INF3190 - Data Communication

Introduction

Carsten Griwodz Email: [email protected]

most slides from: Ralf Steinmetz, TU Darmstadt and a few from Olav Lysne, J. K. Kurose og K. W. Ross

University of Oslo INF3190 – Data Communication Problem area and focus

§ How do we build efficient communication networks?

§ Focus of the course: − provide a functional understanding of building blocks for data communication − show how such building blocks can be combined into operational networks − focus on principles, concepts, and generality

University of Oslo INF3190 – Data Communication Course outline § 1 two-hour lecture per week § 1 two-hour common group exercise § 1 mandatory assignment § 2 home exams (together 40% of the final grade) − we may interview people before grading § Oracle: available for 2 hours every week

University of Oslo INF3190 – Data Communication History

§ Telegraphy

§ Telephony © Steinmetz, Ralf § Telegraphy vs. Telephony

§ Television Technische Television vs. Telephony and Telegraphy

§ Universität

§ The Internet Darmstadt − Forefather of the ARPANET (1965) − The ARPANET (here: ~1967 – 1972) − Standardization (1969 onwards) − Internetworking (~1972 onwards)

§ Since 1980

University of Oslo INF3190 – Data Communication

Telegraphy © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication and before

Source: www.mathematik.uni-muenchen.de © Steinmetz, Ralf Technische

Universität Darmstadt

e.g. 18th century

1791: Semaphoric Telegraph (Chappe)

University of Oslo INF3190 – Data Communication

Morse Telegraph Image source: Wikimedia Commons

Morse transceiver § One switch to send long and short impulses at sender © Steinmetz, Ralf − dahs and dits or − dashes and dots Technische § Dashes and dots

− punched into Universität paper strip at receiver Darmstadt

§ See beginning of first telegraph ‘What hath God wrought’ (Num 23,23) sent in 1844 from Washington to Baltimore

§ Communication network?

University of Oslo INF3190 – Data Communication Morse Telegraph Image source: Wikimedia Commons

Telegraph Network in United States 1916

§ Similarities to

today’s Internet? © Steinmetz, Ralf

§ Signal coding? Technische § Type of switching?

− Packet? Universität − Message?

− Circuit? Darmstadt

§ Type of service? − Connection oriented? − Connectionless?

§ Repeaters? § Routers?

University of Oslo INF3190 – Data Communication Morse Telegraph Image source: Wikimedia Commons § Morse Code − Variable length

− Short code for frequently used letters © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication Baudot Telegraph Image source: Wikimedia Commons Baudot time multiplex system § Forefather of teletypewriters (TTYs) § Baud rate (symbol rate) of transmission named after Baudot

§ Challenge: © Steinmetz, Ralf − to increase number of telegraph messages

§ Solution: Technische − time multiplexing

− To connect multiple telegraphs Universität over same line Darmstadt § First attempts failed − Problems with synchronization of sender and receiver − Reason: • variable length morse code

§ Baudot solved problem − Fixed length (5 bit) code − Synchronized time multiplexing

University of Oslo INF3190 – Data Communication Baudot Telegraph Baudot code § Fixed length 5 bit code

− Allows for 25=32 symbols © Steinmetz, Ralf − Restricted to five bits due to hardware constraints Technische • Workaround by shifting alphabet

to represent more characters Universität Darmstadt § Later standardized by CCITT (ITU-T) − International telegraph alphabet 1 − Forefather of ASCII code

University of Oslo INF3190 – Data Communication Baudot Telegraph Image source: Wikimedia Commons Baudot time multiplex system § Multiple senders/receivers connected to distributor − Copper segments with rotating brushes © Steinmetz, Ralf § Distributors − at sender and

− receiver side synchronized Technische § Serialization of characters typed on Baudot keyboard

§ Time multiplexing of input from multiple keyboards Universität Darmstadt

Sender 2

Sender 1 Receiver

University of Oslo INF3190 – Data Communication Telephony Image source: Wikimedia Commons © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication Telephony Image source: Wikimedia Commons

First telephones in 1870s sold pairwise § With dedicated, direct line © Steinmetz, Ralf Assuming a full mesh § Each customer can call any other customer

à Each customer has n-1 phones Technische

n ⋅ n −1 Universität à ( ) lines required for n customers 2 Darmstadt Scalability? § O(?) phones required? § O(?) lines required?

University of Oslo INF3190 – Data Communication Telephony

Telephone switches reduced complexity of phone network § Line from each phone to central switchboard © Steinmetz, Ralf § Long distance lines between switchboards Technische § First switches

manually Universität operated Darmstadt § Complexity? − O(?) phones required? − O(?) lines required? § Basic principle in use till today

ImageUniversity source: of WikimediaOslo Commons INF3190 – Data Communication Telephony Image source: harvard.edu

Strowger switches automated phone exchange § Stepping switch with two degrees of freedom § Hierarchical use with national & area code © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication Telegraphy vs. Telephony

Telegraph networks § Message switching − Telegram as discrete unit forwarded from sender to receiver via relay stations © Steinmetz, Ralf − No dedicated line between Sender S and Receiver R § Connectionless service

− Subsequent telegrams from S to R may use different lines Technische − E.g. in case of line failures

§ Compare: packet switching in today’s internet Universität

− Messages (packets) limited in size Darmstadt

University of Oslo INF3190 – Data Communication Telegraphy vs. Telephony

Telephone networks § Circuit switching − Dedicated line between Sender S (caller) and Receiver R (callee) © Steinmetz, Ralf − Reserved exclusively for entire call duration § Connection oriented service

− Communication always follows same path Technische − Three phases: connect (dial), talk (data exchange), disconnect (hang up)

§ Concepts still in use in today Universität

− No dedicated lines but reserved resources Darmstadt − E.g., connecting an ISDN call reserves 64kbit/s between caller and callee

University of Oslo INF3190 – Data Communication Television © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication Television Image source: ueberallfernsehen.de

Terrestrial digital TV broadcast - DVB-T § Terrestrial analogue TV replaced

completely by DVB-T in 2009 © Steinmetz, Ralf − Satellite and cable TV will follow § Station at Feldberg,

Frankfurt, Wiesbaden Technische − Cover ~2 million households

Universität

Sample calculation Darmstadt § DVB-T data rate is ~4 Mbit/s § ~2 million households in Rhine/Main area à ~8 Tbit/s (Terabit per second) received during primetime § Compare: global average Internet traffic was ~46 Tbit/s in 2010 § (source: Cisco visual networking index)

University of Oslo INF3190 – Data Communication Television vs. Telephony and Telegraphy

Television developed as broadcast medium § One sender, many receivers − In order of millions for TV stations © Steinmetz, Ralf § Inherent property of radio transmission Technische

Universität Darmstadt

Telephony (and telegraphy) developed as unicast medium § One sender, one receiver § Inherent property of circuit switched network

University of Oslo INF3190 – Data Communication The Internet Image source: Wikimedia Commons © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication Forefather of the ARPANET (1965)

First wide-area network built by Marill and Roberts in 1965 § ‘Toward a Cooperative Network of Time-shared Computers’ − American Federation of Information Processing Systems conference 1966 © Steinmetz, Ralf § Connecting a TX-2 at MIT to a PDP-1 at Santa Monica − TX-2 built at MIT, spin-off: Digital Equipment Corporation (DEC)

− PDP-1 built by DEC Technische § Connection via telephone line at 1200 bits per second

Universität

Motivation: connecting heterogeneous systems Darmstadt § Early software highly specialized for machine it ran on − Software written in assembler code − Platform independent languages yet to come § Using software written for machine A on machine B required high effort − Porting code or rewriting from scratch equally complex tasks

University of Oslo INF3190 – Data Communication The ARPANET (here: ~1967 - 1972) Goals § Load sharing − Send program and data for processing to © Steinmetz, Ralf remote machine Had been − Required identical computers at that time tried before

§ Message service Technische

Universität § Data sharing − Send program for processing to remote Darmstadt data § Program sharing Extended goals − Send data for processing to remote of ARPANET for program heterogeneous § Remote service environments − Send query to remote program and data − Harness specialized hardware and software

University of Oslo INF3190 – Data Communication The ARPANET Image source: Computer network development to achieve resource sharing, AFIPS 1970

Core component: network connections § 50 kbit/s full-duplex leased telephone lines (AT&T) § Minimum two paths between any two IMPs © Steinmetz, Ralf

Topology as planned in 1970 Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication Standardization (1969 onwards)

Problem: developing communication request for comments (RFCs) protocols requires consensus § Provide fast and open access § Different locations, institutions,

manufacturers, operators … involved © Steinmetz, Ralf à Standards required § But

− scientific publication process too Technische slow − industrial standardization process

too slow and to expensive Universität § Remember: ARPANET was research project with restricted funding Darmstadt

Solution: request for comments (RFCs) § At first: memos, minutes of meetings circulated by mail (standard old fashioned, not electronic) § Later: published electronically Internet standardization § http://www.rfc-editor.org/rfc- − FTP, HTTP index.html

University of Oslo INF3190 – Data Communication Standardization Image source: http://www.isoc.org/internet/history/brief.shtml

Who is behind RFCs? § Started in 1969 by ARPANET working group (WG)

§ International Internet growth demanded for more coordination © Steinmetz, Ralf − International Cooperation Board (ICB) − Internet Research Group (IRG)

− Internet Configuration Board (ICB) Technische

§ Continuing growth demanded for restructuring organizational institutions Universität − Task forces (TFs) founded for particular technology areas • Routers, protocols, … Darmstadt − Internet Architecture Board (IAB) coordinates task forces

University of Oslo INF3190 – Data Communication Standardization Image source: http://www.isoc.org/internet/history/brief.shtml

Who is behind RFCs? § Strong activities in practical/engineering aspects − Internet Engineering Task Force (IETF) became major player − Other task forces combined into Internet Research Task Force (IRTF) © Steinmetz, Ralf § Commercialization of the Internet led to shifted interests

− Internet Society (ISOC) coordinates business and research efforts Technische

Development of Word Wide Web (WWW / W3) Universität

§ World Wide Web Consortium (W3C) founded Darmstadt − Responsible for protocols and standards of the web

University of Oslo INF3190 – Data Communication Internetworking (~1972 onwards) § Besides ARPANET many other networks appeared in/after 1970s − E.g. NSFNET by US National Science Foundation

• Advanced research and education networking © Steinmetz, Ralf − E.g. JANET by UK government • Research and education network

− E.g. German DATEX-P by Deutsche Bundespost Technische • Commercial packet switched service

Universität Internetworking concepts proposed by Kahn in 1973 § Darmstadt − Goal: to connect different networks − Ground rules valid until today • No internal changes required to connect a network to the Internet • Best effort communication • Stateless gateways/routers used for connection of networks • No global control • Also: § dealing with packet loss, pipelining, fragmentation, global addressing, flow control, …

University of Oslo INF3190 – Data Communication Internetworking § ARPANET’s NCP does not meet internetworking requirements − TCP/IP presented by Cerf and Kahn at Stanford and BBN in 1974 − Concept of byte streams

− Flow control by sliding window with cumulative acknowledgements © Steinmetz, Ralf − First only TCP (nearly as we know it today) implemented − Research on packet voice demanded for more simple protocol à UDP − Other applications Technische • File and disk sharing, mobile agents

− Not foreseen Universität • proliferation of LANs and PCs • Considered were national level networks Darmstadt • 32 bit IP addresses with 8 bit network address, 24 bit host address

§ TCP/IP evolved to deployment version until 1981 − IPv4 as used today • Details see forthcoming lectures − ARPANET switched to TCP/IP in 1983

University of Oslo INF3190 – Data Communication Since 1980

Mobile telephony §

SMS © Steinmetz, Ralf

Web Technische Peer-to-Peer

Universität and applications Darmstadt § Web services § Streaming services § … § Twitter § Social networks § …

University of Oslo INF3190 – Data Communication

Part I à Part II

§ Part I – History § Part II – Basics © Steinmetz, Ralf − Network Structures − Layers Technische − Layer functions and services

− Terminology Universität Darmstadt

University of Oslo INF3190 – Data Communication

Network Components © Steinmetz, Ralf Technische

Universität Darmstadt Data transfer from end system to end system § END-SYSTEM (ES) also known as Data Terminal Equipment (DTE) − e.g. terminal, computer, telephone − and Data Circuit terminating Equipment (DCE) and Data transfer equipment • e.g: modem, multiplexer, repeater § INTERMEDIATE SYSTEM (IS) also called Data Switching Exchange (DSE) − e.g. router

University of Oslo INF3190 – Data Communication Network Structures

Point-to-point channels § net = multitude of cable and radio connections often also called a

network © Steinmetz, Ralf § whereby a cable always connects two nodes § more prevalent in wide area domains (e. g. telephone) Technische

Topologies:

Universität Darmstadt

University of Oslo INF3190 – Data Communication Network Structures Broadcasting channels § systems share one communication channel

§ one sends, all others listen © Steinmetz, Ralf

Used for Technische § wide area: radio, TV, computer communication

§ local area: local networks Universität Darmstadt Topologies:

University of Oslo INF3190 – Data Communication Network Types

Distance between Processors CPUs jointly located on/in.. Example usually tightly coupled multi- <= 0,1 m Boards processor system

e.g. body area network © Steinmetz, Ralf 1 m Systems e.g. sensor area network e.g. storage area network

10 m Rooms Technische 100 m Buildings LAN

1 km Campuses Universität 10 km Cities MAN 100 km Countries (national) Darmstadt 1.000 km Continents (intern.) WAN >= 10.000 km Planets

− Local Area Network (LAN) e.g. IEEE 802.3 = Ethernet, IEEE 802.11 − Metropolitan Area Network (MAN): • (being replaced by LAN + WAN) e.g. FDDI − Wide Area Network (WAN): example SDH, ATM, all optical networks − Inter-Planetary Internet: http://www.ipnsig.org/

University of Oslo INF3190 – Data Communication Protocols and layers Hva er en protokoll?

En menneskelig protokoll og en maskinell protokoll: © Steinmetz, Ralf Technische

Hei Universität TCP forbindelses req. Hei Darmstadt TCP forbindelse Hva er svar. klokka? Hent http://gaia.cs.umass.edu/ 2.15 index.htm tid

University of Oslo INF3190 – Data Communication Protocols and layers

Problem: engineering communication means − multitude of partially very complex tasks − interaction of differing systems and components Simplification: © Steinmetz, Ralf − to introduce abstraction levels of varying functionalities − general: “module”, preferable: “layer”, “level” Technische Example (here using ISO-OSI reference model, later 5 layers

− biologists with translator and e.g. secured encrypted FAX-office Universität Darmstadt

University of Oslo INF3190 – Data Communication Layer Concept

(only in communication?) layers exist in various areas − e. g. • compression: MPEG • CD technology © Steinmetz, Ralf

Example: CD Digital Audio Technische − here also levels, here also data units

Universität Darmstadt

University of Oslo INF3190 – Data Communication Layers in General (OSI) © Steinmetz, Ralf Technische

§ N-Layer Universität − abstraction level with defined tasks

§ N-Entity Darmstadt − active elements within a layer − process or intelligent I/O module − peer entities: corresponding entities on different systems § N-Service Access Point, N-SAP − service identification § N-Protocol: − a multiple of rules for transferring data between N-entities

University of Oslo INF3190 – Data Communication Protocol: Communication between same Layers © Steinmetz, Ralf Technische

Universität Darmstadt

Definition of protocol § A protocol defines Protocol § the format and § rules for syntax (format) and semantics (contents) § the order of messages − of the data transfer (frames, packet, message) § exchanged between two or more occurring communicating entities, − between the respective, active peer entities § as well as the actions taken on transmission and/or reception of a message or other event

University of Oslo INF3190 – Data Communication Reference Model for Open Systems Interconnection

ISO OSI (Open Systems Interconnection) Reference Model § model for layered communication systems

§ defines fundamental concepts and terminology © Steinmetz, Ralf § defines 7 layers and their functionalities Technische

7 Application Layer Universität

6 Presentation Layer Darmstadt 5 Session Layer 4 Transport Layer 3 Network Layer 2 Data Link Layer 1 Physical Layer

University of Oslo INF3190 – Data Communication Architecture

Actual data flow between two systems © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication OSI Architecture

Real data flow with intermediate systems © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication Layers and theirs Functions

Layer Function Signal representation of bits: sending bit 1 is also received as bit 1 (and not as bit 0): © Steinmetz, Ralf § mechanics: connector type, cable/medium,.. § electronics: voltage, bit length,.. 1 § procedural: Physical § unidirectional or simultaneously bidirectional Technische § initiating and terminating connections

Universität Protocol example: RS232-C = ITU-T V.24; other: ITU-T X.21 Darmstadt Reliable data transfer between adjacent stations with frames § introducing data frames and acknowledgement frames § error recognition and correction within the frame: § manipulation, loss, duplication 2 § Residual & “severe” errors deferred to higher layers Data Link § fast sender, slow receiver: § flow control § distribution network requires access control: § Medium Access Control (MAC)

University of Oslo INF3190 – Data Communication ISO-OSI Layers: Functions

Layer Function

Layer 2 may already include some flow control © Steinmetz, Ralf Goal: protect slow receiver Flow control can be sophisticated (sliding window protocol), For example, avoid slow stop-and-go for satellite Technische connections

Broadcast networks (LAN) often with two sublayers Universität Logical Link Control (LLC) 2 Darmstadt Medium Access Control (MAC) Data Link

Logical Link error detection Control (LLC) Medium Access fair / ordered access to single medium Control (MAC) (CSMA/CD, tokens, …)

University of Oslo INF3190 – Data Communication ISO-OSI Layers: Functions

Layer Function connects (as relationship between entities) end system to end system © Steinmetz, Ralf § (subnets) with packets § routing, i. e. among others § fixed, defined during connect, dynamic § congestion control (too many packets on one path) Technische § quality of service dependent

Universität Node B Node C ?

3 Darmstadt Network Node A End-to-End § varying subnets, Internetworking, § i. e. among others § addressing, packet size § comment: at broadcast networks: § routing often simplified or non-existent, i. e. this layer does often not exist here § example: IP (connectionless), X.25 (connection-oriented)

University of Oslo INF3190 – Data Communication ISO-OSI Layers: Functions

Layer Function Connection (as relationship between entities)

From source (application/process) © Steinmetz, Ralf to destination (application/process) § optimize required quality of service and costs § 1 L4 connection corresponds to 1 L3 connection § increase throughput: Technische § 1 L4 connection uses several L3 connections (splitting)

§ minimize costs: Universität § several L4 connections multiplexed onto 1 L3 connection

4 § process addressing, connection management, error correction Darmstadt Transport § fast sender, slow receiver: transmission delay without fragmentation § flow control § protocol example: TCP

time start end transmission delay with fragmentation

(fragments run in parallel over different hops: “pipelining”)

time start end

University of Oslo INF3190 – Data Communication ISO-OSI Layers: Functions

Layer Function

support a “session” over a longer period

5 § synchronization © Steinmetz, Ralf (during interrupted connection) Session § token management (coordinate the simultaneous processing of different applications) Technische

data presentation independent from the end system

§ negotiating the data structure, Universität 6 § conversion into a global data structure Presentation § examples: Darmstadt § data types: date, integer, currency, § ASCII, Unicode, … application related services 7 § examples: Application § electronic mail, directory service § file transfer, WWW, P2P, … Comment: § layer does not necessarily correspond to the process of the implemented unit § otherwise loss of efficiency

University of Oslo INF3190 – Data Communication OSI 7-Layer Architecture Summary

7. Application Layer A: cooperating entities 6. Presentation Layer P: exchange of data (semantics!) © Steinmetz, Ralf 5. Session Layer S: structured dialogue 4. Transport Layer T: end2end msg. stream betw. individual processes 3. Network Layer N: packet stream between end systems Technische

2. Data Link Layer D: error-recovering frame stream, adjacent sys. Universität § LAN comprises Darmstadt q L.2b: Logical Link Control

q L.2a: Media Access Control 1. Physical Layer PH: unsecure bitstream between adjacent systems

§ Note: − Many service functions carried out in several layers / services ! à Overhead, even reversal in part due to net homogeneity

University of Oslo INF3190 – Data Communication Data Units

§ Application level “messages” are processed as data units.

§ Following notions for data units have become common: © Steinmetz, Ralf − packet: “unit of transportation” (may contain fragments)

− datagram: instead of packet if sent individually (connectionless) Technische − frame: with final envelope, ready to send (next to lowest layer)

− cell: small packet of fixed size Universität Darmstadt § OSI terminology: „message“ is a PDU − PDU: Protocol Data Unit • (N)-PDU: semantics understood by peer entities of (N)-service • (N)-PDU = (N)-PCI plus (N)-SDU; (N)-SDU = (N+1)-PCI plus (N+1)-SDU − PCI: Protocol Control Information: only used by peers − SDU: Service Data Unit = payload - optionally carried in PDU for user

University of Oslo INF3190 – Data Communication Five Layer Reference, Internet Reference Model and a Comparison

§ OSI (Open Systems Interconnection) Reference Model

7 Application Layer

4 Transport Layer Technische

3 Network Layer Universität 2 Data Link Layer Darmstadt 1 Physical Layer

§ TCP/IP Reference Model Internet Architecture − ISO-OSI presentation, session and application layer merged − ISO-OSI data link layer and physical layer merged to form Network Interface

University of Oslo INF3190 – Data Communication TCP/IP Reference Model: Internet Architecture © Steinmetz, Ralf Technische

Universität Darmstadt

University of Oslo INF3190 – Data Communication Internet Protocol Stack

TELNET

FTP Application layer

Transport TCP UDP layer

IP Network + ICMP layer + ARP

Data link and WANs LLC & MAC LANs Physical layer ATM physical MANs

University of Oslo INF3190 – Data Communication Comparing the Reference Models: 5-Layer Model Used Herein

ISO-OSI: standardized too late § implementations usually worse than those of Internet protocols § in general, however, mainly good concepts © Steinmetz, Ralf TCP/IP (Internet) § TCP/IP already prevalent, SMTP too, now e. g. WWW

§ integrated into UNIX Technische Considered here:

Universität Layer Function

application related services incl. ISO-OSI L5 and L6 (as Darmstadt 5 Application far as necessary) connection end/source (application/process) to end/ 4 Transport destination (application/process) 3 Network connection end-system to end-system 2 Data Link reliable data transfer between adjacent stations 1 Physical sending bit 1 is also received as bit 1

University of Oslo INF3190 – Data Communication Example: Layers in Action

What happens in different layers when you use your browser to access a website?

§ Other people say it has only 4 Technische − Everything under IP is irrelevant (layer 1)

− Changes counting. Much more confusing than merging the upper layers! Universität Darmstadt In Internet, layers 3 and 4 are somewhat confused § Transport protocol TCP (or UDP) and network protocol IP § Sometimes hard to draw a clear line where TCP ends and IP begins § But: Basic functionality is clearly separated

So, what happens?

University of Oslo INF3190 – Data Communication Layers in Action

Actual communication (N)-protocol

TCP TCP Technische End-to-End End-to-End

IP IP IP IP Universität Darmstadt Ethernet Eth/FDDI FDDI/Eth Ethernet

Hop-by-Hop Hop-by-Hop PHY PHY PHY PHY

§ Request goes down on layers at browser § Physical layer handles actual sending of message to next (neighbor) node § Network protocol (IP) takes care of routing message to destination − Possibly several hops from one router to another − At each router, message goes up to IP-layer for processing § Transport and application layers converse end-to-end

University of Oslo INF3190 – Data Communication Functionality Recap

Layer 5,6,7 Layer 2 − Create HTTP request − Put data from layer 3 in frames − Invoke layer 4 (= TCP) − Send frames to immediate − Process reply (= web page) neighbor © Steinmetz, Ralf

Layer 4 Layer 1 Technische − Open reliable connection to web server − Actual transmission of a frame as a bitstream

− Make sure data arrives in the order it Universität was sent

− Do not saturate network Darmstadt • Congestion control Each layer performs some critical function Layer 3 − Route messages from client to web Layering not always “clean” server − Who handles congestion control or − Messages passed from router to router reliability? − Layer 3 provides end-to-end service through hop-by-hop actions

University of Oslo INF3190 – Data Communication History und Basics - Summary

History

Basic terminology and concepts − Protocol − Service − Layer

OSI and Internet layer models

TCP/IP layering

University of Oslo INF3190 – Data Communication Networking Protocol Map … (Source www.javvin.com)

University of Oslo INF3190 – Data Communication