Some Likely To Be Important Jargon

more outdated or less important jargon has darker gray background

Some Network Concepts


network A system of lines or channels that cross or interconnect.
computer network This is two or more computer devices linked together for the purpose of sharing information and/or resources.
circuit switching networks In circuit switched networks, a circuit or virtual pathway is established when one device connects to another on a network.  A connection is established.
  • telephone system
packet switching networks In packet switched networks, transmissions are broken up into packets.  A connection isn't established for the entire transmission.  Individual packets may take different paths.
  • Internet
local area network A LAN is a computer network that spans a limited area.  The computers involved in the network are usually physically close to each other.
metropolitan area network A MAN consists of two or more LANs networked together encompassing a metropolitan area.
wide area networks A WAN is a network that spans a large geographic area.
servers A server is a computer that makes its resources such as data, peripherals, and software available for access by other computers across the network.
clients A client is a computer that accesses the resources of a server.
client/server networks These are networks based on interactions where clients access resources on networked servers.  Administration is centralized on a server running a network operating system that does user authentication and authorization.
peer to peer networks These are networks where each computer functions as both client and server and each user administers their own resources.
linear bus networks These networks are laid out in a line, devices are connected sequentially.
  • usually thinnet or thicknet
  • broadcast domain
  • passive due to lack of signal regeneration at each computer
ring networks In these networks there is a line that runs sequentially from one computer to the next and from the last back to the first.
  • usually thinnet or thicknet
  • signal travels in one direction
  • active due to signal regeneration at each computer
star bus networks Each device on the network is connected to a central transceiver, which is a hub or switch.
  • can be passive, active and/or intelligent
star hierarchy network Star hierarchies are developed from having star bus networks linked up to other star bus networks through a hierarchy of switches, hubs and/or routers.
mesh networks Every device on the network has a direct connection to every other device.
hybrid networks These networks make use of more than one of the above topologies.




Some Transmission Media


coaxial cable This is usually referred to as coax.  It has this name because it has two concentric conductors separated by insulation along the same axis.
thinnet Usually 1/4 inch thick coaxial cable used in Ethernet networks.
thicknet Usually 1/2 inch thick coaxial cable used in Ethernet networks.
twisted pair Twisted pair wiring makes use of two relatively thin wires, which are coated and spiraled around each other.  The twisting helps cancel out electromagnetic interference.
UTP - unshielded twisted pair UTP has no extra coating other than what is used for the wires themselves.
STP - shielded twisted pair STP uses an extra layer of foil or braided metallic wire directly below the sheathing.
category 3 UTP Most commonly used for telephone installations.  Offers up to 16 MHz of bandwidth.
category 5 UTP Offers up to 100 MHz of bandwidth becoming ubiquitous in computer networked buildings.
fiber optic cable

Fiber optic cables have a center axis that is made of high-purity optical media that's capable of reliably carrying light patterns over long distances.

infrared The infrared spectrum operates between the visible part of the electromagnetic spectrum and the shortest microwaves. It is actually a form of light which cannot penetrate opaque solids but does reflect off them.
direct infrared Direct infrared is requires devices to have line of sight connections to their transmit/receive devices.
diffuse infrared Diffuse infrared scatters omnidirectionally.  The intent is to bounce signals off ceilings and walls so that the transmit/receive device doesn't need to be in line-of-sight.
narrowband radio Single band or narrowband radio uses a single channel, which is usually sent in the microwave range which are actually high frequency radio waves. Using this spectrum requires FCC licensing due to the signal's properties.
spread spectrum radio Spread spectrum radio is a wideband technology that makes use of multiple frequencies which end up being more secure but less efficient than narrowband approaches.
ISM bands The FCC has specified certain spread spectrum bands of the radio frequency to be used for relatively low wattage industrial, scientific and medical uses.  These are at the 902 - 928MHz and 2.4 - 2.4835GHz bands of the electromagnetic spectrum.
U-NII bands U - NII for Unlicensed National Information Infrastructure at the 5 GHz bands of the electromagnetic spectrum.  Less crowded than the ISM bands.
laser A laser - laser-light amplification by stimulated emission of radiation outputs a coherent electromagnetic field in which all of the waves are the same frequency and aligned in phase. You can think of laser communications within a LAN as single mode fiber optic communication without the fiber optic.




Some Measurement Terminology


bit This is the smallest unit of data in a computer.  A bit can be represented as either 0 or 1, lower or higher voltage.  It results in the binary format used for internal representation of data.
Kbps Kilobits per second is a standard basis of measurement for the amount of data transferred over a network connection.
Mbps Megabits per second is a standard basis of measurement for the amount of data transferred over a network connection.
byte A byte is a unit of measurement to describe a data file, the amount of space on a disk, amount of information on a network or some other device.  A byte usually corresponds eight bits of data.
KB A kilobyte is approximately 1000 bytes, or actually 1024 bytes.  It is often abbreviated as K.
MB A megabyte is approximately 1 million bytes, or actually 1,048,576 bytes.  It is often abbreviated as a meg.
KBps Kilobytes per second is a standard basis of measurement for the amount of data transferred over a network connection.
MBps Megabytes per second is a standard basis of measurement for the amount of data transferred over a network connection.
Hz Hertz is a unit of frequency.  It is the rate of change in the state or cycle in a wave.  It has one cycle per second.
MHz This is pronounced megahertz which is a million cycles per second.
GHz This is pronounced as gigahertz which is 1 billion cycles per second.  This has now become a common measurement for the processing speed of a CPU.



Some Important Standards


IEEE Institute for Electrical and Electronics Engineering
IEEE 802 series Network protocols and specifications that were developed in February of 1980.  The 80 derives from the year, the 2 derives from the month.
CSMA/CD Carrier Sense Multiple Access Collision Detection - When a computer wants to transmit it first listens to the cable to see if any other device is currently transmitting if none are then it transmits.  If at least two devices sense that nothing else is being transmitted they can end up sending at the same instant and causing a collision.  When signals collide they are both eliminated from the network.  Then each computer waits a random amount of time and then resends the same signal.
IEEE 802.3 CSMA/CD and Ethernet specifications
IEEE 802.5 Token Ring specifications
IEEE 802.11 Wireless Networking specifications
Ethernet A baseband LAN specification that makes use of CSMA/CD and particular types of frames for data.  It can be run over a variety of wired and/or wireless media.
Token Ring A Token Ring uses a logical ring topology though not necessarily a physical ring and is usually referred to as a star wired ring with a MSAU - Multistation Access Unit at the hub.  Inside the MSAU the wiring forms a circular data path, creating a logical ring.  A token is passed around this ring and each device cannot transmit until the token gets to it.  The token is used both to initiate transmissions and make sure they get to their destination.  This way there are never any conflicts on the network.
FDDI FDDI makes use of a token passing strategy over two rings of fiber optic cabling.  It allows for multiple frames/packets/tokens to travel over the same network at the same time.  The first ring carries most of the traffic and the second ring is set up for failover.
RFCs Requests for Comments administered by the IESG Internet Engineering Steering Group in the IETF.  These numbered standards are often referred to because of their impact on things such as networking protocols and services.



Some Networking Models


OSI The Open Systems Interconnection model is used to help make sure that systems all around the world can interconnect with each other.  The OSI model divides operating in networks into seven functional layers.  Each layer specifies the functions or set of functions to be performed when data is transferred across a network.
Physical Layer This layer is responsible for the transmission and reception of the bit stream signal.
Data Link Layer When transmitting this layer is responsible for packing instructions, data and so on into frames.  It is also responsible for helping to validate the contents.  When receiving it is responsible for reassembling any binary streams received from the Physical Layer back into frames.
Network Layer This layer establishes the route to be used between the origin and destination computers.  It's used to establish communications with systems that lie beyond the local LAN segment. 
Transport Layer This layer is responsible for the end-to-end integrity of transmissions. It can detect packets that are discarded by routers and automatically send a retransmit request.  When receiving, this layer also resequences packets that have arrived out of order. 
Session Layer The function of this layer is to manage the flow of communications during a connection between two computer systems.
Presentation Layer This layer manages the way data is encoded.
Application Layer This layer provides the interface between the application and the network's services.
TCP/IP TCP/IP is actually a suite of protocols that each perform some function to allow computers to communicate with each other.  It was designed by the Defense Advanced Research Projects Agency (DARPA) in the 1970s and it is now the standard for the Internet.
Internet Layer This defines how IP directs messages through routers over internetworks such as the Internet.  It takes focuses on addressing.
Transport Layer This makes use of TCP - Transmission Control Protocol and defines the how messages are exchanged between computers.




Some Networking Communications Terminology


Analog Signals Analog signals change gradually and continuously.  They have amplitude, frequency and phase.
Digital Signals Digital signals change directly from one state to another almost instantaneously without stopping at an in-between state.
Baseband A baseband signal involves just one signal at a time over some transmission media.
Broadband A broadband signal allows for the capability of dividing the capacity of a link into two or more channels which can each carry a different signal.
Synchronous Transmissions In synchronous transmissions a built in timing mechanism coordinates the clocks/timing of the sender and receiver.
Asynchronous Transmissions Asynchronous transmissions make use of a start bit at the beginning of each transmission in order to help the receiving device to synchronize its clock/timing to the sender's.
Simplex Transmissions Simplex transmissions are also called unidirectional transmissions because the signal travels in only one direction.
Half Duplex Transmissions In half duplex transmissions the signal can travel in each direction but only one end can transmit at a time.
Full Duplex Transmissions In full duplex transmissions two ends of a connection can both transmit at the same time.
Multiplexing Is an approach that enables multiple logical signals to be transmitted across a single physical channel.  In general, signals can be multiplexed based on
  • wavelength/frequency
  • time
EMI - Electromagnetic Interference EMI is the intrusion of outside electromagnetic signals that affect the signal being sent over network media.
RFI - Radio Frequency Interference RMI refers to signal interference caused by radio transmitters and other types of equipment that generate signals on radio frequencies.
Crosstalk Crosstalk is interference in which signals from transmission media, in close proximity in some sort of sense, bleed over one another.
Attenuation Attenuation refers to the reality that signals consume some of their own energy to overcome the resistance inherent in a transmission media.  They also tend to disperse or radiate as they move.
Frangibility Frangibility refers to how easily an electromagnetic wave/signal is broken up.
CSMA/CD Carrier Sense Multiple Access Collision Detection - When a computer wants to transmit it first listens to the cable to see if any other device is currently transmitting if none are then it transmits.  If at least two devices sense that nothing else is being transmitted they can end up sending at the same instant and causing a collision.  When signals collide they are both eliminated from the network.  Then each computer waits a random amount of time and then resends the same signal.
CSMA/CA Carrier Sense Multiple Access Collision Avoidance - When a computer wants to transmit it first listens to the cable to see if any other device is currently transmitting if none are then it transmits an RTS - Request to Send.  If two of these collide, they are dropped.  If not then the device that has just sent an RTS transmits.
Token Passing Token passing is a non-contention method where devices can transmit only if they have possession of a token that moves around the network.
Demand Priority Demand priority makes use of multiport repeaters that conduct round robin searches of connected devices monitoring for requests to transmit.  It is also possible to set priorities for certain types of data.
Collision Domain A collision domain is a segment of a network in which messages will collide if two devices transmit at the same time.
Broadcast Domain A broadcast domain is all of the devices on a segment of a network to which a message will be automatically transmitted.




Some WAN Terminology


modem Modem derives from the necessity of the modulation/demodulation necessary to get digital signal based computers to communicate over analog telephone lines.
ISDN Adapters Typically, ISDN - Integrated Services Digital Network adapters have the capacity to handle the two different 64 kbps digital phone lines necessary for sending and receiving.
CPE - Customer Premises Equipment CPE is a general term used to describe several different types of equipment used to make connections with WAN links such as T-carrier lines and Frame Relay links.
Point to Point WAN A remote access link connects each node in the WAN to the next.
Ring WAN A ring WAN is the same as a point to point WAN except the two end nodes that only have one connection are connected to each other to complete a ring.
Star WAN A concentrator router is used at a central hub node and all the other nodes are connected to this.  In this way no two nodes are more than two hops away from any other.
Multitiered WAN Multitiered WANs make use of concentrator routers just as the star WAN, but there is going to be more than one and they are likely to have direct links to each other.  The other nodes may also have direct connections to each other.
xDSL Digital Subscriber Lines come in a large variety of options depending on bandwidth requirements for uploading and downloading.  They usually make use of telephone lines to provide relatively fast yet inexpensive connections.
T-Carriers They are usually digital circuits leased by large organizations to provide high speed connections.
CSU/DSU A channel service unit/digital service unit is used to transmit and receive digital signals from T - carriers.
T-1 Providing about 1.544 Mbps, these are one of the most common ways for organizations requiring fairly intensive WAN connections.
T-3 Providing about 44.736 Mbps, or capable of being leased in fractional capacity, these are increasingly being used by organizations requiring fairly intensive WAN connections.
Frame Relay

Frame relay switches packets of a shared packet switching network owned by a regional telephone company such as MCI or AT&T.  Frame Relays usually sit on top of T1 or T3 trunks operated by the provider.  These connections are shared among a number of other customers.  Most customers rent PVCs - Permanent Virtual Circuits which give a customer a continuous dedicated connection without paying for a leased line.

ATM - Asynchronous Transfer Mode

ATM was designed to support high speed applications such as video and/or audio streaming.  ATM is actually specified as a Data Link Layer technology on layer 2 within the OSI Reference Model.  ATM sends 53-byte cells instead of variable length packets.  ATM is a switching technology in which virtual circuits are set up before a transmission starts.  These can be either
PVCs - Permanent Virtual Circuits or SVCs - Switched Virtual Circuits.  A virtual circuit is built over a path of various hubs, switches and routers.  Each end of the virtual circuit must agree to the path before the transmission can happen. 

CATV - Cable Makes use of the pre-existing cable television infrastructure to provide network connectivity.
DNS Domain Name System relates to how URLs are translated to IP addresses through receipt of information from DNS Servers.
OC-Sonet SONET - Synchronous Optical Network specifications are set up for various cable speeds or OC - optical carrier levels




Some Interconnection Devices


NIC - Network Interface Card A NIC is the basic component required to interface between the parallel digital signal within the computer into the serial signal appropriate for a particular network architecture.  Many NICs have the transceiver component for sending and receiving signals built in to the card.
RJ Connectors Registered jack connectors consist of a plug and receptacle and are given this name due to their registration with the FCC.
RJ - 45 Connectors These are for Ethernet networks.  They are slightly larger than those used for regular telephone connections.
Repeaters A repeater connects two segments of a network, usually two pieces of cable, and regenerates the signal being transmitted.
Hubs Hubs have multiple ports and broadcast any signals to all the devices that are connected.  They can be passive or active as to whether they regenerate the incoming signal.
Bridges Bridges join two network segments and perform filtering of traffic based on the MAC address.
Switches Switches are usually layer 2 devices working on the Data Link Layer of the OSI model.  They have the capability to choose a path directly to another device based on its MAC address.  Thus they do not broadcast to all of their connected devices like hubs.
Routers Routers are usually layer 3 devices working on the Network layer of the OSI model.  They make use of logical network addresses such as IP addresses in order to choose where packets should be sent.  They are usually used to filter traffic and connect separate networks.



final start



Some Wireless Terminology


BSS - Basic Service Set A BSS is a group of wireless stations that can communicate with each other, except it is done through an AP - Access Point.
AP - Access Point The AP is the central point of interconnectivity for all of the stations in the BSS.
DS - Distribution System Multiple BSSs can be interconnected via their uplink interfaces.  WLAN jargon states that the uplink connects the BSS to the DS - Distribution System.  Such an interconnected collection of BSSs through a DS is known as an ESS - Extended Service Set.
ESS - Extended Service Set An interconnected collection of BSSs through a DS is known as an ESS - Extended Service Set.
CSMA/CA Carrier Sense Multiple Access Collision Avoidance - When a computer wants to transmit it first listens to the cable to see if any other device is currently transmitting if none are then it transmits an RTS - Request to Send.  If two of these collide, they are dropped.  If not then the device that has just sent an RTS transmits.  This is used in wireless.



IP Addressing and Routing


DHCP The Dynamic Host Configuration Protocol is used to hand out IP addresses to clients form a pool of valid ones.
Subnetting Subnetting involves borrowing some of the bits associated with the host address and using them to consolidate a portion of the network into a subnet. 
DNS DNS Servers store databases of IP addresses associated with particular host names and URLs.  A hierarchy of DNS servers exists on the Internet.  Each server contains information for its own zone.  If a particular DNS server doesn't have the IP address associated with a particular domain name it can pass it to another DNS server.
IP Addresses

IP Addressing are 32 bits. They are grouped into four groups of eight or octets.

IP Address Classes IP addressing defines five address classes: A, B, C, D and E.  Classes D and E are for specialized devices.  Class D is used for multicast groups, Class E is reserved for experimental use.  Classes A, B and C are used more commonly for network addresses.  The majority of networks are numbered using class B and C addresses.  In the standard address classes, particular octets are used for network identification.
Classless IP Addressing Classless addressing makes use of a designation appended to each IP address that specifies the number of bits used for the network portion of the address. 


midterm end


Some Terminology related to Routing Protocols


IP Forwarding IP forwarding is a phrase that describes how messages addressed to devices on separate subnets reach their destination.
Static Routing Static routing requires the sys admin to manually enter the IP addresses for desired network addresses into the routing table.
Dynamic Routing Dynamic routing uses protocols to build and change routing tables automatically.  These protocols allow routers to interact and exchange their routing table information.
Distance Vector Protocols When distance vector protocols are used routes are selected primarily based on some sort of distance measure such as the number of hops or amount of time.
Link State Protocols When link state protocols are used, routed depend on the state of the links.  Thus it is necessary to maintain information about the state of particular links.
Router Update Convergence When routers exchange information about other routers these routers must converge to a viable set of correct information and update their routing tables.
Split Horizon Making use of split horizons helps insure that when a router receives update information it doesn't send the same information back to the same router it received it from
Poison Reverse Poison reverse causes a router to set the hop distance of routers that send it update information to one more than the allowable maximum hop distance.
Triggered Updates Triggered updates ensure that updates are sent based on particular trigger events.  Thus some information is sent on immediately.  There are no delays in relaying certain types of  information which can cause looping.
Interior Routing Protocols Interior routing protocols are used by routers within the same  autonomous system.
Exterior Routing Protocols Exterior routing protocols are used between autonomous systems.



Some Network Operating System Terminology


security accounts database This database contains information about each user and their authorizations for network resources.
group accounts Groupings of users so that each user in the group can inherit the permissions set up for the group.
Directory Services Directory services provide an approach to enabling network operating systems to store and access information about network resources, accounts and service.
Namespaces A namespace refers to the way in which each of the directory objects are uniquely identified.  For example, usernames, e-mail addresses and server names.
LDAP LDAP - Light Directory Access Protocol is the most common directory service standard.



Some Desktop Operating System Terminology


Operating System The operating system manages all other programs on the computer..
API Application programs make use of API - Application Programming Interfaces to interface with operating systems and obtain services.
File System Files systems refer to the overall approach used to place, retrieve and do other manipulations on files. They allow files stored on secondary storage devices such as hard drives, floppies and CDs to be organized so they can be located and worked with. 
FAT File Systems FAT was developed for early Microsoft operating systems.  They make use of a file allocation table that provides a mapping of where files are stored.
NTFS NTFS was developed by Microsoft for their NT network operating systems.  It improves on the FAT approach in many ways including increasing security capabilities.
UNIX File System

UNIX file systems are organized as hierarchies of directories and subdirectories in which files can be stored.  In UNIX systems, the root directory is denoted with a /.  Directory paths look like

/directory1/subdirectory1a/subdirectory1ab ...

The UNIX system directories are located immediately off of the root.

NFS Sun Microsystem's NFS - Network File System has become a standard for file servers.  It makes use of RPC - Remote Procedure Call protocols to communicate.  In order for NFS to interoperate, an NFS client must be installed on the requesting computer and both client and server must be running TCP/IP.



Some Terminology about Remote Access


Remote Access Servers Remote Access Servers are servers that connect users to servers and network resources over telephone lines.
Callback Security In order to increase the probability that a particular user is who they claim callback security implements the capability to hang up and dial a particular number to make certain where it is originating from.
Security Host A security host is a device used to authenticate users.  These resources are used in addition to the remote access server's security measures.  These security hosts are actually installed between the remote access client and the server.



Some Terminology about VPN


VPN VPN - Virtual Private Networking gets its name from the idea that certain things should be done to increase the likelihood that information gets to only where it should exactly as it was sent by creating a private network tunneled within the Internet.
VPN Tunnel A VPN tunnel is essentially a logical point to point connection that supports authentication and encryption of data from one endpoint of the tunnel to the other.
Encapsulation Packet Tunneling hides the original packet inside a new packet called the encapsulation packet.



Some Security Terminology


authentication and authorization Typically done with username and passwords to try and verify the identity of a potential user and allocate access to services appropriately.
encryption Using some sort of algorithm to modify the basic message so that it can only be useful to those that can decrypt it.
secret key encryption Secret key encryption requires the secret communication of the means to decrypt messages.
public/private key encryption Public/private key encryption makes use of two different keys, one of which is public and fairly widely available, while the other is private and known only to the user.  Both keys are required to complete a secure communication. 
IPSec IP Security performs the encryption and decryption at the packet level so that there is no need for the specific client applications to even be aware of the encryption done for the transmission.
Digital Signatures Digital signatures consist of encrypted information appended to a document.  This additional information helps verify the sender and the integrity of what was sent.
Digital Certificates Digital certificates are messages that contain the digital signature of a trusted third party or certificate authority.  These certificates are used to help ensure the authenticity of messages that travel across networks such as the Internet.  The certificate authority warrants that a particular public key actually belongs to a specified entity.
Public Key Infrastructure The PKI - Public Key Infrastructure consists of organizations that can provide digital certificates.
Kerberos Kerberos is a particular authentication protocol that is an Internet standard for verifying the identity of a user or computer system.  Kerberos is based on the concept of allocating tickets which are encrypted messages encrypted using secret keys that are used to request service from a server.
Smart Cards Smart cards resemble credit cards, but they also store information such as public/private keys, passwords and other information.
Biometrics Biometrics make use physical characteristics of a potential user in efforts to uniquely identify them in ways that cannot be duplicated.
TCSEC The TCSEC - Trusted Computer System Evaluation Criteria, the orange book, has been developed by the US government to assess the security.
TNI The TNI - Trusted Network Implementation, the red book, has different classes and criteria to have an organization operating system be considered to attain a particular class level of security.
Auditing Auditing is the process of tracking the activities of users and the system. 
Passive Detection Passive detection describes situations where in order to find out particular information a sys admin must actually go and search log files for particular activities. 
Active Detection Active detection describes auditing in which software continually scans the network for signs of intrusion.