Subject: RE: VPLS question on MAC address withdrawal

From: "Andrei Sergeev" <[email-masked]>
Date: Tue, 23 May 2006 11:25:06 +0200

Hi Himanshu,

Sorry for late wake up - your proposal for MAC withdrawal with empty
list enhancement looks vital for VPLS-STP coexistence.

I am wandering is it accepted or not for next release of the draft.

Regards,

Andrei Sergeev,

Siemens

________________________________

From: Andrei Sergeev 
Sent: Tuesday, May 23, 2006 11:19
To: Andrei Sergeev
Subject: VPLS question on MAC address withdrawal

Hi Marc,

It seems that you and pranjal are taking narrower view of the use of

MAC address withdraw mechanism. This being its use during

failovers to backup PE-rs in H-VPLS topology.

My concern is for general cases. If a TCN was triggered 5 hops

deep in C-STP land and is being propagated from root to leaves.

If PE-rs or MTU-s is monitoring such TCN and triggers MAC

address withdraw then empty and non-empty MAC address

withdraw is going to achieve different results at receiving PE-rs

(as was described in my previous emails).

If MAC address withdraw is strictly used for H-VPLS topology

for failover from primary to secondary PE-rs, then you should 

state this restriction in the draft. If not, then may be you need

another qualifier (i.e. flag) for empty MAC address withdraw list which

states for a given VPLS instance,

1) age out all MAC except ones learned on PW receiving this signal (
current )

2) age out all MAC that are learned on PW receiving this signal (new)

3) age out all MAC (new)

regards,

himanshu

-----Original Message-----
From: Marc Lasserre [mailto:marc at riverstonenet.com]
Sent: Wednesday, January 04, 2006 6:22 AM
To: Shah, Himanshu; l2vpn at ietf.org
Subject: Re: VPLS question on MAC address withdrawal

Himanshu,

Sorry to jump a bit late in this discussion.

See my answers below.

Cheers,

Marc

----- Original Message ----- 

From: Shah, Himanshu <mailto:hshah%20at%20ciena.com>  

To: l2vpn at ietf.org <mailto:l2vpn%20at%20ietf.org>  

Sent: Thursday, December 29, 2005 10:19 PM

Subject: VPLS question on MAC address withdrawal

Hope somebody can shed light on the following questions.... 

(1) 
There are two mechanisms described - 
MAC address withdraw List TLV and empty MAC Address withdraw List TLV 

cut-and-paste from draft. 

6.2.2. Address Withdraw Message Containing MAC List TLV
  
  The processing for MAC List TLV received in an Address Withdraw
  Message is:
  
  For each MAC address in the TLV:
     - Remove the association between the MAC address and the AC or
        PW over which this message is received
  
  For a MAC Address Withdraw message with empty list:
     - Remove all the MAC addresses associated with the VPLS
        instance  (specified by the FEC TLV) except the MAC addresses
        learned over the PW associated with this signaling session
        over which the message was received
  
  The scope of a MAC List TLV is the VPLS specified in the FEC TLV in
  the MAC Address Withdraw Message.  The number of MAC addresses can
  be deduced from the length field in the TLV. 

To simplify the problem, lets assume that for a given VPLS instance A
there are only 5 MAC 
addresses and one PW. In this case, for TCN-Triggererd
MAC-address-withdrawal, sending 
a list of 5 MAC address vs sending an empty list achieves opposite
result. That is, sending 
explicit list will cause the receiver to remove all 5 addresses (lets
assume that they all were 
associated with sender). But by sending, empty MAC-address-withdrawal
list, it will remove 
none.  However, the draft says, 

Sending an empty MAC withdraw message will trigger all MACs to be
unlearned (the 5 MACs

in your examples). Only MACs behing the newly active PE-rs would be
preserved.

In order to minimize the impact on LDP convergence time, when the
  MAC list TLV contains a large number of MAC addresses, it may be
  preferable to send a MAC address withdrawal message with an empty
  list. 

(2) 
Is MAC-Address-withdraw mechanism ever intended to be used for U-PW
(user facing PW, MTU-S<->PErs)? 
If so, how, when, implication of withdraw msg from N-PW (PE<->PE) to
U-PW, etc needs to 
be described. 

The main intent is for an MTU-s to trigger MAC withdrawal to its
directly attached PE-rs. The PE-rs will

propagate MAC withdrawal messages to its peer PEs. There is no
withdrawal event to be performed by egress

MTUs. The triggering events for sending MAC withdrawals can be based on
different failure detection

mechanisms (eg STP based TCNs, BFD, etc).

regards, 
himanshu 

Himanshu Shah 
Ciena Corp