6/22/2015 1R. Smith - University of St Thomas - Minnesota CISC 370 - Class Today ProjectsProjects Hubs, Switches, Routers, BridgesHubs, Switches, Routers,

04/18/23 1R. Smith - University of St Thomas - Minnesota

CISC 370 - Class TodayCISC 370 - Class Today

• ProjectsProjects• Hubs, Switches, Routers, BridgesHubs, Switches, Routers, Bridges• Ethernet wrapupEthernet wrapup• Carlson Case StudyCarlson Case Study


ProjectProject

• Select a topic and get approvalSelect a topic and get approval

• Write a 3-page outline Write a 3-page outline – presents an overview of your topic, including major facts that presents an overview of your topic, including major facts that

were uncovered by your initial research.were uncovered by your initial research.

• Write a paper about your topicWrite a paper about your topic– it should be about 10 pages long - 3,000-5,000 words. it should be about 10 pages long - 3,000-5,000 words.

• Give a final, 15-minute presentation Give a final, 15-minute presentation – given at the final classgiven at the final class– Group projects give a longer presentationGroup projects give a longer presentation

• All members participate in the final presentationAll members participate in the final presentation


Project ScheduleProject Schedule

• Topic: TODAYTopic: TODAY

• Outline: April 21Outline: April 21

• Revised Outline (optional): April 28Revised Outline (optional): April 28

• Papers: May 12Papers: May 12

• Presentations: May 12 and 14Presentations: May 12 and 14

A Little More EthernetA Little More Ethernet

• The yellow ‘hose’ in the network labThe yellow ‘hose’ in the network lab– ““Original” Ethernet – vampire tapsOriginal” Ethernet – vampire taps

• Switches, Hubs, Bridges, RoutersSwitches, Hubs, Bridges, Routers

• Long Haul Ethernet (?)Long Haul Ethernet (?)


Bridges, Hubs, Switches, RoutersBridges, Hubs, Switches, Routers

• Different ways to connect LANs togetherDifferent ways to connect LANs together– Router or Gateway – routes at L3 (IP layer)Router or Gateway – routes at L3 (IP layer)– Bridge – routes at L2; “extends” a LANBridge – routes at L2; “extends” a LAN– Hub – a repeater at L2Hub – a repeater at L2– Switch – directs L2 packets at addressed destinationSwitch – directs L2 packets at addressed destination

• TopologiesTopologies– Often physically a starOften physically a star– May logically be a busMay logically be a bus


Bridges and RoutersBridges and Routers

• Router (“L3 Router”)Router (“L3 Router”)– Generally a Layer 3 “Network” deviceGenerally a Layer 3 “Network” device– L2 MAC addresses are left behind when going through routerL2 MAC addresses are left behind when going through router

• Bridge “L2 Router”Bridge “L2 Router”– Connects two separate LANs togetherConnects two separate LANs together– May use a different transfer medium to hook them togetherMay use a different transfer medium to hook them together

• Radio link between LANs in separate buildingsRadio link between LANs in separate buildings– May do a little routing as opposed to simple echoMay do a little routing as opposed to simple echo

• Only forward packets in remote LAN’s address rangeOnly forward packets in remote LAN’s address range


Switches and HubsSwitches and Hubs

• HubsHubs– They echo all the messages they get (de facto broadcast)They echo all the messages they get (de facto broadcast)

• SwitchesSwitches– Store/Forward SwitchStore/Forward Switch– Cut-through switchCut-through switch

• Why did all the hubs turn to switches?Why did all the hubs turn to switches?– For the young folk: a few years ago, all we could buy were For the young folk: a few years ago, all we could buy were

hubs.hubs.– Now, all they sell are switches.Now, all they sell are switches.– What are the trade-offs?What are the trade-offs?


Long Haul Ethernet (?)Long Haul Ethernet (?)

• Ethernet is not supposed to be long haul!Ethernet is not supposed to be long haul!– It’s a LAN, isn’t it?It’s a LAN, isn’t it?

• They want to exploit the rich set of existing They want to exploit the rich set of existing Ethernet-based technologiesEthernet-based technologies

• Optical technologiesOptical technologies– 1000base-LX – single mode fiber = 5 km1000base-LX – single mode fiber = 5 km– 10Gbase-E single mode fiber = 40km (!!)10Gbase-E single mode fiber = 40km (!!)

• Now we’re getting into WAN territory (ATM)Now we’re getting into WAN territory (ATM)


Carlson Case StudyCarlson Case Study

• Let’s do it in classLet’s do it in class

• Take 10 minutes to read it overTake 10 minutes to read it over– Check out some of the references on the InternetCheck out some of the references on the Internet

• Break into 6 or so groupsBreak into 6 or so groups

• Each group takes one of the 3 questions.Each group takes one of the 3 questions.



Carlson Case StudyCarlson Case Study

• What hardware did they start out with?What hardware did they start out with?

– IBM mainframe, HP & Sun servers - what are these things?IBM mainframe, HP & Sun servers - what are these things?

• Software?Software?

– Oracle, MS Exchange, Web servers, PeopleSoft, data Oracle, MS Exchange, Web servers, PeopleSoft, data warehousing appwarehousing app


Original configuration/problemsOriginal configuration/problems

• Where was the data at the start of this process?Where was the data at the start of this process?DAS - direct attached storage, like SATA, IDE, SCSIDAS - direct attached storage, like SATA, IDE, SCSINAS - network attached storage, like NFSNAS - network attached storage, like NFSSAN - storage area network - block i/o across a LANSAN - storage area network - block i/o across a LAN

• Operational problemsOperational problemsData replication procedures - ensuring consistencyData replication procedures - ensuring consistencyBackup and disaster recoveryBackup and disaster recoveryNeed 24/7 operationNeed 24/7 operationExisting fiber channel used for backup and controlExisting fiber channel used for backup and controlArchitecture couldn't scaleArchitecture couldn't scale


New hardwareNew hardware

• Nishan storage switches - convert i/o Nishan storage switches - convert i/o operations into IP SAN operationsoperations into IP SAN operationsHP disk arrayHP disk array

• SAN protocols - SAN protocols - iSCSIiSCSI

• TCP/IP based SCSI commandsTCP/IP based SCSI commandsFiber Channel - proprietary protocolFiber Channel - proprietary protocolNishan has a strategy for mapping fiber Nishan has a strategy for mapping fiber channel onto tcp/ip, used in their switcheschannel onto tcp/ip, used in their switches

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

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

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

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

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’

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 backbone

may have overlapping broadcast proximity

•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

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

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

WEP - Wireless equivalent privacy

• Shared key encryption protocol– 128-bit keys using RC-4

Each 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 time

128-bit keys broken in 64-bit timePossible to modify a packet's contents and CRC without knowing the encryption key

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?)


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6/22/2015 1R. Smith - University of St Thomas - Minnesota CISC 370 - Class Today ProjectsProjects Hubs, Switches, Routers, BridgesHubs, Switches, Routers,