Re: [tsvwg] SCTP ABC
Michael Tuexen <michael.tuexen@lurchi.franken.de> Thu, 24 June 2021 07:54 UTC
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From: Michael Tuexen <michael.tuexen@lurchi.franken.de>
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Date: Thu, 24 Jun 2021 09:53:51 +0200
Cc: Timo Völker <timo.voelker@fh-muenster.de>, tsvwg@ietf.org
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To: "Gorry (erg)" <gorry@erg.abdn.ac.uk>
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Subject: Re: [tsvwg] SCTP ABC
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> On 24. Jun 2021, at 09:45, Gorry (erg) <gorry@erg.abdn.ac.uk> wrote: > > See below: > >> On 23 Jun 2021, at 16:02, Timo Völker <timo.voelker@fh-muenster.de> wrote: >> >> Hi, >> >> SCTP (RFC4960) limits the increase of its cwnd in slow start to one PMTU (or PMDCS as named in the rfc4960-bis document) as stated in Section 7.2.1. This means the cwnd may be increased less when the receiver sends an ack on every second packet compared to on every packet. >> >> --- >> Ex: >> 1. A sender in slow start with PMTU=1200 sends two packets with 1000 byte of data each. >> >>> DATA(len=1000, tsn=1) >>> DATA(len=1000, tsn=2) >> >> 2a. In case the receiver sends an ack on every packet, the sender receives two acks. >> >> < ACK(cum_tsn=1) >> --> cwnd += 1000 >> < ACK(cum_tsn=2) >> --> cwnd += 1000 >> >> resulting in a cwnd increased by 2000 byte. >> >> 2b. In case the receiver sends an ack on every second packet, the sender receives one ack for both packets. >> >> < ACK(cum_tsn=2) >> --> cwnd += 1200 >> >> resulting in a cwnd increased by only 1200 byte due to the PMTU limit. >> --- >> >> TCP's Appropriate Byte Counting (ABC) specified in RFC3465 addresses that with the parameter L set to 2*SMSS. >> >> Adding a note for that in rfc4960-bis would help, I think. >> >> Timo > > What do others think? > > Are the SCTP implementors happy with this proposal? I would support integrating the ABC idea. This has been implemented in the FreeBSD kernel stack and the userland stack for a long time. Best regards Michael > > Gorry
- [tsvwg] SCTP ABC Timo Völker
- Re: [tsvwg] SCTP ABC Gorry (erg)
- Re: [tsvwg] SCTP ABC Michael Tuexen