Protocol Layering Chapter 11 Protocol Layering D E

Protocol Layering Chapter 11: Protocol Layering. D. E. Comer. “Internetworking with TCP/IP: Principles, Protocols and Architecture”, Vol. 1, Prentice Hall, 2000 Presented by Wuilbert Jaramillo

Outline l Part 1 – – l Network problems, protocol and layering concepts Need for protocols and layering Part 2 – – ISO/OSI and TCP/IP models Comparison Common points Final remarks CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 1 l l l Existing problems in communication networks Protocol -definition The need for protocols Set of protocols: Layering What is Layering? Why Layering? CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 2 l l l Example: ISO/OSI 7 -layer model TCP/IP 5 layer reference model ISO/OSI vs. TCP/IP Common points in layering Summary CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Existing Problems in Communication Networks l Hardware failure – l Network congestion – l l Networks have finite capacity Packet delay Data corruption – – l Hosts, routers Electric, magnetic interferences HW failure Data duplication CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Complexity of networks Networks are complex !!! l Parts of a network: – – – – Hosts Routers Media Applications Hardware Software Different OS Different protocols Is there a Solution? l l l Organize all the elements under a same agreement Better yet, use a divide and conquer approach Result: the concept of a communications protocol CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 1 ü Ø l l Existing problems in communication networks Protocol -definition The need for protocols Set of protocols: Layering What is Layering? Why Layering? CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Some definitions for Protocol l an original draft, minute, or record of a document or transaction a code prescribing strict adherence to correct etiquette and precedence (as in diplomatic exchange and in the military services) a set of conventions governing the treatment and especially the formatting of data in an electronic communications system CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Protocol l l Agreement about communication Specifies – – l Format of messages Meaning of messages Rules for exchange Procedures for handling problems Protocols allow to specify or understand communication without knowing the details of a particular hardware CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 1 ü ü Ø l l l Existing problems in communication networks Protocol -definition The need for protocols Set of protocols: Layering What is Layering? Why Layering? CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Need for Protocols l l Hardware is low level Many problems can occur – – Bits corrupted or destroyed Entire packet lost Packet duplicated Packets delivered out of order CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Need for Protocols (continued) l Need mechanisms to distinguish among – – Multiple computers on a network Multiple applications on a computer Multiple copies of a single application on a computer Different Operating Systems (OS) CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 1 ü ü ü Ø l l Existing problems in communication networks Protocol -definition The need for protocols Set of protocols: Layering What is Layering? Why Layering? CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Set of Protocols l l l Work together Each protocol solves part of a communication problem Known as – – l Protocol suite Protocol family Designed in layers CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Plan for Protocol Design l l l Intended for protocol designers Divides protocols into layers Each layer is devoted to one sub-problem CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 1 ü ü Ø l Existing problems in communication networks Protocol -definition The need for protocols Set of protocols: Layering What is Layering? Why Layering? CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

What is layering? l A technique to organize a network system into a succession of logically distinct entities, such that the service provided by one entity is solely based on the service provided by the previous entity. CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Conceptual Layers of Protocol Software Sender Layer n … The modules of Protocol SW are on each machine stacked vertically into layers Layer 2 Layer 1 Receiver Layer n … Layer 2 Layer 1 Network CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Conceptual/Realistic view Conceptual Layers High Level Protocol Layer Software Organization Protocol 1 Internet Protocol Layer Network Interface Layer Protocol 2 Protocol 3 IP Module Interface 1 Interface 2 CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Interface 3 Fall 2003

Example: Internet Protocol Layers l Five layers – Application: supporting network applications l – Transport: host-host data transfer l – ip, routing protocols Link: data transfer between neighboring network elements l – tcp, udp Network: routing of a datagram from source to destination l – ftp, smtp, http ppp, ethernet Application Transport Network Link Physical: bits “on the wire” CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Protocol Layering and Data Application Transport Network Link M Message H M Segment H H M Datagram H H H M Frame Physical CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Layers and packet headers l Each layer – – Appends header to outgoing packet Removes header from incoming packet H H H l M Receiver uses header as demultiplexing key – Sender Multiplexes among several layers CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 1 ü ü ü Ø Existing problems in communication networks Protocol -definition The need for protocols Set of protocols: Layering What is Layering? Why Layering? CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Why layering? l Dealing with complex systems: – – Explicit structure allows identification of complex system’s pieces Modularization eases developing, maintenance, updating of system l Change of implementation of layer’s service transparent to rest of system CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Example: No layering Application Transmission Media FTP Telnet HTTP Coaxial cable Packet radio Fiber optic No layering: each new application hast to be re-implemented for every network technology! CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Example: now with Layers Application Telnet FTP HTTP Transport & Network Transmission Media Coaxial cable Fiber optic Packet radio Solution: introduce an intermediate layer that provides a common abstraction for various network technologies CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 2 Ø l l ISO/OSI 7 -layer model TCP/IP 5 layer reference model ISO/OSI vs. TCP/IP Common points in layering Summary CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

ISO 7 layer model l l Based on early work done by the International Organization for Standardization (ISO) Reference Model of Open System Interconnection (OSI) Contains 7 conceptual layers OSI: conceptually define service, interface, protocol CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

OSI Model concepts*** l l l Service –says what a layer does Interface –says how to access the service Protocol –says how the service is implemented – A set of rules and formats that govern the communications between two peers CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

ISO/OSI Reference Model l Seven Layers – – Lower three layers are hop-by-hop Next four layers are end-to-end Application Presentation Session Transport Network Datalink Physical Medium CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

ISO Layers l l l l Layer 1: Physical (underlying hardware) Layer 2: Data Link (hardware frame definitions) Layer 3: Network (packet forwarding, routing) Layer 4: Transport (reliability, end-to-end) Layer 5: Session (login and passwords, session and connection coordination) Layer 6: Presentation (data representation) Layer 7: Application (individual application program) CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

ISO Graphical View Layer 7 Application Message Passing Layer 6 Presentation Encoding Layer 5 Session Authentication & Encryption Layer 4 Transport Streams & Segments Layer 3 Network Datagrams Layer 2 Data Link Frames & Packets Layer 1 Physical Hardware Signaling & Wiring CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

X. 25 and its relation to the ISO model l Best known and most widely used – – l Established as a recommendation of the ITU Specially popular en Europe Operates much like a telephone system – – Consists of complex packet switches Hosts attach to one of the packet switches CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

X. 25 and its relation to the ISO model CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 2 ü Ø l l l ISO/OSI 7 -layer model TCP/IP 5 layer reference model ISO/OSI vs. TCP/IP Common points in layering Summary CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

TCP/IP History l It originated from research – – l Developed by the Department of Defense (DOD) Network of networks Network of lowest bidders – – – The Army puts a bid on a computer and DEC wins the bid The Air Force puts out a bid and IBM wins The Navy bid is won by Unisys CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

The TCP/IP 5 -Layer Reference Model Conceptual Layer Application Transport Internet Network Interface Objects Passed Between Layers Messages or Streams Transport Protocol Packets IP Datagrams Network-Specific Frames Physical CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

TCP/IP Layer Description l Layer 5: Application – l Layer 4: Transport – l Defines uniformat of packets forwarded across networks of different technologies and rules forwarding packets in routers Layer 2: Network – l Provides reliable delivery of data Layer 3: Internet – l Used for communicating among applications Defines formats for carrying packets in hardware frames Layer 1: Physical CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

TCP/IP practical overview Application Telnet, FTP, e-mail, etc. Transport TCP, UDP Internet IP, ICMP, IGMP Network Interface device driver and interface card Physical CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Two hosts running FTP CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Two networks connected with a router CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Mail with TCP/IP CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

A general background on TCP/IP CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 2 ü ü Ø l l ISO/OSI 7 -layer model TCP/IP 5 layer reference model ISO/OSI vs. TCP/IP Common points in layering Summary CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Layers in both ISO and TCP/IP Application Presentation Application Session Transport Internet Network Interface Datalink Physical CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Comparison CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Differences between ISO and TCP/IP l l Reliability Locus of Authority and control CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Reliability l ISO/X. 25 – – Connection Oriented Complex protocols guarantee error free transport on every layer Retransmission of corrupted packages Flow control on every layer l TCP/IP – – Connection less Reliability is an end-to-end problem Freedom on handling corrupted packets Flow control on transport layer CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Locus of Authority and Control l ISO/X. 25 – – – Network layer is service to transport layer Network handles routing, flow control, acknowledgements internally Complex independent systems working for simple hosts l TCP/IP – – – Host participates in network protocols Host participates in e. g. routing, flow control Simple package delivery system with intelligent hosts CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 2 ü ü ü Ø l ISO/OSI 7 -layer model TCP/IP 5 layer reference model ISO/OSI vs. TCP/IP Common points in layering Summary CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Protocol layering principle l Layered protocols are designed so that layer N at the destination receives exactly the same object sent by layer N at the source CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Protocol layering Host A Host B Application Transport Internet Network Interface Identical message Identical packet Identical datagram Identical Frame Transport Internet Network Interface Physical net CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Protocol Layering with a router CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Layering in the presence of Network substructure Conceptual Layers Transport Software Organization Protocol 1 Internet Network Interface Intranet Protocol 2 Protocol 3 IP Module Interface 1 Interface 2 Interface 3 Point-To-Point (Intranet) CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Multiplexing and Demultiplexing ARP Module IP Module RARP Module Demultiplexing Based on Frame type Frame arrives CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

More Demultiplexing UDP Protocol ICMP Protocol TCP Protocol IP Module Datagram arrives CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Outline Part 2 ü ü Ø ISO/OSI 7 -layer model TCP/IP 5 layer reference model ISO/OSI vs. TCP/IP Common points in layering Summary CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

Summary l Advantages – – Breaks down complex problem into more manageable components Implementation details of one layer are abstracted away from other layers l Disadvantages – – – Information hiding, inefficient implementations Can introduce overhead Could lead to inefficiency CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003

CMPT 880. Protocol Layering – by Wuilbert Jaramillo, wjaramil@sfu. ca. Fall 2003