENDER_TEMPLATE objects which could be varied between

a backup path and a protected LSP is the
"IPv4 (or IPv6) tunnel sender address" in the
SENDER_TEMPLATE.

That is for the path messages for the detours.

Alia

---

From: Alia Atlas <[email-masked]>
Date: Mon, 14 Jul 2003 15:33:33 -0400

2.
should DETOUR object be contained in the head-end LSR in
one-by-one technique? I think the answer is
yes.

I may have misunderstood your question earlier.  If you mean should
the DETOUR object be included in the Path message sent from the head-end
LSP for the detour LSP (as opposed to the primary LSP), then yes,
absolutely.

Alia

---

From: Terry Lee <[email-masked]>
Date: Tue, 15 Jul 2003 09:25:10 +0800

Thanks a lot.
 
I have another question. In section 6.4, it states as following : 
 
   6.4 Signaling for Facility Protection
  
      A PLR may use one or more bypass tunnels to protect against the
      failure of a link and/or a node.  These bypass tunnels may be
      setup in advance or may be dynamically created as new protected
      LSPs are signaled.
 
My question is how to create the bypass tunnels dynamically? 
how do the LSRs in the protected path know to be PLR and to create
bypass tunnel with what attributes like destionation etc.

---

From: Alia Atlas <[email-masked]>
Date: Tue, 15 Jul 2003 04:38:11 -0400

At 09:25 PM 7/14/2003, Terry Lee wrote:

Thanks
a lot.

I have another question. In section 6.4, it
states as following :

6.4 Signaling for Facility
Protection

A PLR may use one or more bypass tunnels
to protect against the

failure of a link and/or a node.
These bypass tunnels may be

setup in advance or may be dynamically
created as new protected

LSPs are signaled.

My question is how to create the bypass
tunnels dynamically?

how do the LSRs in the protected path know
to be PLR and to create bypass tunnel with what attributes like
destionation etc.

An LSR knows that it needs to determine a backup
because it is a PLR based upon the signaling of the FAST_REROUTE object
or SESSION flags.

In the same way that a PLR can dynamically create a detour which meets
its needs, a PLR could create a bypass tunnel to use instead.  This,
naturally, complicates the decision of whether to select an existing
bypass tunnel or create a new one.

Alia

---

From: Alia Atlas <[email-masked]>
Date: Tue, 15 Jul 2003 05:22:58 -0400

At 04:46 AM 7/15/2003, Terry Lee
wrote:

An LSR knows that it needs to determine a backup because it is a PLR
based upon the signaling of the FAST_REROUTE object or SESSION
flags.

[Terry Lee] Then every LSR along the path will attempt to
create
a backup tunnel with the destionation that is possible. Am I
right?

That is the essence of local protection.  There needs to be a backup
path available at every PLR in case of a failure so that no signaling
need occur in order to repair the traffic to provide very fast
rerouting.

Alia

---

From: Alia Atlas <[email-masked]>
Date: Tue, 15 Jul 2003 04:50:59 -0400

At 04:34 AM 7/15/2003, Terry Lee wrote:

But in
section "6.1.2. Backup Path Identification: Path-Specific", it
states :

Thus, the backup
paths use the same SESSION and SENDER_TEMPLATE

objects as the ones used in the protected LSP.
The presence of

DETOUR object in Path messages signifies a
backup path; the

presence of FAST_REROUTE object and/or the
"local protection

requested" flag in the SESSION_ATTRIBUTE
object indicates a

protected LSP.

It seems that the protected LSP's PATH
message doesn't include DETOUR object.

On the other hand, if the head-end LSR of
the protected LSP doesn't include DETOUR object,

how do it control the establish the backup
tunnels?

It uses the FAST_REROUTE object and/or the SESSION ATTRIBUTES flags to
indicate that the LSP requires local protection.  If present, then
the FAST_REROUTE object contains constraints which are applied to the
backup path selection.

Alia

-----Original Message-----

From: Alia Atlas
[mailto:[email-masked]]

Sent: Tuesday, July 15, 2003 3:34 AM

To: [email-masked]

Cc: 'Terry Lee'; [email-masked]; 'prabakarts'

Subject: RE: questions about
draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt

2.

Alia

---

From: Terry Lee <[email-masked]>
Date: Tue, 15 Jul 2003 16:46:14 +0800

Hi,
Please find my comments in paragraphs [Terry Lee].

-----Original Message-----
From: Alia Atlas [mailto:[email-masked]] 
Sent: Tuesday, July 15, 2003 4:38 PM
To: Terry Lee
Cc: Prabakaran T Sampath; [email-masked]'
Subject: RE: questions about draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt

Thanks a lot.

  

An LSR knows that it needs to determine a backup because it is a PLR
based upon the signaling of the FAST_REROUTE object or SESSION flags.

[Terry Lee] Then every LSR along the path will attempt to create a
backup tunnel with the destionation that is possible. Am I right?
In the same way that a PLR can dynamically create a detour which meets
its needs, a PLR could create a bypass tunnel to use instead.  This,
naturally, complicates the decision of whether to select an existing
bypass tunnel or create a new one.

Alia

---

From: Terry Lee <[email-masked]>
Date: Tue, 15 Jul 2003 16:34:00 +0800

But in section "6.1.2. Backup Path Identification: Path-Specific", it
states :
     Thus, the backup paths use the same SESSION and SENDER_TEMPLATE
     objects as the ones used in the protected LSP. The presence of
     DETOUR object in Path messages signifies a backup path; the
     presence of FAST_REROUTE object and/or the "local protection
     requested" flag in the SESSION_ATTRIBUTE object indicates a
     protected LSP.
It seems that the protected LSP's PATH message doesn't include DETOUR
object. 
On the other hand, if the head-end LSR of the protected LSP doesn't
include DETOUR object,
how do it control the establish the backup tunnels?

-----Original Message-----
From: Alia Atlas [mailto:[email-masked]] 
Sent: Tuesday, July 15, 2003 3:34 AM
To: [email-masked]
Cc: 'Terry Lee'; [email-masked]; 'prabakarts'
Subject: RE: questions about draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt

I may have misunderstood your question earlier.  If you mean should the
DETOUR object be included in the Path message sent from the head-end LSP
for the detour LSP (as opposed to the primary LSP), then yes,
absolutely.

Alia

---

From: Terry Lee <[email-masked]>
Date: Tue, 15 Jul 2003 17:17:40 +0800

Hi,

Terry Lee 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Alia
Atlas
Sent: Tuesday, July 15, 2003 4:51 PM
To: Terry Lee
Cc: [email-masked]; [email-masked]
Subject: RE: questions about draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt

It uses the FAST_REROUTE object and/or the SESSION ATTRIBUTES flags to
indicate that the LSP requires local protection.  If present, then the
FAST_REROUTE object contains constraints which are applied to the backup
path selection.

[Terry Lee] Correct. My questions focus the usage of DETOUR object. 
does the PATH message of the head-end LSR of the protected LSP contain
DETOUR object in one-to-one technique? 
If it does, it doesn't seem to be contrary with the statements in "The
presence of    DETOUR object in Path messages signifies a backup path;
the    presence of FAST_REROUTE object and/or the "local protection
requested" flag in the SESSION_ATTRIBUTE object indicates a    protected
LSP." in section 6.1.2. 
If it doesn't,  the DETOUR object seems to be paradox. 
 
Alia

-----Original Message----- 

Alia

---

From: "Prabakaran T Sampath" <[email-masked]>
Date: Tue, 15 Jul 2003 14:50:55 +0530

??Hi Terry Lee,

Creating a bypass tunnel in advance and associating with the interface is a
explicit
thing.  If we want to create a bypass tunnel dynamically during LSPs
signaling means,
In my understanding, it is an implementation  specific,
one possible way could be each PLR can create a bypass tunnels dynamically
based on the  RRO objects, where in we could find the exact path the LSPs
traversed, using this we can make a decision for the node/link which we need
to protect,
using CSPF we can exclude certain link or node for establishing the bypass
tunnel from PLR to MP and then associating with the Protected LSP at the PLR
for FRR operation,
but we also need to take care of Bandwidth protection needed flag operation
while establishing bypass tunnel if it is enabled.
The complexity, scalability and other issues involved in this approach need
to be explored.

Thanks and regards,
Prabakaran T.S.
Future Software Limited,
480-481, Anna Salai,
Chennai - 600035, India.
 -----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of Terry Lee
Sent: Tuesday, 15 July 2003 6:55 AM
To: 'Alia Atlas'; Prabakaran T Sampath
Cc: [email-masked]'; Terry Lee
Subject: RE: questions about draft-ietf-mpls-rsvp-lsp-fastreroute-02.txt

  Thanks a lot.

  My question is how to create the bypass tunnels dynamically?
  how do the LSRs in the protected path know to be PLR and to create bypass
tunnel with what attributes like destionation etc.

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