Subject: RE: Same source ports for different associations

From: [email-masked]
Date: Tue, 5 Nov 2002 16:17:12 -0500

Hi Ivan, Jana, Kavitha & Nivedita,

Thanks for your quick replies. They are really helpful.

Now it is clear to me that all 4 (src & dest ports and src & dest
addresses) should/must be considered to indentify an association. Is it
better to change "It can be used by ..." to a mandatory statement such as
"it MUST be used by ..."?

Simon

                      <Ivan.Arias-Rodriguez                                                                                   
                      @nokia.com>                  To:       <[email-masked]>, <[email-masked]>       
                                                   cc:                                                                        
                       11/05/2002 03:19 PM         Subject:  RE: Same source ports for different associations                 

             Hi Simon!

> -----Original Message-----
> From: ext [email-masked] [mailto:[email-masked]]
> Sent: 05. November 2002 21:41
> To: [email-masked]
> Subject: Same source ports for different associations
>
>
> Hi List,
>
> Per RFC 2960 on Page 17,
>
>   " Source Port Number: 16 bits (unsigned integer)
>
>       This is the SCTP sender's port number.  It can be used by the
>       receiver in combination with the source IP address, the SCTP
>       destination port and possibly the destination IP address to
>       identify the association to which this packet belongs."
>
> Based on the above statement, if 2 associations of a SCTP
> endpoint use 1)
> same source port number & different destination port numbers; 2) same
> source & destination addresses, then the receiving SCTP
> endpoint will have
> problem to identify the association.

             I don't follow you... Why do you say that? Basically we are in
the same situation than in TCP... As far as one of the four elements is
different (either the source or the destination addresses, or ports) you
identify the packet as belonging to one association or another...

             The only thing that I think could confuse you is that "... and
possibly the...". If the peer is not multihomed, it doesn't have to look to
the receiver address, since if it got the packet it means that it went to
his address... This is why the receiver address is not always needed... I
don't know if this is the reason why you have that doubt...

> Does it mean that same source port number is not allowed for different
> associations at a SCTP endpoint?

             This is not allowed only if the source port is the same, but
also the destination port, source address and destination address... i.e.,
it is the same association...

             Otherwise, you don't have any problem to identify the
association to which the packet belongs...

             I hope this helps!

             BR Iván Arias Rodríguez

> Simon

---

From: "Randall Stewart (cisco)" <[email-masked]>
Date: Tue, 05 Nov 2002 17:45:03 -0600

No I don't think any change is needed..
Consider the recevier that is bound to all addresses... and has port 
2222 bound.

When a packet arrives all it need to do is see port 2222 to establish that
it was destined to this endpoint.. it does not need to look at the to 
address.
It WILL need to look at the from address and from port.. to find the correct
association.

It is important not to put MUST's in unless we have a compatibility 
issue involved.
We want to stay away from dictating how to implement things..

R

-- 
Randall R. Stewart
ITD
Cisco Systems Inc.
[email-masked] 815-342-5222(cell) or 815-477-2127(office)