Indp Week 3

PROTOCOLS

The four major protocols for circuit switching and packet switching are as follows:

• X.25

• Frame Relay

• ATM or Asynchronous Transfer Mode protocol

• TCP/IP

X.25 is probably one of the very first of packet switching protocols. It performs really well, especially considering how long it has been around. X.25 uses a virtual circuit approach, mainly using POTS or plain old telephone service lines, which are different from lines such as ISDN. The POTS lines are analog copper lines, so they can experience a lot of errors. But, once the lines have been connected, X.25 connections are really reliable. It's quite an efficient way to send packets across various data networks, with the X.25 protocol redundant error checking at each of the nodes.

Frame relay is different because it doesn't require the need for analog wires or overhead wires like X.25 does. But this means that Frame Relay doesn't have the added framing and processing that X.25 has that provide guaranteed data transfers. It also doesn't have link to link reliability. So if a frame is corrupted, it is discarded, which is different than TCP as it detects and recovers any and all discarded frames.

Asynchronous Transfer Mode protocol is used with either a coaxial cable, twisted pair, or fiber. ATM also takes advantage of a 53-btye cell, having 48 application bytes and 5 bytes are allocated for the ATM headers. ATM shows a lot more enhancements over Frame Relay, as its speed is at 155-622 Mbps data rates. Although theoretically it could go up to rates as high as 1.2 Gbps.

Lastly, TCP/IP is the primary network protocols that is used on the Internet. It's made up of IP or Internet Protocol and TCP or Transport Control Protocol. IP supports unique addressing for computers on a network. Version 6 of IP (IPv6) features address up to 16 bytes in length. IP also is used at layer 3 in the OSI model. However TCP works within layer 4 of the OSI model. So basically, TCP transport is what is used to deliver...