Re: Clarify SCTP max packet size.
Michael Tüxen <[email protected]>
| Newsgroups | gmane.ietf.sigtran |
|---|---|
| Message-ID | <[email protected]> |
On Jul 8, 2009, at 2:13 PM, Brian F. G. Bidulock wrote: > Michael, > >>>> On Jul 7, 2009, at 8:02 PM, Brian F. G. Bidulock wrote: >>>>> Err, the MTU SCTP uses when bundling is the Association Path MTU. >>>>> It subtracts IP header and SCTP header sizes from this Path MTU >>>>> only when considering how many chunks can be bundled. > >>>>> Michael Tüxen wrote: (Tue, 07 Jul 2009 >>>>>> The MTU SCTP uses is the link layer MTU minus the headers for IP >>>>>> and SCTP. I have not seen an implementation which bundles at the >>>>>> SCTP layer and than needs to fragment at the IP layer. I would >>>>>> consider this broken... > > Look at what you wrote. What I am saying is: > > 1. The MTU SCTP uses is _NOT_ the link layer MTU: it is the > association path MTU. > > 2. The MTU SCTP uses is _NOT_ minus the IP and SCTP headers: it > is the association path MTU. This is the MTU used in all > SCTP calculations. > > 3. When SCTP goes to bundle chunks, the packet space available > for bundling chunks is the association path MTU minus the IP > and SCTP headers. > > To summarize, when the association path MTU is 1500 (typical), > the value 1500 is used for the MTU in calculations (windows, > threshold, etc.) However, when SCTP goes to bundle chunks, > the room available for chunks is (1500 - IP hdr - SCTP hdr). I agree, I was just sloppy in writing... Best regards Michael > > --brian > > -- > Brian F. G. Bidulock > [email protected] > http://www.openss7.org/ >