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RE: #540: "jumbo" frames

From: <K.Morgan@iaea.org>
Date: Wed, 25 Jun 2014 09:35:59 +0000
To: <mnot@mnot.net>, <phk@phk.freebsd.dk>
CC: <w@1wt.eu>, <gregw@intalio.com>, <ietf-http-wg@w3.org>, <duerst@it.aoyama.ac.jp>
Message-ID: <0356EBBE092D394F9291DA01E8D28EC201186E0DD6@sem002pd.sg.iaea.org>
On Wednesday,25 June 2014 06:11, mnot@mnot.net wrote:
> The simplest way to address this would be to un-reserve the first two bits of the length
> <http://http2.github.io/http2-spec/#rfc.section.4.1>; that would get us back up to 64k,
> letting Willy get to 35 Gbps. Given that 256k only got him to 40 Gbps, that seems like a
> reasonable stopping point for HTTP/2.

Bad idea IMO.  That would really paint HTTP/2 into a corner.  With no reserved bits left, there would never be a chance to go above 64K frames.  i.e. you could never " back-port bigger frames onto an existing protocol"

> Doing more than 16 bits would take a lot more back-and-forth in the WG,
> and is likely to encounter a lot of resistance from implementers, from what I've seen.

We've been talking about jumbo frames for a week already and there hasn't been any resistance from "implementers".

I'll point out again that jumbo frames are optional.  As Matthew points out, the proposed setting can simply be ignored.

> WRT the "jumbo" frame (i.e., flagging that some prefix of the payload is actually an extension length)
> -- this sort of hack is necessary to back-port bigger frames onto an existing protocol. Let's not do it out of the gate.

Then make the frame length 64 bits and be done with it.  That's a lot of wasted bits though for those who just want to use 16K frames.

So barring a change to 64 bits, you need the CONTINUATION hack or the "jumbo frame" hack.  Which hack is better?

So far I've heard the following arguments in favour of "jumbo frames":
- Willy: higher performance for large data sets
- PHK: higher efficiency due to fewer system calls
- Greg: easier to describe and understand (keith: less error prone)
- "unlimited" HEADERS (albeit capped at some crazy large number)

So far I've heard the following arguments in favour of CONTINUATION:
- Greg: truly unlimited HEADERS

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Received on Wednesday, 25 June 2014 09:37:05 UTC

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