Subject: [tsvwg] Comments on draft-ietf-tsvwg-sctp-ndata-03

From: Magnus Westerlund <[email-masked]>
Date: Tue, 31 Mar 2015 17:18:31 +0200

Hi,

I have reviewed draft-ietf-tsvwg-sctp-ndata-03 and have the following
comments:

1. Section 2.1:

   Reserved: 16 bits (unsigned integer)
      This field is reserved.  It SHOULD be set to 0 by the sender and
      ignored by the receiver.

I think this really needs to be written as:

   Reserved: 16 bits (unsigned integer)
      This field is reserved.  It MUST be set to 0 by the sender and
      MUST be ignored by the receiver.

The reason is that unless you can guarantee pre-extended senders is not
sending a set bit, you can't use a set bit to have semantics. In
addition the ignore part is important. Possbily the reason for this,
i.e. for future extension should be included in text

2. Section 2.3.2:
   When an association resets the SSN using the SCTP extension defined
   in [RFC6525], the two counters (one for the ordered messages, one for
   the unordered messages) used for the MID MUST be reset to 0
   correspondingly.

What happens to messages that are fragmented and partially delivered
when the reset is requested? Is the reset happening after the message,
or is it discarded. What about an interleaved set of in flight messages?

3. Section 3:

The whole section is a To Be Done.

4. Section 6.

Is the risks discussed in the thread that Mo started really fully
mitigated. Can't a malious sender deadlock the thread with any of the
schedulers? Also, what possibilities to starve some messages exists by
playing with others? Please consider a bit more what the implication of
this extension is.

Cheers

Magnus Westerlund

----------------------------------------------------------------------
Services, Media and Network features, Ericsson Research EAB/TXM
----------------------------------------------------------------------
Ericsson AB                 | Phone  +46 10 7148287
Färögatan 6                 | Mobile +46 73 0949079
SE-164 80 Stockholm, Sweden | mailto: [email-masked]
----------------------------------------------------------------------