Subject: [Isis-wg] I-D ACTION:draft-ietf-isis-ieee-aq-00.txt

From: [email-masked]
Date: Tue, 6 Jul 2010 10:00:02 -0700 (PDT)

A New Internet-Draft is available from the on-line Internet-Drafts 
directories.
This draft is a work item of the IS-IS for IP Internets Working Group of the IETF.

	Title		: IS-IS Extensions Supporting IEEE 802.1aq Shortest Path Bridging
	Author(s)	: D. Fedyk, P. Ashwood-Smith, D. Allan, N. Bragg, P. Unbehagen
	Filename	: draft-ietf-isis-ieee-aq-00.txt
	Pages		: 32
	Date		: 2010-7-5
	
   802.1aq Shortest Path Bridging (SPB) is being standardized by the 
   IEEE as the next step in the evolution of the various spanning tree 
   and registration protocols. 802.1aq allows for true shortest path 
   forwarding in a mesh network context utilizing multiple equal cost 
   paths. This permits it to support much larger layer 2 topologies, 
   with faster convergence, and vastly improved use of the mesh 
   topology. Combined with this is single point provisioning for 
   logical connectivity membership (E-LINE/E-LAN/E-TREE etc).  
    
   The control protocol for 802.1aq is IS-IS [IS-IS] augmented with a 
   small number of TLVs while the encapsulating data paths are 
   respectively 802.1ad (Provider Bridges) [PB] and 802.1ah (Provider 
   Backbone Bridges) [PBB]. This memo documents those TLVs while 
   providing some overview. 

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-isis-ieee-aq-00.txt

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

Below is the data which will enable a MIME compliant mail reader
implementation to automatically retrieve the ASCII version of the
Internet-Draft.

---

From: mike shand <[email-masked]>
Date: Fri, 09 Jul 2010 15:50:56 +0100

I've made a first pass at reading this and have noted a few comments.

     Mike

7. IS-IS Area Address and SYSID

The sentence

"Non stand-alone implementations (supporting other NLPIDs) MAY use any 
valid IS-IS area address as required by the other NLPIDs however only 
matching area addresses will form a single SPB domain. "

Requires some clarification. It could be interpreted as:-

1) Using the normal IS-IS rules for the establishment of a level 1 
domain (i.e. multiple area addresses and adjacent routers sharing a 
common area address, but not necessarily all routers having a common 
area address - although this is recommended).

2) Trying to specify a stricter rule that all routers within the SPB 
domain MUST have a common area address.

I assume it is the former, but the wording hints at the latter.

8. Level 1/2 Adjacency

    "SPBV and SPBM will operate either within an IS-IS level 1, or an
    ISIS level 2. As a result the TLVs specified here may propagate
    either in level 1 or level 2 LSPs. IS-IS SPB implementations MUST
    support level 1 and MAY support level 2 operations. Hierarchical SPB
    is for further study therefore these TLV's MUST NOT be leaked
    between level 1 and level 2."

The requirement to be able to operate as a level 2 domain, seems to 
conflict with the requirement in the previous clause, since in standard 
IS-IS there is no requirement for level 2 routers to share an area address.

9. Shortest Path Default Tie Breaking

Are pseudonodes permitted? If so, the first mechanism will result in 
doubling the cost of a pseudonode traversal. Perhaps a special rule is 
required, which says it must use the maximum value of the two links TO 
the pseudonode.

For the second mechanism, again if pseudonodes are permitted (and I 
suspect they are not, but haven't yet seen any text that states that all 
links are P2P), it would need clarification as to whether the hop count 
is that seen by the SPF algorithm (i.e. traversing the pseudonode is two 
hops), or by the data plane, where it is one hop.

11. Hello (IIH) protocol extensions
"SPB neighbors require a mechanism to instantaneously verify that the..."

instantaneously seems a bit ambitious. Rapidly? Efficiently?

Are there some rules somewhere about the frequency of sending hellos? 
ISO/IEC 10589 places restrictions on the minimal interval between hellos 
(see for example clause 8.4.4 of 10589 second edition. It sounds as if 
you want to be able to send IIHs as soon as anything changes.

11.1. SPB Digest sub-TLV

TYPO s/exchanged Agreement digests match./exchanged Agreement Digests 
match./

o  Length: The size of the value defined below.

This is always 133, is it not?

"If MT instance specific digests are desired they may be carried in
    MTIDs != 0. "

So it is NOT possible to have an instance zero specific instance, when 
there are multiple instances. Just checking that is what you mean?

Is the digest sub-TLV always present in every IIH, or is the intention 
that it is only sent when it changes?

I assume the former, but it needs to be clarified either way.

11.2. SPB Base VLAN-Identifiers sub-TLV

o  Use-Flag (1-bit) The Use-flag is set if this bridge, or any
       bridge that this bridge sees is currently using this ECT-
       ALGORITHM and Base VID.

"sees" is ambiguous. Does it mean

1) is adjacent to
2) is present within the LSPDB
3) is present within the LSPDB AND is currently reachable

12.1.  SPB Instance sub-TLV

"   | Num of Trees  |       (1 bytes)"

TYPO: s/bytes/byte/

12.1.1. SPB Instance Opaque ECT-ALGORITHM sub-TLV

"   adjacency or both. This sub-TLV SHOULD be carried within the MT-"

Do you mean "when present this sub-TLV MUST be carried..."? (i.e. the 
optionality is whether or not it is present, not WHERE it is carried.)

14.2. SPBV Mac Address sub-TLV

"   The SPBV-MAC-ADDR sub-TLV SHOULD be carried within the MT-Capability
    TLV and can occur multiple times in any LSP fragment. "

As above.

END of comments

     Mike

---

From: Peter Ashwood-Smith <[email-masked]>
Date: Fri, 09 Jul 2010 17:02:52 -0400

Mike,

   Thanks for the detailed comments. We will get back shortly.

Cheers,

Peter 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of mike shand
Sent: Friday, July 09, 2010 10:51 AM
To: [email-masked]
Subject: Re: [Isis-wg] I-D ACTION:draft-ietf-isis-ieee-aq-00.txt

     Mike

The sentence

8. Level 1/2 Adjacency

11.1. SPB Digest sub-TLV

1) is adjacent to

TYPO: s/bytes/byte/

As above.

END of comments

     Mike

_______________________________________________
Isis-wg mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/isis-wg