Cell Relay Archive

[Brad Reese <reese@alliancedatacom.com>]

Hi George,

Class Y, Available Bit Rate (ABR) service is an emerging ITU service
class. It is similar to Class C service, except that it does not offer
delay guarantees. It uses signaling back to the source to regulate data
presented to the network. In an ATM ABR service, congestion control
signaling is done on a CPE-to-CPE basis, with the network providing
information about the amount of bandwidth available in the network for a
particular virtual circuit to use.

Class C, Connection Oriented Data (COD) service is similar to frame
relay service for bursty applications, but can operate at higher rates.
Although Class C does not offer the consistent delay characteristics of
Class A, parameters are defined about the amount of variability that is
acceptable. Class C traffic, due to its nature, can potentially benefit
from sharing of network resources not actively being used by other
connections, through statistical multiplexing.

Class A service is similar to private line in that it offers the
consistent delay predictability of leased line services at the expense
of dedicated bandwidth. It is for applications such as voice, that
require constant bit rate.

AT&T's ATM Service is positioned to provide emerging rate-based services
like ABR and LAN emulation:

http://www.alliancedatacom.com/high-speed-packet-services.htm

Hope this helps.

Brad Reese
Alliance Datacom Frame Relay Resource Center
http://www.alliancedatacom.com/
11130 Petal Street, Suite 800
Dallas, Texas 75238
800-444-5851 Toll Free
214-503-7400 Office

George wrote:

> So does anyone actually use ABR?  Any carriers offering ABR
> services?  Anyone using it in their local network?  Other?
>
> Thanks.
>
> -George
>  gzs@clark.net