Wireless STM-1 link

Thu Sep 10 12:57:12 UTC 2009

Rens,

Does not sound like the symptoms for what I want to write about, but this is
something you need to consider in any way:

When you run sub-rate links (i.e. 1GE interface with really 155Mbps as the
service) you need to make sure that you do not try to push more traffic than
the link can take.
This is mostly relevant for traffic bursts, which happen all the time with
IP traffic. So even if on average you do not use the bandwidth, still you
have short bursts whenever you start a transaction (like a file transfer
etc).

In order to avoid packets being dropped due to this burst on the link, the
1GE equipment before the link should be doing egress shaping to the rate
(sometimes even it is good to choose a rate slightly lower then the actual
rate) of the link.
This would make sure that the network equipment manages the packet drops (if
you have a child QOS policy) and you do not get random tail drops of the
burst.

This means that you need to choose the right network device that actually
supports egress shaping. Be aware that many L2/L3 switches do not support
this.

Arie

On Thu, Sep 10, 2009 at 12:55 PM, Rens <rens at autempspourmoi.be> wrote:

> All the interfaces are forced to 1Gbps and full duplex.
>
> Maybe I should give some extra info.
> All the traffic seems to pass ok via that link but I have seen that often
> OSPF adjacencies go down/up , I suspect that the HELLO packets are being
> dropped that pass via that link.
>
> That's why I started to look a little deeper and do some ping tests.
>
> -----Original Message-----
> From: Adam Goodman [mailto:adam at wispring.com]
> Sent: jeudi 10 septembre 2009 11:45
> To: Rens
> Cc: <nanog at nanog.org>
> Subject: Re: Wireless STM-1 link
>
> Sounds like this might be an Ethernet negotiaton problem
>
> --------
> Sent from my phone
>
> On Sep 10, 2009, at 12:05 PM, "Rens" <rens at autempspourmoi.be> wrote:
>
> > Hi all,
> >
> >
> >
> > I'm encountering a problem with a wireless STM-1 link which has a
> > switch
> > connected at each end.
> >
> > The wireless link has Gigabit Ethernet interfaces and so have my
> > switches.
> >
> >
> >
> > When I ping between the 2 switches via that wireless link I'm
> > getting a lot
> > of pings that are lost.
> >
> > The wireless link is not saturated but I'm thinking it could have to
> > do
> > something with the gigabit interfaces and only having 155Mbps on the
> > link
> > itself?
> >
> >
> >
> > All ideas welcome.
> >
> >
> >
> > Regards,
> >
> >
> >
> > Rens
> >
>
>
>