Subject: [mpls] Seeking feedback/comments on I-D "LDP Typed Wildcard PW FEC Elements"

From: Kamran Raza <[email-masked]>
Date: Thu, 05 May 2011 12:15:28 -0400

We had presented "LDP Typed Wildcard PW FEC Elements" I-D at IETF79 and
IETF80 [http://tools.ietf.org/html/draft-raza-pwe3-pw-typed-wc-fec-00],
which defines LDP Typed Wildcard FEC elements for PW FECs types (FEC128
PW-Id, and FEC 129 Generalized PW-Id).

We (the authors) are seeking more feedback from the mailing list, and would
be grateful if you could review the document and post comments on the
mailing list.

I-D Abstract:
   An extension to the Label Distribution Protocol (LDP) defines the
   general notion of a "Typed Wildcard Forwarding Equivalence Class
   (FEC) Element".  This can be used when it is desired to request all
   label bindings for a given type of FEC Element, or to release or
   withdraw all label bindings for a given type of FEC element.
   However, a typed wildcard FEC element must be individually defined
   for each type of FEC element.  This specification defines the typed
   wildcard FEC elements for the Pseudowire Identifier (PW Id) and
   Generalized Pseudowire Identifier (Gen. PW Id) FEC types.

[P.S: This I-D was previously submitted as L2VPN WG doc
http://tools.ietf.org/html/draft-raza-l2vpn-pw-typed-wc-fec-01, but was
later resubmitted to PWE3 WG]

Thanks.
-- 
Syed Kamran Raza, Sami Boutros
Cisco Systems, Inc.,
http://www.cisco.com

---

From: Carlos Pignataro <[email-masked]>
Date: Thu, 19 May 2011 17:36:41 -0400

Hi Kamran,

I think the extension of an LDP Typed-Wildcard for the PWid and
Generalized PWid FEC Elements is most useful.

I have some questions/comments about the document:

1. The Typed-wildcard FECs as defined in the document apply to all FECs
   of a given type (all 0x80 or all 0x81). In contrast, RFC 5918
   defines the typed-wildcard for the Prefix FEC Element with finer
   granularity, including also the AFI. Would it make sense to include
   in this case the PW type as part of both typed-wildcard FECs? I
   think that this document can either define the PW Type of 0x0000 as
   all-types for the typed wildcard, or (better) use the existing
   0x7FFF Wildcard PW Type to provide the currently expected all-types
   functionality.

2. I think there might be a bit of overlap with the Group ID from the
   PWid FEC and with the PW Grouping TLV. I think that the document
   could discuss why the typed-wildcard is also needed (e.g.,
   simplicity and different grouping).

I think this is a useful doc.

I also have some editorials that I will unicast.

Thanks,

-- Carlos.

---

From: Kamran Raza <[email-masked]>
Date: Fri, 20 May 2011 00:36:11 -0400

Hi Carlos,

Thanks for the review. Please see inline [skraza]

>    0x7FFF Wildcard PW Type to provide the currently expected all-types

[skraza]: Typed Wildcard for Prefix FEC Element uses "AFI" mainly because
"AFI" is an integral part of basic "Prefix FEC Element". Prefix FEC Element
is a single type defined to include both IPv4/IPv6 prefixes, and hence AFI
field is needed to distinguish b/w IPv4 Prefix and IPV6 prefix element.

In case of PW, we already have different types "0x80", "0x81", "0x82" for
different type of PW FEC Elements. But, I agree that we can use finer
control using fields like pw-type (with wildcard pw-type defined in
rfc4863). 

For FEC 0x80: we can use pw-type based wildcard;
For FEC 0x81: we can use pw-type/AGI-type based wildcard;

So, the Typed Wildcard PW FECs will be defined as:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Typed Wcard   | Type = PWid   |   Len = 2     | PW-Type       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     ...       |
   +-+-+-+-+-+-+-+-+

[PW-Type 0x7FFF: All-Types]

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Typed Wcard   |Type = Gen PWid|   Len = 3     | PW-Type       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     ...       | AGI-Type      |
   +-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-

[PW-Type 0x7FFF: All-Types]
[AGI-Type ?? (0xFF): All-Types]

BTW, since "0" is not defined/available for both pw-type and agi-type
fields, we can pick "0" to mean "all-types" for the consistency reasons.

FEC 0x82 [P2MP PW FEC] Typed Wildcard will be similar to FEC 0x81's.

>    simplicity and different grouping).
[skraza]: Sure, will add a section in the next rev to clarify this.

-- 
Syed Kamran Raza
Technical Leader, SPRSG IOS-XR Routing (MPLS)
Cisco Systems, Inc.,
Kanata, ON, K2K 3E8, Canada
Ph: +1 (613) 254-4520
http://www.cisco.com