Tom, looks like you have switched over to HTML which can be a real conversation-killer. But, to some points you raised that require a response:
>You can't turn it off UDP checksums for IPv6 (except for narrow case of >encapsulation). That sounds like a good reason to continue to use IPv4 – at least as far as end system addressing is concerned – right? >If it's a standard per packet Internet checksum then a lot of HW could do it. >If it's something like CRC32 then probably not. The integrity check is covered in RFC5327, and I honestly haven’t had a chance to look at that myself yet. >LTP is a nice experiment, but I'm more interested as to the interaction >between IP parcels and TCP or QUIC. Please be aware that while LTP may seem obscure at the moment that may be changing now that the core DTN standards have been published. As DTN use becomes more widespread I think we can see LTP also come into wider adoption. >There was quite a bit of work and discussion on this in Linux. I believe the >deviation from the standard was motivated by some >deployed devices required the IPID be set on receive, and setting IPID with DF >equals to 1 is thought to be innocuous. You may >want to look at Alex Duyck's papers on UDP GSO, he wrote a lot of code in this >area. RFC6864 has quite a bit to say about coding IP ID with DF=1 – mostly in the negative. But, what I have seen in the linux code seems to indicate that there is not even any coordination between the GSO source and the GRO destination – instead, GRO simply starts gluing together packets that appear to have consecutive IP IDs without ever first checking that they were sent by a peer that was earnestly doing GSO. These aspects would make it very difficult to work GSO/GRO into an IETF standard, plus it doesn’t work for IPv6 at all where there is no IP ID included by default. IP Parcels addresses all of these points, and can be made into a standard. Fred From: Tom Herbert [mailto:t...@herbertland.com] Sent: Wednesday, March 23, 2022 9:37 AM To: Templin (US), Fred L <fred.l.temp...@boeing.com> Cc: Eggert, Lars <l...@netapp.com>; int-area <int-area@ietf.org>; l...@eggert.org Subject: Re: [EXTERNAL] Re: [Int-area] IP Parcels improves performance for end systems EXT email: be mindful of links/attachments. On Wed, Mar 23, 2022, 9:54 AM Templin (US), Fred L <fred.l.temp...@boeing.com<mailto:fred.l.temp...@boeing.com>> wrote: Hi Tom, > -----Original Message----- > From: Tom Herbert [mailto:t...@herbertland.com<mailto:t...@herbertland.com>] > Sent: Wednesday, March 23, 2022 6:19 AM > To: Templin (US), Fred L > <fred.l.temp...@boeing.com<mailto:fred.l.temp...@boeing.com>> > Cc: Eggert, Lars <l...@netapp.com<mailto:l...@netapp.com>>; > int-area@ietf.org<mailto:int-area@ietf.org>; > l...@eggert.org<mailto:l...@eggert.org> > Subject: Re: [Int-area] IP Parcels improves performance for end systems > > On Tue, Mar 22, 2022 at 10:38 AM Templin (US), Fred L > <fred.l.temp...@boeing.com<mailto:fred.l.temp...@boeing.com>> wrote: > > > > Tom, see below: > > > > > -----Original Message----- > > > From: Tom Herbert > > > [mailto:t...@herbertland.com<mailto:t...@herbertland.com>] > > > Sent: Tuesday, March 22, 2022 10:00 AM > > > To: Templin (US), Fred L > > > <fred.l.temp...@boeing.com<mailto:fred.l.temp...@boeing.com>> > > > Cc: Eggert, Lars <l...@netapp.com<mailto:l...@netapp.com>>; > > > int-area@ietf.org<mailto:int-area@ietf.org> > > > Subject: Re: [Int-area] IP Parcels improves performance for end systems > > > > > > On Tue, Mar 22, 2022 at 7:42 AM Templin (US), Fred L > > > <fred.l.temp...@boeing.com<mailto:fred.l.temp...@boeing.com>> wrote: > > > > > > > > Lars, I did a poor job of answering your question. One of the most > > > > important aspects of > > > > > > > > IP Parcels in relation to TSO and GSO/GRO is that transports get to use > > > > a full 4MB buffer > > > > > > > > instead of the 64KB limit in current practices. This is possible due to > > > > the IP Parcel jumbo > > > > > > > > payload option encapsulation which provides a 32-bit length field > > > > instead of just a 16-bit. > > > > > > > > By allowing the transport to present the IP layer with a buffer of up > > > > to 4MB, it reduces > > > > > > > > the overhead, minimizes system calls and interrupts, etc. > > > > > > > > > > > > > > > > So, yes, IP Parcels is very much about improving the performance for > > > > end systems in > > > > > > > > comparison with current practice (GSO/GRO and TSO). > > > > > > Hi Fred, > > > > > > The nice thing about TSO/GSO/GRO is that they don't require any > > > changes to the protocol as just implementation techniques, also > > > they're one sided opitmizations meaning for instance that TSO can be > > > used at the sender without requiring GRO to be used at the receiver. > > > My understanding is that IP parcels requires new protocol that would > > > need to be implemented on both endpoints and possibly in some routers. > > > > It is not entirely true that the protocol needs to be implemented on both > > endpoints . Sources that send IP Parcels send them into a Parcel-capable > > path > > which ends at either the final destination or a router for which the next > > hop is > > not Parcel-capable. If the Parcel-capable path extends all the way to the > > final > > destination, then the Parcel is delivered to the destination which knows how > > to deal with it. If the Parcel-capable path ends at a router somewhere in > > the > > middle, the router opens the Parcel and sends each enclosed segment as an > > independent IP packet. The final destination is then free to apply GRO to > > the > > incoming IP packets even if it does not understand Parcels. > > > > IP Parcels is about efficient shipping and handling just like the major > > online > > retailer service model I described during the talk. The goal is to deliver > > the > > fewest and largest possible parcels to the final destination rather than > > delivering lots of small IP packets. It is good for the network and good for > > the end systems both. If this were not true, then Amazon would send the > > consumer 50 small boxes with 1 item each instead of 1 larger box with all > > 50 items inside. And, we all know what they would choose to do. > > > > > Do you have data that shows the benefits of IP Parcels in light of > > > these requirements? > > > > I have data that shows that GSO/GRO is good for packaging sizes up to 64KB > > even if the enclosed segments will require IP fragmentation upon > > transmission. > > The data implies that even larger packaging sizes (up to a maximum of 4MB) > > would be better still. > > > > Fred, > > You seem to be only looking at the problem from a per packet cost > point of view. There is also per byte cost, particularly in the > computation of the TCP/UDP checksum. The cost is hidden in modern > implementations by checksum offload, and for segmentation offload we > have methods to preserve the utility of checksum offload. IP parcels > will have to also leverage checksum offload, because if the checksum > is not offloaded then the cost of computing the payload checksum in > CPU would dwarf any benefits we'd get by using segments larger than > 64K. There is plenty of opportunity to apply hardware checksum offload since the structure of a Parcel will be very standard. My experiments have been with a protocol called LTP which is layered over UDP/IP as some other upper layer protocols are. LTP includes a segment-by-segment checksum that is used at its level in the absence of lower layer integrity checks, so for larger Parcels LTP would use that and turn off UDP checksums altogether. You can't turn it off UDP checksums for IPv6 (except for narrow case of encapsulation). As far as I am aware, there are currently no hardware checksum offload implementations available for calculating the LTP checksums. If it's a standard per packet Internet checksum then a lot of HW could do it. If it's something like CRC32 then probably not. LTP is a nice experiment, but I'm more interested as to the interaction between IP parcels and TCP or QUIC. Speaking of standard, AFAICT GSO/GRO are doing something very non-standard. GSO seems to be coding the IP ID field in the IPv4 headers of packets with DF=1 which goes against RFC 6864. When DF=1, GSO cannot simply claim the IP ID and code it as if there were some sort of protocol. Or, if it does, there would be no way to standardize it. There was quite a bit of work and discussion on this in Linux. I believe the deviation from the standard was motivated by some deployed devices required the IPID be set on receive, and setting IPID with DF equals to 1 is thought to be innocuous. You may want to look at Alex Duyck's papers on UDP GSO, he wrote a lot of code in this area. Tom Fred > > Tom > > > Fred > > > > > Thanks, > > > Tom > > > > > > > > > > > > > > > > > > > Thanks - Fred > > > > > > > > _______________________________________________ > > > > Int-area mailing list > > > > Int-area@ietf.org<mailto:Int-area@ietf.org> > > > > https://www.ietf.org/mailman/listinfo/int-area
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