(NOTE: Comments below are mine alone - wearing both my WG member hat and my 
Designated Expert for IS-IS Registries Hat. They do not represent support for 
or against the draft itself.)

draft-li-lsr-isis-area-proxy-06  currently proposes the use of one new sub-TLV 
of Router Capabilities TLV and three new top level TLVs

1)Area Proxy Router Capability - sub-TLV of Router Capability TLV

2)Inside Node TLV - Top level TLV

3)Area Proxy TLV - Top Level TLV with optional sub-TLVs:

   Sub-TLV Area Proxy System ID

   Sub-TLV Area Segment SID

4)Area Segment SID - Top Level TLV


This seems unnecessarily profligate in its consumption of top level TLV code 
points - something to which, as a Designated Expert for the IS-IS registries,  
I pay close attention.

I can imagine an alternative encoding which utilizes a single sub-TLV within 
the Router Capabilities TLV:

Area Proxy Router Capability sub-TLV

  Type: TBD

  Length: Variable

  Value: Flags + Optional sub-TLVs

1 octet of Flags:

      0 1 2 3 4 5 6 7


      |I|L|P| RSVD  |


I If set indicates Inside Node

L If set indicates capable of performing Area Leader functions

P If set indicates Proxy LSP advertisement

RSVD - for future allocation

Followed by optional sub-sub-TLVs

Sub-sub-TLV Area Proxy System ID

Sub-sub-TLV Area SID (Used only when P bit is set)

Please comment on this alternative.

Additional Questions:

It is not clear to me why Area SID requires two different advertisements :

1)As a sub-TLV of Area Proxy TLV and

2)As a top Level TLV in the Proxy LSP

Is it because you wanted a unique codepoint for the Proxy LSP advertisements?

With what I have proposed above, there is only one form of the Area SID 
advertisement but the indication of Proxy LSP is provided.


There is a statement regarding the SR Capabilities sub-TLV advertised by the 
Area Leader as having:

   "an SRGB identical to that advertised by all Inside Routers"

SR does not require all nodes to advertise identical SRGBs. Are you imposing

a new requirement in order to support SR and Area Proxy together? If so, what 
happens if all Inside Nodes do NOT advertise identical SRGBs?


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