Subject: Re: Question for the RFC2961--Refresh reduction--trigger msg

From: "Hong Liao" <[email-masked]>
Date: Mon, 10 Mar 2003 18:26:26 -0500

So you tried to say that as  far as the msgid is  greater than the previous
one with the same epoch, it does not  matter if the other content is the
same  as the one before, it is considered  to be a trigger msg.

or as far as the epoch value is different,  it does not matter if the other
contents in the message are the same  as the  one before, it is considered
as  a  trigger msg, right?

Thanks,
Julia

                    Ping Pan                                                                                
                    <[email-masked]        To:     Hong Liao <[email-masked]>                            
                    om>                  cc:     [email-masked], (bcc: Hong Liao/Telcordia)                    
                                         Subject:     Re: Question for the RFC2961--Refresh                 
                    03/10/2003           reduction--trigger msg                                             
                    04:13 PM                                                                                

Hong Liao wrote:
> Hi,
>
> I have question for the trigger message.
>
> In the RFC2961,section 4.5,
>
>
>>>When a node is sending a trigger message, the Message_Identifier value
>>
> MUST have a value that is greater than any other value previously used
with
> the same Epoch field value.
>
> so basically if it is a trigger message then message id should be greater
> than previous one with the same epoch value;but does this mean that if
the
> message id is greater than previous one for the same epoch value, and the
> rest of the contents are the same as the previous message, then should
the
> message be considered as trigger message ?  Can someone confirm this for
> me?
>

Hi,

A couple of points:

1. What qualify as a trigger message on a receiving node?

The idea of refresh reduction is to avoid looking at the content of the
message. Thus by looking at the message-id, the epoch value, and
RSVP-hop (that is, incoming interface, RSVP phop address), if there is
no match to your local table, this is a trigger message. Process the
message in detail.

2. Why incremental message-id's?

For mis-ordering. When processing a message that carries a message-id,
from SESSION and SENDER_TEMPLATE, find the flow entry first. If the flow
entry records a message-id greater than what you have received, don't
process the message - because this is an old junk. (Actually, I didn't
see this condition in a customer's test net.)

To make sure you are OK with the msg-id roll-over, the routers always
change to a new epoch number and start to assign messag-id from a small
value again.

Hope this will help.

- Ping

---

From: David Charlap <[email-masked]>
Date: Mon, 10 Mar 2003 19:24:23 -0500

> contents in the message are the same  as the  one before, it is considered

No.  Quite the opposite.

If the epoch is the same, and the message ID is lower than the most 
recent one received for the LSP, then it the message is out of order and 
should be ignored - meaning it is definitely not a trigger.

If the message ID is greater, or if the epoch is different, then you 
have to compare the rest of the message's content against your saved 
state to determine if the message is a trigger or not.

-- David