Protocol Meaning
A protocol defines the principles for sending blocks of knowledge (each referred to as a Protocol Data Unit (PDU)) from one node during a network to a different node. Protocols are normally defined during a layered manner and supply all or a part of the services specified by a layer of the OSI reference model. A protocol specification defines the operation of the protocol and should also suggest how the protocol should be implemented. It consists of three parts:
Definition of Protocol Control Information (PCI) format which forms the PDU header
Definition of procedures for transmitting and receiving PDUs
Definition of services provided by the protocol layers
The PDUs exchanged have two parts: a header (also referred to as the Protocol Control Information (PCI)) and a payload (also referred to as a Service Data Unit (SDU)). The protocol doesn't define or constrain the info carried within the payload part. It does specify the format of the PCI, defining the fields which are present and therefore the way during which the patterns of bits are to be interpreted.
A protocol also defines the procedures which determine how the PDU are going to be processed at the transmit and receive nodes. The procedures specify the valid values for the PCI fields, and therefore the action be taken upon reception of every PCI value (usually supported stored control information). samples of procedures which are implemented in protocols include:
error recovery (e.g. the checkpoint procedure, the go-back-n procedure)
flow control
segmentation
service access point selection
connection management
The documents which define a protocol procedures are usually large and are seldom concrete (i.e. they'll not be directly translated to executable programs). They typically define the actions to be taken when a specific condition is detected, but not how the condition is to be detected. it's been said that "Part of what makes a protocol mature is sweet implementation guidelines and folklore". The success of the TCP/IP protocol suite is essentially thanks to the "industrial strength" code available in freely distributed reference implementations.
Protocols are usually implemented by writing variety of programs (processes) which communicate with each other through queues and by function calls. One or more timers also are usually required to make sure correct operation of the protocol. to start out and stop timers, a protocol normally uses an interface to the computer's OS . This interface is additionally wont to request new (empty) buffers for received PDUs (or PDUs created by the layer) and to release buffers which are not any longer needed by the protocol.
Protocols are generally described employing a layered architecture referred to as the OSI reference model. Which abstracts the small print of the protocol and allows an easy description of the service provided by the protocol to the protocol layer above and therefore the service required by protocol layer from the layer below.
Examples of protocols include:
Link Layer - HDLC, MAC, ARP
Network Layer - IP, ICMP
Transport Layer - UDP, TCP
Definition of Protocol Control Information (PCI) format which forms the PDU header
Definition of procedures for transmitting and receiving PDUs
Definition of services provided by the protocol layers
The PDUs exchanged have two parts: a header (also referred to as the Protocol Control Information (PCI)) and a payload (also referred to as a Service Data Unit (SDU)). The protocol doesn't define or constrain the info carried within the payload part. It does specify the format of the PCI, defining the fields which are present and therefore the way during which the patterns of bits are to be interpreted.
A protocol also defines the procedures which determine how the PDU are going to be processed at the transmit and receive nodes. The procedures specify the valid values for the PCI fields, and therefore the action be taken upon reception of every PCI value (usually supported stored control information). samples of procedures which are implemented in protocols include:
error recovery (e.g. the checkpoint procedure, the go-back-n procedure)
flow control
segmentation
service access point selection
connection management
The documents which define a protocol procedures are usually large and are seldom concrete (i.e. they'll not be directly translated to executable programs). They typically define the actions to be taken when a specific condition is detected, but not how the condition is to be detected. it's been said that "Part of what makes a protocol mature is sweet implementation guidelines and folklore". The success of the TCP/IP protocol suite is essentially thanks to the "industrial strength" code available in freely distributed reference implementations.
Protocols are usually implemented by writing variety of programs (processes) which communicate with each other through queues and by function calls. One or more timers also are usually required to make sure correct operation of the protocol. to start out and stop timers, a protocol normally uses an interface to the computer's OS . This interface is additionally wont to request new (empty) buffers for received PDUs (or PDUs created by the layer) and to release buffers which are not any longer needed by the protocol.
Protocols are generally described employing a layered architecture referred to as the OSI reference model. Which abstracts the small print of the protocol and allows an easy description of the service provided by the protocol to the protocol layer above and therefore the service required by protocol layer from the layer below.
Examples of protocols include:
Link Layer - HDLC, MAC, ARP
Network Layer - IP, ICMP
Transport Layer - UDP, TCP
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