Ring Local Area Networks

Content:

FEATURES OF RING LAN

A ring network is a closed path consisting of multiple repeaters, each connected to two other repeaters.

by unidirectional transmission lines. Bit-by-bit data is transmitted sequentially, from repeater to repeater.

repeater.

Repeaters perform three basic functions for a ring to work:

  1. Data insertion.
  2. Data Reception.
  3. Data deletion.

In addition they serve as an active element in the ring they serve as a connection point for devices. The

repeaters check the content of the destination address field of the data packet, if the address is that of

the repeater station makes a copy of the packet. In the ring lan topology the repeaters perform

the insertion and reception of data in a different way from how the sockets do it on a bus or on a tree.

Data deletion is however more complicated in the case of a ring. If there is no elimination

signals would remain circulating indefinitely in the ring until they are eliminated. There are two options

for package removal:

  1. Packets are dropped on arrival at the destination repeater.
  2. The repeater handles packet removal by going around the ring completely.

This last approach is better because: It allows automatic confirmations, and it allows addressing

Multiple, a package to several addresses.

Data insertion:

In the insertion of data, several protocols are used to access the medium, such as the ring with

witness passage.

Repeater Objectives:

The repeater can have two main purposes:

  1. Let all data through.
  2. Being an access point to the stations.

To achieve these two objectives there are two states: Listening and Transmission.

Listening status:

In the listening state, each received bit is retransmitted with a small delay, necessary to allow the

repeater perform basic functions. Ideally, the delay should be of the order of the duration interval of a

bit. The functions are:

  1. Search for bit pattern sequences. (address(es) of connected stations)
  2. As each Captured bit is sent to the station it is retransmitted assuming the packet is addressed to the station.
  3. Modification of a bit while circulating. It can be used in control strategies.

     

Transmission Status:

The repeater enters the transmission state if according to the control strategy, it has permission to do so,

and the station has data to transmit. In this state, the repeater retransmits the bits received from the station to the

starting line.

Here bits can appear from the input line of the ring. There are two possible situations treated differently.

  1. The bits can be from the same packet that the repeater is transmitting, this will happen if the ring bit length is less than the packet size. In this case, the repeater passes the bits to the station, which can check them with the confirmation method.
  2. If the control strategy allows the existence in the ring of a packet other than the one sent, the packet is temporarily stored to transmit it later.

Short circuit status:

In this state, a short-circuit relay can be activated, so that the signals pass directly through the repeater.

without more delay than that of propagation in the medium.

Advantages:

  1. Partial solution to the reliability problem.
  2. Eliminate repeater delays on those stations in the middle that are not active.

cables:

Twisted pair, baseband coaxial cable, and fiber optics can be used in repeater-repeater links. The wire

Broadband coaxial, on the other hand, is not easy to use. Each repeater may be capable of

receive and transmit data asynchronously over multiple channels.