Subject: path taken by a packet feedback

From: "Truong Dieu Linh" <[email-masked]>
Date: Thu, 26 Sep 2002 11:07:48 -0400

Hi all,
I have some questions about the new draft of the group: A Traffic Engineering MIB. (draft-ietf-tewg-mib-03.txt). This question concerns the problem of feedback about the path a packet takes. (From the path I can found the sequence of hop that it takes based on tePathRecordedRoute).

1- A tunnel connect two network nodes (for exemple A and B) consists of severals paths, they are diffirents in bandwith, in classe of resources included and excluded, and each has its hops. When a packet is sent from a node (A) to other (B), the packet will take a path of the tunnel. Which information in the MIB can tell us which path is currently took (that means the packet took).
2- When we change some information of MIB to configure new path for a tunnel, change path of a tunnel. How can we know a paket, which is sent from a source node to a destination node, takes the new path or not.  

Thank you for your help.

Truong Dieu Linh

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From: Kireeti Kompella <[email-masked]>
Date: Thu, 26 Sep 2002 11:11:14 -0700 (PDT)

> I have some questions about the new draft of the group

This "new" draft is over 2 years old, so instead of calling it 'new',
might I suggest 'toddler'?

> 1- A tunnel connect two network nodes (for exemple A and B) consists of =
> severals paths, they are diffirents in bandwith, in classe of resources =
> included and excluded, and each has its hops. When a packet is sent from =
> a node (A) to other (B), the packet will take a path of the tunnel. =
> Which information in the MIB can tell us which path is currently took =
> (that means the packet took).

A path has a status -- 

           "The operational status of the path:
                unknown:
                down:        signaling failed
                testing:     administratively set aside for testing
                dormant:     not signaled (for a backup tunnel)
                ready:       signaled but not yet carrying traffic
                operational: signaled and carrying traffic."

Paths that are operational carry packets.  Others don't.

If a tunnel has multiple operational paths, it is an implementation
decision how packets of an LSP are assigned to paths: round-robin,
hash-based, random, ...  Specifying this in the MIB is not usually
productive, especially as the common answer is hash-based, and the
hashes used are usually proprietary.

Kireeti.

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From: Petre Dini <[email-masked]>
Date: Thu, 26 Sep 2002 12:03:39 -0700

>            "The operational status of the path:

I think one must capture the distinction between a "down_1" due to a 
signaling failure, and an ordered  "down_2", i.e.,  an "abnormal down" 
versus a "normal down".

>                 operational: signaled and carrying traffic."

To avoid naming confusion (operational state and and operational value of 
the operational state), I suggest "functional" for the path operational 
state signaled and carrying traffic.

>hashes used are usually proprietary.

Petre