Chapter 7 networks Flashcards
What is a WAN
wide area network, connecting LANs
How do LANs and WANs differ?
Layers 1 & 2 of the OSI model, access methods, topologies & media
How do WANs transmit data?
public communication networks vs LANs that are internal and owned by a company
What is a NSP
network service provider
How do organizations get dedicated lines?
they lease dedicated lines
How do dedicated lines differ?
capacity and transmission characteristics differ
What is a WAN link?
how WANS are interconnected.
How is a LAN topology different from a WAN topology?
same patterns, longer distances.
BUS topology
on a line, if one fails the remainder fail, does not grow (scale) well
Ring topology
in a ring, if one fails the direction of data travel can be reversed, only practical for 4-5 sites
Star topology
Single site is the central connection point, if a site fails only that site loses connectivity, shorter data paths
drawback of Star
if the central site is overwhelmed with data, the whole system will fail
Mesh topology
interconnected, no site will bring down the whole system. Very expensive
Partial mesh
the most important places are interconnected, and the lower level places have a star topology
Tiered topology
most flexible, easy to expand, hierarchical
PSTN?
Public Switched Telephone network. Sometimes POTS plain old telephone service
What is dial-up?
using the telephone lines, fixed connection time
What kind of line does dial-up use>
PSTN Public switched telephone.
Why is a modem usually necessary in dial up?
Because PSTN is analog and the modem switches signals to digital
What is PON
passive optical network
what is FTTP
Fiber to premises
What is FTTH
Fiber to home
What is OLT
Optical line terminal that splits a signal into 32 channels
Where does a fiber optic network end?
ONU optical network unit
What is ISDN?
Integrated Services Digital Network that transmits over PSTN , used to connect data and voice signals 1992
On which layers does ISDN work?
physical, data link, and transport layers
How is ISDN unique?
can carry two voice calls and one data line at one time, does not covert to analog
What are BRI & PRI?
the two types of ISDN available in N. America. Basic Rate Interface & Primary Rate Interface
What does BRI have?
two B channels and one D channel 2B+D
How much throughput does BRI Have?
Two 64 Kbps channels combine to make 128Kbps and 16-64 on the D channel
How is PRI better than BRI?
23 B channels, 64 Kbps D channel 23B+D = ma of 1.544 Mbps
What is T carrier technology?
for high data transmission
what is a T1 channel?
each circuit has 24 channels, each with 64 Kbps, so one T1 Channel has 1.544 Mbps speed
Why is shielded cable preferable for T1 lines?
the signal is digital, so the less interference the better
Why is fiber optic cable preferred.
b/c coper wires need repeaters every 6000 feet
What is a smart jack?
the end point for a t1 line with lights to show connectivity
What is CSU
channel service unit
what is DSU
data service unit
What does a CSU/DSU do?
terminates the digital signal, ensures connection integrity and converts the t-frames to frames the LAN understands
What does a DSU also have?
a multiplexer
what is terminal equipment?
equipment that is at the end of a T1 connection, usually router or layer 3 higher
What is DSL
Digital subscriber line
How does DSL use current cables?
goes over the telephone wires at a different frequency
What layer does DSL work at?
Physical layer
How many types of DSL are there
8
What is downstream/upstream
down loading to customer and uploading to service provider
What is asymmetrical DSL
you have more download power than upload power
What is different about HDSL and SDSL
they don’t use the telephone line, but use a wire that is inside the telephone wire (not typically used part of the same wire)
What is broadband cable?
Cable TV companies who use their coaxial cable lines for internet service
on what layer do cable modems operate?
the physical and data link layer
What must cable companies have upgraded to be able to offer this service?
HFC hybrid-fiber-coax cables to allow uploading not just downloading
What is the head end?
the cable companies central office, which then connects to the internet
What is BPL?
Broadband over power line.
Why was BPL not well used?
too much interference, interfered with radio signals, more repeaters needed
What is ATM?
Asynchronous transfer mode
On what layer does ATM Work?
the data link layer, packet size is fixed 53 byte, so network performance is predictable.
What is SONET
synchronous optical network
What are the 4 benefits of SONET?
- integrates with other WAN technology, 2. fast data transfers, 3. uses time.clock for transmissions, 4. high fault tollerance
What is SONET known as in other countries?
SDH Synchronous Digital Hierarchy
How does SONETS double ring topology help
Self-Healing: if one ring goes down, it automatically switches to the other ring.
How is the data rate of SONET shown
OC optical carrier level
