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Transcript
Internet and IP infrastructure Internet basics • ARPANET – Advanced Research Project Agency Network developed by US DoD Advanced Research Project Agency introduced in 1969. • World’s first packet-switched network • ARPA renamed as Defense Advanced Research Project Agency (DARPA) and started working on packet-switched as well as LANs, paging and satellite networks • Internet Protocol (IP) was created in 1973 to support an open-architecture network protocol to communicate between the disparate networks via gateways – routers • Internet Assigned Numbers Authority (IANA) – currently operated as Internet Corporation for Assigned Names and Numbers (ICANN) oversees IP address allocation, DNS, root zone management, protocol and port numbers • - Organizations for managing the Internet • Internet Society (ISOC) – focuses on Internet standards, education and policy • Internet Engineering Task Force (IETF) – a community of network designers, operators and vendors to create the technical standards through consensus • Internet Assigned Numbers Authority (IANA) – for assigned names and numbers Organizations for managing the Internet • Regional Internet Registries (RIR) – Registration of IP addresses is managed by 5 RIRs • ARIN – American Registry for Internet Numbers for North America • APNIC – Asia-Pacific Network Information Centre for Asia Pacific region • RIPE NCC – Reseaux IP European Network Coordination Center for Europe, Central Asia and Middle East • LACNIC – Latin American and Caribbean Internet Address Registry • AfriNIC – African Network Information Centre for Africa Internet and how it works • An internetwork composed of a collection of networks, routers, gateways, servers and clients linked by a set of telecommunication protocols – the IP family. • Client – a set of computers that receives services from servers • Server – a computer or software program that provides services to network users or Web services to internet users. • Intranets – internal networks connecting site-to-site LAN interconnections through WAN • Extranet – connections between partnering organizations using IP • Router – the main process that a host uses to deliver packets from one network to other. The Internet and PSTN • Internet • Internet uses packet switching which fragments data into packets and does not require any dedicated connection • Each packet travelled through different routes and reassembled at the destination • PSTN • PSTN uses circuit switching which requires dedicated circuit setup and taken down for each call • This allows PSTN charging based on minutes • PSTN is reliable host host HTTP message HTTP HTTP TCP segment TCP TCP router IP Ethernet interface IP packet router IP packet IP Ethernet interface IP SONET interface SONET interface IP packet Ethernet interface IP Ethernet interface Internet Protocol • Protocols are formal description of messages to be exchanged and of rules to be followed in order for two or more systems to exchange information in a manner that the parties will understand • The set of Internet’s Protocols are • • • • • • • • • IP – Internet Protocol TCP – Transmission Control Protocol UDP – User Datagram Protocol SCTP – Stream Control Transmission Protocol DCCP – Datagram Congestion Control Protocol ICMP – Internet Control Message Protocol IGMP – Internet Group Management Protocol ARP – Address Resolution Protocol RARP – Reverse Address Resolution Protocol IP • IP defines the format and basic unit of data transfer which is known as packet or datagram • Datagram has 4 entities • Data/payload • Protocol (TCP/UDP) • IP • Layer 2 (L2) PDU • IP provides routines to route, to store or forward data among hosts. • IP services include • Host addressing • Error notification • Fragmentation and reassembly • Routing • Packet timeout • Maximum IP packet sizes are 1500 bytes • IP protocol is connectionless, best effort service TCP • • • • • • • • The most common Layer 4 protocol TCP segments data into packets and give a sequence number to each Sequence numbers are used to reassemble the packets at destination for reliable data delivery TCP also ensures data delivery to the right application by assigning port number within the range of 1 to 65,535 Port number resides in the TCP header and is assigned to user sessions and server applications The combination of a port number and IP address is called socket Numbers between 1 to 1023 are reserved for well-known server applications (port 80 for Web server, port 21 for FTP) TCP is responsible for • • • • Virtual circuit setup Flow control Error control Retransmission UDP • Transport Layer (L4) protocol • Provides end-to-end, connectionless, unreliable datagram service • Suitable for query/response application, multicasting, VoIP • UDP has minimum delay, but unreliable as it does not support retransmission • UDP does not provide error correction and sequenced delivery, instead the application under way has to incorporate such services • In order to avoid the connection setup and retransmission overhead of TCP, UDP is preferable for multimedia applications SCTP and DCCP • SCTP and DCCP are Layer 4 protocols • SCTP is introduced • to overcome the limitation of TCP for transport of signaling messages and VoIP networks, Stream Control Transmission Protocol is introduced • Applications such as telephone signaling over IP, multimedia Web browsing, video over IP, IPTV are supported by SCTP • DCCP supports • Congestion control for unreliable dataflow • unreliable transport with acknowledgement, reliable handshake, negotiation of features and congestion control ICMP and IGMP • Internet Control Messaging Protocol (ICMP) • Layer 3 protocol • Best effort delivery of messages over IP header • Provides error-handling, error control and network congestions • Internet Group Management Protocol (IGMP) • Layer 3 protocol • Designed to allow Internet hosts to participate in multicasting IP traffic – formatting, addressing and encapsulation ARP and RARP • Address Resolution Protocol • Layer 3 protocol • Resolves the IP address of a node to physical address (MAC address) from mapping table • Reverse Address Resolution Protocol • Rediscovers physical address to logical address (MAC to IP address conversion) by broadcasting its physical address • A node within the LAN answers with IP address Routing Protocols • Allows routers to communicate with each other • Computes various metrics to compute the destination path efficiently • Distance • Cost • Routing protocols are • RIP (Routing Information Protocol) • IGP (Interior Gateway Protocol) • OSPF (Open Shortest Path First) • EGP (Exterior Gateway Protocol) • BGP (Border Gateway Protocol) Internet addressing and address resolution • Each host in the Internet is assigned a unique 32-bit IP address to route the packets to destination • Bits in IP address indicate the network/subnetwork number and the host • The host portion is examined after the packet reaches to destination network • Information flow in a network can be • Unicast – serves one-to-one communication such as server to host • Multicast – serves one-to-many communication such as a videoconferencing between three remote locations which uses only one IP connection and multicast addresses • Anycast – point-to-point flow of packet between a client and the nearest destination IPv4 addressing • IP address has two parts – network address and host address • Classful IP addressing – addressing to the boundary of 8bits • Classless Interdomain Routing (CIDR) – address are assigned as per ISPs and hosts instead of 8-bit octates • Class A – 126 networks with 16,777,214 hosts • Class B – 16384 networks with 65,534 hosts • Class C – 2,097,152 networks with 254 hosts • Class D – reserves for multicast • Class E – reserved for experimental purposes