> > > The world is not just TCP anymore. QUIC and other UDP-based transports > have already > > shown performance increases using facilities like GSO/GRO which are > essentially a short > > term and non-standard implementation of what parcels promise to do in the > long term. >
Fred, Can you explain why GSO/GRO aren't sufficient and are only short term solutions? We've been using these for almost twenty years now with good effect. These are widely deployed with TCP, TSO works well to offload transmit, LRO is defined and is in much better shape to offload RX now that programmable devices are emerging. For TCP it's hard to see how IP parcels would help significantly, but even for UDP we now have UDP GSO, sendmmsg, and recvmmsg that mitigate the cost of system calls and interrupts to which the draft refers. The reason these aren't standards in IETF is because they're implementation techniques and not protocol (although I will point out that GSO/GRO/sendmmsg/recvmmsg are in all Linux devices so that effectively makes it a de facto implementation standard). I am also concerned about the idea that intermediate devices would perform reassembly. This has a whole bunch of implications like middleboxes are no longer work conserving and seems to have the implicit requirement that it has to be in the path of every packet in a parcel (i.e. even in the case of the last hop performing reassembly. Also, as simply a matter of resources and capabilities, hosts are in a much better position to perform tasks like reassembly. I don't readily see that having intermediate devices perform reassembly would be a win for hosts, and even if it were, host implementations still would need the capability to perform reassembly themselves since they will never rely on the network to always do it for them. Tom > > > Thanks - Fred > > > > *From:* to...@strayalpha.com [mailto:to...@strayalpha.com] > *Sent:* Sunday, December 19, 2021 11:53 AM > *To:* Templin (US), Fred L <fred.l.temp...@boeing.com> > *Cc:* int-area@ietf.org; Wes Eddy <w...@mti-systems.com> > *Subject:* Re: [Int-area] IP parcels > > > > Hi, Fred (et al.), > > > > On Dec 19, 2021, at 10:21 AM, Templin (US), Fred L < > fred.l.temp...@boeing.com> wrote: > > > > Joe, your insistence on using html makes it impossible to respond to all > of your points inline > > which is the reason for my top-posts. > > > > I use MacOS mail, IOS mail, and Thunderbird on Windows, all using default > configurations, FWIW. I appear to be able to post inside everyone else’s > responses. I don’t know if the IETF’s mailers are munging formats, though. > > > > I’ve made my position clear. However: > > > > - You still haven’t shown any evidence that end systems need to do all > this extra work so they can somehow run faster, nor that this will be > noticeably faster than large (i.e., 20-60KB) IPv4 packets. > > > > - You still haven’t shown any reason why this is feasible; in fact, below > you add the idea of on-path fragmentation, which is largely deprecated > because fragments won’t traverse tunnels (in your case, notably for single > chunks larger than 64KB). Nevermind that the fragmentation is both > expensive and slow-path at routers. > > > > - You have claimed that both routers and transports will somehow adopt > this when we can’t even get reasonably large MTUs that already fit within > IPv4 across heterogeneous enterprises. > > > > IPv4 is over; even if you don’t think so, any way forward with larger > packets starts with: > > a) getting ~64KB IP packets across the net > > b) after (a), prove that >64KB are needed based on the > IPv6 jumbo approach > > > > Any way forward with a lot of small packets inside one large one (where > both chunks and total length are less than 64K) starts by proving there’s a > need and it fixing how TCP interacts with its inherent burstiness and loss > correlation. > > > > Only THEN will this issue be worth more discussion. > > > > Joe > > > > > > Parcels that contain a single segment whether 64K or considerably less are > still sent as > > (singleton) parcels and not ordinary packets. That way, nodes in the > network can know > > that it is OK to encapsulate and fragment since by asserting its interest > in receiving parcels > > the destination has also subscribed to being able to reassemble up to a > full 64K. > > > > Parcels do not set (Payload Length / Total Length) to 0; they set it to > the length of the > > first element of the parcel (which is also the same length of each > non-final element of > > the parcel). What happens then is that network equipment will see a unit > with an L3 > > length that may be considerably shorter than the L2 length. You are right > that legacy > > routers might not like this (or, they might truncate the packet according > to L3 length), > > and so for paths that might traverse legacy routers the first-hop node > that recognizes > > parcels instead encapsulates the parcel in an IPv4 or IPv6 header then > performs (source) > > fragmentation if necessary. These IP fragments will then travel through > legacy routers > > just fine. > > > > About RFC793bis, you and Wes Eddy know far more about its status than I > do; I only > > noted that this is something with TCP implications and so made mention of > it in case > > there is still room for a few more engine tweaks while the hood is still > open. > > > > About IPv4, I am currently running IPv4 edge networks with IPv4-in-IPv6 > tunnel endpoints > > connected to an IPv6 transit network and it works really good. End systems > get to use > > smaller addresses and smaller headers, and they can talk to remote > correspondents using > > IPv4 as if they were all on the same IPv4 network. So yes, I think we > might still want to > > consider IPv4 for edge networks like that. > > > > About getting 64K packets across, only the edge networks or end systems > see them as > > large packets; in the core thy are typically broken up into something much > smaller by > > ingress nodes that apply segmentation/fragmentation. We don’t need the > core to move > > to jumbo links; we only need that at the edges. ATM taught us that. > > > > About our “nail”, end systems get to see larger packets/parcels and get to > take advantage > > of the reduced interrupts and system call overhead they provide. That is > what makes it > > worthwhile. > > > > Fred > > > > *From:* to...@strayalpha.com [mailto:to...@strayalpha.com > <to...@strayalpha.com>] > *Sent:* Saturday, December 18, 2021 8:13 PM > *To:* Templin (US), Fred L <fred.l.temp...@boeing.com> > *Cc:* int-area@ietf.org; Wes Eddy <w...@mti-systems.com> > *Subject:* Re: [Int-area] IP parcels > > > > HI, Fred, > > > > If you have one segment that’s less than 64K, you don’t need the parcel > option at all. > > > > If you have something longer than 64K, either as a single segment or > multiple smaller segments, by setting total length to 0, you end up being > dropped by legacy routers, which either ignore options they don’t > understand or drop packets with options they don’t support. > > > > RFC793bis does talk about IPv6 jumbos, but this new work is out of scope > for RFC793bis - furthermore, it’s too late. It has passed WGLC, IETF LC, > and is currently in IESG review for publication. > > > > You also haven’t addressed why the IETF should be taking up this *new* > work for IPv4, which I thought also had been considered ineligible. > > > > But overall, again, what’s the point? We can’t even get 64K IP packets > through the Internet; making them larger doesn’t make that easier or more > likely. Such large sizes are of diminishing benefit; routers already > forward at 40Gbps per link for minimal packets and end systems have other > problems that this exacerbates. > > > > This seems a lot like a huge hammer in search of a nail. Where’s the nail? > > > > Joe > > > > — > > Joe Touch, temporal epistemologist > > www.strayalpha.com > > > > > On Dec 18, 2021, at 7:18 PM, Templin (US), Fred L < > fred.l.temp...@boeing.com> wrote: > > > > Joe, I never said that I wanted to restrict this to small transport > segments; in fact, I want > > just the opposite – I want large segments. A perfectly legal parcel is one > which includes 1 > > ~64KB segment - another legal parcel is one which includes 64 of them! If > you want bigger > > segments than that, then true jumbos are necessary and this spec does not > preclude that. > > > > About RFC793(bis), I see there is a section on Jumbos and IP parcels is > (sort of) an application > > of Jumbos. > > > > Fred > > > > *From:* to...@strayalpha.com [mailto:to...@strayalpha.com > <to...@strayalpha.com>] > *Sent:* Saturday, December 18, 2021 4:57 PM > *To:* Templin (US), Fred L <fred.l.temp...@boeing.com> > *Cc:* int-area@ietf.org; Wes Eddy <w...@mti-systems.com> > *Subject:* [EXTERNAL] Re: [Int-area] IP parcels > > > > EXT email: be mindful of links/attachments. > > > > > Hi, Fred, > > > > Regarding 793bis, new ideas are out of scope. It’s supposed to be a > roll-in of existing items only. > > > > Nevermind the problems below, which “TCP will find a way” doesn’t > magically fix. > > > > The problem is this: > > - end systems need to send larger transport segments (not just IP segments) > > - if they can do that, they should, filling up to the largest IP payload > > > > Having an IP packet have the opportunity to include lots of small > transport packets assumes transport packets either work better or faster > when they’re small. It’s the opposite. > > > > Joe > > > > — > > Joe Touch, temporal epistemologist > > www.strayalpha.com > > > > > > On Dec 18, 2021, at 4:42 PM, Templin (US), Fred L < > fred.l.temp...@boeing.com> wrote: > > > > Joe, TCP will find a way to adapt – it always has. I also see that TCP is > currently undergoing > > a second edition revision so the timing seems right to consider IP parcels > in the analysis. > > I am Cc’ing the second edition editor for his information – Wesley, please > consider this > > new concept called “IP Parcels” as it relates to your document. > > > > Here is the latest draft version – it expands on the “Motivation” section > and adds a number > > of important feature such as a new “Parcels Permitted” TCP option: > > > > https://datatracker.ietf.org/doc/draft-templin-intarea-parcels/ > > > > Fred > > > > *From:* to...@strayalpha.com [mailto:to...@strayalpha.com > <to...@strayalpha.com>] > *Sent:* Friday, December 17, 2021 6:01 PM > *To:* Templin (US), Fred L <fred.l.temp...@boeing.com> > *Cc:* int-area@ietf.org > *Subject:* Re: [Int-area] IP parcels > > > > Hi, Fred, > > > > I’m first concerned at the use of an IP option at all, due to the problems > with *any* options forcing processing to slow-path. > > > > From TCP’s viewpoint, it seems like you’ve just created a nightmare for > SACK and ECN, basically because you will encourage drops of large bursts of > packets. > > > > This will also increase the bustiness of TCP, i.e., rather than letting > the ACKs support pacing. > > > > Any part of the system that currently coalesces TCP packets is likely to > generate errors here, because they might see only the first TCP segment. > > > > However, AFAICT the most significant consideration is that the issue with > per-packet performance is at the TCP and UDP layers, not as much at the IP > layer. > > > > So what problem is this trying to solve? > > > > Joe > > — > > Joe Touch, temporal epistemologist > > www.strayalpha.com > > > > > > > On Dec 17, 2021, at 5:06 PM, Templin (US), Fred L < > fred.l.temp...@boeing.com> wrote: > > > > Here's one that should help with shipping, just in time for Christmas. > Thanks > to everyone for the past and future list exchanges. > > Fred > > -----Original Message----- > From: I-D-Announce [mailto:i-d-announce-boun...@ietf.org > <i-d-announce-boun...@ietf.org>] On Behalf Of internet-dra...@ietf.org > Sent: Friday, December 17, 2021 5:00 PM > To: i-d-annou...@ietf.org > Subject: I-D Action: draft-templin-intarea-parcels-00.txt > > > A New Internet-Draft is available from the on-line Internet-Drafts > directories. > > > Title : IP Parcels > Author : Fred L. Templin > Filename : draft-templin-intarea-parcels-00.txt > Pages : 8 > Date : 2021-12-17 > > Abstract: > IP packets (both IPv4 and IPv6) are understood to contain a unit of > data which becomes the retransmission unit in case of loss. Upper > layer protocols such as the Transmission Control Protocol (TCP) > prepare data units known as "segments", with traditional arrangements > including a single segment per packet. This document presents a new > construct known as the "IP Parcel" which permits a single packet to > carry multiple segments. The parcel can be opened at middleboxes on > the path with the included segments broken out into individual > packets, then rejoined into one or more repackaged parcels to be > forwarded further toward the final destination. Reordering of > segments within parcels is unimportant; what matters is that the > number of parcels delivered to the final destination should be kept > to a minimum, and that loss or receipt of individual segments (and > not parcel size) determines the retransmission unit. > > > The IETF datatracker status page for this draft is: > https://datatracker.ietf.org/doc/draft-templin-intarea-parcels/ > > There is also an htmlized version available at: > https://datatracker.ietf.org/doc/html/draft-templin-intarea-parcels-00 > > > Internet-Drafts are also available by rsync at rsync.ietf.org > ::internet-drafts > > > _______________________________________________ > I-D-Announce mailing list > i-d-annou...@ietf.org > https://www.ietf.org/mailman/listinfo/i-d-announce > Internet-Draft directories: http://www.ietf.org/shadow.html > or ftp://ftp.ietf.org/ietf/1shadow-sites.txt > > _______________________________________________ > 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 >
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