Agententechnologien in der Telekommunikation Sommersemester 2009 Dr. Fikret Sivrikaya fikret.sivrikaya@dai-labor.de Lecture 1 29.04.2009 Agententechnologien in betrieblichen Anwendungen und der Telekommunikation
Telecommunications Assisted transmission of signals over a distance for the purpose of communication. Three basic elements: a transmitter that takes information and converts it to a signal; a transmission medium that carries the signal; and, a receiver that receives the signal and converts it back into usable information. Agententechnologien in der Telekommunikation - 2
Telecommunications 7 March 1876 A new U.S. Patent: "the method of, and apparatus for, transmitting vocal or other sounds telegraphically by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound." Alexander Graham Bell 1847-1922 Agententechnologien in der Telekommunikation - 3
The Telephone & Circuit Switching Agententechnologien in der Telekommunikation - 4
Packet Switching Messages are divided into packets before they are sent. Each packet is then transmitted individually and can follow different routes to its destination. Once all the packets forming a message arrive at the destination, they are recompiled into the original message. Agententechnologien in der Telekommunikation - 5
Packet Switching (vs. Circuit Switching) Great for bursty data Resource sharing No call setup Excessive congestion: packet delay and loss Protocols needed for reliable data transfer, congestion control How to provide circuit-like behavior? Bandwidth guarantees needed for audio/video applications. Agententechnologien in der Telekommunikation - 6
Routing The process of moving packets among routers from source to destination Lots of path selection algorithms local ISP Datagram network: Each packet carries a destination address Destination address used to look up next hop Route (next hop) may change at any time Agententechnologien in der Telekommunikation - 7 company network regional ISP Virtual circuit (path) network: Path determined at call setup time & remains fixed throughout call Packets carry a tag (virtual circuit ID) that determines the next hop Routers maintain per-call path state
The OSI Reference Model Agententechnologien in der Telekommunikation - 8
OSI Reference Model OSI : Open System Interconnection by ISO Basic Reference Model : ISO-7498 Purpose of OSI Model ~ is to open communication between different systems without requiring changes to the logic of the underlying hardware and software. Agententechnologien in der Telekommunikation - 9
OSI Model (cont d) Organization of the Layers Layer 1, 2, 3 (network support layers) ~ deal with the physical aspects of moving data from one device to another Layer 5, 6, 7 (user support layers) ~ allow interoperability among unrelated software systems Layer 4 (transport layer) ~ links the two subgroups and ensures that what the lower layers have transmitted is in a form that the upper layers can use Agententechnologien in der Telekommunikation - 10
The OSI Reference Model Agententechnologien in der Telekommunikation - 11
OSI Model (cont d) Agententechnologien in der Telekommunikation - 12
Physical Layer coordinates the functions required to transmit a bit stream over a physical medium. (deal with the mechanical and electrical specification of the primary connections: cable, connector) Agententechnologien in der Telekommunikation - 13
Physical Media Transmission is the propagation of an electro-magnetic wave (or optical pulse) through a physical medium What do you use? Unshielded Twisted Pair (UTP) Two insulated copper wires Media types Guided media signals propagate in solid media (copper, fiber) Unguided media signals propagate freely (radio, infrared) Category 3 UTP: Traditional phone wires, 10 Mbps Ethernet Category 5 UTP: 100Mbps Ethernet Gigabit possible Distance limited (100 m) Agententechnologien in der Telekommunikation - 14
Physical Media Coaxial cable Wire (signal carrier) within a wire (shield) Baseband: single channel on cable Broadband: multiple channel on cable Bi-directional transmission Largely used for cable TV Fiber optic cable Glass fiber carrying light pulses Higher-speed operation: 100-1,000 Mbps Ethernet High-speed point-to-point transmission (e.g., 10-100 Gbps) Low signal attenuation long distances Low error rate Agententechnologien in der Telekommunikation - 15
Physical Media Radio links Signal carried in electromagnetic spectrum No physical wire Bi-directional Physical environment affects propagation Reflection Obstruction by objects Interference Radio link types: Microwave Up to 45 Mbps channels LAN (e.g., 802.11) 2 Mbps, 11, 56 Mbps Wide-area (e.g., cellular) CDPD, 10 s Kbps Satellite Up to 50Mbps channel (or multiple smaller channels) 270 ms end-to-end delay uplink base station Agententechnologien in der Telekommunikation - 16
Physical Layer (cont d) Agententechnologien in der Telekommunikation - 17
Physical Layer (cont d) Concerned with Representation of bits / Encoding Synchronization of bits Line configuration: point-to-point, multipoint Topology: mesh, star, ring, bus Data transmission mode: simplex, half-duplex, fullduplex Data rate / bit rate bits per second Agententechnologien in der Telekommunikation - 18
Aside some units Speed / Capacity bits per second (bps) bytes per second (Bps) Kilo (K) = 2 10 = 1,024 Mega (M) = 2 20 = 1,048,576 Giga (G) = 2 30 = 1,073,741,824 Kilo (K) ~= 10 3 = 1,000 Mega (M) ~= 10 6 = 1,000,000 Giga (G) ~= 10 9 = 1,000,000,000 Time seconds (s) milli (m) = 10-3 = 0.001 micro (μ) = 10-6 nano (η) = 10-9 Remember: 8 bits = 1 byte Agententechnologien in der Telekommunikation - 19
Data Link Layer is responsible for delivering data units (group of bits) from one station to the next without errors. It accepts a data unit from the third layer and adds meaningful bits to the beginning (header) and end (trailer) that contain addresses and other control information: Frame Agententechnologien in der Telekommunikation - 20
Data Link Layer Data Link Layer Agententechnologien in der Telekommunikation - 21
Data Link Layer (cont d) Specific responsibilities Framing : dividing Packets into Frames Addressing Flow control: for avoiding overwhelming the receiver Error Control: retransmission Access control: for avoiding collision Agententechnologien in der Telekommunikation - 22
Network Layer is responsible for the source-to-destination delivery of a packet across multiple network links Specific responsibilities Source-to-destination delivery(packet) Logical addressing Routing Agententechnologien in der Telekommunikation - 23
Network Layer (cont d) Network Layer Agententechnologien in der Telekommunikation - 24
Addressing Addresses in TCP/IP Agententechnologien in der Telekommunikation - 25
Addressing (cont d) Agententechnologien in der Telekommunikation - 26
Physical address (example) Agententechnologien in der Telekommunikation - 27
IP Addresses (example) Agententechnologien in der Telekommunikation - 28
Transport Layer is responsible for source-to-destination (end-to-end) delivery of the entire message. the network layer oversees the end-to-end delivery of individual packets. Agententechnologien in der Telekommunikation - 29
Transport Layer (cont d) Specific responsibilities End-to-end message delivery Service-point (port) addressing delivery of a message to the appropriate application on a computer running multiple applications Segmentation and reassembly Connection control Flow Control Agententechnologien in der Telekommunikation - 30
Transport Layer (cont d) Transport Layer Agententechnologien in der Telekommunikation - 31
Session Layer is the network dialog controller. Specific responsibilities Session management Synchronization Dialog control: Deciding who sends and when Agententechnologien in der Telekommunikation - 32
Session Layer (cont d) Dialog unit Agententechnologien in der Telekommunikation - 33
Presentation Layer ensures interoperability among communicating devices. is also responsible for the encryption and decryption of data for security purpose and for the compression and expansion of data when necessary for transmission efficiency. Agententechnologien in der Telekommunikation - 34
Presentation Layer (cont d) Agententechnologien in der Telekommunikation - 35
Application Layer enables the user, whether human or software, to access the network. provides user interfaces and support for services. Email, remote file access and transfer, shared database management Agententechnologien in der Telekommunikation - 36
Application Layer (cont d) Application Layer Agententechnologien in der Telekommunikation - 37
Protocol Stack in the Internet Application layer Supporting network applications FTP, SMTP, HTTP Transport layer Host-host data transfer TCP, UDP Network layer Routing of packets from source to destination IP, routing protocols Link layer Data transfer between directly connected network elements Ethernet, 802.11, SONET, Physical layer The insertion of individual bits on the wire Different services specified at each layer interface Agententechnologien in der Telekommunikation - 38
Protocol Stack Data Flow data application transport network link link physical application transport network link link physical link physical application transport network link link physical network link link physical... data application transport network link link physical Agententechnologien in der Telekommunikation - 39
Protocol Stack Data Formats & Encapsulation Send Message Source Destination Receive Message M application application M Message H trans M transport transport H trans M Segment H net H trans M network network H net H trans M Datagram H link H net M link link H link H net H trans H trans M Frame physical physical Agententechnologien in der Telekommunikation - 40
Why switch packets instead of entire messages? 1.5 Mbps 7.5 Mb Message Message switching example Transmit a 7.5 Mb message over a network with 1.5 Mbps links What is the total elapsed time? Agententechnologien in der Telekommunikation - 41
Why switch packets instead of entire messages? 1.5 Mbps 7.5 Mb Message Packet-switching: store and forward behavior 1,500-bit packets, 1 packet forwarded every 1 ms 5,000 Packets 11 22 33 44 55... 4999 5000 11 22 33 44 11 22 33 11 22... 4998 4999 5000... 4997 4998 4999 5000 Agententechnologien in der Telekommunikation - 42... 4996 4997 4998 4999 5000 Time 0.000 0.001 0.002 0.003 0.004... 4.998 4.999 5.000 5.001 5.002
The Internet - nuts and bolts view Millions of connected computing devices: hosts, end-systems PCs, workstations, servers PDAs, phones, toasters running network applications Communication links Different media (fiber, copper wire, radio, satellite) Different transmission rates bits per second (bps) 10 3 (Kbps) to 10 6 (Mbps) to 10 9 (Gbps) Routers: forward data though the network local ISP company network router server regional ISP workstation mobile Agententechnologien in der Telekommunikation - 43
Internet History 1961-1972: Early packet-switching principles 1961: Kleinrock - queueing theory shows effectiveness of packetswitching 1964: Baran - packet-switching in military nets 1967: ARPAnet conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational 1972: ARPAnet demonstrated publicly NCP (Network Control Protocol) first host-host protocol first e-mail program ARPAnet has 15 nodes Agententechnologien in der Telekommunikation - 44
Internet History 1972-1980: Internetworking, new and proprietary nets 1970: ALOHAnet satellite network in Hawaii 1973: Metcalfe s PhD thesis proposes Ethernet 1974: Cerf and Kahn - architecture for interconnecting networks late70 s: proprietary architectures: DECnet, SNA, XNA late 70 s: switching fixed length packets (ATM precursor) Cerf and Kahn s internetworking principles: minimalism, autonomy - no internal changes required to interconnect networks best effort service model stateless routers decentralized control define today s Internet architecture 1979: ARPAnet has 200 nodes Agententechnologien in der Telekommunikation - 45
Internet History 1980-1990: new protocols, a proliferation of networks 1983: deployment of TCP/IP 1982: smtp e-mail protocol defined 1983: DNS defined for name-to-ipaddress translation new national networks: Csnet, BITnet, NSFnet, Minitel 100,000 hosts connected to confederation of networks 1985: FTP protocol defined 1988: TCP congestion control Agententechnologien in der Telekommunikation - 46
Internet History 1990 s: commercialization, the WWW Early 1990 s: ARPAnet decomissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) early 1990s: WWW hypertext [Bush 1945, Nelson 1960 s] HTML, http: Berners-Lee 1994: Mosaic, later Netscape late 1990 s: commercialization of the WWW Late 1990 s: est. 50 million computers on Internet est. 100 million+ users backbone links runnning at 1 Gbps Agententechnologien in der Telekommunikation - 47
Internet Growth Agententechnologien in der Telekommunikation - 48
From the Smokes to Connected Living Agententechnologien in der Telekommunikation - 49
The Telecommunications Market Evolution - 3 Waves New Services Adoption Multiple new Connectivity Services Evolution of the End-User World User-Centric Broadband Services Any device, any connectivity Broadband Single subscription & Authentication Services Consistent personalization Transparent synchronization Fixed BB (DSL) Many new services... Wireless BB (Wi-Fi) but a fragmented use Mobile BB (3G) Mobile Voice LAN Internet Agententechnologien in der Telekommunikation - 50
Worldwide Service Revenues Agententechnologien in der Telekommunikation - 51
Evolution of Global Broadband Subscribers Internet business is broadband today and mobile tomorrow 2.5G/3G penetration will reach 2 billion subscribers in 2009 with Internet-enabled devices Agententechnologien in der Telekommunikation - 52
Current Trends Wired, wireless, and mobile networks are converging to an all-ip heterogeneous network with immense complexity Underlying access network technologies like UMTS/GPRS, WLAN, and WiMAX are going to be integrated in one overall heterogeneous network These underlying access networks have a high variance of characteristics Convergence of PSTN and IP networks evolution towards the IP Multimedia Subsystem (IMS) Agententechnologien in der Telekommunikation - 53
Current Trends Diversity of multi-mode devices is growing rapidly Mobile network operators have to provide their customers with hassle-free access to communication services while taking into account the best possible resource usage of the deployed infrastructures Seamless mobility, intelligent network selection and optimal resource usage are key success factors for next generation heterogeneous telecommunication networks or so-called 4G systems Next generation heterogeneous networks enable ubiquitous access to IP-based services Agententechnologien in der Telekommunikation - 54
Evolution of Networks Agententechnologien in der Telekommunikation - 55
Some Announcements No Exercise (Übung) sessions. There will be a few take home assignments instead. Try to check your emails regularly for course announcements. Course website with the week s lecture notes will be up soon and announced via the email list Lectures will be moved to TEL 1414 starting with the next lecture (06.05.2009). Agententechnologien in der Telekommunikation - 56