Serial Line Internet Protocol (SLIP)

The SLIP is a TCP/IP protocol used for communication between two machines that are previously configured for communication with each other. For example, your Internet service provider may provide you with a SLIP connection so that the provider’s server can respond to your requests, pass them onto the Internet, and forward your requested Internet responses back to you. The dial-up connection to the server is typically on a slower serial line which is rather than on the parallel or multiplex lines such as a line of the network you are hooking up to.

• This protocol was developed by Rick Adams in 1984.

• The initial purpose of this protocol was to connect Sun workstation to the Internet over a dial-up line using the modem.

• Using this protocol, workstations send raw IP packets over the line with a flag byte (OXCO) at the end for the framing purpose.

• If the flag byte occurs inside the IP packet, then character stuffing technique is used to solve this problem. For this, a two-byte sequence (OXDB, OXDC) is sent in its place.

• Although SLIP is the simple protocol, it has some major problems. They are:

  1. It does not perform any error detection and correction.
  2. SLIP supports only IP (Internet Protocol). So it cannot be used for other networks that do not make use of IP.
  3. It does not support the allocation of dynamic IP address as both the communication sites should be assigned to a specific IP address beforehand and both sites should know each other’s address.
  4. The SLIP does not provide any authentication. So both the communicating sites do not know with whom they are communicating.
  5. SLIP is not an approved Internet standard so that many different and incompatible versions can exist and makes networking difficult.

• A special END character (equivalent to decimal 192) marks the end of data.

• If an End character occurs naturally in data, SLIP includes a special ESC character before the END character. Due to this, the receiving computer does not prematurely stop receiving the packet.

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