Point-to-Point Networks
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Point-to-Point Networks are used around the world to provide fast, secure, and reliable communication. A point-to-point network refers to a connection between exactly 2 machines, or networks. Because there is exactly one possible destination over this type of network, network and hardware addresses are not needed.
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Benefits
Point-to-Point networks offer several advantages over shared networks. Since there is only one destination, the possibility of data being intercepted, or of receiving data from an unknown source is greatly reduced. There is also less network congestion, meaning a more consistent connection speed. Also, less network configuration is required to set it up, and many transmission speeds are available: from 64kbps to 2.048Mbps (E1).
Point-to-Point Protocol (PPP)
PPP is the protocol used for communication over a point-to-point link. It does this by transporting datagrams from a predetermined network protocol. The connection passes through four stages. Starting with a link establishment stage, the two parties use LCP (link control protocol) datagrams to ensure a connection is up and running. After which they can enter the configuration stage to negotiate the parameters of the PPP frames that will be sent back and forth. Once the initial parameters are set the connection enters the monitoring stage, which regularly tests the connection to make sure it is running smoothly. A typical point-to-point connection is always on, but a user may choose to terminate the link at any time. This is done using LCP, and is known as the link termination stage.
PPP Frame
The PPP frame is divided into six sections:
Flag
The flag byte is used to indicate the beginning or end of a frame.
Address
Because there is only one destination in a point-to-point network this byte is usually set to the value 11111111, which is known as the broadcast address. This value is ignored by PPP, however it may be assigned a value to add clarity.
Control
One byte in length. It tells the destination what to do with the packet once the frame has been received.
Protocol
This field is two bytes, and these bytes are used to identify the transmission protocol(TCP for instance) used in the data field.
Data
The data field can have a variable length, and contains a datagram of the protocol specified in the protocol field.
Frame Check Sequence
PPP reserves the last 2 bytes of the frame to make it easier to locate the end of the data field. It can also be 4 bytes if necessary to help improve error checking.
References
Comer, Douglas E. Internetworking with TCP/IP Principles, Protocols, and Architecture. vol 1.Fifth Edition. Toronto, Canada: Pearson, 2006.
See also
External Links
Point-to-Point Protocol. [1]
--Stewadr 23:54, 13 April 2008 (EDT)
