[c-nsp] Constant output drops on etherchannel

[Dan Letkeman]

No.

Drops are happening even when its not under load.  Has nothing to do
with bandwidth.

On Fri, Jan 14, 2011 at 9:25 PM, Klementina Miloslava
<kmiloslava at tacorp.us> wrote:
> I'm guesing that your problem is less of a buffer problem and more of a
> bandwidth problem.  I bet you are using etherchanel so that you can have
> more than 1Gbps of bandwidth.
>
> However, what you didn't expect is that the etherchannel isn't evenly load
> balanced.  In fact, it's not load balancing at all, it's load sharing. So,
> as a result you have one interface approaching the 1Gbps mark.  As others
> have already pointed out, you begin to drop when you fill the buffers.
>
> So, instead of adding bandwidth (faking it) with etherchannels you should
> consider adding true bandwidth by increasing the interface speed. Consider
> 10Gbps instead.
>
> I can only assume that the buffers on a 10Gbps interface will be a little
> deeper.  But I'd ask other to comment on this.
>
> So, if you can't add bandwidth, then you should consider re-engineering the
> traffic patterns to reduce bandwidth requirements.  So, since you are
> trunking multilpe vlans over you etherchannel, you should consider carrying
> each vlan over it's one dedicated interface.  This may or may not working
> depending on what's happening on those vlans, but the idea is to reduce the
> load on each of the circuits.
>
> In the end you may be asking too much out of that switch.
>
> Klementina
>
> On Fri, 14 Jan 2011, Dan Letkeman wrote:
>
>> So is there any way to increase the buffers without causing more
>> damage?  Or is this a hardware limitation?
>>
>>
>> On Fri, Jan 14, 2011 at 3:54 PM, Gert Doering <gert at greenie.muc.de> wrote:
>>>
>>> Hi,
>>>
>>> On Fri, Jan 14, 2011 at 12:28:03PM -0600, Dan Letkeman wrote:
>>>>
>>>> 3560 or 3560G.
>>>
>>> Lame switches with too-small buffers.
>>>
>>> [..]
>>>>
>>>> I do have auto qos enabled for some of the phones I have connected to
>>>> the switches, but I don't have any qos on the etherchannel trunks.
>>>
>>> Turning *off* qos will reduce the amount of drops you see (what qos does
>>> is "take tiny buffers, spread over 4 different queues, and all of a
>>> sudden your traffic only has 1/4th the buffer space available").
>>>
>>> Alternatively, you could fiddle with qos to give all buffers to
>>> a single queue, and put all traffic in that queue, but that's
>>> effectively turning it off...
>>>
>>> gert
>>> --
>>> USENET is *not* the non-clickable part of WWW!
>>>
>>> //www.muc.de/~gert/
>>> Gert Doering - Munich, Germany
>>> gert at greenie.muc.de
>>> fax: +49-89-35655025
>>>  gert at net.informatik.tu-muenchen.de
>>>
>>
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