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