Protocols

 Protocols are rules and procedures for communication.

How Protocols Work

The Sending Computer

• Breaks data into packets.
• Adds addressing information to the packet
• Prepares the data for transmission.

The Receiving Computer (same steps in reverse)

• Takes the packet off the cable.
• Strips the data from the packet.
• Copies the data to a buffer for reassembly.
• Passes the reassembled data to the application.

Protocol Stacks (or Suites)

• A combination of protocols, each layer performing a function of the communication process.
• Ensure that data is prepared, transferred, received and acted upon.

The Binding Process

• Allows more than one protocol to function on a single network adapter card. (e.g. both TCP/IP and IPX/SPX can be bound to the came card
• Binding order dictates which protocol the operating systems uses first.
• binding also happens with the Operating System architecture: for example, TCP/IP may be bound to the NetBIOS session layer above and network card driver below it. The NIC device driver is in turn bound to the NIC.

Standard Stacks

• ISO/OSI
• IBM SNA (Systems Network Architecture)
• Digital DECnet
• Novell NetWare
• Apple AppleTalk
• TCP/IP

Protocol types map roughly to the OSI Model into three layers:

Application Level Service Users

Application Layer
Presentation Layer
Session Layer

Transport Services

Transport Layer

Network Services

Network Layer
Data Link Layer
Physical Layer

Application Protocols

Work at the upper layer of the OSI model and provide application to application interaction and data exchange.
Examples:

• APPC-IBM's peer to peer SNA protocol used on AS400's
• FTAM: an OSI file access protocol.
• X.400: international e-mail transmissions.
• X.500: file and directory services across systems.
• SMTP: Internet e-mail.
• FTP: Internet file transfer
• SNMP: Internet network management protocol.
• Telnet: Internet protocol for logging on to remote hosts.
• Microsoft SMB: client shells and redirectors.
• NCP: Novell client shells or redirectors.
• AppleTalk and AppleShare: Apple's protocol suite.
• AFP: Apple's protocol for remote file access.
• DAP (data access protocol): DECnet file access protocol.

Transport Protocols

These protocols provide communication sessions between computers and ensure data is moved reliably between computers.
Examples:

• TCP (transmission control protocol): internet protocol for guaranteed delivery of sequenced data.
• SPX (sequenced packet exchange): Novell protocol suite.
• NWLink: Microsoft implementation of IPX/SPX.
• NetBEUI: establishes communications sessions between computers and provides the underlying data transport services.
• ATP, NBP: Apple's communication session and transport protocols.

Network Protocols

These provide link services
They also

• handle

• addressing and routing,
• error checking and
• retransmission requests.

• Define rules for Ethernet or Token Ring.

Examples:

• IP (Internet Protocol): packet forwarding and routing.
• IPX: (Internetwork Packet Exchange): Novell's protocol for packet forwarding and routing.
• NWLink: Microsoft implementation of IPX/SPX.
• NetBEUI: Transport for NetBIOS sessions and applications.
• DDP (datagram delivery protocol): An AppleTalk data transport protocol.