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

Oliver Hohlfeld oliver at net.t-labs.tu-berlin.de
Thu Mar 28 11:38:28 PDT 2013


> 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

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:
- 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.

- 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.


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