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Basic Networking Principles Communication Netwoks Communication Netwoks Technology Technology and and Introduction Economics Economics Costas Courcoubetis Changes in telecommunications Network convergence � In the new public network: from narrowband to a broadband � Emerging technologies are affecting telecom industries world � Computers are now capable of hearing, speaking, seeing � Portable computing: mobility and wireless � data used to run over a network that was largely built for communication voice � Optical technologies: no bandwidth limit � from single media to multimedia � Intelligence across a wider range of devices: pervasive computing , or ubiquitous computing � from a fixed environment to a mobile environment � From human-to-human communications to an era of � Convergence: the PSTN, the Internet, wireless, broadcast machine-to-machine communications networks, cable TV, are all coming together to service the � New traffic patterns, different requirements for quality same sets of traffic and to deliver the same types of features of service and services � New types of applications: digital entertainment, � Convergence occurs in network services, devices, applications, streaming, e-commerce, m-commerce industries, humans and machines Basic concepts - 3 Basic concepts - 4 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis

What are (communication) networks ? What are communication networks ? Communications Network Circuit (logical) services � Hardware and software ΑΤΜ � Allow exchange of information and access to access Frame Relay SDH services ISDN � Factors that contribute to the creation of Datagram services Networks Ethernet Data transfer service, Internet (IP) • Economies of scale in the production process between high level programs • Economies of Scale in the demand (network externalities) Basic concepts - 5 Basic concepts - 6 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis Network architectures ODN model � Natural View: Composed of: • Computers, Connectors, Routers, Switches, Video conferences, Applications … email, WWW � Logical View: Composed of services Directories, security, Middleware compression, file trans., ... • Simple services -> Composite services ATM, IP, CDPD, • Layering of services (layered architecture) Bearer Frame Relay, X.25 � End-to-end Services SONET, DBS, CATV, Bit ways • Interest the end user wireless links • Service level agreements (SLAs) Basic concepts - 7 Basic concepts - 8 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis

Why networks exist Multiplexing 1 Fixed TDM 2 Point to point connectors Distributed connectors 1 Statistical TDM Statistical multiplexing Convergence of technologies • Economies of scale • Economies of scope 2 Basic concepts - 9 Basic concepts - 10 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis Networking economies Historical example � The telephone network • Alexander Graham Bell 1876 e 100% • 1887: 150000 tel. USA, 26000 UK, 9000 Fr, 7000 r a h Value for the user S Rus. 1990: 181000000 tel. USA t e k 50% � The role of interconnection r a M • 1903s: non-Bell = 50-60%, long distance = 3% 0 • Demand for long distance interconnections after 1900 Number of conventional users Time − Bell System: Smart interconnection strategy, evolved network for long-distance calls. Economies of scale in production and demand: Positive feedback Basic concepts - 11 Basic concepts - 12 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis

Historical example (cont.) Basic Networking Principles � Inter-connectability: Competitive advantage � 1984: End of the ΑΤ &T monopoly � Conclusion: When you control important interfaces or bottlenecks, you must offer Basic netw orking concepts: them in a controlled way, determining LANs, IP, TCP the interconnection rules. � Regulating Policy: Raise of competition Basic concepts - 13 Basic concepts and directions in telecommunications C. Courcoubetis Local Area Networks (LANs) Ethernet � LANs: The simplest networks Ethernet Hub • Retransmits all of the packets � Every computer has: • If more than two simultaneous x,y| data data transmissions, then we have conflict • A name y x z • A network address (Internet) • A local area network address (MAC) 105 37 124 Switched Ethernet Hub Uses a switching table 37 x,y| data Α C data 35 B y -> A LAN y x costas z z -> B 345 alice x -> C 105 37 128 124 Basic concepts - 15 Basic concepts - 16 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis

Address detection Switched LANs and VLANs � Ethernet switches: send packets to destination � To send a packet : Network Address only • How do we find the local address? ARP, RARP � VLANs: assign any terminal to a particular LAN Ethernet Hub x,y| data data y x z ARP table: 105 37 124 124: y 105: z Basic concepts - 17 Basic concepts - 18 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis Internet: the IP protocol LAN interconnection: using routing w2 w3,d S,D data s,r1 S,D data s,r1 S,D data w1 r3,d S,D data Ethernet E2 Ε 2 H H w3 S S w4 Router W h h s s f f Ε 3 Ε 3 E2 Ε 1 Ε 1 d d k k r2 r2 a a r1 r1 D D r3 r3 Ethernet E3 Ethernet E3 Ethernet E1 Ethernet E1 Router R Router R r2, w4 S,D data Routing table: ARP table for Ε 3: Routing table: D, H: E3, ... D: d, H: h, ... D, H: W:E2,… ………. S: E1, ... S: E1, ... Basic concepts - 19 Basic concepts - 20 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis

Internet: routing Routing AS2 � Routing: Fundamental Procedure • destination-> Next router on adjacent LAN � Methodologies: • By hand (Centralized decision for everyone) • Using a public map • Hierarchical routing � Basic Problem: complexity AS1 Autonomous system (AS) Basic concepts - 21 Basic concepts - 22 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis Information transmission Connecting applications � Basic protocol IP � UDP, Τ CP over IP: flow control of packets • connects computers, not applications between program addresses � Problem: � Result: «Micro-flows» • congestion, breakdowns, … • We need to separate them TCP/UDP header • connections at the applications level + Application ids Α 2 � Solution: TCP and UDP Protocol Β 2 Α 1 Β 1 • Detects erroneous packets (UDP+TCP) Ν 1, Ν 2 B1,B2 data Ν 1 Ν 2 • controls flow (TCP) Ν 1, Ν 2 A1,A2 data • Retransmits lost packets (TCP) TCP Flow IP Flow • Places packets in correct order (TCP) Basic concepts - 23 Basic concepts - 24 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis

Connecting applications (2) Simple Transmission : UDP π source program : port number destination • Transmits with maximum rate i A S1 S2 N , : network addr. M • Packets can be lost! • Useful when: Mailboxes for the use - The application dictates the data of applications, types: π 2 π 1 π 2 π 1 π 2 π 1 π 2 π 1 transmission rate TCP, UDP - The connection lasts for a short TCP UDP TCP UDP Flow Control time, small number of packets. UDP modules Μ Ν IP does not guarantee correct transmission! IP UDP IP “Central mailbox” for IP packets = data N, Μ π 1, π 2 data : TCP Algorithm: N, Μ π 1, π 2 data checksum • Always send : UDP port type Basic concepts - 25 Basic concepts - 26 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis Flow Control: TCP Connecting applications (3) Algorithm: • Send only when you receive acknowledgment A S2 • do not send if k > W data • always chose the correct W π 1 π 2 π 3 π 1 π 2 π 3 TCP modules k IP Ν Μ 0 1 2 3 4 χρόνος = data IP: Not designed to offer a = acknowledgements RTT Standard quality of service k = number of packets that are not acknowledged W R = RTT Basic concepts - 27 Basic concepts - 28 Basic concepts and directions in telecommunications C. Courcoubetis Basic concepts and directions in telecommunications C. Courcoubetis