Cell Relay Archive

[Afroz Lateef <afroz.lateef@fnc.fujitsu.com>]

This issue is left more for the vendor implementation.
If, however, the vendor decides to implmement signalling on the Ingress
port too, then it will affect the performance of the switch, which is
not acceptable.

Afroz Lateef


anouch gharagozlou wrote:

> Thanks Afroz,
>
> I agree with you that there is no traffic loss.
> There is however a configuration problem that is not
> signaled to the application.
> Anouch
>
> --- Afroz Lateef <afroz.lateef@fnc.fujitsu.com> wrote:
> > Anouch,
> >
> > In this case, the CAC should have been run on the
> > output port of the
> > unit that is connected to the I-port of the switch.
> > Since this is a CPE
> > and cannot have CAC implemented on it, there is no
> > service affecting
> > problem.
> > Because, traffic cannot exceed more than the link
> > capacity. So in TX
> > side, there is no traffic loss.
> >
> > Afroz Lateef
> >
> > anouch gharagozlou wrote:
> >
> > > Hi,
> > >
> > > Call/Connection Admition control (CAC)in a cell
> > relay
> > > switch is always acting on the ouput port. But
> > what
> > > happens if the input port is out of capacity and
> > that
> > > is not checked?
> > >
> > > Suppose a user connect to the input port (I-port)
> > of a
> > > switch and wants a connection with another user
> > > located just behind the output port (O-port)of the
> > > same switch.
> > >
> > > Assume I-port speed is 45Mbps and O-port speed is
> > > 155Mbps.
> > > The user asks for a 100Mbps connection. The CAC
> > checks
> > > if the O-port has enough bandwidth left and if
> > it's ok
> > > the connection is established (if no other
> > connection
> > > is using the O-port, 100Mbps being < 155Mbps, the
> > call
> > > succeeds).
> > > But the user will never be able to send at 100Mbps
> > > since the I-port where it is connected has a speed
> > of
> > > 45Mbps. The CAC doesn't check that and the
> > > provisioning succeeds while the user isn't aware
> > of
> > > the configuration problem.
> > >
> > > This actually happens on a Nortel 7k/15k Passport
> > but
> > > may also happens on other switches. And it is more
> > > problematic when dealing with asymetrical (e.g.
> > ADSL)
> > > connections.
> > >
> > > Is this a bug, or the CAC should never checks the
> > > input port for incoming traffic?
> > > In the latter case what is the solution?
> > >
> > > Thanks
> > > Anouch
> > >
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