Re: [Bloat] [iccrg] [aqm] AQM deployment status?

["Scheffenegger, Richard" <rs@netapp.com>]

HI Mikael,

[chair-hat off]

> I'd venture to claim that putting RED on a device with a few milliseconds
> worth of buffer depth is pretty much useless (for instance the Cisco 6704
> or 6724 linecards). So most datacenter equipment doesn't have this, or if
> they do, it's not that usable even if they had (who cares about drop
> probability when taildrop is being done at 4-5 ms buffer depth?).

I'd state that people operating datacenters with request-response type data exchange via TCP do care a lot about the microscopic drop distribution. Typically, a tail-drop queue has the unfortunate property of losing the more critical packets of such an exchange, leading to excessive "transaction" (higher level protocol) delays due to lengthy TCP loss recovery.

Agreed, that is not the regular "internet" use case, but the same gear is being deployed there...

Richard Scheffenegger



> -----Original Message-----
> From: iccrg-bounces@irtf.org [mailto:iccrg-bounces@irtf.org] On Behalf Of
> Mikael Abrahamsson
> Sent: Mittwoch, 25. September 2013 21:25
> To: iccrg@irtf.org
> Cc: aqm@ietf.org; bloat
> Subject: Re: [iccrg] [aqm] [Bloat] AQM deployment status?
> 
> On Wed, 25 Sep 2013, Akhtar, Shahid (Shahid) wrote:
> 
> > Please see below examples of support for RED/WRED from switches (from
> ALU and Cisco websites, search for RED or WRED in document):
> 
> I'd venture to claim that putting RED on a device with a few milliseconds
> worth of buffer depth is pretty much useless (for instance the Cisco 6704
> or 6724 linecards). So most datacenter equipment doesn't have this, or if
> they do, it's not that usable even if they had (who cares about drop
> probability when taildrop is being done at 4-5 ms buffer depth?).
> 
> For higher end platforms, for instance all cisco CPU based routers (for
> some value of "all") can be configured with RED, fair-queue or similar,
> but they come with FIFO as default. This has been the same way since at
> least the mid 90ties as far as I know, long way back to cisco 1600 device
> etc.
> 
> Higher end Cisco equipment such as ASR9k, 12000, CRS etc, all support
> WRED, and here it makes sense since they all have ~50ms worth of buffering
> or more. They also come with FIFO as default setting.
> 
> --
> Mikael Abrahamsson    email: swmike@swm.pp.se
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