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What is the function of a NIC (Network Interface Card)
are connectivity devices that enable a device (workstation, server,
printer, etc.) to receive and transmit data via the network media
How does the NIC function on the OSI model?
NICs function at two levels of the OSI model:
Data link layer assembles and disassembles data frames
Physical layer applies signals to the media (encoding)
and interprets signals received from the media(decoding)
What are factors in selecting a NIC?
• Protocol and access method (ex. Ethernet vs token ring)
• Network transmission speed (ex. 100 Mbps vs. 1 Gbps)
• Connector interface (ex. RJ-45 vs. BNC)
• Computer compatibility & bus interface (PCI vs. USB)
• Manufacturer including availability of software (device drivers)
Under what circumstances does a node require multiple NICs?
Recognize that wired and wireless connections, even on the same network, require separate NICs.
A separate NIC is required for each network to which a computer is attached.
Separate NIC functions would also be required if a node communicates via multiple physical level protocols (wired and wireless)
What is an on-board NIC and what is the related concept of the mother board?
are integrated into the computers main circuit board(a.k.a. mother board).
On-board NICs cannot be repaired or replaced; they can be
bypassed using the computers setup mechanism and other types
of NICs used in their place
allows devices such as disks, printers and NICs to access the computer's CPU and memory.
What is a PCIe?
In PC technology, the most common expansion board is the PCIe (Peripheral Component Interconnect Express). Full duplex transmission at speeds up to 1Gbps
What is a PCMCIA (Personal Computer Memory Card International Association) ?
are primarily used on notebook computers
• The ExpressCard 2.0 standard was delivered March 4, 2009
and has transfer speed 500 MB/s or 0.5 GB/s
What is USB?
is a standard interface used to connect multiple types of peripheral devices
• USB 1.1 limited to 12 Mbps
• USB 2.0 can reach speeds of 480 Mbps
• USB 3.0 supports gigabit data transfer speeds
What is a Device Driver?
Software that enables an attached device to communicate with a computer's operating system
In an operating system - Command Layer
command layer that allows users to enter commands directly to the O/S. Command layer tools can be GUI (graphical user interface) or command language (ex. at the command prompt).
In an operating system - Service layer
Service layer consists of a series of services that can be requested by applications and command layer
• Examples of services (in very high level and conceptual
terms) are reading disk, printing, and loading a program
In an operating system - Kernel layer
contains the code to communicate with and manage individual hardware devices
• Loading a device driver is essentially adding the ability
to communicate with and manage that device to the
What are connectivity devices?
are used to connect network devices and exchange data between these devices
What is a repeater?
are any device that puts signal back to full strength and thereby reset the distance limitations for a network function
What are the characteristics of a stand-alone repeater?
(single port in and single port out) are not used in modern networks
The basic function of a hub is to act as a multiport repeater that
repeats the signals to each connected node
What are the limitations of a hub?
Because hubs repeat signals to all connected devices, there can only be one transmission at a time
• If a second device would attempt to transmit, the signals
would collide causing a transmission failure
What are pots in relation to hubs?
connect each node on the hub using the appropriate type of connector (RJ-45 for Ethernet)
• Ethernet hubs are active devices that rebroadcast the signals
• Hubs are classified by the number of ports (ex. 8 port or 16
What are uplink ports?
is used to connect one hub to another in a daisy-chain or hierarchical fashion.
Not all hubs contain uplink ports and compatibility issues can occur when attempting to daisy chain different model hubs
• Networks consisting of daisy chained hubs are still limited
to one transmission at a time due to signals going to all
What is a bridge?
is to reduce network traffic by segmenting the network and isolating traffic to the appropriate segment
• A bridge learns the location of devices by MAC address and stores
this information in its filtering database
• Without a bridge, a hub based network is limited to one transmission at a time because hubs send signals to all attached devices
What is the function of the switch?
logically subdivides the network into smaller segments and limits traffic only to the destination node
What is the effect of using switches instead of hubs on a network?
• Reduces overall network traffic by eliminating the retransmission
created by collisions
• Performs the repeater function thereby extending segment lengths
What are the characteristics of the backbone to implement multiple switches.
• Unlike a hub network where any transmission would also
tie up the backbone, a switch network only sends
transmission to the backbone when the transmission is
intended for a device on another switch
• Because of how backbones function (send transmissions
to all connected devices) there can be only one
transmission between switches at a time
Characteristics of higher level switches when multiple are used.
• Major advance of using a switch instead of backbone is
that a switch with the appropriate circuitry would allow
multiple switches to be communicating an the same time
Cut-through mode switching
a switch will read the frame's header and decide where to forward the data before it receives the entire packet
• High speed switching
• Does not detect corrupted frames because the entire
frame (header, data and trailer) is needed before error
detection can occur
switch reads the entire data frame into its buffer and checks for errors before transmitting
What is a VLAN?
A network within a network that is logically defined by grouping its devices via switch ports
What is trunking?
refers to a single switch that can manage multiple VLANs.
The key to network design using VLANs is to place (if possible)
nodes that have a high level of communication with each other on
the same VLAN
What is a router?
is to integrate (connect) two or more networks
• Routers function by reading a packet's header information
(logical address in the network headers) and:
1. Determining the network on which the receiving node resides
2. Determining how to route (deliver the packet) to the receiving
automatically calculates the best path(s) between the routers and accumulates this information into a routing table
What is best path?
refers to the most efficient route from one node to another. Function of multiple factors including number of hops, link
availability, transmission speed and traffic on the link
(not routable protocols) determine the best path and are the basis of how routers function
What are the characteristics of RIP (Routing Information
Protocol) for IP and IPX) ?
Older routing protocol that only considers
number of hops and ignores link speed
and network traffic
• Maximum of 16 hops
• Routing tables are rebroadcast every 30
• High convergence time
OSPF (Open Shortest Path First) for IP
Attempts to determine the shortest path given link speed and traffic conditions
• Routing information is updated only
when a change or problem occurs
• Can coexist with RIP
EIGRP (Enhanced Interior Gateway Routing Protocol) for IP, IPX and Apple Talk
Fast and efficient protocol supported by Cisco routers
BGP (Border Gateway Protocol) for IP
Routing protocol for Internet backbones
• Complex protocol that can handle an
extremely large number of routes
What is a routing switch?
(a.k.a level-3 switch) combines router and switch functions in a single device
What is a gateway?
are combinations of networking hardware and software that
connect two dissimilar kinds of networks and allow them to
communicate with each other
• The gateway function occurs at multiple levels of the OSI model
• The gateway function can reside on many different types of
devices such as servers, microcomputers and mainframes
Examples of gateways:
• The Internet and the SMTP protocol are considered to be a
gateway that allows multiple e-mail post office and mail client
mechanisms to communicate with each other
• LAN gateways allow dissimilar networks to communicate (for
example, a gateway that allows a TCP/IP network to communicate
with an IPX/SPX network)
• Gateways exist that allow TCP/IP based PC networks to
communicate with mainframe computers that do not use TCP/IP
• Remember that a gateway is not a gateway if the word gateway is
preceded by the word default ... a default gateway is the TCP/IP
term for the default router that your network will use to
communicate with other networks
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