The following are notes from Computer Networks written by Tanenbaum 5th edition.
- There are two types of transmission technology in wide use
- broadcast links
- shared by all machines on network
- one machine sends to all machines, address in packet specifies recipient
- can address to all instead of specified machine
- multicasting
- point to point links
- connect individual pairs of machines
- transmit packets, short messages from one to another
- packet may visit multiple machines before arrival
- one sender one receiver called unicasting
- Classify Networks by scale, distance is important,
- 1m - personal area network
- 10 m -> 1km - local area network
- 10km - Metropolitan area network
- 100km-100km - Wide area network
- 10,000km - Internet (Planet wide)
Personal Area Networks
- PANs(Personal area Networks)
- computer to peripherals
- Bluetooth
- wireless connections
- i.e. music player connects to car
- Master-slave paradigm
- system unit (PC) is master
- master tells slaves
- what addresses to use
- when to broadcast
- length of transmission
- frequency used
- Pacemakers and other medical devices
- user operated remote control
Local Area Networks
- LAN(Local Area Network)
- Privately owned network
- connects personal computers and consumer electronics
- used by companies - Enterprise Networks
- (AP)Access Point
- wireless router
- base station
- relays packets between computers and internet
- IEEE 802.11
- Wired Lans
- Ethernet, built from point to point links
- switched ethernet
- computer speaks to internet protocol
- connects to a box called a switch with point to point links
- switch has multiple ports
- packet relay
- Build larger lans, switches plugged into each other using ports
- use protocols and path finding to reach destination
- Divide a large physical LAN into smaller logical lans
- VLAN (Virtual Lan)
- each port is tagged with "color"
- color is a subgroup of LAN
- i.e. red for finance, green for engineering, broadcast on red will not be seen on green
- classic Ethernet
- Broadcast Networks can be divided into static and dynamic designs based on channel allocation
- Centralized, single entity, base station decides priority in sending
- decentralized each machine decides when and how to send
- Home Networks
- Networked devices have to be easy to install
- foolproof in operation
- due to low consumer tolerance
- low price
- expand reach of network
- security
- Power-line networks
- broadcast from devices that plug into outlets
Metropolitan Area Networks
- MAN(Metropolitan Area Network)
- covers a city
- i.e. cable television networks
- At first these were local ad hoc systems
- Internet caused changes to cable TV network, instead of distribution became MAN
- cable headend
- feed in television signal
- internet
- WiMAX
Wide Area Networks
- WAN(Wide Area Network)
- large geographic area
- i.e. country/continent
- Composed of
- Transmission lines - to move bits between machines
- Switching elements - computers that connect two or more transmission lines
- Offices contain host computers
- connection of hosts is subnet
- carries messages from host to host
- originally only meant collection of routers and lines
- now sometimes definition related to network addressing
- members can be
- individual computers
- LANs
- Owned by different people
- Routers connect different kinds of networking technology
- internetworks
- composite networks made up of more than one network
- VPN(Virtual Private Network)
- company connects offices through internet alone
- Network service provider
- subnet operator
- ISP(Internet Service Provider)
- ISP network
- Routing Algorithm
- how network makes decisions on which path to use
- Forwarding algorithm
- how router makes decision on where to send packet next
- WANs sometime use wireless technology heavily to satellites
- computers hear from satellites
- inherently broadcast
- i.e. cellphone
- first generation analog voice
- second generation digital for voice
- third generation is digital for voice and data
Internetworks
- Internet
- connection of different frequently incompatible networks
- uses ISP networks to connect private networks together
- gateways
- provides a translation for hardware and software between networks and protocols
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