RE: FW: LMP Message ID

[Manoj Agiwal <manoj.agiwal@metro-optix.com>]

Hi Bakhta ,

     Neighbour is only interested in knowing if the message is out-of-order
or not. If retransmission algorithm sends the message with the same Message
Id , Neighbor will not
consider it as out-of-order and process it. Out of order condition being
(int)oldmsgid - (int)newmsgid > 0
In case a new message is received with a greater Message id and latter
Neighbor receives the re-transmitted message , re-transmitted message should
be discarded as it is out-of-order.
     
     
      New message identifies change in configuration and should be send with
a higher message id and should be accepted by neighbor while re-trnasmitted
message represents old values and should be discarded.


     I feel if retransmitted message is sent with the same message Id or new
message id ,
it does not matter , since in either case neighboring node will process it
completely.
Only disadvantage is one will eat away Message Id space at faster rate if
new message id is
generated for every re-transmitted message.

Regards ,
Manoj




-----Original Message-----
From: Baktha Muralidharan [mailto:muralidb@cisco.com]
Sent: Wednesday, May 14, 2003 8:33 PM
To: Manoj Agiwal
Cc: 'Ccamp (E-mail); 'Jonathan.Lang@RinconNetworks.com'
Subject: Re: FW: LMP Message ID


At 12:37 AM 5/13/2003 -0500, Manoj Agiwal wrote:
>Hi ,
>       Lmp drafts tells that Message ID should be monotonically increasing
.
>
>       Section 7 also tells that "Unacknowledge messages sent with
Message_id
>object should be retransmitted until the message is
>       acknowledged or until retry limit is reached."
>
>       Do we have to sent all retransmitted messages with the same Message
Id
>as sent previously or it should be in monotonically
>       increasing order.
>
>Regards ,
>Manoj

Hi Manoj,

An unacknowledged message could have been lost; i.e. might not have reached
the neighbor. So, the neighbor has no way of determining if a message is
a re-transmit and will fail [and nack] a message with out-of-order
message-id.

So, re-transmit attempts should increase message id.

/Baktha Muralidharan
  Cisco Systems.