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Networking in the K-12 Community Rick Bagwell Nichols Research

Networking in the K-12 Community Rick Bagwell Nichols Research A labama R esearch and E ducation N etwork (Formerly the Alabama Supercomputer Network). Local Area Network Options (LAN). Ethernet Shared, Switched, Fast, Gigabit Token Ring FDDI (Fiber Distributed Data Interface)

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Networking in the K-12 Community Rick Bagwell Nichols Research

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  1. Networking in the K-12 Community Rick Bagwell Nichols Research Alabama Research and Education Network (Formerly the Alabama Supercomputer Network)

  2. Local Area Network Options (LAN) • Ethernet • Shared, Switched, Fast, Gigabit • Token Ring • FDDI (Fiber Distributed Data Interface) • ATM (Asynchronous Transfer Mode)

  3. Ethernet Types • Ethernet • 10Base-T (100m, Unshielded Twisted Pair = UTP) • 10Base-2 (~200m, Coax) • 10Base-5 (500m, Coax) • 10Base-FL (2000m=2km, Multimode Fiber) • Fast Ethernet • 100Base-TX (100m over CAT5 UTP) • 100Base-FX (2000m=2km over MM Fiber) • Gigabit Ethernet • 1000Base-SX (300m over MM Fiber) • 1000Base-LX (550m over MM Fiber, 3000m over SM Fiber)

  4. Ethernet • 10 Mbps • CSMA/CD • Carrier Sense Multiple Access with Collision Detection • Can be configured with cable, hubs, or switches

  5. Common Ethernet Topologies (non-segmented)

  6. Limitations of Cascaded Hub Topology • Distance limitations of UTP or Fiber • Network size limited by the 5-4-3 rule • just remember hosts cannot talk to each other if they are connected through more than 4 hubs or repeaters • One Broadcast Domain • collisions likely as number of hosts increases • Users generally don’t know about the 5-4-3 rule and just keep on adding hubs at random points

  7. Limitations of Stacked Hub Topology • All hosts must be within 100m of the stack when using UTP • Using fiber to overcome distance limitations is useful for MDF to IDF connections but is cost prohibitive to the desktop • “Stackables” use proprietary interconnects • One broadcast domain

  8. Limitations of 10Base-2 and 10Base-5 • Difficult to troubleshoot • Terminations, Terminations, Terminations • 5-4-3 rule must be strictly enforced • Cable infrastructure does not support upgrades to Fast or Gigabit Ethernet. • Difficult to troubleshoot • Terminations, Terminations, Terminations

  9. Ethernet: The Next Generation • Layer 2 switches (Ethernet, FastE, GigE) • Switching decisions are made based on MAC address • Segments network into separate traffic domains • Broadcasts are still heard by all hosts • Does not affect IP subnetting

  10. Ethernet: The Next Generation (cont.) • Layer 3 switches (Ethernet, FastE, GigE) • Switching decisions are made based on MAC and IP addresses • High-speed ASIC-based routing • Can usually be configured as Layer2/Layer3 switches on a per-port basis • Layer 3 switching takes place between subnets

  11. Ethernet: The Next Generation (cont. again) • Layer 4 “switches” (Ethernet, FastE, GigE) • Switching decisions are based on Application, MAC and IP addresses • Can usually be configured as Layer2/3/4 switches on a per-port basis • Layer 3 switching takes place between subnets • Layer 4 “switching” is used to provide QoS and multimedia services

  12. Ethernet Network Design Pointers • Use Ethernet switching as much as possible • Limit the number of hosts sharing a switched port • Switched to the desktop is nice but expensive • Use Layer 3 switching (routing) for large (>200 hosts) networks and high-performance. • Use Fiber between MDF and IDFs when distance exceeds 100m (300ft to be conservative) • Do NOT use Fiber to the desktop unless you are made of money

  13. How do I connect my schools to each other and to the Internet? • The same general answer applies for almost every choice of WAN connection technology. • Routers at each school are connected via some WAN technology to the other routers in the school system • Schools are on different IP subnets • Internet access • Usually obtained for the school system by connecting a single location to the Internet with a high-speed connection. • Other schools in the system can access the Internet by routing through the central location. • Can be purchased on a school by school basis • This option can be MUCH more expensive and likely gains little, if anything, in the way of performance.

  14. Typical School System Network

  15. Wide Area Network Options (WAN) • DS1 (a.k.a T1) • Fractional DS1 (Frac. T1) • Frame Relay • Cable Modem • ISDN • xDSL • Private/Leased Fiber (or copper) • Wireless

  16. What is a “T1” and how does it work ?? • High speed “phone” line • digital • 1.544Mbps (if all 24 channels are used) • 24 “phone” lines • Used by phone companies between COs • Used by businesses between offices • Used by Networking folks for Data

  17. Advantages and Disadvantages of T1 Lines for School System Networking • Advantages: • Reasonable WAN speed (1.5Mbps) • An educational tariff is available for T1s in Alabama. • Full T1’s are almost always less expensive than Frame Relay (due to the edu. Tariff) • Telco is responsible for insuring that the line stays operational • Disadvantages: • Bandwidth is limited (1.5Mbps) • Requires more router ports at central site than Frame Relay • but large systems can use Channelized DS3

  18. What is Frame Relay and how does it work ?? • Circuit switched network technology • You purchase access to the “cloud” • usually a T1 or fractional T1 • Virtual connections are made across the cloud to connect schools (PVCs) • A Committed Information Rate (CIR) can be purchased that guarantees a level of performance

  19. Frame Relay Example

  20. Advantages and Disadvantages of Frame Relay for School System Networking • Advantages: • Reasonable WAN speed (64kbps -- 1.5Mbps) • When T1 or Fract. T1 is the transport • Buy bandwidth only when you need it **** • One serial port at the central site can support multiple incoming PVCs • Telco is responsible for insuring connectivity • Disadvantages: • No educational tariff is currently available in Alabama. • Full T1’s are almost always less expensive than Frame Relay (due to the edu. Tariff) • This is true even when low CIRs or no CIRs are compared to T1s

  21. Cable Modems and xDSL • High-speed (256kbps -- 10Mbps) wide area connectivity that can be used to connect schools or for Internet access • Usually only available in the larger cities (Huntsville, Birmingham, Montgomery, Mobile) • Too early to recommend or dismiss as a technology for school system use • Both Cable Modem systems and xDSL can and often are over-subscribed • Some sort of service level agreement should be obtained before either of these technologies are considered

  22. ISDN (Integrated Services Digital Network) • Designed to be a digital phone service • BRI: 2B+D (Basic Rate Interface) • PRI: 23B+D (Primary Rate Interface) • Telco’s frown on “nailing up” ISDN connections • Limited bandwidth (64-128kbps for BRI) • Good solution for “dial backup” • if you can afford dial backup

  23. Private or Leased Fiber Optic Lines • My personal favorite • Extremely high bandwidth available (1Gbps is easily obtained) • Can economically use Fast Ethernet over such and infrastructure (100Mbps) • No recurring costs (T1 min. is $240.00 per month) • Must either obtain right-of-way or have existing fiber donated by telco or power company

  24. Wireless WAN/MAN • Good solution in Flat areas or when a mountain is nearby • line of sight is required !!! • High Bandwidth solutions are available (2Mbps--155Mbps) • 10Mbps is now very economical • No recurring cost (unless leased) • Leasing provides insurance against malfunction or the weather • My second choice if fiber is unavailable

  25. Unconventional Wisdom(at least some people would say so) • Never use managed Ethernet hubs • most of the functionality is never used • much more expensive than “dumb” hubs • exception to this rule: VLANs on hubs • The only use for Fiber Optics is between IDFs and the MDF when the distance is over 300ft • Almost never buy Frame Relay for connecting schools in a single system to each other (Educational T1s are cheaper). • Always compare all WAN options (T1, Frame, Fiber, Wireless, etc.) • Use network appliances and/or LINUX systems for Internet servers. • Having a trained Network Manager makes ALL the difference • Don’t have to rely completely on vendors and contractors • Get network advice from someone other than the vendor before purchasing

  26. Contact Information Rick BagwellNetwork EngineerNichols Research Corporation(Contractor for AREN)Voice: (256) 971-7432FAX: (256) 971-7491Email: Rick@asc.edu -or- bagwellr@nichols.com

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