What Is Frame Relay?
Frame relay is a wide-area networking solution that provides connectivity and communication between multiple locations supporting a variety of applications. Frame relay can help you do the following:
• Improve application and/or network performance.
• Improve network availability and reliability.
• Increase network flexibility to help reconfigure the network quickly.
• Improve network efficiency and use.
• Simplify the network architecture.
• Relegate the maintenance and management of the network to a service provider that has in-depth networking expertise.
• Save on transport, access, and equipment costs.
• Reduce operations costs and overall cost of ownership.
• Provide a migration path to other services, such as ATM (Asynchronous Transfer Mode), IP-based (Internet Protocol-based), and VPN (Virtual Private Networks) services.
• Enable your company to achieve its strategic business and financial goals.
Telecommunications technologies continue to evolve at a rapid pace, and frame relay is no exception. Although frame relay may still be considered the “new kid on the block” in some parts of the world, it is, by far, one of the most mature packet-based technologies. In the early days, many other packet technologies experienced rocky kick-starts and were eventually forgotten, but frame relay weathered the storm and rapidly became implemented worldwide. It created enough momentum not only to propel itself but also to promote the use of complementary technologies, such as ATM, private lines or leased lines, IP-based services, the Internet, and others.
Defining Frame Relay
You can use the words “frame relay” in many different contexts. Frame relay can refer to an interface standard protocol, a switching technology, and a set of public services. When you use all three definitions of frame relay, a single sentence can be constructed: Frame relay services require a frame relay interface that supports information formatted as frame relay “frames” and transported across frame relay or cell switches.
Frame Relay: An Interface Standard Protocol
As an interface standard protocol, frame relay defines the format of the information sent across the interface. When sending information, the information is encapsulated in a frame format to build the frame. This encapsulation process is similar to sending a letter in the mail: you can think of the information as the letter and the envelope as the frame. The frames also vary in size, which is also similar to letter envelopes.
Frame Relay: A Switching Technology
The OSI (Open Systems Interconnection) model is a framework of standards for understanding communications between different systems. The OSI model organizes the communications process into seven different categories. Communications follow the seven layers as information moves up the seven-layer stack, beginning at the physical transport medium (with fiber optics, coaxial cables, and copper wiring) at layer one and terminating at the application at layer seven.
Frame relay belongs to layer two of the OSI model, which is the Data Link layer. Layer two describes the format of the information and determines how the network handles the data. At this layer, some frame relay networks switch frames to deliver them to desired destinations, although some frame relay services switch cells rather than frames. Unlike frames, cells are fixed in length. During cell switching, the network accepts frames from the source and then converts the frames to fixed-length cells before placing them on the logical connection for transmission across the network. The network then converts or reconstructs the cells back to frames before delivery to the final destination.
Frame Relay: A Public Service
You can take advantage of frame relay in a private or public network implementation. A private implementation leaves the design, implementation, maintenance, and management of the frame relay network up to you. In a private network, you own the networking infrastructure, including the frame relay switches and interswitch trunking facilities to support your company’s wide-area applications. This means that you need capital to purchase the necessary frame relay equipment to build the network.
________________________________________
Consider a private implementation if you have an internal networking staff that understands frame relay technology and has the expertise to operate the network.
On the other hand, a service provider or carrier owns and operates a public frame relay network. The service provider designs the network to support multiple companies that subscribe to its public frame relay service.
A frame relay service offers more than the underlying network, interfaces, and interconnections. A frame relay service may include the following:
• Network redundancy and automatic rerouting
• Multiple access alternatives
• Application- and/or protocol-specific support
• Priorities or qualities of service
• Network management
• Fault isolation and troubleshooting
• CPE (Customer Premises Equipment) and maintenance options
• Configuration and management options
• Interworking with other networks and other services
• Other enhanced features, value-added services, and complementary options
________________________________________
Although you have a choice of implementing a private frame relay network or subscribing to a public frame relay service, this book primarily concentrates on the needs of end users that may not have the time, money, resources, or expertise required to implement a private network.