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Communication Systems International Incorporated

Frame Relay

AT&T® Local Frame Relay Service is a seamless data network offering which provides fast, reliable connectivity in support of "bursty" local data applications, particularly those based on distributed processing and Local Area Network (LAN) computing platforms. Utilizing the "Any Distance" Frame Relay network, Local Frame Relay service can seamlessly connect to the U.S. national Frame Relay service to provide customers a complete AT&T® end-to-end solution.

AT&T® Local Frame Relay service transfers data at speeds of up to 1.544 Mbps* (T-1), providing companies with an efficient and cost-effective method for transporting LAN and wide area network (WAN) data traffic.

AT&T® Local Frame Relay Service provides:

  • Network design and engineering support by AT&T®'s experienced network architects and designers
  • Advanced performance features like closed loop congestion management to ensure throughput performance
  • Committed information rates (CIR) from 4k through 1.5366 Mbps, with bursting capabilities to 1.545 Mbps
  • AT&T® ReliaBURST® to sustain traffic bursts beyond your customers' CIR
  • AT&T®'s self-healing Synchronous Optical Network (SONET) loop-based network infrastructure that restores service within milliseconds in the event of a major equipment failure or cable cut.
  • Industry-leading Service Level Agreements (SLAs)
  • Around-the-clock Network Operations Center (NOC) support

Frame Relay Service ensures high reliability and throughput with a feature called ReliaBURST, which gives users sustained bursting capabilities beyond the Committed Information Rate (CIR) for an extended period of time, and proactive congestion management. The ReliaBURST feature allocates excess network capacity fairly among all users and provides optimum protection of network resources by metering access to the network via a closed-loop feedback mechanism, avoiding congestion and potential data drop-outs. The result is high data delivery and throughput, fairly allocated to all network end users.

Network management capabilities:

  • Dedicated Network Management Centers - with a single point of contact. AT&T® Frame Relay Service Network Operations Centers (NOCs) are staffed with experienced, customer-focused technicians available for support 24 hours a day, 7 days a week.
  • Performance Monitoring and Fault Management - The AT&T® NOCs continuously monitor network conditions and perform fault management including proactive, preventive and reactive network management. In many cases, the NOC detects faults and takes corrective action before network conditions affect service.
  • Customer Provisioning Teams - AT&T® has dedicated teams of experts who oversee the complete deployment, installation, testing and activation of the frame relay service.

How Does It Work?
AT&T® Local Frame Relay Service transports the customer's data from location to location through a two-tiered architecture:

  • Frame Relay interfaces at the edge - Data is brought from the customer's premise into the AT&T® premier ATM core backbone through the frame relay connections.
  • ATM core switching architecture - At the core of the AT&T® Frame Relay Service network is a high-speed Asynchronous Transfer Mode (ATM) switching backbone that provides reliability, low network congestion and consistent performance. The backbone uses high-speed ATM cell relay nodes connected by a network of OC3 & OC12 trunks.

Network Performance

Sharing the Frame Relay Backbone
Because frame relay technology provides service to many customers over a shared backbone, it is critically important to ensure one customer's traffic does not interfere with another customer's traffic. To ensure this does not happen, AT&T® provides several key features. First, at the entrance to the network AT&T® provides a separate buffer for each Permanent Virtual Circuit (PVC), so customers with large data transmission needs (for example, high Committed Information Rate (CIR) do not impact the performance of smaller CIR customers. Within the AT&T® Frame Relay network, AT&T® uses a unique "closed loop" congestion management algorithm which ensures customers receive their CIR all the time data is presented, not just over some average time period. Further, excess backbone bandwidth used for bursting is allocated in proportion to each customer's subscribed CIR so that no customer's traffic can unfairly impact the burst capabilities of other customers.

Performance Consistency
The cell relay technology used on AT&T®'s Frame Relay Service from its inception provides lower latency and lower cell-to-cell delay variations than conventional frame switching methods. This allows AT&T® to provide the consistent performance needed by many applications, especially legacy applications throughput is also enhanced by a technique known as pipelining where frames entering the network are broken into cells and transmitted as soon as each cell is filled, not waiting for the whole frame relay frame to arrive at the network interface.

The diagram below illustrates the basic components of this service:

Frame Relay Network


Data Services


Integrated Access

Frame Relay

Private Line/T1/DS3/SONET [PDF]