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WAN Wide Area Networks Review: Capacity Allocation: phone system Bandwidth Allocation: data systems WAN Access Network WAN Intercommunication over public networks Typically slower and more expensive than backbone or LAN Connections Connection Oriented Circuits Have a mechanism to confirm delivery and assure that packets are processed in order Circuits Packet Assembly Devices Non-Connection Oriented Circuits Deliver packets individually without regard to message sequence Wan Resources Bandwidth Access Technology Bandwidth Total transport capacity North American Digital Hierarchy T0 T1 T2 T3 T4 56 + 8 Kbps 1.544 Mbps 6.312 Mbps 44.736 Mbps 274.176 Mbps 64 Kbps 24xT0 96xT0 672xT0 4032xT0 Multiplexing and Wide Area Communication MUX VOICE STREAM WAN LINK Multiplexing and Wide Area Communication MUX DATA STREAM A WAN LINK DATA STREAM B Node Functions Message forwarding Error detection and correction Traffic management CSU/DSU: Digital Service Unit/Channel Service Unit Access Methods of controlling the WAN traffic Traffic Management Access Control Buffering Packet Discard Circuits vs Packets Circuits Switched path setup and teardown Permanent Packets datagram Switches Cut-through switch Store-and-forward switch Switches (Store & Forward) From A H Input Buffer Input Buffer Input Buffer Processor Output Buffer H Output Buffer H Table of Addresses To D Routers From A From B Input Buffer Input Buffer Input Buffer Processor Output Buffer Output Buffer Table of Addresses To C To D Router Functions Layer 1, 2, and 3 functions Packet passing Error correction Message routing Including circuit definition Protocol translation Firewall functions Circuit Logic Source Destination Setup Message & ACK’s Teardown Datagram Logic Packet n Packet 2 Packet 1 Technologies Common WAN technologies. X.25 Older protocol for using packet switched data Operates up to 56.6 Kbps Switched virtual circuit PAD TCP/IP Best Effort Addressing IPv4 vs IPv6 Frame and Header TCP/IP OSI Layer User File Layers Transfer (FTP) Internet Protocols Simple TELNET Routing Information Mail (RIP) Transfer (SMTP) Simple Network Management (SNMP) User Datagram (UDP)l Transport Transmission Control (TCP) Internet Internet Control Message Address Network Protocol (ICMP) Resolution (IP) (ARP) Ethernet, Token Ring, etc. Data Link Twisted Pair, Fiber, Coax, Wireless Physical OSI and TCP/IP OSI TCP/IP 7. Application 6. Presentation Process & Application 5. Session 4. Transport Host to host (TCP) 3. Network Internet (IP) 2. Data link 1. Physical Network access Datagram Routing Best effort Error Control Traffic Management IP Header (Layer 3) Version =4 Header length In bytes Type of service Characteristic of route Total length Length of the packet Source port identifier Port identifier for host process Fragment offset Position (8 byte units) from message start Time to live Allowed seconds Protocol ID of Transport layer protocol (TCP = 6) Header checksum Source address 32 bits Destination address 32 bits Options + Padding Data TCP Header Source port (16 bits) Ports of communicating processes “ Destination port (16 bits) Sequence Number (32 bits) Offset Location of current fragment in message Number of frame to be acknowledged next Number of 32 bit words in header Reserved Not used Acknowledgement Number (32 bits) Flags Window Checksum (16 bits) Urgent Pointer Number of frames sender can accept without buffer overflow IP Addressing 32 bits (4 bytes) Network address + Host address Classes A: B: C: 126 nets, 3 bytes of client addresses 2 bytes of client addresses (e.g. OU) 1 byte of client addresses (256) ISDN Frame Relay Frames relayed without reconstruction End to end error control using CRC error detection at layer 3 level Variable packet size Virtual circuit (usually permanent) Multiple data rates Committed Data Rate Peak data rate (discard eligible) ATM Generic Flow Control Virtual Path Identifier Virtual Channel Identifier Payload Type Identifier Cell Loss Priority Header Error Correction Data Virtual Circuit (not used) 4 bit 1 byte 2 bytes 3 bit 1 = discard eligible 1 bit 48 bytes ATM Traffic Classes Type Type Type Type Type 1 Constant Bit Rate 2 Variable Bit Rate 3 4 5 IP Traffic ATM SNA Connection Oriented Centrally Managed WAN Costs Circuit Charges Committed Bandwidth Peak Bandwidth Discard Priority Latency WAN