From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] netem: add cell concept to simulate special MAC behavior Date: Mon, 12 Dec 2011 09:19:57 -0800 Message-ID: <20111212091957.18660e19@nehalam.linuxnetplumber.net> References: <1323562110-13865-1-git-send-email-hagen@jauu.net> <1323562314-14033-1-git-send-email-hagen@jauu.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, Florian Westphal To: Hagen Paul Pfeifer , David Miller Return-path: Received: from mail.vyatta.com ([76.74.103.46]:36991 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753227Ab1LLRUA (ORCPT ); Mon, 12 Dec 2011 12:20:00 -0500 In-Reply-To: <1323562314-14033-1-git-send-email-hagen@jauu.net> Sender: netdev-owner@vger.kernel.org List-ID: On Sun, 11 Dec 2011 01:11:54 +0100 Hagen Paul Pfeifer wrote: > This extension can be used to simulate special link layer > characteristics. Simulate because packet data is not modified, only the > calculation base is changed to delay a packet based on the original > packet size and artificial cell information. > > packet_overhead can be used to simulate a link layer header compression > scheme (e.g. set packet_overhead to -20) or with a positive > packet_overhead value an additional MAC header can be simulated. It is > also possible to "replace" the 14 byte Ethernet header with something > else. > > cell_size and cell_overhead can be used to simulate link layer schemes, > based on cells, like some TDMA schemes. Another application area are MAC > schemes using a link layer fragmentation with a (small) header each. > Cell size is the maximum amount of data bytes within one cell. Cell > overhead is an additional variable to change the per-cell-overhead > (e.g. 5 byte header per fragment). > > Example (5 kbit/s, 20 byte per packet overhead, cell-size 100 byte, per > cell overhead 5 byte): > > tc qdisc add dev eth0 root netem rate 5kbit 20 100 5 > > Signed-off-by: Hagen Paul Pfeifer > Signed-off-by: Florian Westphal Acked-by: Stephen Hemminger