Is there a way to achieve this with another configuration?

My problem is that if I enforce 96kbps at all times, I start getting high latency on other services such as web pages and such and my WAN download speed (4mbit) degrades to 1 - 2.5 mbit/sec.

Ricardo,

What is your purchased rate (CIR) from the provider in regard to upload; transmit capability?  Has the provider guaranteed you a rate for DSCP EF traffic within the purchased rate?  Some would refer to this a gold CAR.


Thanks,

Chris

Hello Christopher,

I am setting this up for a SOHO, they have a regular Cable Modem connection.  The ISP provider advertises a 4000kbps/768kbps 8:1 ratio (basically 8 customers on the same line).

This means that at peak hours of congestion the ISP WAN connection can do no less than 500kbps/96kbps.

Thus, I'd like to find a way to only enable shaping when they have a VoIP call (codec g729) is on so I can use whatever bandwidth is available from the ISP but guarantee quality for the VoIP call.

I don't know if it is possible to shape the upload rate to 96kbps at all times without the download speed suffering too much (i.e. not having 2000ms+ of latency when surfing the web, ssh conncetions, vnc, etc.) with another QoS configuration.

Thanks!

Ricardo,

frame-realy has something called FECN (forward explicit congestion notification) that informs the router of congestion up ahead and a MINCIR value can then be used by the router to properly shape and queue.  Kinda like when the department of transportation sign tells us about the wreck 10 miles ahead.

Unfortunately Ethernet between a cable modem and a router doesn’t have this mechanism.

You appear to be stuck with the approach you are taking.  Trying to find a shaper value that doesn’t leave to much bandwidth on the table yet ensures some kind of VoIP reliablity.

As I suspect you already know, If you want reliable egress queuing you'll need to purchase a circuit with a service provider guaranteed transmit rate (CIR).

In regard to oversubscribed cable modem circuits, they have an attractive price point but are always troublesome for priority data traffic or any kind of VoIP reliability.  It only takes an upstream neighbor to download a movie and a downstream or peer VoIP call suffers.  Something else to consider in regard to commodity internet circuits for priority business data applications is the issue of 'net neutrality'

http://en.wikipedia.org/wiki/Network_neutrality

Chris

Hi Chris,

I am aware about frame relay mechanisms to handle congestion.  It seems that the only solution could be to pursue a dual wan set up with a line for VoIP.  Unfortunately, dedicated circuits in this location are about $500.00 for 1mbit/1mbit, the amount of voip traffic that will pass through is minimal and will not justify the expense for now.

Do you know any guides to perform a Dual Wan setup?

I am stuck with a cisco 881, it has 1 FA4 port for WAN and 4 (FA 0 - 3) ports for a managed switch.

I tried to create virtual interface say "vlan 5" with "ip address dhcp" and on port FA0 "switchport access vlan 5" but as soon as I connect to the second provider and get an ip address I lose connectivity to the internet.

Any ideas?

Thanks,

Ricardo