[188876] in North American Network Operators' Group
Re: Latency, TCP ACKs and upload needs
daemon@ATHENA.MIT.EDU (Tony Finch)
Wed Apr 20 12:12:53 2016
X-Original-To: nanog@nanog.org
Date: Wed, 20 Apr 2016 17:12:36 +0100
From: Tony Finch <dot@dotat.at>
To: Leo Bicknell <bicknell@ufp.org>
In-Reply-To: <20160420142753.GA58668@ussenterprise.ufp.org>
Reply-To: Tony Finch <fanf2@cam.ac.uk>
Cc: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
Leo Bicknell <bicknell@ufp.org> wrote:
>
> 1460 byte payloads down, maybe 64 byte acks on the return, and with SACK
> which is widely deployed an ACK every 2-4 packets. You would see about
> 2,140 packets/sec downstream (25Mbps/1460), and perhaps send 1070 ACKs
> back upstream, at 64 bytes each, or about 68Kbps. Well under the 1Mbps
> upstream bandwidth.
Note that with delayed ACKs (RFC 1122) there is an ACK for every other
packet; SACK should do better than that.
Tony.
--
f.anthony.n.finch <dot@dotat.at> http://dotat.at/ - I xn--zr8h punycode
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