Μάθηµα Εισαγωγή στις Τηλεπικοινωνίες

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1 Μάθηµα Εισαγωγή στις Τηλεπικοινωνίες Ενότητα 7η Τηλεπικοινωνιακά ίκτυα και ίκτυα εδοµένων IP/TCP Βασικές έννοιες - Μάθηµα 8ο Καθ. Θωµάς Σφηκόπουλος thomas@di.uoa.gr Κατσιάνης ηµήτρης, Επιστ. Συνεργάτης dkats@di.uoa.gr Τσίπουρας Άρης, Επιστ. Συνεργάτης aris@di.uoa.gr ΕΘΝΙΚΟ & ΚΑΠΟ ΙΣΤΡΙΑΚΟ ΠΑΝΕΠΙΣΤΗΜΙΟ ΑΘΗΝΩΝ Τοµέας Επικοινωνιών και Επεξεργασίας Σήµατος Τµήµα Πληροφορικής & Τηλεπικοινωνιών

2 ίκτυα Επικοινωνιών και το Internet 2

3 Advanced Research Projects Agency ARPANET 3 (a) Structure of the telephone system. (b) Baran s proposed distributed switching system.

4 ARPANET (2) The original ARPANET design. Interface Message Processors 4

5 ARPANET (3) 5 Growth of the ARPANET (a) December (b) July (c) March (d) April (e) September 1972.

6 National Science Foundation NSFNET The NSFNET backbone in

7 Αρχιτεκτονική του Internet 7

8 Χρήση του Internet Traditional applications ( ) News Remote login File transfer 8

9 The IP Protocol The IPv4 (Internet Protocol) header. 9

10 The IP Protocol (2) 5-54 Some of the IP options. 10

11 IP Addresses IP address formats. ICANN (Internet Corporation for Assigned Names and Numbers) 11

12 IP Addresses (2) 12 Special IP addresses.

13 Subnets A campus network consisting of LANs for various departments. 13

14 Subnets (2) A class B network subnetted into 64 subnets(-2) 14

15 CIDR Classless InterDomain Routing 5-59 A set of IP address assignments. 15

16 NAT Network Address Translation Placement and operation of a NAT box /8 (16,777,216 hosts) /12 (1,048,576 hosts) /16 (65,536 hosts)

17 Mobile IP Goals?! 1. Each mobile host must be able to use its home IP address anywhere. 2. Software changes to the fixed hosts were not permitted. 3. Changes to the router software and tables were not permitted. 4. Most packets for mobile hosts should not make detours on the way. 5. No overhead should be incurred when a mobile host is at home 17

18 IPv6 (IPv4) Today's IPv4. What is IPv6? Why IPv6? Representation of IPv6 addresses Generating IPv6 addresses Multiple addresses per device Special Characteristics of IPv6 with respect to autoconfiguration, headers, security, etc. 18

19 IP v4 A unique number is necessary to identify every computer in a network. The Internet uses IPv4 : a 32 bit identifier, up to billion ( ) v4 addresses can exist. NAT (Network Addressing Topology) or IP masquerading is rampant. There are just not enough addresses left due to unequal distribution (Class A, B, etc.) 19

20 Why IP v Support billions of hosts, even with inefficient address space allocation. 2. Reduce the size of the routing tables. 3. Simplify the protocol, to allow routers to process packets faster. 4. Provide better security (authentication and privacy) than current IP. 5. Pay more attention to type of service, particularly for realtime data. 6. Aid multicasting by allowing scopes (περιοχές πεδίων δράσης) to be specified. 7. Make it possible for a host to roam without changing its address. 8. Allow the protocol to evolve in the future. 9. Permit the old and new protocols to coexist for years.

21 The Main IPv6 Header 21 SIPP (Simple Internet Protocol Plus) IPv6

22 Headers Sizes IPv4 : 20 bytes long, 8 for To and From addresses. IPv6 : 40 bytes long, 32 for To and From addresses. IPv6 Header Specifications Contains Version, Priority, Flow Label, Payload Length, and Hop Limit. The Next Header Field : indicates if a next 8 bit header exists. 22

23 Extension Headers IPv6 extension headers.

24 IPv6 address Hexadecimal format IPv6 Address: Hexadecimal Equivalent: (Follows the method: 0000= 0 ;1101= D ;1111= F ; etc) D514:0051:5570:0199:FFE2:0000:0000:0003 This address is condensed to D514:51:5570:199:FFE2::3 24 In a browser: Address:

25 Characteristics Payload increase Ipv4 restricts payload length, while IPv6 provides for single packets to have unlimited lengths. High bandwidth networks can thus improve data transfer speeds immensely. QoS (Quality of Service) Packet efficiency is improved by using Flow Labels to indicate direction of flow. IP-Sec! Security at the IP layer instead of for the contents. 25

26 The Internet Transport Protocols UDP User Datagram Protocol Πρωτόκολλο εδοµενογραφηµάτων! Χρήστη Χωρίς Σύνδεση TCP- Transmission Control Protocol Πρωτόκολλο Ελέγχου Μεταφοράς Με σύνδεση 26

27 UDP Header 27

28 TCP Transmission Control Protocol Πρωτόκολλο Ελέγχου Μεταφοράς 28

29 The TCP Service Model Port Protocol Use 21 FTP File transfer 23 Telnet Remote login 25 SMTP 69 TFTP Trivial File Transfer Protocol 79 Finger Lookup info about a user 80 HTTP World Wide Web 110 POP-3 Remote access 119 NNTP USENET news Some assigned ports. 29

30 The TCP Service Model (2) (a) Four 512-byte segments sent as separate IP datagrams. (b) The 2048 bytes of data delivered to the application in a single READ CALL. 30

31 The TCP Segment Header 31 TCP Header.

32 The TCP Segment Header (2) The pseudoheader included in the TCP checksum. 32

33 TCP Connection Establishment (a) TCP connection establishment in the normal case. (b) Call collision.

34 TCP Connection Management Modeling 34 The states used in the TCP connection management finite state machine.

35 TCP Congestion Control 35 (a) A fast network feeding a low capacity receiver. (b) A slow network feeding a high-capacity receiver.

36 Wireless TCP and UDP Έµµεσο TCP (indirect TCP) 36

37 Performance Issues Performance Problems in Computer Networks Network Performance Measurement System Design for Better Performance Fast TPDU Processing Protocols for Gigabit Networks 37

38 Performance Problems in Computer Networks 38 The state of transmitting one megabit from San Diego to Boston (a) At t = 0, (b) After 500 µsec, (c) After 20 msec, (d) after 40 msec.

39 Network Performance Measurement The basic loop for improving network performance. Measure relevant network parameters, performance. Try to understand what is going on. Change one parameter. 39

40 Protocols for Gigabit Networks Time to transfer and acknowledge a 1-megabit file over a 4000-km line. 40

41 ATM Virtual Circuits ATM - Asynchronous Transfer Mode A virtual circuit. 41

42 ATM Virtual Circuits (2) ATM cell. 42

43 The ATM Reference Model 43

44 The ATM Reference Model (2) 44 ATM layers and sublayers and their functions.

45 Resources Andrew S. Tanenbaum, Computer Networks, Fourth Edition, Prentice Hall, 2003 ISBN : William Stallings, Business Data Communications, Fifth Edition, ISBN (feb 2004), fourth Edition 2001 ISBN: , Publisher: Prentice Hall A. Leon-Garcia and I. Widjaja, Communication Networks: Fundamental Concepts and Key Architectures, January 2000 ISBN: X 45