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Internetworking in computer networks ppt

internetworking terms and concepts ppt and mobile data internetworking standards ppt
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Dr.ShivJindal,India,Teacher
Published Date:19-07-2017
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Internetworking: philosophy, addressing, forwarding, resolution, fragmentation Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 1Overview  Internetworking: heterogeneity & scale  IP solution:  Provide new packet format and overlay it on subnets.  Ideas: Hierarchical address, address resolution, fragmentation/re-assembly, packet format design, forwarding algorithm etc  Chapter 3,4,5,7 in Comer  Reading: Clark: "The Design Philosophy of the DARPA Internet Protocols":  Reading: Cerf, Kahn: "A Protocol for Packet Network Intercommunication"  Reading: Mogul etal: "Fragmentation Considered Harmful"  Reading: Addressing 101: Notes on Addressing: In PDF In MS Word  Reading: Notes for Protocol Design, E2e Principle, IP and Routing: In PDF  Reference: RFC 791: Internet Protocol (IP) Spec.: In HTML Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 2The Problem  Before Internet: different packet-switching networks (e.g., ARPANET, ARPA packet radio)  only nodes on the same network could communicate Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 3A Translation-based Solution ALG ALG ALG ALG  application-layer gateways  inevitable loss of some semantics  difficult to deploy new internet-wide applications  hard to diagnose and remedy end-to-end problems  stateful gateways inhibited dynamic routing around failures  no global addressability Shivkumar Kalyanaraman Rensselaer Polytechnic Institute  ad-hoc, application-specific solutions 4The Internetworking Problem  Two nodes communicating across a “network of networks”… How to transport packets through this heterogeneous mass ? A B Cloud Cloud Cloud Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 5Declared Goal  “…both economic and technical considerations lead us to prefer that the interface be as simple and reliable as possible and deal primarily with passing data between networks using different packet switching strategies” V. G. Cerf and R. E. Kahn, 1974 Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 6The Challenge: Heterogeneity  Share resources of different packet switching networks  interconnect existing networks  … but, packet switching networks differ widely  different services e.g., degree of reliability  different interfaces e.g., length of the packet that can be transmitted, address format  different protocols e.g., routing protocols Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 7The Challenge: Scale  Allow universal interconnection  Mantra: Connectivity is its own reward  … but, core protocols had scalability issues  Routing algorithms were limited in the number of nodes/links they could handle and were unstable after a point  Universal addressing to go with routing  As large numbers of users are multiplexed on a shared system, a congestion control paradigm is necessary for stability  No universal, scalable naming system… Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 8The Internetworking Problem  Problems: heterogeneity and scaling  Heterogeneity: How to interconnect a large number of disparate networks ? (lower layers) How to support a wide variety of applications ? (upper layers)  Scaling: How to support a large number of end-nodes and applications in this interconnected network ? Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 9Solution Network Layer Gateways Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 10The IP Solution … IP IP IP IP  internet-layer gateways & global addresses  simple, application-independent, lowest denominator network service: best-effort datagrams  stateless gateways could easily route around failures  with application-specific knowledge out of gateways:  NSPs no longer had monopoly on new services  Internet: a platform for rapid, competitive innovation Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 11Network-layer Overlay model Define a new protocol (IP) and map all applications/networks to IP  Require only one mapping (IP - new protocol) when a new protocol/app is added  Global address space can be created for universal addressibility and scaling Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 12Before IP (FTP – File Transfer Protocol, NFS – Network File Transfer, HTTP – World Wide Web protocol) FTP NFS HTTP Application Telnet Coaxial Fiber Packet Transmission cable optic radio Media  No network level overlay: each new application has to be re-implemented for every network technology Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 13IP  Key ideas:  Overlay: better than anyany translation. Fewer, simpler mappings.  Network-layer: efficient implementation, global addressing FTP NFS HTTP Telnet Application Intermediate Layer (IP) Coaxial Fiber Packet Transmission cable optic radio Media Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 14What About the Future ?  Internet is running out of addresses  Solutions Classless Inter Domain Routing (CIDR) Network Address Translator (NATs) Dynamic Address Assignments … IPv6  Why not variable-sized addresses? Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 15Service to Apps  Unbounded but finite length messages byte streaming (What are the advantages?)  Reliable and in-sequence delivery  Full duplex  Solution: Transmission Control Protocol (TCP) Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 16Original TCP/IP (Cerf & Kahn)  No separation between transport (TCP) and network (IP) layers  One common header use ports to multiplex multiple TCP connections on the same host 32 32 16 16 8n Source/Port Source/Port Window ACK Text  Byte-based sequence number (Why?)  Flow control, but not congestion control Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 17Today’s TCP/IP  Separate transport (TCP) and network (IP) layer (why?) split the common header in: TCP and UDP headers fragmentation reassembly done by IP  Congestion control (later in class) Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 18IP Datagram Format 0 4 8 16 32 Vers H Len TOS Total Length Identification Flags Fragment Offset Time to live Protocol Header Checksum Source IP Address Destination IP Address IP Options (if any) Padding Data Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 19IP Datagram Format (Continued)  First Word purpose: info, variable size header & packet. Version (4 bits) Internet header length (4 bits): units of 32-bit words. Min header is 5 words or 20 bytes. Type of service (TOS: 8 bits): Reliability, precedence, delay, and throughput. Not widely supported Total length (16 bits): header + data. Units of bytes. Total must be less than 64 kB. Shivkumar Kalyanaraman Rensselaer Polytechnic Institute 20