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72 Cards in this Set

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Define "physical topology"; What does it not specify?
the basic physical layout of a network; it does not specify devices, connectivity methods, or addresses on the network
What are the 3 fundamental geometric shapes of Physical Topologies?
bus, ring, and star
Define "bus topology"
a single cable connecting all nodes on a network, without intervening connectivity devices
What is required on a bus network to prevent "signal bounce"?
each end requires a 50-ohm resistor, called a "terminator". These stop signals after they have reached their destination.
Define "ring topology"
each node is connected to the two nearest nodes; the entire network forms a circle.
How is data transmitted in a ring topology?
data is transmitted in one direction around the ring. Each workstation handles packets addressed to it, then forwards the rest to the next workstation
Define "star topology"
each node is connected through a central device (such as a hub). The hub retransmits the data to the rest of the network segment where the destination node can pick it up
What is the stability advantage of a star topology?
any single physical wire on a star network connects only two devices, so a cabling problem will affect only two nodes
What is the most common kind of topology for a large LAN?
a hybrid of more than one simple physical topology
Define "star-wired ring" topology
a network that uses the physical layout of a star and the token-passing data transmission method
Give an example of a star-wired ring
Token Ring (IEEE 802.5)
Define "star-wired bus" topology
workstations are connected in a star; each star connects to a hub; the hubs are networked via a single bus
What are advantages of star-wired bus topology?
it allows you to cover longer distances and easily interconnect or isolate different network segments
What are disadvantages of star-wired bus topology?
it is more expensive than the star or bus topology alone
Give an example of a star-wired bus
star-wired bus topology commonly forms the basis for Ethernet and Fast Ethernet networks
Describe "daisy-chaining"
hubs that service star-wired bus or star-wired ring topologies can be daisy-chained to form a more complex hybrid topology
What hybrid topology designates hubs at different layers to perform different functions?
a hierarchical hybrid topology
What is "the backbone"?
cabling that connects each hub, or different levels of the hierarchy
What is a backbone sometimes called?
“a network of networks”
Why do backbones usually transmit data at faster speeds than workstations?
because backbones handle larger loads
What is the simplest kind of backbone?
a serial backbone
What does a serial backbone consist of?
two or more hubs connected to each other by a single cable
What does a distributed backbone consist of?
a number of hubs connected to a series of central hubs or routers in a hierarchy
What is a collapsed backbone topology?
the collapsed backbone topology uses a router or switch as the single central connection point for multiple subnetworks
What is the most robust enterprise-wide topology?
a parallel backbone
What does a parallel backbone consist of?
it is a variation of the collapsed backbone topology, with more than one connection from the central router or switch to each network segment
What does a mesh network consist of?
routers interconnected with other routers so that at least two pathways connect each node
Name 5 types of WAN topology
peer-to-peer, star, ring, mesh, tiered
Give 3 reasons for the greater complexity in WAN topologies versus LAN
1) the distance they must cover; 2) the higher number of users they serve; 3) and heavier traffic they often handle
What is a peer-to-peer WAN topology?
a WAN with single interconnection points for each location
What are the 2 conditions for peer-to-peer WAN topology to be appropriate?
1) organization has only a few sites; 2) access to dedicated circuits
What is a star WAN topology?
A single site acts as the central connection point for several other sites
Why is a star WAN topology more reliable?
there are several routes for data to follow between any two sites
What is a ring WAN topology?
a WAN where each site is connected to two other sites so that the entire WAN forms a ring pattern
What is a mesh WAN topology?
a WAN with many directly interconnected nodes, analogous to an enterprise-wide mesh
What is the advantage of a mesh WAN topology?
mesh WANs are the most fault-tolerant configuration
What is the disadvantage of a mesh WAN topology?
connecting every node on a WAN is very expensive
What is a tiered WAN topology?
a WAN with sites connected in star or ring formations, interconnected at different levels, with the interconnection points organized in layers
Network logical topologies are also called?
transmission methods
Define "Network Logical Topologies"
a set of rules specifying how data are packaged and transmitted over network media
Name 5 network logical topologies, and the most popular
Token Ring, LocalTalk, FDDI, ATM, and the most popular, Ethernet
What manages the filtering and forwarding of packets between nodes in a networks logical topology?
switching
What are the 3 types of switching?
circuit switching, message switching, packet switching
When and by whom was Ethernet developed?
by Xerox in the 1970s
What other companies worked on Ethernet?
Digital Equipment Corporation and Intel, in addition to Xerox
Name 3 advantages to Ethernet
runs on a variety of network media; offers excellent throughput; has a reasonable cost
What network access method does Ethernet use?
Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Ethernet networks at any speed of any frame type use CSMA/CD
Why do Ethernet networks suffer decreased performance as the number of nodes increase?
collisions increase
What device separates a network segment into smaller segments?
a switch
What is the relationship between network segments?
each is independent and supports its own traffic
How does switched Ethernet increase the effective bandwidth of a network segment?
fewer nodes compete for the same time on the transmission media
What are the 4 types of Ethernet data frames?
Ethernet IEEE 802.3, Novell Proprietary 802.3 ("raw"), Ethernet II, and IEEE 802.3 SNAP
How do the Ethernet frame types differ?
each differs slightly in the way it codes and decodes data frames
What speeds do Token Ring networks run at?
4Mbps, 16Mbps, 100Mbps, and 1Gbps
Which IEEE specification defines Token Ring?
IEEE 802.5
What is a disadvantage of Token Ring?
generally more expensive than Ethernet
What is an advantage of Token Ring?
high reliability and fault tolerance
What network logical topology uses token-passing and a star-ring hybrid physical topology?
Token Ring
What device do Token Ring nodes use to connect to the network?
Multistation Access Units (MAUs)
What type of cabling do Token Ring networks use?
shielded or unshielded twisted-pair cabling
What does "FDDI" stand for?
Fiber Distributed Data Interface
What standards organizations specified FDDI?
ANSI (in the mid-1980s), later refined by ISO
What transmission medium does FDDI use?
dual fiber-optic ring
What is the maximum speed of FDDI?
100 Mbps
What are advantages of FDDI?
its dual fiber rings offer greater reliability and security than twisted-pair copper wire
What is the disadvantage of FDDI?
much greater expense versus Fast Ethernet
What is the maximum ATM data transfer rate?
9953 Mbps
What is the type, name, and layout of an ATM frame?
fixed packet size
called a "cell"
48 bytes of data with 5-byte header
What is the advantage of ATM's fixed packet size?
predictable traffic patterns and better bandwidth control
What does "ATM" stand for?
Asynchronous Transfer Mode
Contrast ATM and Ethernet data transmission
an ATM switch establishes a path before the network transmits data; Ethernet transmits first and lets the routers and switches find a path
ATM relies on what to make logical point-to-point connections?
virtual circuits

these require ATM switches to determine the optimal path between sender and receiver