Subject: I-D ACTION:draft-mo-mpls-protection-00.txt

From: [email-masked]
Date: Fri, 07 Jul 2000 07:04:46 -0400

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

	Title		: General Considerations for Bandwidth Reservation in 
                          Protection
	Author(s)	: L. Mo
	Filename	: draft-mo-mpls-protection-00.txt
	Pages		: 5
	Date		: 06-Jul-00
	
Protection issues for MPLS LSP have been discussed in recent IETF meetings.
Various drafts have different proposals on establishing the working
and protection LSP ([1]-[5]). But how to reserve bandwidth for the
protection LSP has not be discussed. If the bandwidth for the
protection LSP is reserved in a similar fashion as that of the working
LSP, the bandwidth utilization in the network would be very poor.
In this draft, an algorithm for reserve bandwidth for protection LSP
is presented which enables very efficient bandwidth reservation for
single fault protection.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-mo-mpls-protection-00.txt

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-mo-mpls-protection-00.txt".

A list of Internet-Drafts directories can be found in
http://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:
	[email-masked].
In the body type:
	"FILE /internet-drafts/draft-mo-mpls-protection-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 reader
implementation to automatically retrieve the ASCII version of the
Internet-Draft.

---

From: Andrew Bender <[email-masked]>
Date: Fri, 07 Jul 2000 12:14:26 -0400

If I read this correctly, there are only gains when the working and
protect paths incorporate a common node; although this could happen is
practice, it is not the preferred alignment.

If "X" is in a protect path which is disjoint from the working path,
"X" must still reserve the protect path, without any reduction. For
every new "Y", this seems to be compounded, if I understand the
algorith presented. 

If we are resigned to the notion of maintaining state on all of the
working and protect paths passing through "this" node, it would be
desirable to have a provision / means to accommodate only the maximum
of outbound link reservations for any given Y failure, rather than all
Y failures. Doing so would allow for less UPSR [sic] -like allocation,
in the case where single node resiliency is sufficient.

>     Signaling protocol (either CR-LDP or RSVP-TE) needs to be
> improved to convey the following information in order to establish the
> D(Y|L,X) and P(Y|L,X).
> 
>     ò   list of node IDs (router IDs) where the working LSP traverse
>     ò   nature of the setup signaling, either working LSP setup or the
>         protection LSP setup
	:
	:
>     This algorithm does not require any node to have the complete
> bandwidth reservation picture inside the network. Any nodes will only
> store the information when it is part of the working or the protection
> LSP.

Wouldn't a "node list" for the intended "protect LSP" have to be
distributed as well, in order for this to work?

>     This algorithm can also be extended to cover multiple faults
> inside the network for efficient bandwidth reservation and such
> extensions will not be pursued here.

For each compound failure case involving one common node, different
protect paths might be preferable / selected in each case. How would
"X" be so notified, or which ones would "X" choose? 

Regards,
Andrew Bender
thrupoint.net