Communication Networks

Transcription

1 Communication Networks Chapter 2 Fundamentals Communication Networks: 2. Fundamentals 30 Overview. Communication Network 2. Standardization 3. Communication Associations 4. Communication Architectures 5. Telecommunication Services and Protocols Communication Networks: 2. Fundamentals 3 Prof. Jochen Seitz

2 . Communication Network Example of a Telecommunication Network (Repetition) Backbone LAN Mobile Users URL Web Page Wireless LAN 3 LAN 2 Communication Networks: 2. Fundamentals 32. Communication Network Components Terminal Equipment (End Nodes) User interface to communication service Host for applications / server Source and/or sink of information flows Switching Equipment (Intermediate Nodes) Forwarding of information Routing decision Physical Media Links between terminal equipment and switching equipment switching equipment and terminal equipment Need for international standards Communication Networks: 2. Fundamentals 33 Prof. Jochen Seitz 2

3 . Communication Network Communication Service Tele Service Bearer Service Terminal Equipment Network Terminal Equipment User Network Interface (UNI) Application / User Interface Communication Networks: 2. Fundamentals 34. Communication Network Main Task Transmission of information from one terminal equipment to another Information transmission for different applications / use cases Information transmission on demand to an arbitrary terminal equipment Possibly, transformation of information required Speech Communication Transmission of Bits Network Communication Networks: 2. Fundamentals 35 Prof. Jochen Seitz 3

4 . Communication Network Fully Meshed Network Direct links between all end nodes of the network No switching equipment needed For communication simply select the correct link For n end nodes: ½ (n * (n-)) links required End Node Example: Network of 7 end nodes 2 links End Node 2 End Node 3 End Node 7 End Node 6 End Node 4 End Node 5 Communication Networks: 2. Fundamentals 36. Communication Network Partially Meshed Network At least one path through the network for all pairs of end nodes Switching equipment on the path forwards information accordingly Communication association between end devices / users Control of communication association required Resources in the network might be limited Network Communication Networks: 2. Fundamentals 37 Prof. Jochen Seitz 4

5 2. Standardization Standardization Bodies (I) International Standardization Organizations International Organization for Standardization (ISO) ISO Reference Model for Open Systems Interconnection (OSI) International Telecommunication Union (ITU) Telecommunication Standardization Sector, ITU-T Radiocommunication Sector, ITU-R Telecommunication Development Sector, ITU-D Institute of Electrical and Electronics Engineers (IEEE) Regional / National Standardization Organizations European Telecommunication Standards Institute (ETSI) American National Standards Institute (ANSI) Deutsches Institut für Normung (DIN) Communication Networks: 2. Fundamentals Standardization Standardization Bodies (II) Standardization of the Internet Internet Engineering Task Force large number of working groups and informal discussion groups (BoF Birds of a Feather) working groups organized into areas by subject matter area directors, together with the IETF Chair, form the Internet Engineering Steering Group (IESG) Special Interest Groups (SIGs) Bluetooth-SIG Ecma International (former European Computer Manufacturers Association) The Open Group (former OSF and X/Open) ZigBee Alliance Communication Networks: 2. Fundamentals 39 Prof. Jochen Seitz 5

6 2. Standardization Standardization by ISO Technical Committee (TC) SubCommittee (SC) Working Group (WG) ISO Working Groups Meetings each 6 to 9 months National bodies need to agree on concepts to be standardized Process Draft Proposal (DP) Draft International Standard (DIS) International Standard (IS) International Reconcilement Communication Networks: 2. Fundamentals Standardization Standardization in the Internet IETF responsible for standardization IESG controls standardization process Two results Request for Comments (RFC) For Your Information (FYI) For each draft standard, two interoperable and independent implementations must exist Proposal Proposed Standard Draft Standard Experimental Informal Full Standard Communication Networks: 2. Fundamentals 4 Prof. Jochen Seitz 6

7 2. Standardization Standards of the Internet Examples RFC Title Date RFC 768 User Datagram Protocol (UDP) August 980 RFC 79 Internet Protocol (IP) September 98 RFC 792 Internet Control Message Protocol (ICMP) September 98 RFC 793 Transmission Control Protocol (TCP) September 98 RFC 959 File Transfer Protcol October 985 RFC 945 Hypertext Transfer Protocol HTTP/.0 May 996 RFC 2460 Internet Protocol, Version 6 (IPv6) Specification December 998 RFC 822 see Default External BGP (EBGP) Route Propagation Behavior without Policies July 207 Communication Networks: 2. Fundamentals Communication Association Communication Association Temporary service provided by the network to transfer information from one UNI to some freely selected UNI Requirements: Addressing of the UNI / user Fulfillment of user / application requirements: throughput / goodput delay / delay variation (jitter) reliability (bit errors / packet loss / communication breakdown) security / authenticity / trustworthiness availability Communication Networks: 2. Fundamentals 43 Prof. Jochen Seitz 7

8 3. Communication Association Communicating Entities Man to Man one-way ( ) or dialogue (telephony, chat) text ( , chat) or speech (telephony) synchronous (telephony) or asynchronous ( , chat) Man to Machine client/server-based applications (www, online banking, ) peer-to-peer applications (gnutella, ) Machine to Machine distributed processes for smart home, industry 4.0, internet of things pervasive computing Communication Networks: 2. Fundamentals Communication Association Number of Communication Entities Number of Senders Number of Receivers Communication Association Example Unicast lecture (?) Dialogue telephony < n < all Multicast pay TV all Broadcast normal TV m > Concast tele-voting m > n > Multipeer video conference n > Anycast DHCP Communication Networks: 2. Fundamentals 45 Prof. Jochen Seitz 8

9 3. Communication Association Communication Links Serial Communication Parallel Communication bit per time interval, physical link 8 bits per time interval, 8 physical links t t Universal Serial Bus (USB) (serial transmission) Centronix (8 bis in parallel) Communication Networks: 2. Fundamentals Communication Association Direction of Communication Simplex Duplex Half Duplex - Radio / TV Broadcast - Fire Detector - Sensor Node - Telephony - Internet - Video Game - Citizen s Band - Walkie-Talkie Communication Networks: 2. Fundamentals 47 Prof. Jochen Seitz 9

10 3. Communication Association Order of Delivery According to sending sequence (First In, First Out (FIFO)) FIFO + Priorities Random delivery order Network Communication Networks: 2. Fundamentals Communication Association Quality of Service Many criteria Optimization of all criteria at the same time not possible Reliability: Transmission Errors Comm. Breakdown Service Reliability Security: Information Integrity Confidentiality Authenticity Non-Repudiability Suitability: Complexity Scalability Usability Costs: Investment Costs Operating Costs Performance: Signal Runtime Response Time Throughput Communication Networks: 2. Fundamentals 49 Prof. Jochen Seitz 0

11 4. Communication Architectures Principles Different components in a communication architecture with dedicated functionality: Interface to the physical medium Interface to the application / user Several communication entities to realize the required communication service to provide the required quality of service Structured in a layered architecture Interface to the Application / User Communication Entities Interface to the Physical Medium Communication Networks: 2. Fundamentals Communication Architectures The Layered Approach Refinement of Communication Entities layer arbitrary number of layers Each layer offers service to the upper layer utilizes service of the lower layer Advantages Concentration on a specific communication aspect in each layer Exchange of a layer without side effect on the other layers Communication Entities Layer X Layer X- Layer X-2 Layer X-n+ Layer X-n Communication Networks: 2. Fundamentals 5 Prof. Jochen Seitz

12 4. Communication Architectures Point-to-Point Physical Medium Sender Receiver Medium Access Point Medium Access Point Physical Transmission Channel Physical Medium Communication Networks: 2. Fundamentals Communication Architectures Shared Physical Medium Sender A Receiver A Receiver B Sender B Receiver A2 Physical Transmission Channel Physical Medium Communication Networks: 2. Fundamentals 53 Prof. Jochen Seitz 2

13 Vertical Communication Service Service Vertical Communication 4. Communication Architectures The Layers Application Horizontal Communication Interface Application Horizontal Communication Service Access Point (SAP) Layer i Abstract Medium for Layer i Physical Medium Communication Networks: 2. Fundamentals 54 Service and Protocol (I) Service User Service User 2 Layer i+ Layer i Service Provider Protocol Service Provider 2 System A System B Communication Networks: 2. Fundamentals 55 Prof. Jochen Seitz 3

14 Service and Protocol (II) Peer entities on one layer utilize the service of the layer below (if there is one) offer their service to the layer above (if there is one) only know the interface to the service beneath, but not its implementation communicate with each other according to specific rules receive input generate events Service offered by a layer is based on the cooperation of the communicating peer entities in the layer Communication Networks: 2. Fundamentals 56 Telephony Service (I) Telephony Service Pick Up Dial Tone Enter the Telephone Number Ringing Tone End of Ringing Tone Ringing Pick Up Hang Up Conversation Busy Tone Time Hang Up Communication Networks: 2. Fundamentals 57 Prof. Jochen Seitz 4

15 Telephony Service (II) Telephony Service Pick Up Dial Tone Enter the Telephone Number Ringing Tone End of Ringing Tone Ringing Pick Up Hang Up Conversation Busy Tone Time Hang Up Communication Networks: 2. Fundamentals 58 Telephony Service (I) Network Pick Up Dial Tone Enter the Telephone Number Ringing Tone End of Ringing Tone Response Ringing Pick Up Hang Up Disconnect Conversation Disconnect Busy Tone Hang Up Time Communication Networks: 2. Fundamentals 59 Prof. Jochen Seitz 5

16 Definition of Service Service = set of functions in one layer delivered by cooperating entities of the layer communicating according to a specific Protocol offered at the Services Access Point (SAP) of the layer defined by a set of Service Primitives and rules for their usage Service Primitive types Request Indication Response Confirmation Communication Networks: 2. Fundamentals 60 Illustration of a Telecommunication Service Communicating Entity I i+ Communicating Entity I i+ 2 Communicating Entity I i+ N- Communicating Entity I i+ N Service Interface of Layer i Exchange of Service Primitives Service Access Point (SAP) Abstract Medium M i Communication Networks: 2. Fundamentals 6 Prof. Jochen Seitz 6

17 Service of Layer i Set of functions offered by layer i at its Service Access Point vertical communication Delivered by peer entities in layer i communication with each other utilizing the service of layer i- horizontal communication Entities of layer i+ only know the service interface of layer i SAP of Layer i Entity of Layer i+ I i+ Entity of Layer i+ I i Protocol Layer i Entity 2 of Layer i+ I i+ 2 Entity 2 of Layer i+ I i 2 SAP of Layer i Communication Networks: 2. Fundamentals 62 Different Kinds of Services Confirmed Service Confirmed by service user Request Indication Response Confirmation Unconfirmed Service Initiated by the service user Request Indication Initiated by the service provider Indication Indication Communication Networks: 2. Fundamentals 63 Prof. Jochen Seitz 7

18 Connection Establishment Data Transmission Connection Release Connection-oriented Service Three phases: Connection Establishment Creation of context in terminal and switching equipment Connect Request Connect Confirmation Connect Indication Connect Response Data Transmission Based on established context Connection Release Deletion of context Deallocation of resources Data Request Data Request Disconnect Request Data Indication Data Indication Disconnect Indication Communication Networks: 2. Fundamentals 64 Connection End Points Connection End Point (CEP) = Identification of a connection within a SAP Entity of Layer i+ I i+ Entity 2 of Layer i+ I i+ 2 Entity 3 of Layer i+ I i+ 3 Entity 4 of Layer i+ I i+ 4 SAP of Layer i Connection End Point SAP of Layer i Entity of Layer i+ I i Protocol Layer i Entity 2 of Layer i+ I i 2 Communication Networks: 2. Fundamentals 65 Prof. Jochen Seitz 8

19 Datagram Service Connectionless service: shoot and pray no phases for connection setup/release required no creation of context in the network no guarantee for ordered delivery unconfirmed service Data. Request Data. Request 2 Data. Indication 2 Data. Indication Communication Networks: 2. Fundamentals 66 Protocol Service Interface of Layer i Entity of Layer i+ I i+ SAP of Layer i SAP of Layer i Abstract Medium M i Entity 2 of Layer i+ I i+ 2 Service Interface of Layer i- Entity of Layer i I i Protocol of Layer i Entity 2 of Layer i I i 2 Abstract Medium M i- Communication Networks: 2. Fundamentals 67 Prof. Jochen Seitz 9

20 The Idea Behind Protocols Rules for concurrently running cooperating entities Enhancement of the quality (QoS) and the funcitons of the layer below Distributed algorithm Important problem: Failures and faults in the lower layer must be taken into account Specification of protocols: In most cases only for two entities (Extended) Finite State Machine ((E)FSM) Message Sequence Chart (MSC) Communication Networks: 2. Fundamentals 68 Protocol Function Elementary atomic function to be included in different communication architectures in different protocols in different layers Cannot be further divided into parts Communication Networks: 2. Fundamentals 69 Prof. Jochen Seitz 20

21 Protocol Function Encapsulation Entity I i+ Entity I i+ 2 User Information User Information Abstract Medium M i Entity I i Protocol Entity I 2 i of Layer i User Information User Information Abstract Medium M i- Communication Networks: 2. Fundamentals 70 Protocol Function Segmentation and Reassembly Entity I i+ Entity I i+ 2 User Information User Information Abstract Medium M i Entity I i Protocol Entity I 2 i of Layer i Abstract Medium M i- Communication Networks: 2. Fundamentals 7 Prof. Jochen Seitz 2

22 Protocol Function Connection Management Connection establishment Connection maintenance resource allocation Connection release Handling of connection breakdowns Handling of orphaned connection Further tasks related to connection management Addressing Address mapping Communication Networks: 2. Fundamentals 72 Protocol Function Routing Selection of the optimal physical medium interface and of the next node Different criteria (monetary) cost data rate availability / reliability delay / number of intermediate hops to the destination current load Optimum might vary according to current network state Probably duplication of sent information flooding multicast Communication Networks: 2. Fundamentals 73 Prof. Jochen Seitz 22

23 Protocol Function Data Transfer Desired: ordered data transfer data is delivered in the same order as it was sent data might have to be reordered after receiving Desired: different priorities for different data normal versus expedited data transfer no overtaking of important data by normal data data might have to be reordered before forwarding Communication Networks: 2. Fundamentals 74 Protocol Function Load Control on terminal environments Load Control in the network Flow Control reactively Network Overload Control preventively Congestion Control Traffic Control Communication Networks: 2. Fundamentals 75 Prof. Jochen Seitz 23

24 Protocol Function Error Detection and Correction Error Detection Redundancy Parity Checksum Acknowledgements Stop & Wait Credit-based Timeout Numbering of packets Sequence control Error Correction Redundancy Forward Error Correction (FEC) Retransmission Selectively Go-back-N Reset Abort Communication Networks: 2. Fundamentals 76 Protocol Function Multiplex and Bundling Multiplex One entity serves several entities on the layer above Bundling On entity utilizes the services of several entities in the layer below Entity I i+ Entity I i+ 2 Entity I i+ Entity I i Layer i Entity I i Entity I i 2 Layer i Communication Networks: 2. Fundamentals 77 Prof. Jochen Seitz 24

25 Protocol Function Shared Medium Access Controlled Medium Access Alternatives centrally controlled without central control (e.g. token based) No collision Problem: Part of bandwidth might be unused Arbitrary Medium Access No central control Each nodes decides whether it may send Problem: Collisions possible Combination: Hybrid Medium Access Communication Networks: 2. Fundamentals 78 Protocol Function Synchronization Different contexts: Signal level clock, sensing, Medium Access time slots, start of sending after last transmission Transmission start and end (bits, octets, frames, packets, ) Connection establishment, release Data transfer progress of data transfer in case of restart Communication Networks: 2. Fundamentals 79 Prof. Jochen Seitz 25

26 The ISO/OSI Basic Reference Model Standardization of protocols and services to implement open systems (OSI = Open Systems Interconnection) Base for interoperability of components of different companies Nota bene: ISO/OSI Basic Reference Model is mainly a framework to explain and classify communication architectures Implementation especially in public networks, but not relevant any more Important standard: ISO/IEC IS 7498: Information Processing Systems Open Systems Interconnection Basic Reference Model, International Standard, October 5, 994 Adopted by CCITT resp. ITU-T in recommendation X.200 Communication Networks: 2. Fundamentals 80 Principles OSI End System Terminal system that adheres to the ISO/OSI standard (N)-Layer All entities/instances in the layer N (N)-Entity Implementation of a process providing the service of the layer N Might be instantiated several times in one open system in one layer Peer Entities Cooperating entities in one layer to deliver a certain service End System A End System B (N)-Entity (N)-Layer (N)-Entity Communication Networks: 2. Fundamentals 8 Prof. Jochen Seitz 26

27 Connection and Association (N)-Connection Relation between two or more (N+)-Entities Connection established between (N)-CEPs in the (N)-SAPs (N)-Entities offer connection-oriented service (N)-Association Cooperative relation between two or more (N)-Entities Can be based on (N)-Connection (N+)-Association Entity I N+ Entity I 2 N+ connectionless service of (N)-Layer (N)-Connection Entity I N Entity I N 2 Communication Networks: 2. Fundamentals 82 Generic Communication over SAP (N+)-Layer (N)-Layer (N)-IDU SAP (N)-PCI (N)-SDU (N)-ICI (N)-PDU (N )-PCI (N)-SDU (N-)-ICI (N-)-Layer (N-)-IDU SAP (N-)-SDU (N-)-ICI Communication Networks: 2. Fundamentals 83 Prof. Jochen Seitz 27

28 Data and Information Units (N)-IDU Interface Data Unit exchanged between (N+)- and (N)-Entities via an (N)-SAP composed of (N)-ICI and (N)-SDU (N)-ICI Interface Control Information exchanged between (N+)- and (N)-Layer used to control service delivery contains e.g. addresses (N)-SDU Service Data Unit consists of information to be transparently transferred between (N)-SAPs (N)-PCI Protocol Control Information exchanged between Peer Entities of the (N)-Layer used to control protocol functions contains e.g. sequence numbers, check sums etc. (N)-PDU Protocol Data Unit exchanged between (N)-Entities on utilizing the service of the (N-)-Layer composed of (N)-PCI and (N)-SDU corresponds to the (N-)-SDU Communication Networks: 2. Fundamentals 84 Exchange of Data Units (N+)-Layer (N)-Service SAP (N)-IDU (N)-IDU SAP Entity of Layer N I N (N)-PDU Protocol of Layer N Entity 2 of Layer N I N 2 (N-)-Service SAP (N-)-IDU (N-)-IDU SAP (N-)-Layer Communication Networks: 2. Fundamentals 85 Prof. Jochen Seitz 28

29 The OSI Layers Applicationoriented Layers Transportoriented Layers Layer 7 (A Layer) Layer 6 (P-Layer) Layer 5 (S-Layer) Layer 4 (T-Layer) Layer 3 (N-Layer) Layer 2 (DL-Layer) Layer (Ph-Layer) Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Communication Networks: 2. Fundamentals 86 Service Primitives (N)-Service.Primitve Layer Service Primitive Ph -Connect.Req (Request) DL -Data.Ind (Indication) N -Disconnect.Rsp (Response) T -UserAbort.Cnf (Confirmation) - Note: Service Primitives in Application Layer named according to the related Application Service Element (ASE) Communication Networks: 2. Fundamentals 87 Prof. Jochen Seitz 29

30 Connection Establishment Data Transfer Connection Release Communication Example DL-Connect.Req DL-Connect.Cnf DL-Data.Req DL-Data.Req DL-Disconnect.Req DL-Connect.Ind DL-Connect.Rsp DL-Data.Ind DL-Data.Ind DL-Disconnect.Ind Communication Networks: 2. Fundamentals 88 Transport-oriented Layers Do not consider the contents of the transported information Only deal with bit sequences Apply the same procedures to all transported information Consist of the following layers Transport Layer Network Layer Data Link Layer Physical Layer Transportoriented Layers Layer 4 (T-Layer) Layer 3 (N-Layer) Layer 2 (DL-Layer) Layer (Ph-Layer) Communication Networks: 2. Fundamentals 89 Prof. Jochen Seitz 30

31 Physical Layer Transfers (unstructured) bit sequences in form of physical signals Implements channel coding Defines the physical interfaces (connectors, jacks, sockets, ) Might not be able to deal with transmission errors Bits Physical Layer Entity Bits Physical Layer Entity 2 Physical Signals Eventually Disturbed Physical Signals Physical Transmission Channel Physical Medium Communication Networks: 2. Fundamentals 90 Transmission over Physical Layer Taken from F. Halsall (2000) Transmitted Data +V Transmitted Signal -V Typical Received Signal Sampling Instants Received Data Bit Error Communication Networks: 2. Fundamentals 9 Prof. Jochen Seitz 3

32 Data Link Layer Responsible for detection and correction of bit errors For detection: adding redundancy (parity bits, cyclic redundancy check, ) For correction: several mechanisms Forward Error Correction (FEC) Acknowledgements Sequence Numbers Timeout & Retransmission Flow Control Reset Medium Access Control (MAC) for shared medium Addressing receiver (especially in case of a shared medium) e.g. MAC address Control information and user information frame structure: Header User Data Trailer Communication Networks: 2. Fundamentals 92 Network Layer Links several point-to-point associations (of the Data Link Layer) to an and system association Network Layer Entity Data Link Layer Entity End System A Data Link Association Network Association Network Layer Entity 2 DL Layer Entity 2. DL Layer Entity 2.2 Intermediate System Data Link Association Network Layer Entity 3 Data Link Layer Entity 3 End System A Is responsible for finding the optimal path through the network (routing) and forwarding the information on this path Should control network load Works connection-oriented or connectionless Is based on world-wide unique addresses (e.g. telephone number or IP address) Communication Networks: 2. Fundamentals 93 Prof. Jochen Seitz 32

33 Transport Layer Data transfer between different pairs of applications on the end systems Abstracts from the underlying networking technologies Adds Quality of Service (QoS) to the service provided by the Network Layer as required by the applications Works connection-oriented or connectionless Transport Layer Entity Network Layer Entity Data Link Layer Entity Data Link Association Network Layer Entity 2 DL Layer Entity 2. DL Layer Entity 2.2 Data Link Association Transport Layer Entity 3 Network Layer Entity 3 Data Link Layer Entity 3 End System A Intermediate System End System A Communication Networks: 2. Fundamentals 94 Application-Oriented Layers Depend on the application and its semantics Are aware of the kind of information to be transferred (not just bits) Must be directly controlled by the application Consist of the following layers: Application Layer Presentation Layer Session Layer Applicationoriented Layers Layer 7 (A Layer) Layer 6 (P-Layer) Layer 5 (S-Layer) Communication Networks: 2. Fundamentals 95 Prof. Jochen Seitz 33

34 Session Layer Allows organizing and synchronizing the dialogue of two applications Is built on sessions which abstract from network connectivity Session Transport Layer Connections Controls the exchange of information (which application entity might send information at a specific point in time) Provides synchronization points for restarting whenever the connectivity is interrupted during transmission t Communication Networks: 2. Fundamentals 96 Presentation Layer Provides coding of information so that the receiver understands the syntax and the semantics of the transmitted bits Is based on abstract data syntax forms which the application can choose from Transfers information according to the associated transfer syntax Overcomes the ambiguity and heterogeneity of different syntaxes in various operating systems or processor architectures Presentation Layer Entity End System A Presentation Layer Entity 2 End System B Communication Networks: 2. Fundamentals 97 Prof. Jochen Seitz 34

35 Application Layer Provides a set of different services suitable for different applications File Transfer, Access and Management (FTAM) Message Handling System (MHS, ISO/OSI ) Remote Operations (ROSE) Association Control (ACSE) Consists of several Application Service Elements (ASEs) forming an application layer entity Common Application Service Element (CASE) Specific Application Service Element (SASE) Single Association Control Function (SACF) to control the cooperation of ASEs Multiple Association Control Function (MACF) to control several SACFs Communication Networks: 2. Fundamentals 98 The Seven Layers End System A Layer 7 Entity Layer 6 Entity Layer 5 Entity Layer 4 Entity Layer 3 Entity Network Layer 3 Entity End System B Layer 7 Entity Layer 6 Entity Layer 5 Entity Layer 4 Entity Layer 3 Entity Layer 2 Entity Layer 2 Entity Layer 2 Entity Layer 2 Entity Layer Entity Layer Entity Layer Entity Layer Entity Communication Networks: 2. Fundamentals 99 Prof. Jochen Seitz 35

36 Send Encapsulation AH Application Header NH Network Header PH Presentation Header DLH Data Link Header SH Session Header DLT Data Link Trailer TH Transport Header Data Application Layer Presentation Layer PH AH Data Data Receive Application Layer Presentation Layer Session Layer SH Data Session Layer Transport Layer TH Data Transport Layer Network Layer NH Data Network Layer Data Link Layer DLH Data DLT Data Link Layer Physical Layer Bits Physical Layer Communication Networks: 2. Fundamentals 00 Comparison with the Internet Protocol Suite Application Layer Transport Layer Internet Layer Network-to-Host Layer Application specific functions concentrated in one layer only (subsumes Session, Presentation and Application Layer) Data transfer end-to-end between two applications on two computers Routing and forwarding in the Internet layer of the Internet Protocol Network to host interface implemented on the network card in the device (subsumes Data Link and Physical Layer) Communication Networks: 2. Fundamentals 0 Prof. Jochen Seitz 36

37 Theoretic Model: Three Layer Architecture Application-oriented Layer Transport-oriented Layer Network Access Layer Corresponds to OSI layers 5 7 Corresponds to OSI layers 2b 4 Corresponds to OSI layers 2a Less processing overhead Prevention of redundant functions High performance networking But: not compatible to current architectures / best practice Communication Networks: 2. Fundamentals 02 References Halsall, Fred (2005): Computer Networking and the Internet. 5th edition. Harlow, England: Addison-Wesley. Halsall, Fred (2000): Data Communications, Computer Networks and Open Systems. 4th edition, reprint. Harlow: Addison-Wesley. Kurose, James F.; Ross, Keith W. (207): Computer Networking. A Top-Down Approach. 7th edition. Hoboken, New Jersey: Pearson. Nutt, Gary J. (992): Open Systems. Englewood Cliffs, N.J.: Prentice-Hall (Prentice- Hall Series in Innovative Technology). Stallings, William (204): Data and Computer Communications. 0th edition. Upper Saddle River, N.J.: Pearson. Tanenbaum, Andrew S.; Wetherall, David J. (20): Computer Networks. 5th edition. Boston: Pearson Prentice Hall. Communication Networks: 2. Fundamentals 03 Prof. Jochen Seitz 37