Subject: Re: RSVPTE questions, please help me for this, thanks

From: "Hong Liao" <[email-masked]>
Date: Thu, 8 Nov 2001 13:04:40 -0500

Hi,

Sorry I brought up the old topic, but I found something.

I found that draft rsvpte 09.txt, the section 3 LSP Tunnel related message
formats,

Object name                       Applicable RSVP message

Label object        Resv

Does it mean that the Label object is only in the Resv msg? But
if that is the case, the ResvTear msg still use the FF flow descriptor from
Resv formate, I know ResvTear msg was not redefined.

So my question is that if there Label msg should not be in the ResvTear msg
at all or it is optional, just like you mentioned in you last email,

>>When it's your turn to send out ResvTear messages, you should be able to
>>include the LABEL object, even if you did not receive one.  You should
>>do so if it is at all possible.  This is being conservative in what you
>>send.

I just want to confirm this.

Thanks,

Julia

                    David Charlap                                                                                   
                    <David.Charlap@ma        To:     Hong Liao <[email-masked]>                                
                    rconi.com>               cc:     [email-masked], (bcc: Hong Liao/Telcordia)                        
                                             Subject:     Re: RSVPTE questions, please help me for this, thanks     
                    11/05/01 11:01 AM                                                                               

Hong Liao wrote:
>
> In the rsvpte ResvTear msg, is there any label object in the FF/SE
> flow descriptor list?
>
>  <ResvTear Message> ::= <Common Header> [<INTEGRITY>]
>                                          <SESSION> <RSVP_HOP>
>                                          [ <SCOPE> ] <STYLE>
>                                          <flow descriptor list>
>
>              <flow descriptor list> ::= (see earlier definition)
>
> For my understanding, the flow descriptor list here in ResvTear msg
> will be the same as the one in the Resv msg???, if I am correct,
> then the Label object should be in the ResvTear msg????   I
> observed that there is one vendor, it sends out the resvTear msg
> without the label object.

It is ambiguous, IMO.  RSVP-TE does not re-define ResvTear, but it does
re-define flow descriptors.  Nowhere is it explicitly stated whether the
redefined flow descriptors should retroactively apply to all RSVP
messages from other drafts/RFCs.

IMO, you should follow the internet mantra - be conservative in what you
send, be liberal in what you accept.

It is unlikely that you will require the label value in order to process
the ResvTear, so you should just ignore if it is missing.  This is being
liberal in what you accept.  If, for some reason, your implementation
can't process ResvTear without the LABEL object, then you will have to
reject the message, although you may want to see if you can change your
design to not require it.

When it's your turn to send out ResvTear messages, you should be able to
include the LABEL object, even if you did not receive one.  You should
do so if it is at all possible.  This is being conservative in what you
send.

-- David

---

From: David Charlap <[email-masked]>
Date: Thu, 08 Nov 2001 20:08:24 -0500

Hong Liao wrote:
> I found that draft rsvpte 09.txt, the section 3 LSP Tunnel related
> message formats,
> 
> if that is the case, the ResvTear msg still use the FF flow
> descriptor from Resv formate, I know ResvTear msg was not redefined.

It's only required in the Resv message.

It is still wrong, IMO, to reject a message simply because it contains
an object you don't require.  If you don't need it, ignore it,.

Note, however, that this is only if the unnecessary object is of a known
class.  If you get an unknown class object, you should still handle it
according to the unknown-object processing rules (reject the message,
ignore the object, or forward the object, depending on class number.)

> So my question is that if there Label msg should not be in the
> ResvTear msg at all or it is optional, just like you mentioned in
> you last email,

I don't think it should be there.  But I don't see a compelling reason
to reject the message if it is present.

-- David