[Asterisk-Users] Public vs. Private Network

[qrss]

With frame relay, you don't actually have a "private circuit" in the same
sense that you would with a point to point T1 for example.  Instead, you
order a PVC which is a virtual circuit between locations.  The provider is
supposed to guarantee a certain amount of bandwidth across a PVC that is
at least equal to the CIR that you order.  Under heavy traffic conditions,
the provider will allow you to burst above the CIR up to perhaps several
times your CIR but no more than the port speed of the frame switch. The
actual amount of burst capability usually varies from provider to provider
and some will allow bursts up to full port speed.  This usually works
quite well for data applications where occasional bursting may be required
during large downloads etc, but where normal traffic is closer to the CIR.
 With voice, you may find that a larger CIR is required to guarantee that
your voice bandwidth is sufficient to handle the number of simultaneous
conversations that you are going to allow.  If you are running only voice
traffic across the PVC, then in order to guarantee that bandwidth, you may
find that you need to order a PVC that is approaching or equal to your
port speed.  On the other hand, if you are running data across the PVC in
addition to voice, then you might want to have a larger port speed to take
advantage of the bursting capability.  In that case, you would likely need
to apply some traffic shaping such as QOS to prioritize your voice
traffic. Another option is to have separate PVCs for voice and data
traffic sharing the same access T1.  When you first install frame, you
will want to keep a close eye on latency and if necessary work with the
provider to tune the PVC for better performance.  They don't always give
you the best path during the original provisioning but will generally work
with you to improve performance if latency is a little high.  You might
also want to ask your provider about MPLS as an alternative to frame
relay.  MPLS can provide a similar level of service and possibly save you
some money compared to the cost of frame relay with large CIRs.

-----Original Message-----
From: David Sampson
Sent: Thu, May 19, 2005 1:26 pm

Does anyone else have info regarding the port speed matching the CIR?

-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Eric
Wieling aka ManxPower
Sent: Thursday, May 19, 2005 11:55 AM
To: Andrew Latham; Asterisk Users Mailing List - Non-Commercial
Discussion
Subject: Re: [Asterisk-Users] Public vs. Private Network


>>I am looking at connecting 7 - 10 locations together using Asterisk
and
>>possibly some VoIP gateway appliances.  I need to insure best voice
quality
>>as these trunks will be used primarily for customer calls.  I am
considering
>>implementing a full T1 frame relay circuit to each location which can
be
>>done for a reasonable cost.  DSL and Cable are currently at each
location
>>and setup for automatic failover.  Should I remove one of my public
>>connections and replace it with a private circuit for best quality?

To run VoIP over Frame Relay you need your Port Speed to be the same
as your CIR.  Cisco has extensive docs about this, but I'm too lazy to
look them up right now.
--
Always do right. This will gratify some people and astonish the rest.
Mark Twain
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