Frame Relay
Overview
Frame relay is a form of data networking based on packet switching. The packets are variable in length. Frame relay can be deployed using either private or public switching equipment. Frame relay is appropriate for organizations with bursty data, three or more locations, and mid- to high-bandwidth needs (PacBell, Frame Relay). Frame relay requires connection-oriented virtual circuits. Access speeds that Pacific Bell supports with its public frame relay network are 56Kbps, 128Kbps, 384Kbps, and 1.544Mbps.
Frame relay forwards data elements between source and destination without applying any internal error detection or correction. This is in direct contrast to X.25 networks that expend considerable overhead providing these facilities (Implementing, pg 3). This allows frame relay services to make more efficient use of bandwidth by reducing overhead. This is achieved by reducing the delay associated with each node in the network (Implementing, pg 4). The frame relay standard places responsibility for error recover and flow control on the user. This is necessitated by eliminating OSI level 3 functionality from the standard (Implementing, page 7). The resulting connection resembles a data line from the user's perspective. Another way that frame relay makes more efficient use of bandwidth is through statistical multiplexing. The improved efficiency can be illustrated through a comparison to fixed multiplexing schemes in T1 service. Studies have found that actual circuit use may be as low or lower than 50% (Implementing, page 6). Frame relay can either make this resource available or halve the bandwidth required to support the same data transmission needs (Implementing, page 6).
Services
This is an evolution compared to traditional packet switching communication specified in X.25 standards.
- Aims at reducing network delays, equipment costs and efficient bandwidth utilization.
- Accomodates applications such as wide area interconnection of LANs at 56kps and 1.544 Mbps.
- Service Providers: AT&T, PacBell, BT North America, MCI, Network Services, US Sprint, Wiltel
Cost
Costs associated with frame relay service (Implementing, page 22):
- Access charges
- DSU/CSU costs
- Internetworking Customer Premise Equipment (CPE) costs
- per-Virtual Circuit pricing
- aggregate Committed Information Rate (CIR) pricing
Levels of those costs for Pacific Bell Frame Relay Services by bandwidth.
Required components are:
- Access facility to the Frame Relay Network
- Frame Relay port
- Data Link Connection Identifier
No usage or mileage charges
Port Costs:
- 56 Kb/s = $375 one-time installation plus $75 per month
- 128 Kb/s = $375 one-time installation plus $150 per month
- 384 Kb/s = $375 one-time installation plus $400 per month
- 1.544 Mb/s = $375 one-time installation plus $500 per month
Access
Costs: (Service Area tariff prices)
- 56 Kb/s = $630 one-time installation plus $50 per month
- 128, 384 and 1536 Kb/s = $634 one-time installation plus $175 per month
Access Costs: (Inter-state tariff prices)
- 56 Kb/s = $375 one-time installation plus $50 per month
- 128, 384 and 1536 Kb/s = $634 one-time installation plus $120 per month
Data Link Connection Identifiers: (based on number of connections on
each port)
- 1 connection = no charge
- 2-6 connections = $15 each
- 7-11 connections = $10 each
- 12+ connections = $5 each
Sources
- Pacific Bell Frame Relay Tariff Information
- Minoli, Daniel. "Technology Overview: Frame Relay", DATAPRO, Communications Series on Broadband Networking.
- "Implementing Frame Relay Networks" CIMI Corporation. (1991).
WAN Technologies