Subject: Comments on draft-agarwal-mpls-ttl-00

From: Francis Arts <[email-masked]>
Date: Sat, 03 Mar 2001 14:31:00 +0100

Puneet,

Please find included some comments to your draft
draft-agarwal-mpls-ttl-00.

Kind regards,

    Francis.

--------------

1) Section 2.2.

The text states that oTTL = iTTL -1 and that it is checked whether oTTL
is greater than 0.

However, this does not cover the receipt of an (erroneous) MPLS packet
with a TTL of 0. In this case setting oTTL = iTTL - 1, would result in a
oTTL value different from 0. So the MPLS packet would still pass the
oTTL check while it should not have.

Therefore, I propose to check the iTTL, rather than the oTTL:
* A check is done whether or not the iTTL value is strictly larger than
1. This check on the iTTL value should only be done once it has been
determined that the packet is routed (as an IP or MPLS packet) to a next
node.

2) Section 2.2.

The text states that 'the oTTL check is performed only if an outgoing
TTL is set to oTTL'.

However, this is inconsistent with the statement in section 2.4 - 3rd
bullet: "PHP case - The oTTL check should be performed irrespective of
whether the oTTL is used in any outgoing label / IP header".

3) Section 2.3.

The text states that '... we are performing a push / swap /  PHP, then
the iTTL is the TTL ...'.

I propose to remove the 'push' since this is irrelevant for the incoming
TTL determination; the push is handled in section 2.4 (outgoing TTL
determination).

---

From: Bora Akyol <[email-masked]>
Date: Sat, 3 Mar 2001 21:36:38 -0800 (PST)

> draft-agarwal-mpls-ttl-00.

Francis,

I believe the text says to check for oTTL > 0/

> whether the oTTL is used in any outgoing label / IP header".

This will be fixed in the next version of the draft.

> the iTTL is the TTL ...'.

We put the word "push" there to clearly differentiate against the "POP"
case. Even when you are pushing, you still need to determine the iTTL so
that you can determine the TTL for the label that is being pushed.

---

From: Bora Akyol <[email-masked]>
Date: Sat, 3 Mar 2001 21:36:38 -0800 (PST)

Francis,

---

From: Ashley Shi <[email-masked]>
Date: Thu, 08 Mar 2001 19:16:46 -0500

> > TTL determination; the push is handled in section 2.4 (outgoing TTL

About the ospf configuration on CE, is there anything special you need to do,
or just the regular ospf configuration as we have discussed today.

Ashley

---

From: Ashley Shi <[email-masked]>
Date: Thu, 08 Mar 2001 19:55:55 -0500

Oops, I replied to the wrong message, please discard my previous message and
this one too.

-Ashley