The MPLS WG Archive

["Arashmid Akhavain" <arashmid@nortelnetworks.com>]

Title: RE: [mpls] Requesting your feedback - issues/errors/clarifications

Please see my comments below:

+ I agree with Luca. I have not seen much use for loop detection in
  DU mode of operation. So, it would be nice to either clarify its use.

+ I also agree with removal of the HOST FECs. Although they are
+ supported
  by the protocol, I have not seen them being advertised.

+ I agree that the selection of FECs for which LDP sends label mapping
+ message
  should not be a requirements of the protocol spec. The FECs should be either
  determined by the applications as Ina mentioned, or controlled via policies.

+ As for the use of DU in conjunction with independent control mode of
+ operation,
  I agree with Vach that DU and IC can result in black holes or packet misrouting
  in the network. The scheme works fine for IP forwarding, but as Vach pointed out
  in his e-mail, it creates issues in VPN networks.

Arashmid

-----Original Message-----
From: Luca Martini [mailto:lmartini@cisco.com]
Sent: Thursday, August 26, 2004 5:19 PM
To: Ina Minei
Cc: mpls@ietf.org; vach.kompella@alcatel.com
Subject: Re: [mpls] Requesting your feedback - issues/errors/clarifications

Ina,

Please note the following points:

- the LDP loop detection mechanisms do not make much sense in DU mode.
This is the hop count TLV,  and the Path Vector TLV. ( When LDP
interoperability testing was just starting , I had most vendors out
there remove it for DU mode ). We should add something explicitly that
says that these TLVs should not be used in DU mode. ( This is the
current practice in all implementations that I know of )

- The Host FEC is accepted by most implementations I worked with , but
sent by none. So I also think it's probably a good idea to remove it.

Luca

Ina Minei wrote:

>>>Issue: do we really have to send all FECs in our database whenever we
>>>have an LDP session between two peers?
>>>     
>>>
>>This should not be a requirement of the protocol spec, the application
>>which is using the protocol should determine which FECS get sent.
>>   
>>
>
>       I agree. This is not a specification issue, but rather a best-practice
>based on the application for which the protocol is used. If you only
>need the loopbacks as FECs for your application, then it is best if you
>_ask_ LDP to only redistribute the loopbacks, because it will make your
>network easier to troubleshoot.
>
>                               Ina
>
>
> 
>
>>>Issue: with all the combinations of Downstream Unsolicited,
>>>Downstream on Demand, Ordered Control, Independent Control, etc., it
>>>makes sense to define a mandatory combination.  DU/OC seems to be the
>>>favored one.
>>>     
>>>
>>I believe  this would  put a majority  of the  deployed LDP speakers
>>out of spec.  Such a change cannot be made as part of going to DS.
>>
>>   
>>
>
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>
> 
>

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