Hi Tom, > -----Original Message----- > From: Tom Herbert [mailto:t...@herbertland.com] > Sent: Wednesday, March 23, 2022 6:19 AM > To: Templin (US), Fred L <fred.l.temp...@boeing.com> > Cc: Eggert, Lars <l...@netapp.com>; int-area@ietf.org; 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> wrote: > > > > Tom, see below: > > > > > -----Original Message----- > > > From: Tom Herbert [mailto:t...@herbertland.com] > > > Sent: Tuesday, March 22, 2022 10:00 AM > > > To: Templin (US), Fred L <fred.l.temp...@boeing.com> > > > Cc: Eggert, Lars <l...@netapp.com>; 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> 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. As far as I am aware, there are currently no hardware checksum offload implementations available for calculating the LTP checksums. 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. Fred > > Tom > > > Fred > > > > > Thanks, > > > Tom > > > > > > > > > > > > > > > > > > > Thanks - Fred > > > > > > > > _______________________________________________ > > > > Int-area mailing list > > > > Int-area@ietf.org > > > > https://www.ietf.org/mailman/listinfo/int-area _______________________________________________ Int-area mailing list Int-area@ietf.org https://www.ietf.org/mailman/listinfo/int-area
