Subject: RE: [Isis-wg] Fwd: Re: Last Call: draft-ietf-isis-bfd-tlv (IS-IS BFD EnabledTLV) to Proposed Standard

From: "Les Ginsberg (ginsberg)" <[email-masked]>
Date: Wed, 22 Sep 2010 09:51:09 -0700

(Stewart - thanx for calling this to our attention)

Jiaxing -

Sorry for the delayed response, but as you did not copy the IS-IS WG your post was not seen.
Responses inline.

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On
> Behalf Of Stewart Bryant (stbryant)
> Sent: Friday, September 03, 2010 12:19 PM
> To: isis-wg
> Subject: [Isis-wg] Fwd: Re: Last Call: draft-ietf-isis-bfd-tlv (IS-IS
> BFD EnabledTLV) to Proposed Standard
> 
> This LC comment only appeared on the main IETF list
> 
> Please will the authors address this issue
> 
> -------- Original Message --------
> Subject: 	Re: [Isis-wg] Last Call: draft-ietf-isis-bfd-tlv (IS-IS BFD
> EnabledTLV) to Proposed Standard
> Date: 	Mon, 26 Jul 2010 17:04:40 +0800
> From: 	lan7801 <[email-masked]> <mailto:[email-masked]>
> 
> To: 	ietf <[email-masked]> <mailto:[email-masked]>
> CC: 	iesg <[email-masked]> <mailto:[email-masked]>
> 
> 
> Hi,
>     I have some comments about this draft.
> 
> 
>     section 3.2.  Adjacency Establishment and Maintenance
> 
> 	   Whenever ISIS_BFD_REQUIRED is TRUE the following extensions to
> the
> 	   rules for adjacency establishment and maintenance MUST apply:
> 	   o  ISIS_NEIGHBOR_USEABLE MUST be TRUE before the adjacency can
> 	      transition from INIT to UP state
> 
> 
> 
>    This rule assumes that both the BFD and IS-IS configurations are
> correct and they  work well.  But This isn't  the way all
> the time.
>    AS we know that the establishment  of the BFD session is bootstraped
> by IS-IS,If the BFD enabled interface have two or
> more address, which address should be used to create the BFD session ?
> If the two addresses of the BFD session  are not on
> the same subnet,the BFD session will fail ,and the IS-IS adjacency can
> never be ceated.That is a risk.
>  Cisco  router  encodes the primary ip address of the inteface in IS-IS
> hello's ip interface address(es) TLV, however,Juniper
> router encodes all addresses of the interface in ip interface
> address(es) TLV,How about the other router ?
>  To resove this problem,this draft should specify which address should
> be used .The choosed address may be included in the
> BFD enabled TLV.

I am reluctant to add this option to the TLV. Local configuration is required to specify which IP address should be used in cases where multiple addresses are configured on the interface. If there is a mismatch between what is configured on two neighbors then having the advertisement will not help us insure that matching subnets are used - so it seems that we have not made life any easier/better by adding this information in the TLV.

>  To avoid confusion,it is better to specify that the IS-IS must
> triggere BFD session establishment before the adjacency is in UP state.
>

The point of the draft is to REQUIRE that the BFD session be UP before the IS-IS adjacency transitions to UP - but only when it is known that BFD is enabled on both neighbors. This avoids failure to bring up an adjacency simply because of mismatched configurations (i.e. one IS has BFD support and the other does not).
 
>  There is another scenario we must consider. When the state of IS-IS
> adjacency is UP and the administrator trys to configure BFD or modify
>  BFD configuration, IS-IS should discard the  first BFD session failure
> ,IS-IS can trust BFD session state only after
>  BFD session has informed IS-IS a BFD session success.

This point is addressed in Section 4 of the draft.

   Les

> 
> 
> 
> 
> 
> ________________________________
> 
> Jiaxing Lan
> 2010-07-25
> ________________________________
> 
> 发件人： The IESG
> 发送时间： 2010-07-13 02:42:14
> 收件人： IETF-Announce
> 抄送： isis-wg
> 主题： [Isis-wg] Last Call: draft-ietf-isis-bfd-tlv (IS-IS BFD
> EnabledTLV) to Proposed Standard
> 
> The IESG has received a request from the IS-IS for IP Internets WG
> (isis)
> to consider the following document:
> - 'IS-IS BFD Enabled TLV '
>    <draft-ietf-isis-bfd-tlv-02.txt> as a Proposed Standard
> The IESG plans to make a decision in the next few weeks, and solicits
> final comments on this action.  Please send substantive comments to the
> [email-masked] mailing lists by 2010-07-26. Exceptionally,
> comments may be sent to [email-masked] instead. In either case, please
> retain the beginning of the Subject line to allow automated sorting.
> The file can be obtained via
> http://www.ietf.org/internet-drafts/draft-ietf-isis-bfd-tlv-02.txt
> IESG discussion can be tracked via
> https://datatracker.ietf.org/public/pidtracker.cgi?command=view_id&dTag
> =17118&rfc_flag=0
> _______________________________________________
> Isis-wg mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/isis-wg