Joe, I will do my best to respond to your points in the following top posts;
you may not
like it but it is the best I can do:
- 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.
There is evidence supplied in the latest parcel draft versions, beginning with
the -02.
- 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.
This will involve unpacking of the parcel and placing the unpacked sub-parcels
into a tunnel as the (unfragmented) transit packet. Then, if any fragmentation
is necessary, the OMNI link ingress fragments the *tunnel* packet; not the
*transit* packet. And, this work will occur only at OMNI ingress and egress
nodes and not at any high-speed routers on the path. Those routers will see
only MTU-sized and smaller IP packets whizzing past at line rate.
- 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.
No, not routers. Routers will continue to see only line-rate and MTU or smaller
sized IP packets. Only the end systems and the OMNI ingress/egress nodes need
to do any extra work.
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
I still have IPv4 working really good in environments where the longer IPv6
addresses
are not necessary, and the network layer headers are only half the size. Why
would I
throw that away? About getting ~64KB across the net, parcels have that covered
with
IP fragmentation/reassembly used if necessary. And end systems only receive
parcels
if they ask for them, which means that they assert they can reassemble all the
way up
to 64KB as opposed to restricting to something smaller like the 576/1500
minimum.
About exceeding 64KB, we will want to start out doing that with parcels that
contain
multiple smaller segments instead of sending just a single large segment for
peers that
are located in different edge networks joined by an OMNI link. You may be right
that
peers in the same edge network with huge link MTUs may eventually want to use
true
jumbos (i.e., that carry large segments) but for going over the core parcels
are a better.
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.
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.
Thanks - Fred
From: [email protected] [mailto:[email protected]]
Sent: Sunday, December 19, 2021 11:53 AM
To: Templin (US), Fred L <[email protected]>
Cc: [email protected]; Wes Eddy <[email protected]>
Subject: Re: [Int-area] IP parcels
Hi, Fred (et al.),
On Dec 19, 2021, at 10:21 AM, Templin (US), Fred L
<[email protected]<mailto:[email protected]>> 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: [email protected]<mailto:[email protected]>
[mailto:[email protected]]
Sent: Saturday, December 18, 2021 8:13 PM
To: Templin (US), Fred L
<[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>; Wes Eddy
<[email protected]<mailto:[email protected]>>
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<http://www.strayalpha.com/>
On Dec 18, 2021, at 7:18 PM, Templin (US), Fred L
<[email protected]<mailto:[email protected]>> 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: [email protected]<mailto:[email protected]>
[mailto:[email protected]]
Sent: Saturday, December 18, 2021 4:57 PM
To: Templin (US), Fred L
<[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>; Wes Eddy
<[email protected]<mailto:[email protected]>>
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<http://www.strayalpha.com/>
On Dec 18, 2021, at 4:42 PM, Templin (US), Fred L
<[email protected]<mailto:[email protected]>> 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: [email protected]<mailto:[email protected]>
[mailto:[email protected]]
Sent: Friday, December 17, 2021 6:01 PM
To: Templin (US), Fred L
<[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>
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<http://www.strayalpha.com/>
On Dec 17, 2021, at 5:06 PM, Templin (US), Fred L
<[email protected]<mailto:[email protected]>> 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:[email protected]] On Behalf Of
[email protected]<mailto:[email protected]>
Sent: Friday, December 17, 2021 5:00 PM
To: [email protected]<mailto:[email protected]>
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<http://rsync.ietf.org/>::internet-drafts
_______________________________________________
I-D-Announce mailing list
[email protected]<mailto:[email protected]>
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
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Int-area mailing list
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