Re: Clarify SCTP max packet size.
Michael Tüxen <[email protected]>
| Newsgroups | gmane.ietf.sigtran |
|---|---|
| Message-ID | <[email protected]> |
Brian, I'm trying to figure out what my mistake is... Are you saying that the SCTP layer will construct SCTP messages which needs to be fragmented at the IP layer? (not considering the case where the path MTU drops and retransmissions are required) I think Pierre assumed that SCTP constructs SCTP messages of 1500 bytes which have no space anymore for the IP header when sent over an 1500 byte MTU ethernet interface. And I do not think that this is the case. Am I wrong? Best regards Michael On Jul 8, 2009, at 1:19 AM, Brian F. G. Bidulock wrote: > Michael, > > I believe I was correcting your statement. > > --brian > > Michael Tüxen wrote: (Wed, 08 Jul > 2009 00:43:33) >> Hi Brian, >> >> sorry, I do not understand what you want to say... >> >> Best regards >> Michael >> >> On Jul 7, 2009, at 8:02 PM, Brian F. G. Bidulock wrote: >> >>> Michael, >>> >>> 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. >>> >>> --brian >>> >>> Michael Tüxen wrote: (Tue, 07 Jul 2009 >>> 18:51:09) >>>> On Jul 7, 2009, at 8:50 AM, <[email protected]> >>>> <[email protected] > wrote: >>>> >>>>> Dear all, >>>>> >>>>> Just to add with the SCTP bundling feature. If the "SCTP MTU" is >>>>> 1500, and the system is bundling messages at the SCTP level, you >>>>> should have the risk to segment at the IP level (because of the IP >>>>> header). So it is not efficient >>>> 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... >>>>> to bundle sctp messages and to segment them at the IP level. Some >>>>> vendors limits "SCTP MTU" to avoid that. This is only the Maximum >>>>> transmission unit. If one SCTP message to transmit is greater, >>>>> they >>>>> will segment it. >>>>> >>> >>> -- >>> Brian F. G. Bidulock >>> [email protected] >>> http://www.openss7.org/ >>> >> > > -- > Brian F. G. Bidulock > [email protected] > http://www.openss7.org/ >