fFRAME RELAY
frame relay was standardised initially in 1990, leaving the remaining to be standardised in 1991 by both ANSI and the ITU-T [7].
What it is: Frame Relay is a packet switched connection orientated network. It is in the physical and data link layer of the OSI model. It is a virtual connection between devises, it can transmit data, video and voice this is done via frames and it supports a bandwidth of up to 1.5M and up.[9]
What does packet switched connection oriented mean? This means that there has to be a connection made between two devises before any data can be sent or recieved.
Why it came about: When it first emerged it was a less complicated version of the X.25 protocol. Cisco helped to standardise it. It was to be used as a transport method via Integrated Services Digital Network (ISDN) interfaces. It then became a standalone technology, apart from ISDN as ISDN was too slow [1].
Why so popular: Frame Relay is extremely popular as:
1. To configure a router to the ways of frame relay is fairly easy to do
2. Uses less equiptment
3. Not complicated to use
4. It has a high bandwidth
5. Is quite reliable and most importantly
6. It doesn’t cost that much.
Classification: Frame Relay is classified under the same class as ATM (Asynchronous Transfer Mode).
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It is used for telecommunications networks and transfers data voice and video. It is a widely used WAN protocol. It is used between Local Area Networks (LAN) over the Wide Area Network (WAN).
All users get a personal line to a Frame Relay node. These nodes are enabled, to point frames in the right direction with the smallest amount of processing required. The link layer has a large address field in frame relay[4]. The network deals with the transmission of these data files over a path which changes quite often. This path is invisable to to the users.
Error handling: Frame relay does not try to fix any errors that may be trying to be transmitted; it lets the end points figure that out. If there is an error found in the frame, that frame is then not sent. The end points now have to find out what frame or frames were dropped and have to try to send them again [3].
Only PVC (permanent virtual circuit) is standardised in frame relay. This is set up when the user signs up to the service.
Header Structure: The header is 2 bytes long and has the following format:
Figure 1: Header Structure [4]
DLCI: 10-bit DLCI field is the unique address of the frame and matches up to a PVC. [4]
C/R: If it is a command or response the C/R assigns it to the frame. [4]
“EA: Extended Address field signifies up to two additional bytes in the Frame Relay header, thus greatly expanding the number of possible addresses.”[4]
FECN: Forward Explicit Congestion Notification >> Changed to 1 when traffic occurs and is sent down the line toward the destination during transmission. Therefore all nodes and the connected user devices find out about the traffic build up on the line. [4]
BECN: Backward Explicit Congestion Notification >> In response, it too is changed to 1, going back to the source of transmission on the line where the traffic build up is. Therefore the node is alerted to this and is to delay the transmission until the traffic settles down. [4]
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Introduction This is a formal report that contains two parts. In part one it is to describe 4 types of telephone network services with their features and comparative costs and in part two there are 4 types of services that I need to consider when a business / corporation would use each service in particular situation. Terms of Reference In part one I gave an fully explain for each telephone ...
“DE: Discard Eligibility >> provides the network with a signal to determine which frames to discard” [4]
The Flag denotes the start of each frame and the end of each frame [5] .
A main disadvantage of frame relay is the fact that it does not use fixed length packets, it uses variable length packets.
What is a variable length packet: This is where the packet can have a large amount of data sent or a small amount of data sent. With larger packets to be sent, this can cause traffic which in turn slows down the network
What is a fixed length packet: This is where the size of the packet can not be any more than the stated size. With only being able to send a restricted amount, it is extremely less likely to slow down the network. [6]
FRAD (Frame Relay Assemble/Disassemble).
This is a bit of equipment which builds outgoing data frames and un-builds incoming data frames [8].
Bibliography
1. (n.d.).
Retrieved January 24, 2011, from 149.153.105.99/ccna:
3. (n.d.).
Retrieved January 24, 2011, from searchenterprisewan.techtarget.com: http://searchenterprisewan.techtarget.com/definition/frame-relay
4. (n.d.).
Retrieved January 26, 2011, from www.protocols.com:
5. (n.d.).
Retrieved January 28, 2011, from www.techfest.com:
6. (n.d.).
Retrieved January 28, 2011, from www.happy-monkey.net: http://www.happy-monkey.net/papers/frame-relay-paper.pdf
7. (n.d.).
Retrieved 01 29, 2011, from www.nwconfig.com:
8. (n.d.).
Retrieved January 29, 2011, from www.dcbnet.com: http://www.dcbnet.com/notes/framerly.html
9. (n.d.).
Retrieved January 29, 2011, from books.google.ie: http://books.google.ie/books?id=tROBDX-OBrEC&pg=PR15&lpg=PR15&dq=cool+things+about+frame+relay&source=bl&ots=k8ziILOrzw&sig=FlbF78toXaSH00ZIIV44_H5ZQKQ&hl=en&ei=VAxETdzUCZK5hAewv4DnAQ&sa=X&oi=book_result&ct=result&resnum=12&sqi=2&ved=0CHEQ6AEwCw#v=onepage
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