CS 551: Distributed Operating Systems
Computer and Network Protocols

Computer and Network Protocols

"In a distributed system, the network is the medium that connects the computers. On the lowest layer, it takes the form of a physical transmission medium. In current use are copper wire, optical fiber, and wireless media.

"Above the physical layer, we have a hierarchy of protocols. A protocol is an agreed-upon set of rules, which describe actions or sequences of actions that initiate and control the transmission of data along the physical connections. In the protocol hierarchy, each layer provides a richer functionality than the layer below it, and each layer implements its functionality on the basis of the lower layer's functionality. A variety of protocol hierarchies and individual protocols are in current use.

(Leopol01)

Protocol (Webster):

1. "an original draft or record
2. "a preliminary memorandum of diplomatic negotiation
3. "a code of diplomatic or military etiquette
4. "a set of conventions for formatting data in an electronic communications system"

Protocol (not Webster):

• "defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission or receipt of a message or other event" (KurRos00)
• "A design that specifies the details of how computers interact, including the format of messages they exchange and how errors are handled" (Comer99)
• "An accepted or established set of procedures, rules, or formal specifications governing specific behavior or language. When applied to networks, a network protocol is a formal specification that defines the vocabulary and rules of data communication." (GalHan00)

ISO/OSI Protocol

"The OSI reference model provided a framework for talking about the overall communications process and hence was intended to facilitate the development of standards. The reference model incorporated much of the available knowledge from the research community and has served a useful role in network design for more than two decades." (L-GWid00)

"The communication between peer processes is virtual in the sense that no direct communication link exists between them"

(L-GWid00)

The Internet Protocol Stack

A five-layer protocol

• Application Layer
• Transport Layer
• Network Interface
• Link Layer
• Physical Layer

Bridges only use the bottom two layers

Routers or gateways use the bottom three layers

(KurRos00)

The TCP/IP Network Architecture

A four layer protocol:

• Application Layer
• Transport Layer
• Internet Layer
• Network Interface

on top of the hardware (Physical) layer

Routers or gateways only use the bottom two layers

plus the hardware layer

(L-GWid00)

The ATM Network Architecture

A six layer protocol:

• Application Layer
• Transport Layer (TCP/UDP)
• Network Layer (IP)
• AAL (ATM Adaptation Layer)
• ATM Layer
• ATM Physical Layer

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Comments:
Copyright © 2001-2003: Colorado State University for CS 551. All rights reserved.

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