Token RingToken ring (IEEE 802.5) is a communication protocol in a local area network (LAN) where all stations are connected in a ring topology and pass one or more tokens for channel acquisition. A token is a special frame of 3 bytes that circulates along the ring of stations. A station can send data frames only if it holds a token. The tokens are released on successful receipt of the data frame.Token Passing Mechanism in Token RingIf a station has a frame to transmit when it receives a token, it sends the frame and then passes the token to the ... Read More

Token Bus (IEEE 802.4) is a standard for implementing token ring over the virtual ring in LANs. The physical media has a bus or a tree topology and uses coaxial cables. A virtual ring is created with the nodes/stations and the token is passed from one node to the next in a sequence along this virtual ring. Each node knows the address of its preceding station and its succeeding station. A station can only transmit data when it has the token. The working principle of the token bus is similar to Token Ring.Token Passing Mechanism in Token BusA token is ... Read More

Bit-map protocol is a collision free protocol that operates in the Medium Access Control (MAC) layer of the OSI model. It resolves any possibility of collisions while multiple stations are contending for acquiring a shared channel for transmission. In this protocol, if a station wishes to transmit, it broadcasts itself before the actual transmission. Every station gets its turn for transmission in a predefined order. A method to accomplish this is to use the method of token passing.Token Passing MechanismA token is a small message that circulates among the stations of a computer network providing permission to the stations for ... Read More

RSVP is a transport layer protocol that is used to reserve resources in a computer network to get different quality of services (QoS) while accessing Internet applications. It operates over Internet protocol (IP) and initiates resource reservations from the receiver’s end.FeaturesRSVP is a receiver oriented signalling protocol. The receiver initiates and maintains resource reservation.It is used both for unicasting (sending data from one source to one destination) and multicasting (sending data simultaneously to a group of destination computers).RSVP supports dynamic automatic adaptation to changes in network.It provides a number of reservation styles. It also provides support for addition of future ... Read More

Reservation protocols are the class of protocols in which the stations wishing to transmit data broadcast themselves before actual transmission. These protocols operate in the medium access control (MAC) layer and transport layer of the OSI model.In these protocols, there is a contention period prior to transmission. In the contention period, each station broadcasts its desire for transmission. Once each station announces itself, one of them gets the desired network resources based upon any agreed criteria. Since each station has complete knowledge whether every other station wants to transmit or not before actual transmission, all possibilities of collisions are eliminated.Examples ... Read More

Bit-map protocol is a collision free protocol that operates in the Medium Access Control (MAC) layer of the OSI model. It resolves any possibility of collisions while multiple stations are contending for acquiring a shared channel for transmission.In this protocol, if a station wishes to transmit, it broadcasts itself before the actual transmission. This is an example of Reservation Protocol.Working PrincipleIn this protocol, the contention period is divided into N slots, where N is the total number of stations sharing the channel. If a station has a frame to send, it sets the corresponding bit in the slot.Suppose that there ... Read More

In computer networks, when more than one station tries to transmit simultaneously via a shared channel, the transmitted data is garbled. This event is called collision. The Medium Access Control (MAC) layer of the OSI model is responsible for handling collision of frames. Collision – free protocols are devised so that collisions do not occur. Protocols like CSMA/CD and CSMA/CA nullifies the possibility of collisions once the transmission channel is acquired by any station. However, collision can still occur during the contention period if more than one stations starts to transmit at the same time. Collision – free protocols resolves ... Read More

Multi-access ChannelsMulti-access channels are network channels that allow several transmitters to communicate with a common receiver via a shared channel. These channels are also called multiple access (MAC) channels. The network channel may be a single cable or optical fiber connecting multiple nodes, or a portion of the wireless spectrum.Random Access ChannelsRandom-access channels (RACH) are shared channels used in wireless communication systems to allow mobile devices for call set-up. RACH also handles bursty data transmission. RACH is popularly used by GSM mobiles for transmission over cellular networks.Multiple Access SchemesBoth multi-access channels and random access channels require a scheme to allow ... Read More

Link Control Protocol (LCP) is a part of Point – to – Point Protocol (PPP) that operates in the data link layer. It is responsible for establishing, configuring, testing, maintaining and terminating links for transmission. It also imparts negotiation for set up of options and use of features by the two endpoints of the links.Working PrincipleWhen PPP tries to communicate, it sends out LCP packets prior to the establishment of connections over the point – to – point link. The LCP packets check the communication line to ascertain whether it can sustain the data volume at the required speed. Accordingly, ... Read More

Serial Line Internet Protocol (SLIP) is a simple protocol that works with TCP/IP for communication over serial ports and routers. They provide communications between machines that were previously configured for direct communication with each other.For example, a client may be connected to the Internet service provider (ISP) with a slower SLIP line. When a service is required, the client places a request to the ISP. The ISP responds to the request and passes it over to the Internet via high speed multiplexed lines. The ISP then sends the results back to the client via the SLIP lines.SLIP was developed by ... Read More