Re: FW: Two-octet bandwidth values

[Qingming Ma <qma@cisco.com>]

Hello everyone,

Thanks for comments!  As Dean pointed out, the focus of this
draft is on space, particular ISIS sub-TLV space,  which is
limited to 244 bytes (255 - 11). As stated in Tony Li's ISIS-TE
extensions draft that there is no defined mechanism for extending
sub-TLV space and wasting sub-TLV space is discouraged.

Considering the current situation, the total sub-TLV size for generic
TE extensions, GMPLS extensions, and DiffServ TE extensions
together is 222 bytes without taking into account of alignment.
There is no enough sub-TLV space for the proposed LSP
restoration draft if we want to go with them. More extensions related to
TE and/or Optical Control may be proposed in future. New TLVs
may have to be defined  to accommodate new extensions if we do not
conserve sub-TLV space now. By using two-octet BW values, the
total sub-TLV size for all three types of extensions mentioned above
can be reduced to 138 bytes.

For OSPF, the sub-TLV space is not a urgent issue at this time.
But short LSAs are always encouraged to reduce routing overhead.

For backward compatibility, we may define new types for BW
sub-TLVs that use two octets. Since there are plenty of unused
types, it should not be a problem.

Thanks,

Qingming

At 03:26 PM 3/26/01 -0800, Cheng, Dean wrote:


>Also, since the "draft-katz-yeung-ospf-traffic-03.txt"
>may be going to a RFC soon, would it be necessary to
>consult with the OSPF WG at this point as well ?
>
>-----Original Message-----
>From: Kireeti Kompella [mailto:kireeti@juniper.net]
>Sent: Sunday, March 25, 2001 8:06 PM
>To: ccamp@ops.ietf.org
>Subject: Two-octet bandwidth values
>
>
>Let's get the ball rolling.  Please send questions and comments to the
>list.  Here are mine:
>
>Questions to vendors:
>1) Is floating point arithmetic a burdensome requirement?  Is having
>    a new library of functions for the two-octet "floating point"
>    representation a burdensome requirement?
>
>I think the point for the two-octet approach is to save
>packet space (or link resource), not work complexity.
>
>2) Is halving the size of the bandwidth TLVs a big win (keep in mind
>    that more bandwidth TLVs are being proposed)?
>    (a) for ISIS?
>Yes
>    (b) for OSPF?
>Yes
>    (c) if the answers for ISIS and OSPF differ, is it acceptable to
>        have different formats for the two protocols?
>
>Questions to vendors & carriers:
>1) Is 10 bits of dynamic range (0.1% accuracy) good enough?
>
>Yes
>2) Are you in favor of this draft, or against?
>
>Yes
>
>Kireeti.
>
>Dean