Point-to-Point Networks
From Computing and Software Wiki
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 a point-to-point network, network and hardware addresses are not needed.
Benefits
Point-to-Point networks offer several advantages over share networks. Since there is only one destination, the possibility of data being intercepted, is greatly reduced. There is also less network congestion, meaning a more consistent connection speed. 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 across the link. The connection passes through four stages starting with a link establishment stage where 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 over the connection. 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.
PPP Frame
The layout of a standard PPP frame:
|---|---|---|---|---|---| | i | ii|iii| iv| v | vi| |---|---|---|---|---|---|
i.Flag (1 byte) The flag byte is used to indicate the beginning or end of a frame.
ii. Address(1 byte) Because there is only one destination in a point-to-point network this byte is usually set to the value 11111111 known as the broadcast address. This value is ignored by PPP, however it may be assigned a value for clarity.
iii. Control (1 byte) Tells the destination what to do with the packet once the frame has been received.
iv. Protocol (2 bytes) These bytes are used to identify the transmission protocol(TCP for instance) used in the data field.
v. Data The data field can have a variable length, and contains a datagram of the specified protocol in the protocol field.
vi. Frame Check Sequence Reserves the last 2 bytes of the frame to make it easier to locate it's end. It can also be 4 bytes if necessary to help improve error checking.
