[c-nsp] GRE tunnel bandwidth

[John Neiberger]

I am having them check their window size settings, but I just found an
MTU problem in the path. They're using jumbo frames, but the next hop
in the path after the tunnel source had an MTU of 1500. I've corrected
that and I bet they'll see a lot better performance.

Thanks!
John

On Sat, Aug 4, 2012 at 10:48 AM, Lee <ler762 at gmail.com> wrote:
> On 8/4/12, Chuck Church <chuckchurch at gmail.com> wrote:
>> Tunnel bandwidth command (or any interface bandwidth) is used for
>> statistics-computation only.  It does factor into QOS too if you use
>> percentage type commands.
>
> It's also used for eigrp route metrics.
>
> I suspect routing isn't the issue here tho
>> > I have some users experiencing slow file transfers over a GRE tunnel. The
>> > tunnel is riding over 10-gig links.
>
> To be able to use all the bandwidth, the tcp window size needs to be
> at least <bandwidth in bytes/sec> * <round trip time in seconds>
> So, for example, on a 10Gb link with a 2ms round trip time the tcp
> window needs to be 2.5MB.  I remember WinXP defaulting to 16KB...
>
> Regards,
> Lee
>
>
>>  I'm guessing there are two possible things to
>> look at.  The CPU of the devices doing the tunnel endpoints is high because
>> of the encapsulation, or else the tunnel MTU is affecting the clients (if
>> TCP).
>>
>> Chuck
>>
>> -----Original Message-----
>> From: cisco-nsp-bounces at puck.nether.net
>> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of John Neiberger
>> Sent: Saturday, August 04, 2012 11:57 AM
>> To: cisco-nsp at puck.nether.net
>> Subject: [c-nsp] GRE tunnel bandwidth
>>
>> I have some users experiencing slow file transfers over a GRE tunnel. The
>> tunnel is riding over 10-gig links. I see that the default tunnel bandwidth
>> is 8 Mbps. Does that mean that the tunnel is rate limited to that value? If
>> so, is the simple solution raising the bandwidth with the "tunnel bandwidth
>> transmit" command?
>>
>> Thanks,
>> John
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