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Computer Networks

Computer Networks. Other Network Protocols. Motivation.

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Computer Networks

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  1. Computer Networks • Other Network Protocols

  2. Motivation Even though TCP/IP may have won the protocol wars, you will be able to understand networking and even TCP/IP better if you learn about contrasting solutions and implementations. This may help you to avoid reinventing the wheel or perhaps to borrow from the past's good ideas to solve seemingly new problems.

  3. Novell IPX/SPX • Novell proprietary • Based on Xerox's XNS protocol system • Runs on top of Ethernet, Token Ring, etc. • Usually used with NetWare OS's • Very popular in corporate environments • Declining usage

  4. Novell Protocol Stack Illustrated

  5. Internetwork Packet eXchange (IPX) • 32-bit network, 48-bit node/host address • Network is generally fixed at 32-bits • Node address = IEEE 802 MAC address • Dynamic host address assigment • Many features IP wishes it had!

  6. IPX Routing • IPX Routing Information Protocol • TTL counts up • NLSP • Similar to OSPF and IS-IS • Never took off • Concept of internal IPX numbers

  7. Sequenced Packet eXchange (SPX) • Similar to TCP, but with no sliding window! • SPX II addressed the window size problem • Though, not really well • Most Novell based apps avoided SPX • It was inefficient and just got in the way • Some newer apps used SPX II (e.g. Notes)

  8. Service Advertisement Protocol (SAP) • Services are advertised periodically • The anti-DNS system • e.g. "I'm a Netware printer, here I am!" • Default interval was every 60 seconds • Very chatty on large networks • Does not scale • NDS was supposed to help

  9. NetWare Core Protocol (NCP) • Novell's layer 5, 6 and 7 layers - kinda • File access protocol • Print services • Login/authentication requests • Messaging/management services • Provided "burst mode" for file read/writes

  10. NetWare Directory Services (NDS) • Hierarchical database of network objects • Based on X.500 and works with LDAP • Logical and physical objects represented • Leafs, containers, users, drive mapping, etc. • Naming structure similar to DNS • e.g. jdoe.networks.acme_us. • Partitions and replicas stored on servers

  11. AppleTalk • De Facto standard from Apple for Macs • Very easy for end users • Very chatty - scaling problems • Runs on top of LocalTalk, Ethernet, Token Ring, etc. • TokenTalk and EtherTalk technologies developed to support AppleTalk over IEEE LANs

  12. This Picture is Wrong!

  13. AppleTalk Network Layer Addressing • Only 3 bytes for network layer addresses! • 2 bytes for network, 1 byte for host/node • Networks can be ranges • e.g. 135-141 • Arbitrary size, unlike IP (x2) • Looks/Requests network address • Chooses host/node address at random! • Sends an AARP and looks for a reply

  14. AppleTalk Routing • Routing Table Maintenance Protocol (RTMP) • Similar to RIP • Seed Router • 1 router configured with network, others learn • Nodes can optimize best exit router by examining received packets • Associates NET with ROUTER ADDRESS

  15. AppleShare • Centralized file sharing system • Runs on top of AppleTalk • Also allows for • Printer sharing • Peer to peer sharing • Mail handling • Security functions (ids and passwords)

  16. ISO Network Layer • Connectionless Network Layer Protocol (CNLP) • Variable length, 20 bytes max • Address specifies a host rather than an interface • Was considered to replace IPv4 • Provided for autoconfiguration like IPv6 and IPX

  17. ISO Routing • Intermediate System to Intermediate System (IS-IS) • Link state routing protocol • Very similar to OSPF • Widely used by many ISPs • Runs directly on top of a layer 2 protocol

  18. ISO Transport Layer • Transport Protocol (TP) • Four classes of transport layer protocols • TP0, TP1, TP2, TP3, TP4 • Each provide increasing degree of features • TP4 is similar to TCP • Three-way handshake • Sliding window • Retransmission timer

  19. ISO Protocol Stack Illustrated

  20. DECnet • Most commonly referred to as Phase IV • Earlier phases and Phase V also defined • DECnet Phase V was CLNP or IP • Only 2 bytes for addresses in Phase IV! • 6 bits for network (area), 10 bits for host/node • Traditionally implemented on Digital Equipment Corp. machines (e.g. VAX) • Ported to many other systems

  21. DECnet Protocol Stack Illustrated

  22. Systems Network Architecture (SNA) • Proprietary architecture from IBM • There is no true layer 3 function in legacy SNA - no routing! • Historically built for token ring and source routing (that was the layer 3 network) • Central control (dumb terminals) • APPN came later to provide distributed control

  23. SNA Protocol Stack Illustrated

  24. SNA Components • Hosts (mainframe) • Communications controller/FEP • Cluster controllers - like a hub • Terminals and printers • Software (VTAM, NCP, emulation) • Physical and logical concepts (PUs/LUs)

  25. Network Basic Input Output System (NetBIOS) • A simple API for LAN applications • Assigns names for nodes on the network • Very chatty - does not scale • No network layer • Often uses the NetBIOS Extended User Interface (NetBEUI) • Server Message Block (SMB) used to provide file/print sharing (e.g. Samba)

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