All Ch. Key Terms.txt

A digital network used to send data between computers

1. Collection of computers, printers, routers, switches and other devices that can communicate with each other over some transmission medium.

2. Command that assigns a NIC-based address to which the router is directly connected.

The network that combines enterprise networks, individual users, and ISPs into a single global IP network.

To transfer data from the computer functioning as a server to the client computer you are using

Real-time communication between two or more people through text.

Ex: MSN, AIM, YahooMessanger....

Events or signals that show output as fas as possible, or as they happen.

Website where entries are made in journal style, created by a user who is in control of the style , visitors may leave comments, aka: weblog.

Digital media file(s) that are distributed over the Internet using syndication feeds, for playback on portable media players and PCs.

A website that lets visitors add, edit, and delete content typically anonymously.

A tool that helps people communicate & collaborate

• Examples:
• Wikidocs, Google Docs, Microsoft Sharepoint....

A drag-and-drop network simulator developed by Cisco to design, configure, and troubleshoot network equipment within a controlled simulated program environment.

A corporate system such as a website that is explicitly used by internal employees. Can be accessed internally or remotely.

Part of a company's intranet that is extended to users outside the company (that is, normally over the Internet).

Allows communication without needing physical connectivity.

Including cell phones, PDAs, wireless access points, wireless NICs

An internationally recognized definition of technical specifications that ensure worldwide consistency.

Binary digit used in the binary numbering system

Digits are units of information storage and communication in computing.

Each bit is either a 1 or 0

A numbering system characterized by 1s & 0s

The origin of the PDU. This can be a process, a host, or a node, depending on the layer to which you are referring.

A network device, typically connected to a range of LAN & WAN interfaces, that forwards packets based on the destination IP addresses.

A network device that accesses a service on another computer remotely by accessing the network.

Internet Protocol

Network layer protocol in TCP/IP stack for a connectionless internetwork servic. Provides features for Addressing, type-of-service specification, fragmentation, reassembly and security.

RFC 791

Transmission Control Protocol

Layer 4 protocol of the TCP/IP model

Lets applications guarantee delivery of data across a network.

A form of network that aggregates various forms of traffic such as voice, video and data on eeh same network infrastructure.

&/OR

Process by which routers recognize that something has occurred that changes some of the routers routes and reacts to the event to find another best route.

The design on networks that can continue to operate without interruption in the case of hardware, software, or communication failures.

A network architecture designed to eliminate network downtime caused by a single point of failure.

The ability of a protocol, system, or component to be modified to fit a new need.

A combination of many IP subnets and networks, as created by building a network using routers.

Used to avoid confusion with the term network since an internetwork can include several IP networks.

[Generically]

refers to end-user data along with networking headers and trailers that are transmitted through a network.

[Specifically]

Is end-user data, along with network or Internet layer headers and an higher layer headers, but no lower-layer headers or trailers.

Quality of Service

Control mechanism that can provide different priorities to different users of data flows, or guarantee a certain level of performance to a data flow in accordance with requests from the application program.

Networking measurement of the speed of bits that can be transmitted over a particular link. It is the amount of data that can be transmitted in a certain amount of time. For digital bandwidth, it is usually expressed in bits per second (bps).

A routing feature in which frames in an interface output queue are prioritized based on various characteristics such as packet size and interface type.

A process used to verify the identity of a person or process.

Any combination of hardware device and/or software application designed to protect network devices from outside network users and/or malicious applications and files.

A system or network design characterized by one or more major components that are required to maintain operation.

A communication path over a medium used to transport information from a sender to a receiver.

Multiple channels can be multiplexed over a single cable.

TCP process of taking a large chunk of data and breaking it into small-enough pieces to fit within a TCP segment w/o breaking any rules about the max amount of data allowed in each segment.

Process where multiple digital data streams are combined into one signal.

Ethernet Layer 2 device

Requires electrical signal in one port, interprets the bits, and makes a filtering or forwarding decision about the frame.

• Forwards a regenerated signal.
• Has many ports (RJ-45)

A device such as a desktop or mobile device that is used by an end user.

Network device that has an IPv4 address assigned to it to communicate over a network.

A network device that accesses a service on another computer remotely by accessing the network

IPv4 address of a network host - Network Layer Address

Device that connects end devices to the network or interconnects different networks.

Ex: Routers

Data link layer address

Ex: MAC address.

To change energy levels transmitted over some networking medium to transmit bits over that medium.

Local-Area Network

Network created for devices located in a limited geographic area, through which the company owning the LAN has the right to run cables.

Internet Service Provider

Company that helps create the internet by providing connectivity to enterprises and individuals,

as well as interconnecting to other ISPs to create connectivity to all other ISPs.

Written specification that defines what tasks a service or device should perform.

Defines messages (headers), rules, process by which the messages are used to achieve some stated purpose.

Delineation of networking protocols and standards into different categories, called layers, along with definitions of which sets of standards and protocols need to be implemented to create products that can be used to create a working network.

Institute of Electrical and Electronics Engineers

International, nonprofit organization for the advancement of technology related to electricity.

Maintains standards defining many LAN protocols.

Internet Engineering Task Force

Standards body responsible for the development and approval of TCP/IP standards.

Model that consists of various layers that enable the development and explanation of technology to be done on a modular basis.

Allows interoperability among different technologies among the different layers.

Transmission Control Protocol/Internet Protocol

Network model defined by the IETF that has been implemented on most computers and network devices in the world.

Process in which a device adds networking headers and trailers to data from an application for the eventual transmission of the data over the medium.

Process in which the end-device receives data from a transmission and examines the headers and trailers at each stack layer

aka de-encapsulation

Protocol Data Unit

Generic term from OSI that refers to the data, headers, and trailers about which a particular networking layer is concerned.

1. Collision domain that is a section of a LAN that is bound by bridges, routers, or switches.

2. LAN w/ bus topology it is a continuous electrical circuit that is often connected w/ repeaters.

3. W/ TCP it serves as a verb referring to the work TCP does to accept a large piece of data from an end device breaking it into smaller pieces. OR as a noun it refers to one of those smaller pieces of data.

Layer 2 PDU that has been encoded by a data link layer protocol for digital transmission.

• Ex:
• Ethernet frames
• PPP frames

Open System Interconnection

International standardization program created by ISO and ITU-T to develop standards for data networking that facilitate multivendor equipment interoperability.

International Organization for Standardization

International standards body that defines many networking standards. Also, the standards body that created the OSI model.

multiple meanings in networking

On a Ethernet hub, switch = interface (physical connector in the device you plug the cable into)

Application layer protocol data unit.

The device that is originating the PDU.

Domain Name System

Internet-wide system by which hierarchical set of DNS servers collectively hold all the name-IP address mappings, with DNS servers referring users tot he correct DNS server to successfully resolve a DNS name.

Requests for Comments

Series of documents and memoranda encompassing new research, innovations, and methodologies applicable to Internet technologies.

Reference for how technologies should work.

The structure and order of words in a computer language.

A related set of communications transactions between two or more network devices.

Network device that accesses a service on another computer remotely by accessing the network.

Can refer to computer hardware that is to be used by multiple concurrent users.

Can refer to computer software that provides services to many users.

Example: consists of web server software running on some computer.

Computer program that runs in the background and is usually initiated as a process.

Ofter support server processes.

A host or node that participates in some form of a group.

Peers that participate jointly in the same activity, each having a server and client component.

A plan, design, or program of action to be followed.

Sometimes an addressing plan is called an addressing scheme.

32-bit number written in dotted decimal notation, used by the IP to uniquely identify an interface connected to an IP network.

Also used as a destination address in an IP header to allow routing.

Or as a source address to allow a computer to receive a packet and to know which IP address to send a response to.

Name defined by DNS that uniquely identifies a computer in the Internet.

Corresponds with the IP address

ex: www.cisco.com ip address

A dotted decimal number defined by the IPv4 protocol to represent a network or subnet.

REpresents the network that hosts reside in.

AKA a network number or network ID

DNS data records.

Precise format is defined in RFC 1035.

Important fields: name, class, type, and data.

Client end of the DNS client-server mechanism.

Creates queries sent across a network to name a server, interprets responses, and returns information to the requesting programs.

A part of a computer network that every device communicates with using the same physical medium.

Can be extended by hubs or repeaters.

A request for information.

Queries are answered with replies.

Temporary storage where data that has been retrieved or calculated and is accessed frequently can be stored.

Reduces the average access time and reduces the overhead of recalculating the data.

A source of information that is highly reliable and known for its accuracy.

In a web browser, an application the browser uses, inside the browser window, to display some types of content.

Ex: typically uses a plug-in to display video.

Hypertext Transfer Protocol

Defines the commands, headers, and processes by which web servers and web browsers transfer files.

Method of computer processing in which different parts of a program run simultaneously on two or more computers that are communicating with each other over a network.

Information systems that allow the creation of a document(s) that can be edited by more than one person in real time.

Process of obscuring information to make it unreadable.

Applies mathematical formula to the data along with a secret number (encryption key) resulting in an encrypted data packet and is sent through the network.

Post Office Protocol

A protocol that allows a computer to retrieve e-mail from a server.

Simple Mail Transfer Protocol

Application protocol typically not used by an end user.

Used by the network management software and networking devices to allow a network engineer to monitor and trouble shoot network problems.

Mail User Agent Program

Used to download and send e-mail.

• Use POP3 to receive e-mails
• Use SMTP to send e-mails

Unsolicited commercial e-mail.

Relatively general term referring to different kinds of networking devices.

{Routers were once galled gateways}

Dynamic Host Configuration Protocol

Used to dynamically assign IP config's to hosts.

Services defined by the protocol are used to request & assign IP addresses, default gateway, and DNS server address to a network host.

A dotted decimal number that helps identify the structure of IP addresses.

Mask represents the network and subnet parts of related IP addresses with binary 1s and the host part of related IP addresses with 0s.

A form of transmission where one device transmits to all devices within the network or on another network.

Server Message Block

An application level network protocol mainly applied to shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network.

A multiuser, multitasking operating system (196/70s)

AT&T employees developed

Interpret as Command

In Telnet application, commands are always interfaced by a character with the decimal code 255, known as an IAC character

The management of data flow between devices in a network.

Used to avoid to much data arriving before a device can handle it, causing data overflow.

Data that directs a process. A flag in a data-link frame is an example of control data.

Internet Assigned Numbers Authority

An organization that assigns the numbers important to the proper operation of the TCP/IP protocol and the Internet, including assigning globally unique IP addresses.

• Used by TCP and UDP, with values between 0 - 1023
• these ports are allocated by high-privilege processes.

Used so that all clients know the correct port number to connect to.

• Using values between 1024 - 49,151
• these numbers are equivalent to well-known ports in concept,

but they are specifically used for non-privileged application processes.

TCP & UDP ports that range from 49152 - 65535 and are not used by any defined server applications.

a 1-bit flag in the TCP header used to indicate that the receiving host should notify the destination process to do urgent processing.

a 1-bit flag in the TCP header that indicates that acknowledgment field is valid.

a 1-bit flag in the TCP header that is used to request to the higher layers for immediate delivery of the packet.

a 1-bit flag in the TCP header that is used to request that a connection be re-established.

a 1-bit flag in the TCP header used to indicate the initial value of the sequence number.

Flag is only set in the first two segments of the three-way TCP connection establishment sequence.

a 1-bit field in the TCP header that is used by a device that wants to terminate its session with the other device.

This done by inserting the FIN flag in the flag field found in the TCP segment.

a notification sent from one network device to another to confirm that some event (like a receipt of a message) has occurred.

As filed in the TCP header that is set in a sent segment, signifies the maximum amount of unacknowledged data the host is willing to receive before the other sending host must wait for an acknowledgment.

Used for flow control.

Path through an internetwork through which packets are forwarded.

The IP address of the originating-host that is placed into the IP packet header.

Header defined by the IP.

Used to create IP packets by encapsulating data from higher layer protocols with an IP header.

Process:

1. router receives frame

2. discards data-link header & trailer

3. makes forwarding decision based on destination IP add.

4. adds new data-link header & trailer based on outgoing interface

5. forwards frame out the appropriate interface.

The passage of a data packet between two network nodes (for example, between two routers).

A network that is connected to a device's interface.

For example, networks that interface with the router are known to be directly connected.

Devices learn their initial IP routes based on being connected to these subnets.

Communication where the sender and receiver must prearrange for communications to occure; otherwise, the communication fails.

Any communication in which the sender and receiver do not prearrange for communications to occur.

Layer 3 address to which the data is going.

Resources used to manage or operate the network.

• Consumes bandwidth
• Reduces the amount of data that can be transported across the network.

Network protocols or technologies that do not use the acknowledgment system to guarantee reliable delivery of information.

Networking layers that are not affected by the media being used.

In Ethernet these are all of the layers from the LLC sublayer of the Data Link layer and above.

Maximum Transmission Unit

Largest IP packet size allowed to be sent out a particular interface.

Ethernet defaults to 1500 because the data field is limited to 1500bytes [the IP packet sits within the Ethernet frames data field].

The dividing of IP datagrams to meet the MTU requirements of the Layer 2 protocol.

Time To Live

Field in the IP header that prevents a packet from indefinitely looping around an IP internetwork.

Routers decrease TTL field at each hop, once TTL=0 the packet is discarded.

Group of IP addresses that have the same value in the first part of the IP address.

For identifying a group by that part of the address.

IP addresses with the same subnet are typically on the same network medium - not separated by routers.

Short for subnetwork

A logical network composed of all the computers and networking devices that can be reached by sending a frame to the data link layer broadcast address.

Addressing scheme in which a network is partitioned into sections.

Each section identifier forming one part of each destination's address and the destination identifier forming another.

Group of 8 binary bits.

Used to divide IPv4 addresses into four components.

Device on a network that serves as an access point to other networks.

Is used by a host to forward IP packets that have destination addresses outside the local subnet.

List that a router holds in memory for the purpose of deciding how to forward packets.

Routing table entry that is used to direct frames for which a next hop is not explicitly listed in the routing table.

Is used to forward a packet when no other known route exists for a given packet's destination address.

Entry in an IP routing table that was created bc a network admin entered the routing config manually.

Routing that adjusts automatically to network topology or traffic changes.

Protocol used between routers so they can learn routes to add to their routing tables.

IPv4 multicast address that is restricted to a local group or organization

see also limited-scope address

One of 3 basic binary logic operations.

ANDing yields the following results:

• 1 AND 1 = 1
• 1 AND 0 = 0
• 0 AND 1 = 0
• 0 AND 0 = 0

Range of IP addresses that can be assigned by the DHCP server.

Address used to represent transmission from one device to all devices.

• Ethernet the address = FFFF.FFFF.FFFF
• is used to send the frame to all devices on the Ethernet LAN.

IPv4 each subnet has a single broadcast address (aka subnet or directed broadcast address)

• Unicast IP address that is considered to have three parts:
• 1. network part
• 2. subnet part
• 3. host part

"glassful rules are first applied to the address and then the rest of the address is separated for subnetting"

Class A, B, C, D & E

IPv4 address scheme using subnet masks that do not follow classful addressing limitations.

Flexibility when dividing ranges of IP address into separate networks.

Considered best for current networks.

Consists of the AND, OR and IF operations

aka Boolean algebra

Convention for writing IP addresses with four decimal numbers that range from 0 - 255 (inclusive)

Each octet (decimal number), 8-bits of the 32-bit address.

Four octets are separated by a decimal.

[Rather than being sent to all hosts in a particular network]

A single copy of the packet is routed to the specific network it's destined for - where it is then broadcast to all hosts on that network.

Unique addresses that are public domain addresses.

Portion of the binary number that carries the most weight.

(the one written furthest to the left)

Are the 1s in a network mask.

High-speed line or series of connections that forms a major pathway within a net-work.

Often used to describe the main network connections comprising the Internet.

Internet Control Message Protocol

Part of the TCP/IP Internet Layer.

Defines protocol messages used to inform network admin how well the internetwork is operating.

EX: ping command sends ICMP messages to verify that a host can send packets to another host.

• IPv4 address in the range of:
• 169.254.1.0 - 169.254.254.255

Communication is limited to local network w/ TTL = 1

Reserved IPv4 address: 127.0.0.1

Used to test TCP/IP applications (testing the stack)

Does not require a working NIC as packet does not leave the computer.

Multicast address that is restricted to a local group or organization.

see also administratively scoped address

Broadcast that is sent to a specific network or series of networks.

= host portion of the IP subnet mask.

Represent the 0s in the binary number.

Bit position in a binary number having the greatest value.

Typically the leftmost bit.

Member of a multicast group.

Each client in group has same IP address.

• Multicast addresses range:
• 224.*.*.* - 239.*.*.*

Group that receives multicast transmissions.

All members have same IP address and receive all transmissions to that multicast address.

Network Address Translation

Translation of RFC 1918 addresses to public domain addresses.

(RFC 1918 addresses are not routable on the Internet)

Network Time Protocol

For synchronizing the clocks of computers over packet-switched data networks.

Uses UDP port 123 as it's transport layer.

Numeral system in which each position is related to the next by a constant multiplier (common ratio that is the base of that numeral system)

aka place-value notation

(IP Subnetting)

Refers to the portion of a set of IP addresses whose value must be identical for the addresses to be in the same subnet.

IP address that has been registered with IANA or another agency.

Ensures a globally unique public IP address that can be used to send packets through the Internet.

Defined in RFC 1918

IP address that is not globally unique bc the address exists inside packets only when the packets are inside a single private IP internetwork.

Popular with companies who can then use NAT for a globally unique IP address.

Round-Trip Time

Time between sending a PDU and receiving a response.

The time for [some] PDUs to be sent and received & a response PDU sent and received.

Regional Internet Registries

Organizations that are responsible for the allocation and registration of Internet number resources within a particular region of the world.

• ARIN North America
• RIPE Europe & Middle East
• APNIC Asia & the Pacific
• LACNIC South America
• AfriNIC Africa

• IPv4 multicast addresses between:
• 224.0.0.0 - 224.0.0.255

Used for mulicast groups on a local network.

Packet TTL always = 1

Number of various unique digits - including 0

radix aka base

EX: binary system is base 2 (radix=2)

Extent of a certain item from beginning to end

Ex: address scope

Uses forward slash ( / ) to express the network prefix after the IP address.

EX: 192.168.254.0/24

Represents 24-bit network prefix

• IPv4 address block:
• 192.0.2.0 - 192.0.2.255 (192.0.2.0/24)

Set aside for teaching and learning purposes.

Data Link layer term describing a device connected to a network.

Connection of devices on a common media.

AKA network segment

Group of devices associated by the arrangement of a hierarchical addressing scheme.

Devices share common network portion of their Layer 3 addresses.

Part of a computer network that every device communicates with using the same physical medium.

Can be extended by hubs or repeaters.

Network Interface Card

Computer Hardware - used for LANs

Allows a computer to connect to a networking cable it can then send and receive data over the cable at the direction of the computer.

Logical Link Control

IEEE 802.2 standard that defines the upper sublayer of the Ethernet Layer 2 specifications (and other LAN standards).

Media Access Control

Lower of the two sublayers of the IEEE standard for Ethernet.

Defined by 802.3

Indicates whether the performance of a device, attached to a particular type of LAN can be accurately predicted (determined).

EX: Token Ring, LANs

Carrier Sense Multiple Access

Media access method in which transmitting node listens for a signal on the media before transmitting.

Will wait to transmit if a signal is detected.

Signal on a medium used to support the transmission of data.

• Data is "carried" over the medium by modulation
• (combining data signal w/ carrier signal)

(Ethernet)

Results of two nodes transmitting simultaneously.

Causes damage to signals requiring them to be retransmitted.

Carrier Sense Multiple Access / Collision Avoid

Mechanism used to regulate the transmission of data onto a network medium.

Device requests right to send in order to avoid collisions.

Used in 802.11 WLANs

When communication can only be transmitted in one direction at one time.

One station receives what the other transmits and must wait till completion to send the response.

Communication that allows transmission and receipt at the same time.

No collisions!

Arrangement of the nodes in a network and the physical connections between them.

Representation of how media is used to connect the devices.

Map of the devices on a network representing how the devices communicate with each other.

Logical connection between two devices in which the frames are passed between the devices.

Independent of the physical structure and may be established through multiple physical devices.

Access method used with some LANs

Devices access media in a controlled manner managed by a small frame called a token.

Devices can only send when they have claimed the token.

Cycle Redundancy Check

Type of hash function (one-way encryption) that is used to produce small, fixed-size checksum of a block of data, such as a packet or a computer file.

CRC is computed & appended before transmission/storage and verified by the recipient to confirm nothing was changed during transmission.

Retransmission delay used with CSMA/CD when a collision occurs.

Forces each sender that detected the collision to delay a random amount of time before attempting to retransmit.

Association Identity

Number used in the 802.11 header to specify the session between a wireless client and the access point.

Address Resolution Protocol

Method for finding a host's hardware address (MAC) from its IPv4 Network Layer address.

Cabling & connectors used to interconnect the network devices.

Optical or electrical impulse on a physical medium for purposes of communication.

To change the energy levels transmitted over some networking medium to transmit bits over that medium.

Time required to send a single bit over some transmission medium.

• Calculated as 1/speed
• (Speed = number of bits per second sent over the medium)

Non-Return to Zero

Line code represented by one significant condition and 0s are represented by another.

Line code in which each bit of data is signified by at least one voltage level transition.

Grouping of code that meets a certain specified condition for entering in that ceratin group.

Encoding scheme

Uses 5-bit symbols or codes to represent 4 bits of data

Used in 100BASE-TX Ethernet

kbps

Unit of measurement of the number of times 1000 bits can be transmitted in 1 second.

1kbps = 1000bps

Mbps

Unit of measurement of the number of times 1,000,000 bits can be transmitted in 1 second.

1 Mbps = 1,000,000 bps

Actual data transfer rate between two computers at some point in time.

Impacted by the slowest-speed link used to send data between the two computers.

(In addition to any other outside factors.)

Application-level throughput.

Number of useful bits per unit of time from a certain source address to a certain destination.

Excluding protocol overhead & retransmitted data packets.

Loss of communication signal on the media.

Due to degradation of the energy wave over time.

General term referring to any energy signal on a transmission medium that is not part of the signal used to transmit data over that medium.

Unshielded Twisted-Pair cable

General type of cable, cable holds twisted pairs of copper wires and the cable itself having little shielding.

A rectangular cabling connector with eight pins, often used with Ethernet cables.

Defines which wires in a cable should connect to each pin on the connectors on both ends of a cable.

UtP cable pinout that specifies that the wire at pin 1 connects to pin 1 on the other end, pin 2 to pin 2, pin 3 to pin 3, etc.

EX: connecting PC to hub or switch

UTP cable used in Ethernet

Some pairs of twisted-pair wires are crossed at either ends of the RJ-45.

Cisco proprietary cable

UTP pinout that specifies RJ-45 pinout connects pin 1 to pin 8, pin 2 to pin 7, pin 3 to pin 6, etc.

Cisco console cables for routers and switches.

Cable.

Consisting of a hollow outer cylindrical conductor that surrounds a single inner wire conductor.

• Three different layers of material surrounding the inner conducting material:
• the outer conductor
• the insulator
• the protective outer jacket

Hybrid Fiber-Coax

Network that incorporates both optical fiber along with coaxial cable to create a broadband network.

Shielded Twisted-Pair cable

Type of network cable that includes twisted-pair wires, with shielding around each pair of wires,, as well as another shield around all wires in the cable.

Physical medium that uses glass or plastic threads to transmit data.

Transmit data via light waves.

Certification method for fiber.

Tool for testing fiber measuring the time to shine in one end and out the other noting the imperfections in between.

Communication that does not use a common clock between the sender and receiver.

Additional info is sent to maintain timing, synch and receive circuit to the incoming data.

10Mbps Ethernet device does not send sync signals.

Logical storage in host's RAM to store ARP entries.

Technique to attack an Ethernet network by sending fake ARP messages to an Ethernet LAN.

Frames contain false MAC addresses that "confuse" network devices (ex: switches).

Causes frames intended for one node could be sent to another by mistake.

Device that connects multiple network segments at the data link layer of the OSI model.

Predecessor to the LAN switch.

Used by a switch or bridge that associates MAC addresses with the outgoing port.

Uses table as reference for forwarding & filtering.

Process of forwarding frames in a switch or bridge from one port to another port from segment to segment.

Burned-In Address

MAC address that is permanently assigned to a LAN interface or NIC.

• Burned onto the chip on the card.
• Can not be changed.

aka UAA (Universally Administered Address)

Carrier Sense Multiple Access / Collision Detect

MAC algorithm used by Ethernet devices in a shared media.

Protocol requires a node listen for existing signal on the media before attempting to send its data.

If signal is found the node waits until the media is clear before transmit.

If collision occurs and/or is detected the sending node issues a back-off algorithm before retransmitting.

Physical or logical area in a LAN where the signal sent by the interfaces may be subject collision.

Every device in the same collision domain receives frames sent out by other devices on that same segment.

• Hubs increase the size of the collision domain.
• Switches separate them.

Field of a frame signals the beginning or end of a frame.

Network topology characterized by a central location connected to multiple hubs.

Hierarchical topology but typically drawn w/ central site in the center.

aka hierarchical star

Physical interface transceivers.

Deals with Layer 1 of Ethernet.

Switch/bridge process to forward broadcasts & unknown destination unicasts out all ports except the one frame is received on.

Ethernet switch/bridge process that decides not to forward a frame out another port.

Ethernet switch/bridge process that decides to forward a frame out another port.

Common name for Ethernet technology that operates at 100 Mbps.

Ethernet that transmits data at 1,000,000,000 (1billion) bits per second.

Group defined by a class D address

(multicast, ranging 224.0.0.0 - 239.255.255.255)

Hosts can pertain to multicast groups.

Groups = hosts with same multicast address

Ethernet device that receives an electrical signal in one port -interprets the bits- regenerates the signal out all ports.

• Several ports
• Extends networks - collision domains
• Repeaters
• Usually RJ-45

Time period between Ethernet frames that inserts a space between frames.

{allows fairness with the CSMA/CD algorithm }

A shared media Ethernet network signal generated when a collision is detected.

Lasts long enough for all devices to receive.

Part of CSMA/CD.

Locally Administered Address

MAC address that can be configured on a device.

Can be used in place of BIA.

Allows NIC to be replaced or device substituted w/o changing the address used by the network to access the station.

Time that passes while some event occurs.

Refers to the time that occurs between when something is sent in a network until it is received by another device.

Table on a switch that lists all known MAC addresses and the association port for forwarding frames.

Metropolitan-Area Network

Networks geographic size - between LAN and WAN [in size].

Used by ISPs to create high-speed networks in metropolitan areas.

Organizational Unique Identifier

First half of MAC address.

Manufacturers must register the value of the OUI with the IEEE.

Identifies manufacturer of Ethernet NIC or interfaces.

Part of the Ethernet frame that fills in the data field to ensure that the data field meets the minimum size requirement of 46 bytes.

Process that uses the same ARP messages as normal ARP however a router replies instead of the host listed in the request.

Router acts on behalf of the host to respond to the ARP request with the router's MAC address listed in the ARP reply so that the device can reach the intended host that it otherwise would not be able to reach.

Pulse Amplitude Modulation

Form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses.

Transmits data by varying the amplitudes (voltage/power levels) of the individual pulses.

Obsolete: replaced by PCM (Pulse Code Modulation)

Type of memory on which data has been prerecorded.

Can not be removed - only read.

Main working area [temporary storage] used by the CPU for most processing and operations.

Requires electrical power to maintain data storage. (Power turned off before saving - data is lost.)

aka read-write memory

Ethernet frame that is less than 64 bytes in size

Caused by collisions

• aka collision fragments
• { minimum frame size = 64 bytes }

Decisions to forward packets are made dynamically, hop by hop based on conditions on downstream nodes.

Internal processing by LAN switches.

Switch must receive the entire frame before it sends the first bit of the frame.

(Cisco switches)

Associates MAC addresses with their corresponding port.

see also bridge table.

Communication that uses a common clocking signal.

One of the communicating devices generates a clock signal into the circuit - additional timing info is not required in the header.

Minimum time a NIC or interface can take to send an entire frame.

Slot time, then implies a minimum frame size.

Common term for 10BASE5 Ethernet.

Thicker than 10BASE2 coax cable used for Thinnet.

Common term for 10BASE2 Ethernet.

Thinner than 10BASE5 cable for Thicknet.

Device learns source addresses of incoming frames and adds them to the bridging table (switch table, etc.)

For forwarding frames received on one of the interfaces.

Universally Administered Address

• aka
• BIA - burned in Address
• MAC Address

Voice data encapsulated in an IP packet that allows it to traverse already implemented IP networks w/o needing its own network infrastructure.

Network of computers that behave as if they are connected to the same network segment - even if they are located on different segments of a LAN.

• Configured through software on the switch and router.
• (IOS on Cisco routers/switches)

Port on Cisco devices to which a terminal or computer with a terminal emulator is connected to the network device in order to communicate and configure the network device.

Channel Service Unit / Data Service Unit

Device that connects a local digital phone loop for a WAN circuit to a serial interface on a network device (typically a router).

Performs physical layer layer1 signaling on WAN circuits.

Data Communications Equipment

Devices and connections of a communications network that comprise the network end of the user-to-network interface.

• Physical connection to the network
• Forwards traffic
• Provides clocking signal used to synch data transmissions between DTE & DCE

Ex: modems, Interface cards, etc...

Data Terminal Equipment

Device the user end of a user-network interface serving as a data source, destination or both.

Ex: computers, protocol translators, multiplexers, etc...

Connects data network through a DCE device (modem) and uses clocking signals generated by DCE.

Electromagnetic Interference

Interference by magnetic signals caused by the flow of electricity.

Causes reduced data integrity and increased error rates on transmission channels.

{ The electrical current creates magnetic fields, which in turn cause other electrical current in nearby wires. Induced electrical currents can interfere with proper operation of the other wire. }

Glass fibers inside certain cables over which light is transmitted to encode 1s & 0s.

Media-Dependent Interface

Normal mode of operation of Ethernet ports on hubs .

Mapping of the wire pairs used in the hub port is a normal config.

Media-Dependent Interface, Crossover

Alternative operation of Ethernet ports on a hub.

Mapping of the wire pairs used on the hub port is a crossover config. that allows for the use of a straight-through cable. (interconnects a hub to a hub)

Radio Frequency Interference

Radio frequencies that create noise that interfeares with information being transmitted across unshielded copper cabling (UTP).

Application that runs a terminal for a remote host such as a router, switch, etc.

34-pin female v.35 serial cable conector

enters privileged EXEC mode

copy the active configuration to NVRAM

copy the configuration in NVRAM to RAM

erase the configuration located in NVRAM

ping to that address

trace each hop to that address

display statistics for all interfaces on a device

show the time set in the router

• Displays:
• -currently loaded IOS version
• -hardware
• -device information

display the ARP table of the device

display the saved configuration located in NVRAM

display the content of the currently running configuration file

display IP statistics for interface(s) on a router

enter terminal configuration mode

assigns host name to a device

set an unencrypted enable password

set a strongly encrypted enable password

encrypt display of all passwords except secret

set a message-of-the-day banner

enter console line configuration mode

enter virtual terminal (Telnet) line configuration mode

enter interface configuration mode

enable password checking at login

set line password

set interface IP address and subnet mask

set interface description

set clock rate for DCE device

set interface to up

administratively set interface to down

Additional data provided by entering a command at the CLI then the argument.

Removable component of memory storage space.

Used on the router or switch for storing the compressed operating system image.

From privileged mode,

For configuring global parameters or enter other config submodes.

Follows a CLI command.

Are parameters that are used with the command from a set of predefined values.

Collection of data that establishes a reference for network performance and behavior over a period of time.

Used in the future to assess the health and relative growth of network utilization.

Nonvolatile RAM (Random-access memory)

Does not lose its contents when the computer is shut down.

Network scanning technique used to identify which host IP addresses are operational.

Secure Shell Protocol

Provides a secure remote connection to a host through a TCP application.

Password that is complex and a minimum of 8 characters.

Use both numbers and letters.

Limited CLI mode

Can change terminal settings, perform basic tests & list system information.

virtual terminal line

Reference to text based logical interfaces on an IOS device.

Accesses using Telnet or SSH to perform admin tasks.

aka virtual type terminal