Communication Network Management Flashcards
Computer network:
Computer network – an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areas
Local area network:
Local area network – networks that are small in geographic size spanning a room, floor, building, or campus
Metropolitan area network:
Metropolitan area network – networks that serve an area of 1 to 30 miles, approximately the size of a typical city
Wide area network:
Wide area network – a large network that encompasses parts of states, multiple states, countries, and the world
Personal area network:
Personal area network – a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices
Voice network:
Voice network – a network that transmits only telephone signals (almost extinct)
Data network:
Data network – a network that transmits voice and computer data (replacing voice networks)
Networks are composed of many devices, including:
–Workstations (computers, tablets, wireless phones, etc) –Servers –Network hubs and switches –Routers (LAN to WAN and WAN to WAN) –Telephone switching gear
LANs:
LANs use the eternet protocoal and therefore copper based wire primarily
MANs:
MANs are metro-area networks which use sonnet which is a ring typology they also use fiber optic cable.
WANs:
WANs (wide-area networks) use what’s known as a mesh. Essentially a big spider web of conducted metro areas that are composed of lcoal area networks. Kind of chaotic representation of the internet known as a mesh
Communications Networks – Basic Layouts
- Microcomputer-to-local area network
- Microcomputer-to-Internet
- Local area network-to-local area network
- Personal area network-to-workstation
- Local area network-to-metropolitan area network
- And others…
Microcomputer-to-Internet Layout
- Popular with home users and small businesses
- For some, a dial-up modem is used to connect user’s microcomputer to an Internet service provider
- Technologies such as DSL and cable modems are replacing modems
Local Area Network-to-Local Area Network Layout
- Found in systems that have two or more LANs and a need for them to intercommunicate
- A bridge-like device (such as a switch) is typically used to interconnect LANs
- Switch can filter frames
LAN-to-LAN Network Layout
If you don’t need to cross land segments the switch drops it. If it needs to cross the switch it lets it through.
The switch connects the two LAN segments.
Hub switches and routers heavy on the next exam.
They rely on a star typology* This diagram is a star typology
If one computer goes down then the other computers on the network are not affected.
Hub is very simple, mechanical, they don’t break down.
A switch is also very simple. A switch makes a decision based on a series of MAC addresses. A unique address burned into your network ethernet card on your computer or you wifi adaptor. It is a unique number unique to your particular card.
You can have networks like this that aren’t connected to the internet. ex: the military
on a single network traffic is moved btwn. computers based on MAC address (single LAN)
NOTE: IP doesn’t come into play unless things are being routed across the internet
Personal Area Network-to-Workstation Layout
Interconnects wireless devices such as PDAs, laptops and notebooks, and music playback devices
•Used over short distances such as a few meters
Personal Area Network-to Workstation Layout
Personal area network: Devices that you are carrying around can communicate with each other.
ex: Smartphone and a bluetooth makes you a personal area network.
Local Area Network-to-Metropolitan Area Network Layout
- Used to interconnect companies (usually their local area networks) to networks that encompass a city
- High-speed networks with redundant circuits
- Metro Ethernet is latest form of metropolitan LAN
Local Area Network-to-Metropolitan Area Network Layout (continued)
Each of these buildings will have its own local area network. Each of these are separate LANs but they are all connected so it is a metro-area network.
Metro Area networks are known as a sonet network. MAN=SONET and SONET=fiber optic cable (vs. ethernet).
Fiber optic ring is sonet. Fiber optic cable doesn’t transmit electricity it transmits light.
Fiber optic cable is the fastest BUS period bc it moves at the speed of light. Also the most expensive.
Sonet is a ring typology. (Less fault tolerant than a star typology.)
Local Area Network-to-Wide Area Network Layout
- One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network)
- A router is the typical device that performs LAN to WAN connections
- Routers are more complex devices than switches
Wide Area Network-to-Wide Area Network Layout
•High-speed routers and switches are used to connect one wide area network to another
•Thousands of wide area networks across North America, many interconnected via these routers and switches
-This is the internet. Comcast to Verizon to Brighthouse when you keep doing this you build up to the internet. Wide area network and the internet are interchangeable.
Sensor-to-Local Area Network Layout
Not all local area networks deal with microcomputer workstations
•Often found in industrial and laboratory environments
•Assembly lines and robotic controls depend heavily on sensor-based local area networks
Sensor-to-Local Area Network Layout (continued)
The construction plant has a local area network.
An assembly line that is automated.
Satellite and Microwave Layout
•Typically long distance wireless connections
•Many types of applications including long distance telephone, television, radio, long-haul data transfers, and wireless data services
•Typically expensive services but many companies offer competitive services and rates
•Newer shorter-distance services such as Wi-Max
-Like a dish network.
Cell Phone Layout:
- Constantly expanding market across the U.S. and world
- Third generation services available in many areas and under many types of plans with fourth generation services starting to appear
- Latest generation includes higher speed data transfers (100s to 1000s of kilobits per second)
Cell Phone Layout (continued)
There is one cell phone tower in a cell. Your phone communicates with one tower at once. Gets sent to the telephone company which passes the signal over land-lines.
Terminal/Microcomputer-to-Mainframe Computer Layout
- Predominant form in the 1960s and 1970s
- Still used in many types of businesses for data entry and data retrieval
- Few dumb terminals left today – most are microcomputers with terminal emulation card, a web browser and web interface, Telnet software, or a thin client
Terminal/Microcomputer-to-Mainframe Computer Layout (continued)
Terminal to mainframe. like the DMV this is a dumb terminal. Just a monitor and a keyboard and they are connected to a cable that connects to the mainframe. Mainframe stores massive amounts of data that can be used by multiple people simultaneously.
The two major categories of media include:
–Conducted media
–Wireless media
Twisted Pair Wire
- One or more pairs of single conductor wires that have been twisted around each other
- Twisted pair wire is classified by category. Twisted pair is currently Category 1 through Category 7, although Categories 1, 2 and 4 are nearly obsolete
- Twisting the wires helps to eliminate electromagnetic interference between the two wires
- Shielding can further help to eliminate interference
Twisted Pair Wire (continued)
Ethernet cable. If you cut it open there are eight wires twisted in pairs.
They are twisted bc it cancels out the noise.
Main Point: Reduce noise, insulate against the radiation
Twisted Pair Wire (speeds)
CAT1-CAT7:
kbps: kila bits per second 8 bits in a bite.
**There is a trade-off btwn. distance and speed but you don’t need to know the speeds.
Twisted Pair Summary
- Most common form of wire
- Relatively inexpensive
- Easy to install
- Carries high data rates (but not the highest)
- Can suffer from electromagnetic noise
- Can be easily wire-tapped
Coaxial Cable
Coax cable, One thicker wire.
Cable companies use coax bc it can support a wide frequency range. Telephone and internet over the same wire.
Coaxial Cable Summary
- A single wire surrounded by a braided shield
- Because of shielding, can carry a wide bandwidth of frequencies
- Thus is good with applications such as cable television
- Not as easy to install as twisted pair
- More expensive than twisted pair
Fiber-Optic Cable
- A thin glass cable approximately a little thicker than a human hair surrounded by a plastic coating and packaged into an insulated cable
- A photo diode or laser generates pulses of light which travel down the fiber optic cable and are received by a photo receptor
Fiber-Optic Cable (continued)
- Fiber-optic cable is susceptible to reflection (where the light source bounces around inside the cable) and refraction (where the light source passes out of the core and into the surrounding cladding)
- Thus, fiber-optic cable is not perfect either. Noise is still a potential problem
Fiber-Optic Cable Summary
- Fiber optic cable can carry the highest data rate for the longest distances
- Initial cost-wise, more expensive than twisted pair, but less than coaxial cable
- But when you consider the superiority of fiber, initial costs outweighed by capacities
- Need to fibers for a round-trip connection
- Not affected by electromagnetic noise and cannot be easily wiretapped, but still noise
Wireless Media
- Radio, satellite transmissions, and infrared light are all different forms of electromagnetic waves that are used to transmit data
- Technically speaking – in wireless transmissions, space is the medium
- Note in the following figure how each source occupies a different set of frequencies
Terrestrial Microwave Transmission
- Land-based, line-of-sight transmission
- Approximately 20-30 miles between towers
- Transmits data at hundreds of millions of bits per second
- Signals will not pass through solid objects
- Popular with telephone companies and business to business transmissions
Satellite Microwave Transmission
- Similar to terrestrial microwave except the signal travels from a ground station on earth to a satellite and back to another ground station
- Can also transmit signals from one satellite to another
- Satellites can be classified by how far out into orbit each one is (LEO, MEO, GEO, and HEO)
Satellite Microwave Transmission (continued)
low earth orbit usually used for satellite phones.
Cellular Telephones
- Wireless telephone service, also called mobile telephone, cell phone, and PCS
- To support multiple users in a metropolitan area (market), the market is broken into cells
- Each cell has its own transmission tower and set of assignable channels
Bluetooth
- Bluetooth is a specification for short-range, point-to-point or point-to-multipoint voice and data transfer
- Bluetooth can transmit through solid, non-metal objects
- Its typical link range is from 10 cm to 10 m, but can be extended to 100 m by increasing the power
Bluetooth (continued)
- Bluetooth will enable users to connect to a wide range of computing and telecommunication devices without the need of connecting cables
- Typical uses include phones, pagers, modems, LAN access devices, headsets, notebooks, desktop computers, and PDAs
Media Selection Criteria
- Cost
- Speed
- Distance and expandability
- Environment
- Security
Cost
•Different types of costs
–Initial cost – what does a particular type of medium cost to purchase? To install?
–Maintenance / support cost
•ROI (return on investment) – if one medium is cheaper to purchase and install but is not cost effective, where are the savings?
Speed
•Two different forms of speed:
–Propagation speed – the time to send the first bit across the medium
•This speed depends upon the medium
•Airwaves and fiber are speed of light
•Copper wire is two thirds the speed of light
–Data transfer speed – the time to transmit the rest of the bits in the message
•This speed is measured in bits per second
Expandability and Distance
- Certain media lend themselves more easily to expansion
* Don’t forget right-of-way issue for conducted media and line-of-sight for certain wireless media
Environment
•Many types of environments are hazardous to certain media
–Electromagnetic noise
–Scintillation (sun-spots) and movement
–Extreme environmental conditions
Security
•If data must be secure during transmission, it is important that the medium not be easy to tap
–Make the wire impervious to electromagnetic wiretapping
–Encrypt the signal going over the medium
-wireless communication is less secure than wired communication
Local Area Networks (LANs)
- A local area network is a communication network that interconnects a variety of data communicating devices within a small geographic area and broadcasts data at high data transfer rates
- Since the local area network first appeared in the 1970s, its use has become widespread in commercial and academic environments
Primary Function of Local Area Networks
•To provide access to hardware and software resources that will allow users to perform one or more of the following activities:
–File serving
•A large storage disk drive acts as a central storage repository
–Print serving
•Providing the authorization to access a particular printer, accept and queue print jobs, and providing a user access to the print queue to perform administrative duties
–Video transfers
•High speed LANs are capable of supporting video image and live video transfers
—Two ways to test different networks is to ask yourself if they are owned by the same people.
Advantages and Disadvantages of Local Area Networks
•Advantages
–Ability to share hardware and software resources
•Disadvantages
–Security
A Modern LAN – The Star-Wired Bus
•Logically operates as a bus, but physically looks like a star
•Star design is based on hub
–All workstations attach to hub
•Unshielded twisted pair usually used to connect workstation to hub
•Originally, hub takes incoming signal and immediately broadcasts it out all connected links
•Hubs can be interconnected to extend size of network
Star-Wired Bus (continued)
•Modular connectors and twisted pair make installation and maintenance of star-wired bus better than standard bus
•Hubs can be interconnected with twisted pair, coaxial cable, or fiber-optic cable
•Biggest disadvantage = when one station talks, everyone hears it
–This is called a shared network
•All devices are sharing the network medium
Medium Access Control Protocols
•How does a workstation get its data onto the LAN medium?
•A medium access control protocol is the software that allows workstations to “take turns” at transmitting data
•Two basic categories:
–Contention-based protocols
–Round-robin protocols
Contention-Based Protocols
•Essentially first-come, first-served
•Most common example is carrier sense multiple access with collision detection (CSMA/CD) (Carrier sense multiple access collision defense)
•If no one is transmitting, workstation can transmit
•If someone else is transmitting, workstation “backs off” and waits
•If two workstations transmit at same time, collision occurs
–When two workstations hear collision, they stop transmitting immediately
–Each workstation backs off a random amount of time and tries again
–Hopefully, both workstations do not try again at exact same time
•CSMA/CD is an example of a non-deterministic protocol
