Frame Relay

Frame Relay is a computer system to be used in connection with the face of packet communications method. It is mainly used in public or special online LAN and wan connection interconnected. Most public telecommunication bureau provide frame relay service and use it as establish high-performance virtual wide-area connection of a kind of way. Frame relay is into the bandwidth ranges from 1.544 56Kbps to the wide-area grouping Mbps of switching user interface.

produce

Frame Relay (Frame Relay) Frame Relay from integrated services digital network in developed, and in 1984 recommended for international telephone &telegraph advisory committee (CCITT) a standard, in addition, authorized by the American national standards association of American TIS standards committee also to Frame Relay made some preliminary work. Due to the optical fiber network than the early telephony ber much lower, therefore, can reduce x.25 some error-controlling process which can reduce nodes of the processing time, increase network throughput. Frame relay is produced in this environment. Frame relay is provided for the data link layer and physical agreement standard, any high-rise agreement to be independent of frame relay agreement, therefore, are greatly simplified frame relay is realized. At present the main application of frame relay is one of LAN interconnected, especially in LAN are interconnected via the wan, USES frame relay more can reflect its low network time delay, low cost, high bandwidth utilization equipment etc.

characteristics

Frame relay key features are: use fiber as transmission medium, so ber is extremely low, can realize the approximate without frame relay transmission, reduce the errors on error checking expenses, improve the network throughput, Frame relay is a kind of broadband packet switching, use multiplexing technique, the transmission rate but $44.6 Mbps. But, frame relay is not suitable for transmission, such as voice, TV, real information, it is limited to transmit data.

Linked methods

Most major telecommunications companies like AT&T, MCI, US Sprint, and local bell operating companies provide frame relay service. With fname relay connected, need a router and a users from site to exchange frame relay entrance line. This line is generally like T1 that rent digital circuit, but depends on the traffic and decide. Two possible wide-area connection methods, such as what narrate below:

In this way - fenpi method, every sites will need three special (rent) lines and associated with other routers, so that each frame relay a type of one, so that you will need 6 special line and 12 router.

Frame relay method in this - public method, every type of need only a special (rent) lines and associated router until fname relay. At this moment, in other nets between in fname relay switching is handled within. From multiple user group is multiplexed onto one even to frame relay online lines, through fname relay they were sent to one or more objective stand.

Permanent virtual circuits (PVC) is through fname relay connects two three-way handshake of pre-defined pathways. Frame relay service providers according to the customer request, in between two specified node distribution of PVC. These channels keep continuous uninterrupted operation and provide a customer negotiation of assigned a level of service. Switched virtual circuit in late 1993 was added to the frame relay standard: so, frame relay will become a real "rapid grouping" switching telephone network.

Improved Packet Switching to improve the Packet Switching

In the past few years, exchange in American domestic and international online has installed a lot of fiber optic cable, this will increase the bandwidth. In order to make full use of the advantages of high bandwidth, new communications solutions to remove the original scheme inherent in conventional overhead, become more practical available. Frame relay by waiving the network itself flow control and error handling of doing this, avoids network itself do these things and cause delays. In comparison, the old x.25 nets technology executes expand inspection wrong is caused by using unreliable telephone data transmission.

In the frame relay eliminate this feature won't appear problem, even an error occurred. Frame relay imagine a three-way handshake equipment is programmable intelligent machine, they can perform error handling. The system will not because of this error control and overload, because usually have few mistakes. Relative to character, x.25 imagine networks need to check the wrong correction three-way handshake is even because to host the terminal.

In the frame relay, the intermediate nodes (switch) only along the predetermined pathways relay frame. In x.25, intermediate nodes must fully receiving each packet, and in forwarding before inspection wrong, if there is error occurs, node requirements sender retransmission. Using this approach, once the packet loss, the sender will re-issue a grouped as soon as possible. In x.25 in each middle node using state table to process management, flow control and inspection wrong and in frame relay is not needed.

If a packet because of congestion fname relay was damaged or lost, detection frame lost and request retransmission is receiving system work. Fname relay put all your energy were used to pass the group. In the exchange the nodes are not subnet performing any error correction, although they can detect the damaged grouping, once detected, group will be rejected.

Setting Up Re1ay Frame Connections establish Frame relay connection

In order to establish the frame relay connected with and the US, you need to sprint, MCI, AT&T or local place bell operating companies, such as telecommunications companies contact, usually like below as communications speed options, and private sidings communication or switched communication options.

- by Switched - 56 service or integrated services digital network (ISDN) provide 56/64Kbps Switched access; Advanced digital network (ADN) propose frame relay

For private sidings visit.

Twenty two ISDN lines or two ADN lines provide 128Kbps visit.

Through a T1 line or part - a T1 line can be used to 384Kbps 1.544 Mbps of connection.

Once you have selected a kind of service, you will plan a from your site to frame relay service provider links. In your site placed routers and frame relay access equipment to build into providers of frame relay port connection, as shown in figure F - 11 shown.

Frame relay port general use PVC connection. PVC is logical link, it has a particular end point and service characteristics. They provide in mesh topology structure, and logical connection before use for exchange provides a sure service characteristics and rate method. They also provide fast in the contacts between connected. Get in the service provider, you can for PVC prescribed some service characteristics, below enumerates some of the service characteristics.

- visit rate is this line speed, it decided on the Internet with the speed of data transmission. In the United States, general access rate is 1.544 Mbps (T1) and 56Kbps.

- commitment information rate (CIR) CIR is frame relay the way the highest average data transfer rate. It is usually better than transmission rate slow. When transferring data, sudden transmission speed can exceed CIR.

The group - commitment data sizes (CBS) is a network provider in certain CBS at regular intervals and normal network conditions allowed by the maximum amount of data transmission (digits).

- extra group data size (EBS EBS is the biggest not submitted more than CBS data quantity, CBS data is network will in certain interval of time send out the data. EBS data were the Internet as can discard data.

Frame relay

Below will list some other by fname relay provides properties.

Network services under the management characteristic and service in fname relay can be adopted:

- a virtual circuit state news distance service in the network and provide communications between users. It ensures PVC exist and report deleted PVC.

- broadcast this optional services make a user can send multiple objective stand. Frame

- global addressing this optional services make fname relay has the same skill. Like LAN

- simple flow control this optional service for those who need flow control of the equipments and XON/XOFF flow control mechanism.

Congestion control when fname relay congestion, frame can be properly discarded (three-way handshake is responsible for re-issue them), or according to user assigned level discarded. For example, the user can point to some transactions operation is not very key communication frames can be discarded (DE). A router or frame relay switches can use to identify DE la coque frames, the use of provides a method, ensure important information through network transmits, not important information in network can not too busy when retransmission.

Security frame relay has a few security options:

- with only the dedicated circuit can access networks.

- need password access networks.

- not activities sites beyond a certain time will be cancelled.

Frame Relay is of Frame Relay norms

In public packet-switched online, a fname relay to connect two local area network (LAN). This process is very simple -- from LAN frames to be put in the frame relay frame, and through the network of bottom (frame relay reticular links) to the destination. Statistical multi-channel practical technology from customer site multiple source data effectively alternately on a single line to upload fname relay. Frame relay is a senior data link control procedures (in HDLC) of improvement, so it can be used for some a bridge and routers upgrades. Frame relay because it grow longer frame format and do not suit voice and video communication.