Overview • Approximately 80,000 hosts • Approximately 2.5 terabytes of data passed on and off campus daily – – – – – export an average of 170Mbps import 125Mbps perform over 300,000 email deliveries daily Users send over 120,000 email messages daily 3 million web server hits daily, 52 gigabytes of data • TCP/IP and Appletalk based Protocols • Protocols define how entities communicate – Ethernet - low level communication between hosts – TCP/IP - higher level host-to-host communication – IMAP - Internet Message Access Protocol – SMTP - Simple Mail Transfer Protocol Protocols (cont.) – HTTP - HyperText Transfer Protocol – SNMP - Simple Network Management Protocol – PPP - Point-to-Point Protocol • PAP - Password Authentication Protocol • CHAP - Challenge Handshake Authentication Protocol • IPCP - Internet Protocol Control Protocol The ISO Reference Model Application Presentation Session Transport Network Data Link Physical The ISO Model and Protocols • Ethernet – Covers both Physical (wiring) and Data Link layers • IP - Internet Protocol – A Network layer protocol • TCP - Transmission Control Protocol – A Transport layer protocol Network Technology • Backbone Network – Used to interconnect other networks – Covers the scale from buildings to nations • Repeater – Works with a specific media (i.e. Ethernet) – Works at Layers 1 and slightly in 2 – Passes all traffic Network Technology (cont.) • Bridge – Usually works with a specific media – Works at layer 2 – Used to segment traffic (only traffic that needs to cross the bridge is allowed to do so) – Switches can be thought of as multiport bridges Network Technology (cont.) • Router – Can support multiple media types – Works at layer 3 – Used to forward packets from one network to another based on routing tables – Communication servers, used to support dialup users, are based on routers Network Technology (cont.) • Some other network devices – Media Converters • used to convert between physical connections • not part of the Ethernet specification – How lucky do you feel? – Firewalls • Used to provide some control over data flows for security purposes • Actually covers a multitude of devices Network Technology (cont.) • Other devices (cont.) – Wireless LAN Access Points (APs) – dominate standard is the IEEE 802.11 family • • • • 802.11 – 2Mbps, 2.4Ghz 802.11a – 54Mbps, 5Ghz 802.11b – 11Mbps, 2.4Ghz 802.11g – 54Mbps, 2.4Ghz – MIT has coverage in most classrooms, libraries, and many common spaces MITnet - Campus Backbone • Core switch with 100Mbps or 1Gbps links – 1 legacy FDDI router • 8 routers – Ethernet connectivity to buildings – A variety of links to the Internet and off-campus sites Building Backbones repeater switch repeater router switch switch repeater repeater OLD switch NEW Wide Area Connections • MIT Off-campus sites – ILGs - multiplexed T1 lines – Remote offices • laser links • leased lines (T1, 56kbps) Internet Connections • Links to the following networks – Genuity - our default service – vBNS - MCI high speed backbone, shared with Harvard – Northern Crossroads (NOX) • Abilene (Internet 2), RCN, other New England universities – ESNet - Energy Science Network MITnet - Remote Access • MIT provided – “56k” modem based PPP service – Legacy terminal service to Athena • Other ISPs – Traditional modem-based services – AT&T, RCN cable modem service – DSL? Design Philosophy • Simplicity – Keep topology and technology standardized as much as possible