CIT 470: Advanced Network and System Administration Slide #1

CIT 470: Advanced Network and System Administration

Networks

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Topics

1. Network Topology2. Structured Cabling3. Simple Host Routing4. Overlay Networks5. Monitoring

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Network Topology

Arrangement of network elements, showing physical or logical interconnections between nodes. Does not include info about:– Distance– Transmission rates– Protocols– Cabling types

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Star Topology• Network connected to

a central node using a single link.

• All data transmitted between nodes goes through central node.

• Easy to understand, simple, affordable.

• Single point of failure.

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Ring Topology• Each node is connected

to two other nodes, with first and last node connected to each other.

• All devices have two connections to network, so any link can fail w/o causing a problem.

• Dual ring has two connections to each node.

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Structured CablingTelecom cabling infrastructure consisting of

Entrance facilities: where building interfaces to ouside world.

Equipment room: more complex equipment (routers, major cable terminations.)

Building backbone: star topology providing access to all wiring closets, equipment rooms, and entrance facilities.

Telecom closet: wiring closet where horizontal cable for floor is terminated.

Horizontal cabling: extends from telecom closet to end user devices in the work area.

Work area: office space, labs, etc. where computers and other equipment are located.

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Wiring ClosetsSmall room wherecables are connectedfrom main network tolocal devices, a/k/aa distribution frame.

Needs: Reliable power A/C Physical security

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IDFs and MDFs

Intermediate Distribution Frame (IDF)– One per floor.– Connects end users to network.

Main Distribution Frame (MDF)– Connects all the MDFs.– Often located in data center.

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Patch PanelA panel that houses cable connections.

– Front: short patch cables.– Back: longer permanent cables.

Allows you to change cable path w/o new cables.

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Patch Panel

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Star Topology Cabling

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Star Topology Wiring Advantages

1. Central wiring hubs make it easier to move, add, or change cabling.

2. Central cabling points allow faster troubleshooting.

3. Independent point to point links prevent cable problems from affecting other links.

4. Central wiring hubs can allow easier upgrades to new technologies.

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Cabling Contractors• Cabling an entire building is a major project.• Cable contractors know how

– Plan cabling for an entire building– Estimate cabling and install hosts– Structured cable standards– Electrical safety standards– Fire safety standards

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Documentation• Logical map

– Logical network topology– Network numbers, names, speeds

• Labeling– Label both ends of each cable.– Cables can be difficult to label, but

manufacturers will print serial numbers.– Include text comment on each interface in

router/switch software.

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Simple Host Routing

Machines with one NIC only need two routes:– Local subnet: direct connection.– Everything else goes to local gateway router.

Don’t enable routing protocols on PCs.– Makes networking more complex.– Decreases network performance w/ broadcasts.– Badly configured PC can send bad routes to

other PCs and routers, breaking network.

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Overlay Networks

A logical topology on top of physical topology.– VPN: connect remote users/sites to main site as

if a single secure WAN existed over Internet.– VLAN: treat any connection as belonging to any

subnet, no matter what the physical cabling is like. Eliminates need to recable to move machines to different subnets.

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Monitoring

Need two types of monitoring– Real-time alerts: alert when network interface

goes up or down, heavy load, security, etc.– Historical trends: record overall network usage

in order to plan for future capacity and detect behavorial abnormalities before they become problems.

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References

1. Thomas A. Limoncelli, The Practice of System and Network Administration, 2nd ed, Addison-Wesley, 2007.

2. Kennedy Clark and Kevin Hamilton, Cisco LAN Switching, Cisco Press, 1999.

3. Charles E. Spurgeon, Ethernet: The Definitive Guide, O’Reilly, 2000.

4. John Vacca, The Cabling Handbook, 2nd ed, Pearson PTR, 2000.