[Bloat] Bufferbloat in switches and routers

[Bloat] Bufferbloat in switches and routers

[Ketan Kulkarni]

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Hi,
We have been talking about the bloated buffers mostly on the home routers.
The Cisco PIE too has been standardized by docsis meant to be for cable
modems

I think we would have similar concerns for switches and routers. (E.g.
cat3k switches or Cisco 5760 controllers just to name)

I would like to know your views about what you think about it .
Are the theories so far and the AQMs  (codel and pie) stand true for such
devices too?

What would it take to measure the bloat levels of these devices? Do we
still need to use the netperf wrapper to get the characteristics of such
devices?

Thanks
Ketan

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Re: [Bloat] Bufferbloat in switches and routers

[Steinar H. Gunderson]

On Sat, Apr 18, 2015 at 12:07:26PM -0700, Ketan Kulkarni wrote:
> I think we would have similar concerns for switches and routers. (E.g.
> cat3k switches or Cisco 5760 controllers just to name)

For Cat3k switches, I can assure you there's no bufferbloat -- they are badly
underbuffered.

/* Steinar */
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Re: [Bloat] Bufferbloat in switches and routers

[Ketan Kulkarni]

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Thanks Steinar.
I do have some follow up questions.

Thanks
Ketan

On Apr 18, 2015 12:12, "Steinar H. Gunderson" <sgunderson@bigfoot.com>
wrote:
>
> On Sat, Apr 18, 2015 at 12:07:26PM -0700, Ketan Kulkarni wrote:
> > I think we would have similar concerns for switches and routers. (E.g.
> > cat3k switches or Cisco 5760 controllers just to name)
>
> For Cat3k switches, I can assure you there's no bufferbloat -- they are
badly
> underbuffered.
>
Generically does that mean bufferbloat is the problem predominantly seen
for the cable industry?

Also otherwise how do we go about finding the devices other than home
routers for the bloating levels?

Cat3k was just an example. There are series of numerous other routers by
many vendors.

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Re: [Bloat] Bufferbloat in switches and routers

[Steinar H. Gunderson]

On Sat, Apr 18, 2015 at 12:24:28PM -0700, Ketan Kulkarni wrote:
>> For Cat3k switches, I can assure you there's no bufferbloat -- they are
>> badly underbuffered.
> Generically does that mean bufferbloat is the problem predominantly seen
> for the cable industry?

No. There are tons of other devices that have much larger buffers.
Take DSLAMs, for instance. Or higher-end routers.

> Cat3k was just an example. There are series of numerous other routers by
> many vendors.

But Cat3k isn't a router; it's an L3 switch. The difference is somewhat
arbitrary, but if you buy something marketed as a router, it's much more
likely to have ample buffering and AQM.

/* Steinar */
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Homepage: http://www.sesse.net/

Re: [Bloat] Bufferbloat in switches and routers

[David Lang]

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On Sat, 18 Apr 2015, Ketan Kulkarni wrote:

> Hi,
> We have been talking about the bloated buffers mostly on the home routers.
> The Cisco PIE too has been standardized by docsis meant to be for cable
> modems
>
> I think we would have similar concerns for switches and routers. (E.g.
> cat3k switches or Cisco 5760 controllers just to name)

remember that bufferbloat shows up where there is a difference in bandwidth from 
one side of the router to the other (i.e. a bottleneck)

This is almost always going to happen at the edge of your LAN where you go from 
your Gig-E (or in a datacenter, possibly 10Gig-E to your WAN link. It can happen 
at places inside your datacenter, but isn't as likely

> I would like to know your views about what you think about it .
> Are the theories so far and the AQMs  (codel and pie) stand true for such
> devices too?

If they are bottlenecks, yes. If they are not bottlenecks it won't hurt (no 
queues will build up

> What would it take to measure the bloat levels of these devices? Do we
> still need to use the netperf wrapper to get the characteristics of such
> devices?

the same approach works. you may need beefier systems to generate sufficient 
load.

David Lang

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Re: [Bloat] Bufferbloat in switches and routers

[Ketan Kulkarni]

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On Apr 18, 2015 13:33, "David Lang" <david@lang.hm> wrote:
>
> On Sat, 18 Apr 2015, Ketan Kulkarni wrote:
>
>> Hi,
>> We have been talking about the bloated buffers mostly on the home
routers.
>> The Cisco PIE too has been standardized by docsis meant to be for cable
>> modems
>>
>> I think we would have similar concerns for switches and routers. (E.g.
>> cat3k switches or Cisco 5760 controllers just to name)
>
>
> remember that bufferbloat shows up where there is a difference in
bandwidth from one side of the router to the other (i.e. a bottleneck)
>
Thanks this makes the devices easier to target.

> This is almost always going to happen at the edge of your LAN where you
go from your Gig-E (or in a datacenter, possibly 10Gig-E to your WAN link.
It can happen at places inside your datacenter, but isn't as likely
>
Agree. As per my (limited) knowledge of such deployment goes, these
probably never run to their peak capacity in the production/live system
probably not even to saturate the lowest of the links( I may be wrong
though) . Given this, what is the gravity of the effect of the bufferbloat?
Or such study has never been done before?

Having AQM won't definitely hurt, however is it indeed a real problem to
solve for such edge routers?

At the same time I hear codel or pie finding the space in data centers. So
there are definitely some pieces I am missing.

Sorry for being little naive but the answers will definitely help me
understand the problem space and spread more awareness about bufferbloat.

>
>> I would like to know your views about what you think about it .
>> Are the theories so far and the AQMs  (codel and pie) stand true for such
>> devices too?
>
>
> If they are bottlenecks, yes. If they are not bottlenecks it won't hurt
(no queues will build up
>
>
>> What would it take to measure the bloat levels of these devices? Do we
>> still need to use the netperf wrapper to get the characteristics of such
>> devices?
>
>
> the same approach works. you may need beefier systems to generate
sufficient load.
>
> David Lang
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat
>

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