IT 300 GMU Final

Types of Lans 4

Bus, Ring, Partial Mesh, Star

Physical vs logical topology?

Logical topology - Shows the method or order of how devices are connected

Physical topology - differ form logical, shows physical location

MAC? Define and what is it?

Medium Access Control

Process where devices on the network can access the shared medium

Centralized control?

A central device determines when a station on the local network can access the medium.

This is done through token/polling

Failure of the central unit destroys the whole network

Centralized control - Deterministic access control?

node that is given full access to transmit data without collisions

Decentralized Control?

Each station of the LAN assumes responsibility for access to that network. (Ethernet is used)

Decentralized control - Non-deterministic access control?

no guarantees that data wont collide

CSMA/CD? What is it?

a common MAC method that is used in HDX Ethernet LANS

Whats does each portion of the CS-MA-CD in CSMA/CD mean?

CS - Carrier sense = each station always listens to traffic on the network

MA - Multiple Access = Numerous stations hare a base band medium

CD - Collision detect = If two station on the network transmit data at the exact same time, the frames will collide, this detects that the event occurs.

CSMA/CD - Jamming Signal?

If any node on the network detects that a data collision has occurred, it sends out a signal that tells all devices to wait for a period of time before sending any info again.

Wireless LANS use what type of technology?

IEEE 802.11 and CSMA/CA and HDX

How does CSMA/CA work? 3 parts

ACKnowledgement (ACK) - Checks the medium for availability to send.

Request to send (RTS) - packet sent by the transmitter with the source/destination of the transmitting - if this is clear...

Clear to Send (CTS) - Destination responds with CTS packet.

Shared vs switched LANS?

Shared - use CSMA/CD often HDX but could be FDX and often use a hub.

Switched - Often use a switch, FDX, no collisions so no CSMA/CD required.

Ethernet 802.3?

Describes layers 1 and 2 of OSI

uses CD and UTP, Coax , fiber optic

LLC? (Logical Link Layer)

Handles the communication between upper and lower layers

Adds control info to IP

MAC? (Media Access Control)

Data encapsulation - framing, addressing, error detection

Places frames on the media

connection based so CD or CA

100Base-T cable?

Cat 5e over

HDX - two wire pairs

FDX - four wire pairs

1000Base-T cable?

cat 5e

FDX - uses ALL four wire pairs all the time

10G base-T

10Gbps over a cat 6/7 cable

Switched Ethernet - FDX all four pairs

split up by 3Gbps + 3Gbps + 3 Gbps + 3Gbps

WLAN - CM?

Control Module - allows for wireless devices to connect to the ethernet switch

regulates access

RF Based IEEE 802.11

Layer 1 and 2

workstations fitted with radio transceiver and antenna

access points in central location

DSSS for bandwidth

OFDM

Uses CDMA/CA

Bands where in the 2.4 and 5ghz range unlicensed

Frame exchange protocol? / Whats the flaw?

Works if ALL nodes are in reception of each other.

For example, if A wants to send a message to B, A first listens for an empty medium, then C sees that the network is busy and waits. B sends an ACK request. C sees this and after medium is clear, is allowed to transmit data

If a network is just out of range from the reception point, then it can't listen to the conversation and might try and send data when the path is not clear.

Four Frame exchange protocol?

A sends an RTS to B. C, which is not in the reception of A hears B's CTS and waits. Once A sends the data, B sneds an ACK and C knows its not clear to send info again.

IEEE 802.11a?

Used 54Mbps speed in the 5GHZ range but never actually got that range.

Used COFDM

IEEE 802.11b?

Used very widely

2.4Ghz single band max of 11Mbps

IEEE 802.11g

2003,

2.4GHz dual band

Backwards comp with b

24Mbps

IEEE 802.11n

2009

comp with b and g

max of 600Mbps

2.4GHz or 5GHz band used

IEEE 802.11ac

2013

1Gbps with MIMO technology

5GHz band

M'ary modulation

IEEE 802.3af PoE

Power over ethernet

provides data and electrical power to low powered devices with cat 5, 5e and 6

802.15 WPAN?

Wireless personal Area Network

short range communication with low cost and energy for long battery life

Bluetooth?

protocol that addresses interconnection of many devices wirelessly - short distances

Bluetooth characteristics? 3

uses FHSS to minimize collision

operates at 2.4GHz

point to point or point to multiple point

Bluetooth - piconet?

8 possible devices can be linked togeather. 7 devices would be the slave and 1 master

Bluetooth - scatternet?

network of multiple piconets

a device that is in multiple piconets is a?

bridge device and can forward info

Bluetooth - piconet packets?

made of a access code, header and payload

access code is made by the master and is unique to a piconet.

Bluetooth - ZigBee? (IEEE 802.15.4)

simple, flexible inexpensive bluetooth-like protocol.

PSTN? (Public Switched Telephone Network)

Originally an analog voice network

Now a digital network used to connect networks ex. Internet

POTS?

Plain Old Telephone Network

WAN? (Wide Area Network)

Connects small networks like LANs and MANs together

1876? Who did what?

Alexander Graham Bell demonstrates the first telephone

1885?

AT&T makes a long distance telephone network

1913?

The Kingsbury Agreement

- AT&T agrees to stop by other telcos and Wilson drops anti-trust proceedings

- Seen as a regulated monopoly from 1913-1984

FCC established in?`

1934

Hush-a-phone decision?

1956 allowed devices not made by AT&T to be connected to telephones

1968?

Carterfone decision removed many restrictions to force others to use AT&T

FCC Telecommunication Act of...?`

1996 - allowed new companies to enter the market. Internet was at the center of this act.

ITU-T? (Internationl Telecommunication Union)

Regulation of the world networks by the UN

ISO? (International Organization for Standardization)

Non government

comprises national-level standards from 156 countries

large influence over standards

NPA? (Numbering Plan Administration)

Enables phones to connect to eachother - This is how we assign phone numbers.

15 digit max plus 1 to 3 digit country code

PSTN - Central Office?

Facility where local loops connect to the PSTN infrastructure

PSTN - IGF? (International Gateway Facilities)

Allows international carriers to connect

PDN? (Public Data Network)

network like internet provided to the user by the carrier.

Supports digital voice using PCM 64kbps

Traditional PSTN?

4kHz analog voice signal

VoIP?

digital voice stream using upper level protocols. Used over the internet

Permanent Virtual Circuit vs Switched Virtual Circuit?

Permanent - physical routing of the virtual circuit is always the same.

Switched - virtual circuit assigned to the users for the duration of the call. Like Circuit switched but not physical

CPE? (Customer Premises Equipment)

equipment on the customers end. like a cell phone or computer. PBX - switch owned by the user

Demarcation Point?

point where something becomes a customer side equipment and part of the carrier network

CCS? (Common Channel Signaling)

Sub-network that does signaling and controlling

two types

In-band signaling and controlling

Out-of-Band Signaling and controlling

In-Band signaling and controlling?

Functions take place on the same physical path as a conversation. This can be disruptive. Not really ever used.

Out-of-Band signaling and controlling?

Takes place outside of the conversation physical path. No interference with the conversation.

T-Carrier?

digital - leased line service that uses TDM and multiplexing

1.544 Mbps

Can now support voice, data and video

Channelized T-1 vs Unchannelized T1?

Channelized - supports 24 DS0 64Kbps voice channels

Unchannelized T1 - application data not stuck to 65kbps

T-1 frame?

Frame used in channelized T-1 that is split into 24 bytes.

SONET? (Synchronous Optical Network)

NA standard for broadband on a SMF network.

Uses a central timing clock

SONET vs SDH? (Synchronous Digital Hierarchy)

SDH - international version of SONET

OC? (Optical Carrier)

what SONET and SDH are based on

Based in levels like OC-1, OC-2

STS? (Synchronous Transport Signal)

Electrical equivalent of the SONET OC-1

STM in SDH

WDM? (Wavelength Division Multiplexing)

multiplexing many colors of light which allows more than one channel on a single fiber

DWDM? (Dense WDM)

even more colors on the wavelength than WDM

ATM? (Asynchronous Transfer mode)

fast cell switched tech that is still offered.

Has a predictable latency so it can provide better QOS

uses SONET or SDH

FR? (Frame Relay)

Cheaper alternative to T-1 and T-3

Variable sized data

connection oriented on the Data link layer

Shared Ethernet?

Traditional LAN so it can experience some data collision

Switched Ethernet?

Reduces data collision for HDX, no data collision with FDX

Carrier Ethernet?

native ethernet for layer 2. used to support MAN and WAN.

PBX? (Private Branch Exchange)

user owned and controlled switch.

often used by large organizations

Requires technicians

Centrex?

Similar to PBX, but you pay the ISP to have the switch and provide the maintenance.

ACDs? (Automatic Call Distributor)

PBX's that switch incoming calls to a call center

DTE vs DCE?

DTE is a computer, server, something that receives a transmission

DCE is a switch or something that transmits data

Some devices can be both like a router

What does a crossover cable do?

Allows devices that are both the same type (DCE or DTE) to connect and communicate by having the TX of one connect to the RX of the other and vice versa.

Four methods to access high data rates?

DSL, CATV, PONS, WLL

xDSL? (Generic Digital Subscriber line)

group of digital access tech

ADSL? (Asymmetric DSL)

Uses the unused frequency on the Bandwidth of a UTP local loop.

Gets is name because more bandwidth is for the downstream(cust) than to the upstream(net).

ADSL uses what type of modulation?

Uses DMT and type of OFDM where the waves don't cross each other but are finely places next to each other.

Several conditions must be met to use ADSL on a network, what are they? (4)

Loop length must be within 18,000 feet to the central office (85% of Americans)

Loading Coils - passive devices to filter frequencies must be removed

Electronics like amplifiers need to be removed

Splices and mixed gauges cause echoes and signal reflection

Near-End Crosstalk vs Far-End Crosstalk?

Near-End Crosstalk - When the outgoing stream is at the best strength but the incoming is at the lowest stength.

Signals can couple here

Far-End Crosstalk - Occurs near the customer. Not a huge issue except for big companies.

CATV? (Cable Television or Community Antenna Television)

supports two-way communication, distributes TV programming

DOCSIS? (Data Over Cable Service Interface Specification)

support for data transmission - modems using this include TDMA and QAM

PON? (Passive Optical Network)

Fiber optic local loop network

does have any active electronics

uses inexpensive optical spliters to deliver signal

SMF

WLL? (Wireless local loop)

local loop connectivity with RF or IR

Good:

Quick deployment

easy reconfig

Bad:

limited distance

LOS

Security

WiMAX? two types and some characteristics

Split into two types:

802.11d and 802.11e this is a 4g

Last mile solution, licensed band

NAP? (Network Access Point)

Originally name of the Internet Exchange points

IXP? (Internet Exchange Point)

Allows different ISP's to exchange internet traffic between networks through mutual peering agreements.

Layer 1 and 2 vs layer 3?

Layer 1 and 2 can be specific to an Org or service provider.

Layer 3 is end to end over the internet.

The IP protocol is what kind of connection? What must it contain? Whats it made from? Any guarantee?

Connection-less protocol

A source and destination

Made of packets

No guarantee of sequence or even arrival.

ARP? (Address Resolution Protocol)

This maps the IP address to the MAC player.

This broadcasts the IP address to all devices on a local network and the one with the correct IP accepts the packet

DHCP? (Dynamic Host Configuration Protocol)

Assigns IP address and subnet mask to a device.

Stores a pool of IP addresses.

NAT? (Network Address Translation protocol)

Translates a private IP address to a public one when sending outgoing messages.

Can fall short if a message has security functions and the integrity is broken

ICMP? (Internet Control Message Protocol)

Provides feedback to routers with issues during the transfer of packets.

Not allowed within a network

TCP? (Transmission Control Protocol)

Three way handshake, provides error control and flow control