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CISC 370 - Class Today

CISC 370 - Class Today. Projects Hubs, Switches, Routers, Bridges Ethernet wrapup Carlson Case Study. Project. Select a topic and get approval Write a 3-page outline presents an overview of your topic, including major facts that were uncovered by your initial research.

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CISC 370 - Class Today

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  1. CISC 370 - Class Today • Projects • Hubs, Switches, Routers, Bridges • Ethernet wrapup • Carlson Case Study R. Smith - University of St Thomas - Minnesota

  2. Project • Select a topic and get approval • Write a 3-page outline • presents an overview of your topic, including major facts that were uncovered by your initial research. • Write a paper about your topic • it should be about 10 pages long - 3,000-5,000 words. • Give a final, 15-minute presentation • given at the final class • Group projects give a longer presentation • All members participate in the final presentation R. Smith - University of St Thomas - Minnesota

  3. Project Schedule • Topic: TODAY • Outline: April 21 • Revised Outline (optional): April 28 • Papers: May 12 • Presentations: May 12 and 14 R. Smith - University of St Thomas - Minnesota

  4. A Little More Ethernet • The yellow ‘hose’ in the network lab • “Original” Ethernet – vampire taps • Switches, Hubs, Bridges, Routers • Long Haul Ethernet (?) R. Smith - University of St Thomas - Minnesota

  5. Bridges, Hubs, Switches, Routers • Different ways to connect LANs together • Router or Gateway – routes at L3 (IP layer) • Bridge – routes at L2; “extends” a LAN • Hub – a repeater at L2 • Switch – directs L2 packets at addressed destination • Topologies • Often physically a star • May logically be a bus R. Smith - University of St Thomas - Minnesota

  6. Bridges and Routers • Router (“L3 Router”) • Generally a Layer 3 “Network” device • L2 MAC addresses are left behind when going through router • Bridge “L2 Router” • Connects two separate LANs together • May use a different transfer medium to hook them together • Radio link between LANs in separate buildings • May do a little routing as opposed to simple echo • Only forward packets in remote LAN’s address range R. Smith - University of St Thomas - Minnesota

  7. Switches and Hubs • Hubs • They echo all the messages they get (de facto broadcast) • Switches • Store/Forward Switch • Cut-through switch • Why did all the hubs turn to switches? • For the young folk: a few years ago, all we could buy were hubs. • Now, all they sell are switches. • What are the trade-offs? R. Smith - University of St Thomas - Minnesota

  8. Long Haul Ethernet (?) • Ethernet is not supposed to be long haul! • It’s a LAN, isn’t it? • They want to exploit the rich set of existing Ethernet-based technologies • Optical technologies • 1000base-LX – single mode fiber = 5 km • 10Gbase-E single mode fiber = 40km (!!) • Now we’re getting into WAN territory (ATM) R. Smith - University of St Thomas - Minnesota

  9. Carlson Case Study • Let’s do it in class • Take 10 minutes to read it over • Check out some of the references on the Internet • Break into 6 or so groups • Each group takes one of the 3 questions. R. Smith - University of St Thomas - Minnesota

  10. Carlson Case Study • What hardware did they start out with? • IBM mainframe, HP & Sun servers - what are these things? • Software? • Oracle, MS Exchange, Web servers, PeopleSoft, data warehousing app R. Smith - University of St Thomas - Minnesota

  11. Original configuration/problems • Where was the data at the start of this process?DAS - direct attached storage, like SATA, IDE, SCSINAS - network attached storage, like NFSSAN - storage area network - block i/o across a LAN • Operational problemsData replication procedures - ensuring consistencyBackup and disaster recoveryNeed 24/7 operationExisting fiber channel used for backup and controlArchitecture couldn't scale R. Smith - University of St Thomas - Minnesota

  12. New hardware • Nishan storage switches - convert i/o operations into IP SAN operationsHP disk array • SAN protocols - iSCSI • TCP/IP based SCSI commandsFiber Channel - proprietary protocolNishan has a strategy for mapping fiber channel onto tcp/ip, used in their switches R. Smith - University of St Thomas - Minnesota

  13. Wireless Applications • o LAN extension - save money on installation • o Building to Building - directed beam • o Nomad access - like at the airport • o Ad hoc networking - just need to set up a LAN without spending effort on wires

  14. General Requirements • o Throughputo Number of nodeso Backbone connection - backhaulo Service area - rangeo Power consumption in portable (battery driven) deviceso Transmission robustness - how good is the signal?o Security - can outsiders interfere?o Colocated wireless LANso FCC and broadcast licensing - none should be neededo Roaming/handoffo Dynamic configuration

  15. Distinguishing requirements • for the 4 applications - yes/maybe/no • Backbone connectivity - backhaul • Per-node communication privacy • Access authorization • Service metering (charging for connection) • Number of nodes • Directionality

  16. Technologies • Infrared, Spread Spectrum, Radio • Infrared – remote controls, some short haul (25 m) • Spread Spectrum – general purpose, up to 250m • Radio – narrowband microwave, up to 40m • Licensing – a potential pain • Some bands require FCC licensing (costly, political) • Industrial/Scientific/Medical – typical for 802.11 • no license needed for some uses • 802.11 Standards • Direct sequence spread spectrum • 2.4Ghz, 1-2Mbps • Frequency hopping spread spectrum, same band same speeds • 80211b - DSSS - 5.5 to 11 Mbps

  17. Spread Spectrum?? • FHSS – Frequency Hopping • Hedy Lamarr/George Antheil; SIGSALY (AT&T) • Systematically switching between radio channels/frequencies • Lamarr’s system used a piano roll (88 frequencies) • DSSS – Direct Sequence • Uses a single very wide ‘carrier’ signal that sounds like noise • Embeds small signals (‘chips’) in the larger carrier • Most chips are noise; some chips contain ‘part’ of a bit • Reconstruct the ‘real’ bits from selected chips • Allows multiple stations to ‘talk’ at the same time • By using different ‘chips’ they don’t interfere with each others’ transmissions • 54 Mbps/2.4 GHz carrier signal = 44 separate ‘channels’

  18. Architecture • BSS - Basic Service Set • A group of wireless stations sharing the same medium = in broadcast proximity to one another and sharing data • SSID - Service Set Identifier - a marker to indicate which network a wireless packet is intended for • One station might serve as an Access Point (AP)APs connect to distribution systems (DSes) • Extended Service Set - ESS • Two or more BSSes connected by a common backbonemay have overlapping broadcast proximity

  19. IEEE 802.11 Services • o Association - establishing the initial link to a stationo Reassociation - moving from one station to anothero Disassociation - moving out of range or shutting downo Authenticationo Privacy

  20. Medium access control • reliable data delivery • Normally 2 frame exchanges: send the data, get an ACK immediately • Sometimes 4 frame exchanges: RTS, CTS, then other 2 • This reduces risk of collision in crowded airwaves by exchanging short control messages instead of longer data packets • access control - how they take turns • DFWMAC - distributed foundation wireless MAC • One choice - distributed coordination similar to CSMA/CD • Other choice - centralized control - PCF - point coordination function • Wireless hub coordinates handshaking instead of leaving it to individual stations

  21. Wireless Security • We can disable SSID broadcast - makes networks harder to find • “Security through obscurity” • WarGames example • We can filter on MAC addresses - only talk to devices with accepted addresses • Cryptographic security

  22. WEP - Wireless equivalent privacy • Shared key encryption protocol • 128-bit keys using RC-4Each packet has an IVPer-packet key constructed of key + IV • The secret part is much smaller than the encryption key • Poorly constructed encryption • 64-bit keys broken in 40-bit time128-bit keys broken in 64-bit timePossible to modify a packet's contents and CRC without knowing the encryption key

  23. Wireless Protected Accesss • WPA – first try • designed as stopgap since WEP was so bad • 128-bit keys using RC-4 • Pre-shared keys updated using TKIP - Temporal Key Integrity Protocol • Better integrity protection • Larger effective keys • Key update protocol • WPA2 - 802.11i - full implementation of WPA • Use permanent keys to authenticate; temporary keys to encrypt • Can use RADIUS authentication server (protocol called 802.1X) • (what is this RADIUS thing about?)

  24. Creative Commons License This work is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/us/ or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA. R. Smith - University of St Thomas - Minnesota

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