[e2e] Do we have buffer bloat on edge routers or on core routers?

Detlef Bosau detlef.bosau at web.de
Thu Mar 28 12:31:00 PDT 2013

Am 28.03.2013 19:38, schrieb Oliver Hohlfeld:
> Hi,
>> Perhaps my question is a stupid one, however, can someone help me here?
> While there is a lack of evidence, I tend to believe the answer
> is no for most networks.
> Let me briefly elaborate on this issue. It is hard to provide a
> definite answer due to the multitude of possible devices and
> configurations. I tried conducting a survey of typical hardware
> combinations and talk to more operators, but had to give up at some
> point.
> Signs of buffer bloat:
> - I remember having read reports of queuing delays of up to
>   one second in the Level 3 network. Unfortunately, I can't
>   find the reference any more.
> Contra buffer bloat:

Sounds a bit as if buffer bloat is rarely "directly observed" but 
typically concluded from symptoms?

> - By working with a tier-1 network, I never found evidence for potential
>   buffer bloat in their core and aggregation network (might be
>   different for other networks). The aggregation network has been put
>   under load and none of the devices showed excessive queuing. In
>   fact, queuing delays were minimal.
>   In the core, the buffers are "reasonably" sized and don't allow for
>   excessive queuing.

Hence, buffer bloat is anticipated by appropriate network design here? 
In other words: The tier-1 network is designed that way that tier-1 
routers hardly are the bottlenecks for any flow?
> - Typical buffer sizes are around 100ms. Juniper "M-Series" routers
>   are at 200ms.
> - While it is theoretically possible to have bloated buffers in the
>   core, affording excessive buffering is getting more expensive /
>   infeasible with increasing line card speed (e.g., 100GE).
> - The switching infrastructure in the aggregation network is
>   typically not equipped with a lot of buffer space.
> In conclusion, from what I have seen so far, I believe that buffer
> bloat is mostly a problem at the edge.
> Oliver

Detlef Bosau
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