Design and Documentation

1. Design and Documentation Honolulu Community College Cisco Academy Training Center Semester 1 Version 2.1.1

2. Overview • Design of physical and logical topologies. • Documentation. • Wiring closet specifications. • Wiring and electrical techniques.

3. General Design Process • 1. Select the technology (Ethernet). • 2. Develop Layer 1 LAN topology. • type of cable. • physical (wiring) topology (extended star). • Type of Ethernet. • Logical topology. • 3. Develop Layer 2 LAN topology. • Segmentation - reduce congestion & collision domain size.

4. General Design Process • 4. Develop Layer 3 topology. • Implement routing to build scalable internetworks. • logical structure. • segmentation - minimize broadcast domain. • Other concerns: • Placement of servers. • LANs link to WANs and to the Internet. • document your physical and logical topologies.

5. Network Design Issues • First step: gather information about the organization. • 1.organization's history and current status • 2.projected growth • 3.operating policies and management procedures • 4.office systems and procedures • 5.viewpoints of people who will be using LAN • Purpose is to identify and define any issues or problems that need to be addressed.

6. Network Design Issues (cont.) • Second step: make a detailed assessment of current and projected requirements. • Third step: identify resources and constraints of the organization. • document existing computer hardware and software. • identify and define projected hardware and software needs. • Purpose: determine how much training will be required, and how many people will be needed to support the LAN.

7. Network Design Issues (cont.) • These steps will allow you to estimate costs and develop a budget for the implementation of a LAN.

8. Wiring Closet Selection • Most important decision is selection of MDF. • Secure location, close to POP. • POP is where telecommunications services connect to the building's communication facilities. • TIA/EIA-568-A specifies that in an Ethernet star topology, every device must be connected to the hub (in wiring closet) by horizontal cabling. • To find location(s) of wiring closet(s), begin with a floor plan of the building, indicating all devices that will be connected to the network.

9. Wiring Closet Selection (cont.) • Next identify potential locations for wiring closets.

10. Determing Number of Wiring Closets • Draw circles of radius 50 m from each potential wiring closet locations. • Number of wiring closets is determined by what is needed to cover the building.

11. Extended Star Topology • MDF of an extended star topology Ethernet LAN is usually centrally located. • In high rise building, MDF usually located on a middle floor, even if POP is on the first floor.

12. MDF - multi-building campus • MDF: a central location, close to the POP,. • IDFs are located in each building. • Note: main building also requires an IDF.

13. Backbone Cabling • Cabling between wiring closets is backbone or vertical cabling. • Backbone cabling include: • MCC (main cross-connects), • ICC (intermediate cross-connects), • mechanical terminations • backbone cable runs. • Cabling between MDF and POP • Recommended backbone is 62.5/125 µm fiber-optic cable.

14. Backbone Cabling (cont.) • TIA/EIA 568A specifies four types of networking media for backbone cabling: • 100W UTP, 150W STP, 62.5/125 µm fiber optic, and single-mode fiber optic cable. • TIA/EIA 568A recognizes 50 W coaxial cable, but it is not recommended for new installations. • Recommended backbone is 62.5/125 µm fiber-optic cable (multi-mode fiber).

15. MDF to IDF Cabling • MCC (main cross connect) is in MDF. • connects backbone cabling to the Internet. • HCC (horizontal cross connect) is in IDF.

16. MDF to IDF - another method • ICC (intermediate cross connect) in an IDF. • No work areas or horizontal wiring connects to ICC. • HCC (horizontal cross connect) in another IDF.

17. No more than one ICC between MCC and HCC.

18. Backbone Cabling Lengths • TIA/EIA 568A also specifies max lengths when ICC is used.

19. Specs for Backbone Cabling • TIA/EIA 568A specifies max lengths for backbone cabling.

20. Electrical Concern - Noise • AC line noise, can create errors: • adding unwanted voltages to signals. • preventing detection of leading and trailing edges of square wave signals. • Problems can be compounded with poor ground connections.

21. Electrical Concern - ESD • Charges can be separated by friction, e.g. by shuffling you feet across a carpet. • Very high voltages (thousands of volts) can be generated , referred to as static electricity. • When you reach for a metal object, a spark occurs - this is current flow, as the high voltage pushes the free electrons to the metal object. • This is ESD or electro-static discharge. • can randomly damage computer chips and/or data.

22. Grounding Network Equipment • AC power is supplied though a 3 prong plug. • Top 2 connectors are the power. • Other connector is safety ground (earth ground). • Any exposed metal is connected to safety ground. • Computer motherboard’s ground plane is connected to the chassis and safety ground. • Ground helps dissipate static electricity.

23. Safety Ground • Purpose - to prevent exposed metal parts from becoming energized with high voltage should a wiring fault occur. • A wiring fault will cause current through the ground connection, and activate protective devices such as circuit breakers to disconnect the power.

24. Safety Ground Connection Problems • Using copper media, such as UTP to connect grounds in different buildings or from different power panels can present an electrical shock hazard. • Different ground voltages can also severely damage delicate computer memory chips. • Minimize danger by using “one-hand rule”. • “One-hand Rule” - touch electrical equipment with only one hand (current will not pass across your body through your heart).

25. Safety Ground Connection Problems (cont.) • TIA/EIA 568A specifications permit the use of fiber-optic cable for backbone cabling. • Fiber does not conduct electricity, eliminating the shock hazard. • Fiber-optic cable is recommended for the backbone cabling between buildings, and also for linking wiring closets on different floors. • Fiber also beneficial in areas with lightning; it will not conduct lightning strike into the building.

26. Classifying Power Problems • Three connections on AC power: • Hot, neutral, and safety ground. • Power problems classified by which wires are affected. • Normal mode problems - between hot and neutral. • Common mode problems - between safety ground and either hot or neutral. • Common mode problems are more serious. • Normal mode problems are intercepted by the computer’s power supply, UPS, or AC line filter.

27. Typical Power Line Problems • Power disturbance is unwanted excess energy that is sent to electrical equipment. • Typical power disturbances include: • surges • sags • spikes • oscillations.

28. Typical Power Disturbances • Surge - 10% voltage increase for few secs. • Causes most hardware damage in devices, particularly hubs (sensitive low voltage lines). • Spike - a momentary >100% increase in voltage for 0.5 to 100 msecs (very short duration). • Sag - voltage drops below 80% of normal voltage for less than 1 sec. • Brownout - voltage below 80% of normal for greater than 1 sec. • Oscillations - AC voltage harmonics or noise, caused by excessively long wires.

29. Surges and Spikes • Causes: • Lightning. • Utility company switching operations. • Cycling equipment like HVAC, elevators, copy machines. • Problems: • Altered or loss data, lockups, damage to electrical devices or electronic chips. • Addressed with surge suppressors.

30. Sags and Brownouts • >20% decrease in line voltage (below 80% of normal). • Sags - short duration (<1sec). • Brownouts - longer duration (>1sec). • Can cause system crashes, and loss of data. • Solved by using an UPS (uninterruptible power supply).

31. Oscillations • Can cause excessive noise and erroneous data. • Solved by rewiring, to ensure clean and direct power and ground connections.

32. Effectiveness of Surge Suppressors • Individual surge suppressors - placed at wall outlet, close to networking device. • Most use a MOV, metal oxide varistor. • Capable of absorbing very large currents without damage (diverts currents to ground). • May not be very effective! • Diverting surges to ground avoids equipment damage, but can cause garbled data by changing ground voltage. • MOVs have limited lifetime; are not the best choice for network protection.

33. Best Surge Suppressor • Use large commercial grade surge suppressor at the power panel. • By diverting surges to ground at the power panel you minimize effect of changing ground potentials at your networking devices.

34. UPS - for problem of sags & brownouts • What devices should be supported by UPS? • Factors to consider: cost, importance of service, quality of ac line power. • Every network file server should have power backup. • Any critical devices (hubs, bridges, switches, routers) should be backed up. • UPS - for outages of short duration. • For extended periods of time, a generator is needed.

35. UPS Components • Batteries - storage of electrical energy (DC). • Larger batteries (greater storage capacity); UPS can supply backup power longer. • Battery Charger - keeps batteries fully charged when ac line power is available. • Power Inverter - converts DC voltage from batteries into AC line voltage.

36. UPS Operation • Basic UPS: • Monitors power line. • When line power is interrupted, UPS switches to inverter powered by batteries. • Transfer time - time UPS takes to switch over to inverter power (typically few milli-secs). • More expensive on-line UPS: • operates continuously on-line, supplying AC power from inverter. Batteries are charged from AC line voltage. • Transfer time is zero.

37. Basic UPS Block Diagram • S1 & S2 normally closed, S3 & S4 normally open. • When AC voltage is lost, the inverter switches on, S1 & S2 open, and S3 & S4 close.

38. On-line UPS Block Diagram • Operates continuously on-line. • Transfer time is zero.

39. Intelligent UPS • Has data communications capability. • Communicates with file server, informing it when battery power is running low. • Informs workstations when a power outage has occurred.

40. Summary • General design process. • Select technology (Ethernet, Token Ring, etc) • Layer 1 topology. • Layer 2 topology. • Layer 3 topology. • Network Design Issues • 1.Gather information. • 2.Analyze requirements. • 3.Identify resources and constraints. • Wiring closet specs - TIA/EIA 569. • Selecting wiring closets • MDF - secure, central location, close to POP.

41. Summary (cont.) • Horizontal and Backbone Cabling. • Cat 5 UTP for horizontal cabling. • Multi-mode fiber for backbone. • Electrical concerns: • AC line noise. • ESD. • Ground problems. • Power Line Problems. • Normal mode and common mode. • Surges, spikes, sags, brownouts, oscillations. • Surges & spikes addressed with surge supressors.

42. Summary (cont.) • MOV, metal-oxide varistor, found in individual surge suppressors. • Commercial grade surge suppressor, installed at the power panel, is best. • UPS • Basic and on-line. • Troubleshooting • work up through the OSI model. The End