PROTOCOLS

Protocols are rules and procedures for communicating. When several computers are network, the rules and technical procedures governing their communication and interaction are called Protocols. Network communication protocols are defined within the context of a layered architecture, usually called a protocol stack. The OSI protocol stack is often used as a reference to define the different types of services that are required for systems to communicate. The protocol stack defines how communication hardware and software interoperate at various level. Layering is a design approach that specifies different functions and services at levels in the protocol stack. A Protocol Stack is a combination of protocols. Each layer specifies a different protocol for handling a function or subsystem of the communication process.  Each layer has its own set of rules. As in the OSI model, the lower layers in the stack specify how vendors can make their equipment connect to equipment from other vendors. The upper layers specify rules for conducting communications sessions an dthe interpretation of applica-tions. The higher in the stack, the more sophisticated the tasks and their associated protocols become.

Network Introduction Network Cabling Wireless Network Network Interface Card OSI Model Protocols Ethernet - Network architecture Token Ring - Network architecture AppleTalk and ArcNet - Network architectures Repeaters, Bridges, Routers, and Gateways E-mail Standards Modem & Async Comm. T1, T3, and Switched 56 Digital Connectivities Packet-Switching Network,Frame Relay and ATM ISDN & FDDI

Data being sent from one LAN to another along any of several available paths is routed. The protocols that support multipath LAN-to-LAN communications are known as Routable Protocols.

As LAN technology matured, and the data communication needs of business expanded, LANs became components in larger data communication networks where LANs talked to each other. Because routable protocols can be used to tie several LANs together and create new wide-area environments, they are becoming increasingly important.

a. TCP/IP

Transmission Control Protocol/Internet Protocol (TCP/IP) provides communication in heterogeneous environment. It provides routable, enterprise networking protocol and access to the worldwide Internet and its resource.

b. X.25

X.25 is set of protocols incorporated in a packet switching network made up of switching services. The switching services were originally established to connect remote terminals to main frame host systms.

c. IPX/SPX

IPX/SPX is a protocol stack that is used in Novell® networks. It is a relatively small and fast protocol on LAN, but it does not supoort routing. IPX/SPX is a derivative of XNS.

d. X.25

X.25 is a set of protocols incorporated in a packet switching network made up of switching services. The switching services were originally established to connect remote terminals to main frame host systems.

e. AppleTalk

AppleTalk is AppleComputer's proprietary protocol stack designed to enable Apple Macintosh® computers to share files and printers in a networked environment.

The IEEE protocols at the physical layer are:

a. 802.3 (Ethernet)

This is a logical bus network that can transmit data at 10Mbps. Data is transmitted on the wire to every computer. Only those meant to receive the data acknowledge the transmission. The CSMA/CD protocol regulates network traffic by allowing a trans-mission only when the wire is clear and no other computer is transmitting.

b. 802.4 (Token Passing)

This is a bus layout that use a token passing scheme. Every computer receives all of the data but only the ones addressed respond. A token that travles the wire determines which computer is able to broadcast.

c. 802.5 (Token Ring)

This is a logical ring network that transmits at either 4 Mbps or 16 Mbps. Even though this is called a ring, it looks like a star with each computer branching off a hub. The ring is actually inside the hub. A token traveling around the ring determines which computer may send data.

Protocols have several roles both at the sending computer and the receiving computer.

At the sending computer, the protocol:

1. Breaks the data into smaller sections, called packets, that protocol can handle

2. Adds addressing information to the packets so the destination computer on the network will know the data belongs to it.

3. Prepares the data for actual transmission through the NIC and out onto the cable.

1. Takes data packets off the cable.

2. Brings the data packets into the computer through the network adapter card.

3. Strips the data packets of all of transmitting information added by the sending computer.

4. Copies the data from the packets to a buffer for reassembly.

5. Passes the reassembled data to the application in a usable from.

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