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CCNA Guide to Cisco Networking


Chapter 4: Network Topology And Network Design
Objectives
Discuss the different physical topologies
Describe various network architecture models
Determine which types of network media to use given a set of requirements
Understand horizontal cabling standards and wiring closets
Consider performance requirements and improvements for given situations
Objectives (continued)
Install a telecommunications connector
Wire a patch panel
Test network cable
Discuss LAN design
Describe the function that network-management tools perform on a network
Physical Topologies
Bus topology
Bus topology advantages
Inexpensive
Easy to design
Easy to implement
Bus topology disadvantages
Difficult to troubleshoot
Requires termination
Physical Topologies (continued)
Physical Topologies (continued)
Star topology
Star topology advantages
Break in one cable does not affect other devices (except up links)
Easy to locate problems
Easy to install
Does not require termination like bus topology
Star topology disadvantages
Center of star topology device (hub) can be expensive
Hub failure can affect entire topology
Amount of cable is expensive
Physical Topologies (continued)
Physical Topologies (continued)
Ring topology
Ring topology advantages
Prevents network collisions
Each station acts like a repeater
Ring topology disadvantages
Cable break can affect all devices
Temporarily shut down network to add a new station
Maintenance and monitoring is difficult
Influence Of The 5-4-3 Rule On Topologies
Influence Of The 5-4-3 Rule On Topologies (continued)
Network Architecture
IEEE 802
Logical Link Control (IEEE 802.2)
CSMA/CD (802.3)
Token Ring (802.5)
Wireless Technologies (802.11)
FDDI
Network Architecture (continued)
Media
Twisted-Pair cabling have the following in common
Copper based data transmission
Copper wires come in pairs
Each Wire of a pair is twisted around each other
Copper wires are enclosed in a sheath
All wire pairs are enclosed in a sheath
Media (continued)
Unshielded twisted-pair (UTP)
Advantages of UTP cable
Thin and flexible
Easy to install
Many modern buildings come with CAT 5 installed
Small size does not fill up wiring ducts fast
Inexpensive per foot
Disadvantages of UTP cable
Susceptible to interference
Cable length is 100 meters or 328 feet
Register Jacks (RJ)
RJ-45
Media (continued)
Media (continued)
Shielded twisted-pair (STP)
Advantages of STP cable
Greater protection from interference
Thin and flexible
Overall it is easy to install
Disadvantages of STP cable
Inexpensive per foot but more than UTP
STP must be grounded, problems exists if not grounded properly
More difficult to install than UTP
Small size but does fill up wiring ducts faster than UTP
Media (continued)
Coaxial cabling (Thicknet and Thinnet)
Advantages of coaxial cabling
Cable lengths are longer than UTP/STP
Less susceptible to interference than UTP
Hubs are not required, direct connection
Disadvantages of coaxial cabling
Thicknet is very difficult to install
More expensive than UTP
Difficult to troubleshoot
Media (continued)
Media (continued)
Media (continued)
Thinnet and Thicknet Connectors
RG-58 cabling
BNC
Attachment unit interface (AUI)
Barrel connectors
T-connectors
Terminators
Media (continued)
Media (continued)
Fiber-Optic cable
Advantages of fiber-optic cabling
Transmit data over long distances
Not susceptible to EMI
High transmission rates
Not susceptible to eavesdropping
Small cable size
Disadvantages of fiber-optic cabling
Expensive
Cable can be easily damaged during install making installations more difficult
Manual termination of ends is time consuming
Media (continued)
Media (continued)
Media (continued)
Signal Degradation
Three internal factors of attenuation
Resistance
Inductive reactance
Capacitive reactance
All three combined are called impedance
External signal degradation
Electromagnetic interference (EMI)
Radio frequency interference (RFI)
Signal Degradation (continued)
Reduce EMI/RFI
Do not place copper media next to
Fluorescent lights
Generators/motors
High-voltage electrical wire
Proper installation
Use quality cable
Use shielded cabling
Use repeaters to strengthen signal on long cable runs
Horizontal Cabling Standards
Twisted-pair or fiber-optic connections between wiring closets
Electronic Industries Alliance and Telecommunications Industry Association (EIA/TIA)
EIA/TIA-568
UTP horizontal cable run max: 90 meters
Horizontal cross connect max: 6 meters
Workstation to horizontal drop max: 3 meters
Horizontal Cabling Standards (continued)
Wiring Closets
Wiring closets
EIA/TIA-568 and EIA/TIA-569
Catchment area
Main distribution facility (MDF)
Intermediate distribution facility (IDF)
Wiring Closets (continued)
Proximity to the POP
Backbone
Sometimes called vertical cabling
EIA/TIA-568 specifies four different cables for backbone installations
100-ohm UTP
150-ohm STP
62.5/125-micron optical fiber
Single mode optical fiber
Wiring Closets (continued)
Wiring Closets (continued)
Performance Considerations
Connection speeds
Throughput
Utilization
Video or audio streaming/teleconferencing
Client/server applications
Host/terminal applications
Routing protocols
Routine maintenance tasks
Broadcast traffic
Ethernet collisions
Performance Considerations (continued)
Solutions for reducing network utilization
Segment network with switch, bridge, or router
Reduce the number of services provided on the network
Reduce the number of protocols on the network
Control access to bandwidth intensive applications or protocols
Performance Considerations (continued)
Calculating bandwidth and throughput
Transmission Time = file size/bandwidth
(T = Fs/Bw)
Throughput = file size/download time
(Tp = Fs/Dt)
Collisions and contention
Protocol analyzer
Resource placement
Performance Considerations (continued)
Installing Telecommunications Connectors
Installing Telecommunications Connectors (continued)
Installing Telecommunications Connectors (continued)
Patch Panel
Patch Panel (continued)
Patch Panel (continued)
Testing Cable
Cable testers
Wire map
Attenuation
Noise
Near end crosstalk (NEXT)
Distance measure
Baseline
Error rates
Collision rates
Network utilization
Testing Cable (continued)
Testing Cable (continued)
Testing Cable (continued)
Testing Cable (continued)
LAN Design Models
Two basic design strategies
Mesh
Hierarchical
Three-layer network model
Core
Distribution
Access layer
Two-layer network model
One-layer network model
LAN Design Models (continued)
LAN Design Models (continued)
LAN Design Models (continued)
Network Management Tools
Common tools
Cable testers
Network monitors
Network analyzers
Network monitors and network analyzers have in common
Agent
Manager
Administration system
Network Management Tools (continued)
Simple Network Management Protocol (SNMP)
Management information base (MIB)
Management tasks include
Network traffic monitoring
Automatic disconnection of problem nodes
Connection or disconnection of nodes based on time and/or date
Port isolation for testing purposes
Remote management capabilities
Common management information protocol (CMIP)
Network Management Tools (continued)
Network Management Tools (continued)
Network Management Tools (continued)
Summary
There are three basic physical LAN topologies: bus, star, and ring
These topologies, or layouts, typically involve cable, such as UTP, STP, coaxial, or fiber
The network architecture used on a LAN defines the physical topology, the media used, and the network access method
The most popular architectures are 10BaseT, 100baseTx and Token Ring
The IEEE has defined many standards that have influenced the way networks are designed and implemented
Summary (continued)
It has also defined different network access methods, which include CSMA/CD, token-passing, and CSMA/CA
One of the largest contributions from the IEEE is the 802 standard, which has subsets that define Ethernet (802.3),Token Ring (802.5), and wireless (802.11) network architectures
The 802.2 standard from the IEEE subdivided the OSI Data Link layer into two parts to make functional distinctions between the Media Access Control (MAC) sublayer and the Logical Link Control (LLC) sublayer
Ethernet is also known by its access method, CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
Summary (continued)
Token Ring uses an entirely different access method that is governed by token passing
The token, a small data frame, is passed from station to station around the ring, and a station can transmit only when it has the token
FDDI uses token-passing like Token Ring networks, but it is not subject to the same limitations
CSMA/CA is a network access method specified by the wireless LAN standard—802.11
This standard supports spread spectrum and infrared technologies for use on wireless LANs
Summary (continued)
CSMA/CA nodes listen before sending but determine when to send based on a random backoff factor
Before transmitting, CSMA/CA nodes send a notification that they are going to transmit
Installing media on a network is a multifaceted project
The layout of the network should be determined and documented
The number of wiring closets necessary, as well as their locations, must be determined
Summary (continued)
Standards for wiring closets, cable runs, distances, and cable must be considered when the routes are established
Obstructions and EMI/RFI must be overcome
After you install cable, you should test it for wiring, performance, and configuration problems
Cable testers can be used to determine if cables are wired correctly, if they meet length standards, and if they have attenuation or noise problems
When implementing a network, you can choose one of three hierarchical network models: one-layer, two-layer, or three-layer
Summary (continued)
The one-layer network model is the least complex, and is a flat structure where all components function at essentially the same level
The two-layer model separates the WAN from the rest of the internal network, which is usually done by adding routers with packet filters
In the three-layer model, the internal LANs are further divided by backbone cabling, which has additional routers with packet filters
In this model, the WAN connection is called the core layer, the backbone cabling and routers form the distribution layer, and the individual LANs function at the access layer
Summary (continued)
Network administrators use network monitors and network analyzers to manage a network on a daily basis
These tools can also be used to troubleshoot abnormal situations
The main difference between a network monitor and network analyzer is the level of service provided
The network analyzer typically offers more advanced features, such as SNMP querying, remote administration, and even automatic problem correction