Subject: Same source ports for different associations

From: [email-masked]
Date: Tue, 5 Nov 2002 14:40:53 -0500

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.

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

Simon

---

From: Nivedita Singhvi <[email-masked]>
Date: Tue, 05 Nov 2002 12:35:27 -0800

> associations at a SCTP endpoint?

I'm replying here to the list just to clarify my own very limited 
knowledge so far of SCTP. From what I understand, an association 
exists between 2 SCTP endpoints, and can span multiple addresses.
So the src port # is the same, while multiple addresses (or a single
wildcard address) can be specified for that association. 
i.e. A particular endpoint will use a particular port, and can
have multiple transport addresses associated with it. You cannot 
have two different associations using the same port number.

Can some SCTP person confirm that?

thanks,
Nivedita

---

From: Janardhan Iyengar <[email-masked]>
Date: Tue, 5 Nov 2002 15:52:38 -0500 (EST)

Simon,

> problem to identify the association.

This is the standard 4-tuple {srcIP, srcPort, dstIP, dstPort} used to
identify connections (in TCP) and associations (in SCTP). In the case you
mention, the receiver can still identify the association to which the
packet belongs due to the different destination port numbers.

Hope that helps.

cheers,
jana

-----------------------------------------------------------------------
Janardhan R. Iyengar				   [email-masked]
University of Delaware		       http://www.cis.udel.edu/~iyengar
-----------------------------------------------------------------------

---

From: Kavitha Baratakke <[email-masked]>
Date: Tue, 05 Nov 2002 15:14:20 -0600

> Can some SCTP person confirm that?

Multiple associations can use the same source IP address as well as port
(as long as the 4-tuple is unique)
In case of UDP-style assoc for example multiple associations use the
same socket, which is bound to a specified port/ephemeral port (if not
bound explicitly) . The incoming messages to the different associations
using this socket can be identified based the foreign port and address
combination (assuming that this is unique for two diff assocs)

Thanks,
Kavitha

-- 
Thanks, 
Kavitha
_________________________________________________________________

Ms. Kavitha V. Baratakke     IBM Corporation
Office : (512)-838-1226      AIX TCP/IP Kernel Development & Support
T/L : 678-1226               11501, Burnet Road, Austin TX 78758