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Basic Infrastructure for Electronic Business on the Internet

Basic Infrastructure for Electronic Business on the Internet. Authors: Miroslava Mitrovic (mirka@galeb.etf.bg.ac.yu) Veljko Milutinovic (vm@galeb.etf.bg.ac.yu). Network. A network is a group of computers and peripherals connected together by some medium The connection can be

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Basic Infrastructure for Electronic Business on the Internet

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  1. Basic Infrastructure for Electronic Business on the Internet Authors: Miroslava Mitrovic (mirka@galeb.etf.bg.ac.yu) Veljko Milutinovic (vm@galeb.etf.bg.ac.yu)

  2. Network • A network is a group of computers and peripherals connected together by some medium • The connection can be direct (through a cable) or indirect (through a modem) • The different devices on the network communicate with each other through a predefined set of rules (protocol)

  3. Network Hardware • Physically connects computers in the network together • Main hardware components: Nodes Communication equipment Additional components Topology

  4. Nodes • Network node (computer, printers, routers) • Computers in network can be used as work stations or servers or both • PC computers need NIC (Network Interface Card) to be able to be part of LAN (Local Area Network) • Different standards, different network cards! (Ethernet, Token Ring, ARC net)

  5. Communication equipment • Cables : (coaxial cables, fiber-optic cables, twisted pairs) • Wiring centers : (HUB , concentrator, MAU (Multi station Access Units)) • Intranetwork links : (connectors, transceivers, repeaters) • Internetwork links : (bridges, gateways, routers, switches) • Wireless components

  6. Additional Components • Peripherals : (printers, fax machines, modems, cd readers) • Safety devices : UPS (Uninterruptible Power Supply), SPS (Standby Power Supply) • Network tools

  7. Topology • Defines rules for connecting network nodes • Logical topology differs from physical topology! • Logical topology defines rules for transmitting information's (bus, ring, star) • Physical topology defines rules for electrical connection components in network

  8. Topology

  9. Topology

  10. Network Software • Enables using hardware for communication and exchanging information • Protocols (set of rules) give formulas for passing messages, specifying the details of message formats, and for describing how to handle error conditions

  11. Internetting • Connecting many disparate physical networks and make them function as a coordinate unit • Internet technology hides the details of network hardware and permits computers to communicate independent of their physical network connection

  12. Internetting

  13. Internet • Internet is network of all networks • Interconnected computer networks that communicate, usually via TCP/IP • Internet and internet • Set of application programs that use the network to carry out useful communication tasks (user’s point of view) • No one owns the Internet!

  14. Internet architecture • How are networks interconnected to form a internet work? • Computers that interconnect two networks and pass packets from one to the other are called internet gateways or internet routers

  15. Internet architecture

  16. Internet architecture

  17. Internet architecture • Gateways provide all interconnections among physical networks • Usually minicomputers • Gateways route packets based on destination network, not on destination host!

  18. Internet architecture

  19. Internet architecture

  20. Open Systems • Architecture is not secret • The definition applies equally well to software and hardware • UNIX-classic example for an open software platform • Open system networking: network based on well-known and understood protocol • Three most popular services: File Transfer Electronic mail Remote login

  21. The ISO OSI-RMInternational Organization for StandardizationOpen System Interconnection Reference Model • ISO has developed an architecture that defines seven layers of network protocol

  22. Grouping of OSI Layers

  23. Upper Layers Application/Presentation/Session • Applications oriented • Presents the interface to the user • Don’t care how data gets to the application!

  24. Middle LayerTransport • Separate application oriented upper layers from network oriented lower layers

  25. Lower LayersNetwork/Data Link/Physical • Oriented toward data transmission • Packages, routes, verifies and transmits datagrams • Type of data for application doesn't matter • Has no application dependencies !

  26. Communication in OSI-RM

  27. Application Layer • Highest layer in the OSI reference model • Concerned with the user’s view of the network • Handles network transparency, resource allocation and problem partitioning • Sends data and program tasks to the presentation layer, which is responsible for coding data from application layer in the appropriate form

  28. Presentation Layer • The second highest layer in the OSI reference model • Converts network data to application format • Performs function as text compression , code or format conversion to try to smooth out differences between hosts • Serves application layer, uses session layer

  29. Session Layer • The third highest layer in the OSI reference model • Synchronized data exchange between upper and lower layers • Manages the current connection, or session, between two computers • Handles security and creation of the session • Establishing connection • Closes connection • Uses the transport layer to establish a connection between processes on different hosts • Used by the presentation layer

  30. Transport Layer • The middle layer in the OSI reference model • Uses the network layer to provide a virtual, error-free, point-to-point connection so that host A can send messages to host B and they will arrive uncorrupted and in the correct order • Hides details necessary to actually make a connection between two computers • Establishes and dissolves connections between hosts • Used by the session layer

  31. Network Layer • The third lowest layer in the OSI reference model • Determines addresses • Responsible for routing packets across the network • Establishing logical link between two nodes • Used by the transport layer, uses the data link layer

  32. Data Link Layer • The second lowest layer in the OSI reference model • Splits data into frames for sending on the physical layer • Receives acknowledgment frames • Performs error checking and retransmission • Provides an error free virtual channel to the network layer • Split into an upper sublayer Logical Link Control (LLC) and lower sublayer Media Access Control (MAC)

  33. Physical Layer • The lowest layer in OSI model • Transmits data • How bits are passed over the network medium, what control signals are used, and the mechanical properties of the network itself (cable size, connector, and so on) • Only layer in which actual communication occur • Used by the data link layer

  34. Data Transfer over the Internet

  35. OSI vs. TCP/IP

  36. TCP UDP IP ICMP RIP OSPF ARP DNS RARP BOOTP FTP Telnet EGP GGP IGP BGP NFS NIS RPC SMTP SNMP The TCP/IP protocol family

  37. Transport • Transmission Control Protocol (TCP): connection-based services • User Datagram Protocol (UDP): connectionless services

  38. Routing • Internet Protocol (IP): handles transmission of information • Internet Control Message Protocol (ICMP): handles status messages for IP • Routing Information Protocol (RIP): determines routing • Open Shortest Path First (OSPF): alternate protocol for determining routing

  39. Network Addresses • Address Resolution Protocol (ARP): determines addresses • Domain Name System (DNS): determines addresses from machine names • Reverse Address Resolution Protocol (RARP): - determines addresses

  40. User Services • Boot Protocol (BOOTP): starts up a network machine • File Transfer Protocol (FTP): transfers files • Telnet: allows remote logins

  41. Gateway Protocols • Exterior Gateway Protocol (EGP): transfers routing information for external networks • Gateway-to-Gateway Protocol (GGP): transfers routing information between gateways • Interior Gateway Protocol (IGP): transfers routing information for internal networks • Border Gateway Protocol (BGP) newer than EGP, used within an autonomous network

  42. Others • Network File System (NFS): enables directories on one machine to be mounted on another • Network Information Service (NIS): maintains user accounts across networks • Remote Procedure Call (RPC): enables remote applications to communicate • Simple Mail Transfer Protocol (SMTP): transfers electronic mail • Simple Network Management Protocol (SNMP): sends status messages about the network

  43. Datagram • Basic unit of data send thought an internet • Moving packets between routers and/or hosts • Consists of a header followed by the data • Header: information necessary to move the packet across the Internet • Connectionless transport mechanism

  44. Datagram

  45. Field Function ver The version of the IP protocol that created the datagram. IHL The length of the IP header in 32-bit words (the minimum value is 5). Type of service The quality of service (precedence, delay, throughput, and reliability) desired for the datagram. Total length The length of the datagram (both header and user data), in octets. Identification A 16-bit value assigned by the originator of the datagram, used during reassembly. Datagram

  46. Flags Control bits indicating whether the datagram may be fragmented, and if so, whether other later fragments exist. Fragment offset The offset in the original datagram of the data being carried in this datagram, for fragmented datagrams. Time to live The time in seconds the datagram is allowed to remain in the internet system. Protocol The high level protocol used to create the message (analogous to the type field in an Ethernet packet). Header checksum A checksum of the header. Datagram

  47. Source IP address 32-bit IP address of the sender. Destination IP address 32-bit IP address of the recipient. Options An optional field primarily used for network testing or debugging. Padding All bits set to zero - used to pad the datagram header to a length that is a multiple of 32 bits. User data The actual data being sent. Datagram

  48. Internet Addresses • Globally accepted method of identifying computers • Each host on a TCP/IP internet is assigned a unique 32-bit address that is used in all communication with that host • Must not be confused with physical addresses! • Each address is a pair (netid, hostid), where netid identifies a network, and hostid identifies a host on that network • In practice, each IP address must have one of the first three forms shown in the picture that follows

  49. Class Maximum number ofpossible networks Maximum number ofhosts per network A 127 16,777,216 B 16,384 65,536 C 2,097,152 255 D Reserved Class E Reserved Class Internet Addresses

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