These is a significant number of operators that use PPPoE, and L2TP. Either simply for backhaul (where old ATM based DSL is still deployed and elsewhere) and/ or wholesale. I checked BBF TR-92 which would be the like source of any recommendations on using sequencing but it is silent on the subject.
Dave -----Original Message----- From: Int-area <[email protected]> On Behalf Of Joel Halpern Direct Sent: Wednesday, June 9, 2021 6:10 AM To: Stewart Bryant <[email protected]>; Joel Halpern <[email protected]> Cc: Carlos Pignataro (cpignata) <[email protected]>; Ignacio Goyret <[email protected]>; intarea IETF list <[email protected]>; Derek Fawcus <[email protected]>; [email protected] Subject: Re: [Int-area] L2TP sequencing: Commonly disabled for IP data? Or always? BNGs are still a big busienss. And BNG resale /emote control uses L2TP in many cases. The BBF has been working on (and published a first version of) protocol for control of split BNG. L2TP is commonly used for these use cases. Yours, Joel On 6/9/2021 7:50 AM, Stewart Bryant wrote: > Which applications still use it Joel? > > Stewart > >> On 9 Jun 2021, at 12:42, Joel M. Halpern <[email protected]> wrote: >> >> There is plenty of L2TP still in use. >> Yours, >> Joel >> >> On 6/9/2021 6:23 AM, Stewart Bryant wrote: >>> Sequence number checking in the forwarder is always a problem because it is >>> stateful so I doubt that many high-scale or high-speed forwarders ever did >>> this. >>> I think there is an undisclosed assumption that go up enough levels and its >>> IP so sequence number checking in the transport network (as opposed to the >>> transport layer) is not really needed. >>> I doubt that there is much L2TP still out there. It was in its prime with >>> dialup modems. L2TPv3 which was intended to replace it became niche with, >>> as Andy says, operators who did not want MPLS. Much of what L2TPv3 was >>> intended for was actually done with PW over MPLS with some replacement with >>> by Mac in Mac for cost reasons. >>> If Carlos does not know the answer, Mark T would be my next port of call. >>> Stewart >>>> On 8 Jun 2021, at 22:41, Andrew G. Malis <[email protected] >>>> <mailto:[email protected]>> wrote: >>>> >>>> Bob, >>>> >>>> In addition to the cases listed by Derek, L2TPv3 can also carry non-IP >>>> pseudowire data, such as Ethernet frames (see RFC 4719 for example). Even >>>> though 4719 says that sequencing is optional, I would certainly recommend >>>> it :-). >>>> >>>> But I guess that's really not what you were asking about, since you >>>> specifically mentioned IP data. But it is a case where you would probably >>>> see sequencing in use. >>>> >>>> Back in the day, Sprint made good use of Ethernet over L2TPv3, as they >>>> were in the anti-MPLS camp at the time. But that's water over the bridge, >>>> and I really don't know if this solution continues to be in active use. >>>> Mark Townsley might know. >>>> >>>> Cheers, >>>> Andy >>>> >>>> >>>> On Sat, Jun 5, 2021 at 10:07 AM Derek Fawcus >>>> <[email protected] >>>> <mailto:dfawcus%[email protected]>> wrote: >>>> >>>> On Fri, Jun 04, 2021 at 03:13:15PM +0100, Bob Briscoe wrote: >>>> > The L2TP RFC says sequencing /can/ be disabled for IP data, but it >>>> > doesn't say SHOULD or MUST. Is it possible that some operators >>>> enable >>>> > L2TP sequencing for IP data? And if so, do you know why they would? >>>> > Also, are you aware of any other types of tunnel that might try >>>> to keep >>>> > IP data packets in sequence? >>>> >>>> How many intermediate headers are you considering between L2TP and >>>> where >>>> a carried IP header may exist? >>>> >>>> Maybe I'm getting the wrong end of the stick, but surely this engages >>>> the text from section 5.4 of RFC 2661: >>>> >>>> "For example, if the PPP session being tunneled is not >>>> utilizing any stateful compression or encryption protocols and is >>>> only carrying IP (as determined by the PPP NCPs that are >>>> established), then the LNS might decide to disable sequencing as IP >>>> is tolerant to datagram loss and reordering." >>>> >>>> This would then suggest if L2TP is carrying PPP, the PPP session >>>> is not >>>> multi-link, and is making use of compression (including one of the >>>> versions of IP header compression) in some form for IP packets, then >>>> reordering will impact the ability to decompress. >>>> >>>> So such an L2TP data session may well make use of sequence numbers to >>>> prevent reordering. >>>> >>>> I guess similarly in L2TPv3 when the PW is for PPP, and possibly also >>>> the fragmentation scheme in RFC 4623 which requires sequence numbers; >>>> and such PWE3 links could ultimately be carrying IP packets. >>>> >>>> >>>> DF >>>> >>>> (not an operator) >>>> >>>> _______________________________________________ >>>> Int-area mailing list >>>> [email protected] <mailto:[email protected]> >>>> https://www.ietf.org/mailman/listinfo/int-area >>>> <https://www.ietf.org/mailman/listinfo/int-area> >>>> >>>> _______________________________________________ >>>> Int-area mailing list >>>> [email protected] <mailto:[email protected]> >>>> https://www.ietf.org/mailman/listinfo/int-area >>> _______________________________________________ >>> Int-area mailing list >>> [email protected] >>> https://www.ietf.org/mailman/listinfo/int-area > _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area
