Identifying Network Components
stateful firewall
(any firewall that performs stateful packet inspection (SPI) or stateful inspection) is a firewall that keeps track of the state of network connections (such as TCP streams, UDP communication) traveling across it. The firewall is programmed to distinguish legitimate packets for different types of connections. Only packets matching a known active connection will be allowed by the firewall; others will be rejected.
LC connector
A Lucent connector connects to a terminating device by pushing the connector into the terminating device, and it can be removed by pressing the tab on the connector and pulling it out of the terminating device.
optical fiber cable (fiber optic cable)
A cable containing one or more optical fibers. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube suitable for the environment where the cable will be deployed.
Network as a service (NaaS)
A category of cloud services where the capability provided to the cloud service user is to use network/transport connectivity services and/or inter-cloud network connectivity services. NaaS involves the optimization of resource allocations by considering network and computing resources as a unified whole.
single-mode fiber (SMF)
A category of optical fiber designed to carry only a single ray of light (mode). Single-mode fibers used in telecommunications operate at 1310 or 1550 nm and require more expensive laser sources. Single mode fibers exist for nearly all visible wavelengths of light. Used in applications over 1 km in distance.
multimode fiber (MMF)
A category of optical fiber mostly used for communication over short distances, such as within a building or on a campus. Typical multimode links have data rates of 10 Mbit/s to 10 Gbit/s over link lengths of up to 600 meters (300 m for 10 Gbit/s). The main difference between multi-mode and single-mode optical fiber is that the former has much larger core diameter, typically 50-100 micrometers; much larger than the wavelength of the light carried in it. Because of the large core and also the possibility of large numerical aperture, multi-mode fiber has higher "light-gathering" capacity than single-mode fiber. In practical terms, the larger core size simplifies connections and also allows the use of lower-cost electronics such as light-emitting diodes (LEDs) and vertical-cavity surface-emitting lasers (VCSELs) which operate at the 850 nm and 1300 nm wavelength. Used mainly in LAN application.
passive hub
A central connecting device in a network that joins wires from several stations in a star configuration. It does not provide any processing or regeneration of signals.
active hub
A central connecting device in a network that regenerates signals on the output side to keep the signal strong. Also called a "multiport repeater."
coaxial cable (coax)
A coaxial cable is composed of two conductors. One of the conductors is an inner insulated conductor. The inner conductor is surrounded by another conductor. The second conductor is sometimes made of a metallic foil or woven fiber.
DB-9 (RS-232)
A common connector used on twisted-pair cables. A 9-pin D-subminiature connector is commonly used as a connector for asynchronous serial communications. One of the more popular uses of a DB-9 connector is to connect the serial port on a computer with an external modem.
RJ-11
A common connector used on twisted-pair cables. A type 11 registered jack has the capacity to be a six-pin connector. However, most RJ-11 connectors have only two or four conductors. A RJ-11 connector is found in most home telephone networks. However, most home phones only use two of the six pins.
RJ-45
A common connector used on twisted-pair cables. A type 45 registered jack is an eight-pin connector found in most Ethernet networks. However, most Ethernet implementations can only use four of the eight pins.
network switch
A computer networking device that links network segments or network devices. The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer (layer 2) of the OSI model. Switches that additionally process data at the network layer (layer 3) and above are often called layer-3 switches or multilayer switches.
multilayer switch (MLS)
A computer networking device that switches on OSI layer 2 like an ordinary network switch and provides extra functions on higher OSI layers. The major difference between the packet switching operation of a router and that of a Layer 3 switch is the physical implementation. In general-purpose routers, packet switching takes place using software that runs on a microprocessor, whereas a Layer 3 switch performs this using dedicated application-specific integrated circuit (ASIC) hardware.
cache engine or content engine
A dedicated appliance used to perform content caching.
hub AKA Ethernet hub, active hub, network hub, repeater hub, or multiport repeater
A device for connecting multiple Ethernet devices together and making them act as a single network segment. It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming. A hub works at the physical layer (layer 1) of the OSI model. The device is a form of multiport repeater. Repeater hubs also participate in collision detection, forwarding a jam signal to all ports if it detects a collision.
router
A device that forwards data packets between computer networks, creating an overlay internetwork. A router is connected to two or more data lines from different networks. When a data packet comes in one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node.
Media Access Unit (MAU, also called Multistation Access Unit, MSAU)
A device to attach multiple network stations in a star topology in a token ring network, internally wired to connect the stations into a logical ring. The MAU contains relays to short out non-operating stations. Multiple MAUs can be connected into a larger ring through their Ring In/Ring Out connectors.
multimode delay distortion
A distortion mechanism, occurring in multimode fibers (MMF), in which the signal is spread in time because the velocity of propagation of the optical signal is not the same for all modes. With all of its bouncing, the first bit has to travel further than the second bit, which might cause the bits to arrive out of order. So, MMF typically has shorter distance limitations.
MTRJ connector
A media termination recommended jack connector has two fiber strands (a transmit strand and a receive strand) that are included in a single connector. It's connected by pushing the connector into the terminating device, and it can be removed by pulling the connector from the terminating device.
dynamic DNS
A method of updating, in real time, a Domain Name System (DNS) to point to a changing IP address on the Internet. This is used to provide a persistent domain name for a resource that may change location on the network.
bridge
A network bridge is a network device that connects more than one network segment. In the OSI model bridging acts in the first two layers. Bridging is distinct from routing which allows the networks to communicate independently as separate networks. Bridges have largely been replaced with switches.
smart or intelligent hub
A network device that performs a variety of processing functions, including network management, bridging, routing and switching.
content switch
A network device that routes traffic to the appropriate Web server based on the content of the packet. Also known as a "URL switch," "Web content switch," "layer 7 switch" and "layer 4-7 switch," the Web switch is designed to provide improved load balancing for a Web site, because different requests can be routed to the servers configured to handle them.
Dynamic Host Configuration Protocol (DHCP)
A network protocol that is used to configure network devices so that they can communicate on an IP network. DHCPDISCOVER, DHCPOFFER, DHCPREQUEST, DHCPACK
110 block
A popular type of cross-connect block. A 110 block is a type of punch block used to connect sets of wires in a structured cabling system. The "110" designation is also used to describe a type of insulation-displacement connector used to terminate twisted pair cables which uses a similar punch-down tool as the older 66 block. The 110 block has been slowly replacing the 66 block, especially for data communications usage. 110 style blocks allow a much higher density of terminations in a given space than older style termination blocks (66 style or wire wrap). Some 110 blocks meet specifications for higher bandwidth data protocols such as Category 5 and higher.
66 block
A popular type of cross-connect block. A 66 block (also M-Block or B-Block) is a type of punchdown block used to connect sets of wires in a telephone system. 66 blocks are designed to terminate 22 through 26 AWG solid copper wire. The 66 series connecting block was the first IDC (Insulation Displacement Connector) type connecting block in the Bell System, introduced in 1962. Used in 10-Mbps LANs, these blocks were used to cross-connect Cat 3 UTP cabling. It does not support higher-speed LAN technology, like 100-Mbps Ethernet networks.
network segment
A portion of a computer network. The nature and extent of a segment depends on the nature of the network and the device or devices used to interconnect end stations.
collision domain
A section of a network where data packets can collide with one another when being sent on a shared medium or through repeaters, in particular, when using early versions of Ethernet. A network collision occurs when more than one device attempts to send a packet on a network segment at the same time. Collisions are resolved using carrier sense multiple access with collision detection in which the competing packets are discarded and re-sent one at a time. This becomes a source of inefficiency in the network.
proxy server
A server that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server and the proxy server evaluates the request as a way to simplify and control its complexity. Because all requests are sourced from the proxy, IP addresses of network devices are hidden from the Internet.
media converter
A simple networking device that makes it possible to connect two dissimilar media types such as twisted pair with fiber optic cabling. They were introduced to the industry nearly two decades ago, and are important in interconnecting fiber optic cabling-based systems with existing copper-based, structured cabling systems.
wiring closet
A small room commonly found in institutional buildings, such as schools and offices, where electrical connections are made. While they are used for many purposes, their most common use is for computer networking. Many types of network connections place limits on the distance between end user equipment, such as personal computers, and network access devices, such as routers. These restrictions might require multiple wiring closets on each floor of a large building.
virtual switch
A software program that allows one virtual machine (VM) to communicate with another.
Extension mechanisms for DNS (EDNS)
A specification for expanding the size of several parameters of the Domain Name System (DNS) protocol which had size restrictions that the Internet engineering community deemed too limited for increasing functionality of the protocol.The restrictions in size of several flags fields, return codes and label types available in the basic DNS protocol were not sufficient to support some desirable features. Since no new flags could be added in the DNS header, EDNS adds information to DNS messages in the form of pseudo-resource-records included in the "additional data" section of a DNS message. Note that this section exists in both requests and responses.
ST connector
A straight tip connector is sometimes referred to as a bayonet connector. Most commonly used with MMF. An ST connector connects to a terminating device by pushing the connector into the terminating equipment and then twisting the connector housing to lock it into place.
SC connector
A subscriber connector, standard connector, or square connector. The SC connector is connected by pushing the connector into the terminating device, and it can be removed by pulling the connector from the terminating device,
Address Resolution Protocol (ARP)
A telecommunications protocol used for resolution of network layer addresses into link layer addresses, a critical function in multiple-access networks.
private branch exchange (PBX)
A telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public.
Ethernet hub
A wireless AP is much like a hub, in that all wireless devices associated with the AP belong to the same collision domain. One collision domain - One broadcast domain.
patch panel
AKA a patch bay, patch field or jack field. A number of circuits, usually of the same or similar type, which appear on jacks for monitoring, interconnecting, and testing circuits in a convenient, flexible manner.
uniform resource locator (URL)
Also known as web address, is a specific character string that constitutes a reference to an internet resource. In most web browsers, the URL of a web page is displayed on top inside an address bar. An example of a typical URL would be "http://en.example.org/wiki/Main_Page". A URL is technically a type of uniform resource identifier (URI), but in many technical documents and verbal discussions, URL is often used as a synonym for URI.
electromagnetic interference (EMI)
An electromagnetic waveform that can be received by network cable (possibly corrupting data traveling on the cable) or radiated from a network cable (possibly interfering with data traveling on another cable). Sometimes used interchangeably with radio frequency interference (RFI).
application-specific integrated circuit (ASIC)
An integrated circuit (IC) customized for a particular use, rather than intended for general-purpose use. For example, a chip designed to run in a digital voice recorder is an ASIC.
intermediate distribution frame (IDF)
An intermediate distribution frame (IDF) is a free-standing or wall-mounted rack for managing and interconnecting the telecommunications cable between end user devices and a main distribution frame (MDF). For example, an IDF might be located on each floor of a multi-floor building routing the cabling down the walls to an MDF on the first floor. The MDF would contain cabling that would interconnect to the phone company or to other buildings.
crossover cable
Are very much like straight-through cables with the exception that TX (transmit) and RX (receive) lines are crossed (they are at opposite positions on either end of the cable. Crossover cables are most commonly used to connect two hosts directly.
unshielded twisted-pair (UTP) cable
Blocks EMI from the copper strands making up a twisted-pair cable by twisting the strands more tightly (that is, more twists per cm). By wrapping these strands around each other, the wires insulate each other from EMI. Common categories include Cat 3, Cat 5, Cat 5e, Cat 6, Cat 6a.
firewall
Can either be software-based or hardware-based and is used to help keep a network secure. Its primary objective is to control the incoming and outgoing network traffic by analyzing the data packets and determining whether it should be allowed through or not, based on a predetermined rule set. A network's firewall builds a bridge between an internal network that is assumed to be secure and trusted, and another network, usually an external (inter)network, such as the Internet, that is not assumed to be secure and trusted.
Cat 6a cable
Cat 6a, or augmented Cat 6, supports twice as many frequencies as Cat 6 and can be used for 10GBASE-T networks, which can transmit data at a rate of billion bites per second (10 Gbps).
RG-59
Common type of coax. Used for short-distance applications. Has loss characteristics so not appropriate for long-distance applications. Has a characteristic impedance of 75 Ohms.
RG-6
Common type of coax. Usually used by cable companies to connect homes to the company's distribution network. Has a characteristic impedance of 75 Ohms.
Medium Dependent Interface (MDI)
Describes the interface (both physical and electrical) in a computer network from a physical layer implementation to the physical medium used to carry the transmission.
media
Devices need to be interconnected via some sort of media. This media could be copper cabling or fiber-optic cabling. Media might not even be a cable, as in the case with networks, where radio waves travel through the media of air.
virtual server
Each OS "sits" on its own partition, or section/place on the server, to keep it separate from other sites.
virtual private network (VPN)
Extends a private network and the resources contained in the network across public networks like the Internet. It enables a host computer to send and receive data across shared or public networks as if it were a private network with all the functionality, security and management policies of the private network. This is done by establishing a virtual point-to-point connection through the use of dedicated connections, encryption, or a combination of the two. The VPN connection across the Internet is technically a wide area network (WAN) link between the sites but appears to the user as a private network link—hence the name "virtual private network".
RG-58
Has loss characteristics and distance limitations similar to those of RG-59. However, the characteristic impedance of RG-58 is 50 Ohms and this type of coax was popular with early 10BASE2 Ethernet networks.
rollover cable
Have opposite Pin assignments on each end of the cable or in other words it is "rolled over". Pin 1 of connector A would be connected to Pin 8 of connector B. Pin 2 of connector A would be connected to Pin 7 of connector B and so on. Rollover cables, sometimes referred to as Yost cables are most commonly used to connect to a devices console port to make programming changes to the device. Unlike crossover and straight-wired cables, rollover cables are not intended to carry data but instead create an interface with the device.
application service provider (ASP)
Internet hostinprovides computer-based services to customers over a network. Software offered using an ASP model is also sometimes called on-demand software or software as a service (SaaS). The most limited sense of this business is that of providing access to a particular application program (such as customer relationship management) using a standard protocol such as HTTP.
Cat 6 cable
Like Cat 5e, Cat 6 is commonly used for 1000BASE-T Ethernet networks. Cat 6 cable has thicker insulation and offers reduced crosstalk, as compared with Cat 5e.
cladding
One or more layers of materials of lower refractive index, in intimate contact with a core material of higher refractive index. The cladding causes light to be confined to the core of the fiber by total internal reflection at the boundary between the two.
collide
Only one device in the collision domain may transmit at any one time, and the other devices in the domain listen to the network in order to avoid data collisions. Because only one device may be transmitting at any one time, total network bandwidth is shared among all devices. Collisions also decrease network efficiency on a collision domain; if two devices transmit simultaneously, a collision occurs, and both devices must retransmit at a later time.
plenum
Plenum cabling is fire retardant and minimizes toxic fumes released by network cabling if that cable were to catch on fire. As a result, plenum cabling is often a requirement of local fire codes for cable in raised flooring or in other open air return ducts.
shielded twisted-pair (STP) cable
STP cabling prevents wires in a cable from acting as an antenna, which might receive or transmit EMI. STP cable might have a metallic shielding, similar to braided wire that acts as an outer conductor in a coax cable.
Fully Qualified Domain Name (FQDN)
Sometimes also referred as an absolute domain name, is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). It specifies all domain levels, including the top-level domain and the root zone. A fully qualified domain name is distinguished by its lack of ambiguity: it can only be interpreted one way.
straight-through cable
Straight-through refers to cables that have the pin assignments on each end of the cable. In other words Pin 1 connector A goes to Pin 1 on connector B, Pin 2 to Pin 2 ect. Straight-through wired cables are most commonly used to connect a host to client.
VPN concentrator
The VPN concentrator uses a strong encryption algorithm to encrypt the data and transmits it through the tunnel to the VPN client. The VPN client software decrypts the information so you can read it on your remote PC. If you update the data, the VPN client encrypts and returns the data to the network through the VPN concentrator.
Medium Dependent Interface Crossover (MDIX)
The X refers to the fact that transmit wires on an MDI device must be connected to receive wires on an MDIX device. Straight through cables connect pins 1 and 2 (transmit) on an MDI device to pins 1 and 2 (receive) on an MDIX device. Similarly pins 3 and 6 are receive on an MDI device and transmit on an MDIX device.
virtualization
The creation of a virtual (rather than actual) version of something, such as a hardware platform, operating system (OS), storage device, or network resources. The usual goal of virtualization is to centralize administrative tasks while improving scalability and overall hardware-resource utilization. With virtualization, several operating systems can be run in parallel on a single central processing unit (CPU). This parallelism tends to reduce overhead costs and differs from multitasking, which involves running several programs on the same OS. Using virtualization, an enterprise can better manage updates and rapid changes to the operating system and applications without disrupting the user. "Ultimately, virtualization dramatically improves the efficiency and availability of resources and applications in an organization. Instead of relying on the old model of "one server, one application" that leads to under utilized resource, virtual resources are dynamically applied to meet business needs without any excess fat".
Domain Name System (DNS) server
The most important function of these DNS servers is the translation (resolution) of human-memorable domain names and hostnames into the corresponding numeric Internet Protocol (IP) addresses, the second principal Internet name space which is used to identify and locate computer systems and resources on the Internet.
public switched telephone network (PSTN)
The network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by switching centers, thus allowing any telephone in the world to communicate with any other. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core and includes mobile as well as fixed telephones.
encryption
The process of encoding messages (or information) in such a way that eavesdroppers or hackers cannot read it, but that authorized parties can. There are two basic types of encryption schemes: symmetric-key and public-key encryption. In symmetric-key schemes, the encryption and decryption keys are the same. Thus communicating parties must agree on a secret key before they wish to communicate. In public-key schemes, the encryption key is published for anyone to use and encrypt messages. However, only the receiving party has access to the decryption key and is capable of reading the encrypted messages. Public-key encryption is a relatively recent invention: historically, all encryption schemes have been private-key schemes.
content caching
The service of copying the pages of a Web site to geographically dispersed servers and, when a page is requested, dynamically identifying and serving page content from the closest server to the user, enabling faster delivery.
twisted-pair cable
Today's most popular media type is twisted-pair cable, where individually insulated copper strands are intertwined into a twisted-pair cable. Two categories include shielded twisted pair (STP) and unshielded twisted pair (UTP)
DNS record type
Types of resource records (database records) stored in the zone files of the Domain Name System (DNS)
virtual desktop
Ways in which the virtual space of a computer's desktop environment is expanded beyond the physical limits of the screen's display area through the use of software. A user's data is stored in a data center rather than on an office computer's hard drive. By providing authentication credentials, a secure connection can be established between the centralized repository of user data and that user's device.
mode of propagation
When the light wave is guided down a fiber-optic cable, it exhibits certain modes. These are variations in the intensity of the light, both over the cable cross section and down the cable length. These modes are actually numbered from lowest to highest. In a very simple sense, each of these modes can be thought of as a ray of light. For a given fiber-optic cable, the number of modes that exist depends on the dimensions of the cable and the variation of the indices of refraction of both core and cladding across the cross section.
Voice over IP (VoIP, abbreviation of voice over Internet Protocol)
Where voice is encapsulated inside data packets for transmission across a data network. The steps involved in originating a VoIP telephone call are signaling and media channel setup, digitization of the analog voice signal, encoding, packetization, and transmission as Internet Protocol (IP) packets over a packet-switched network. On the receiving side, similar steps (usually in the reverse order) such as reception of the IP packets, decoding of the packets and digital-to-analog conversion reproduce the original voice stream.
Cat 5e cable
an updated version of Cat 5 cable and is commonly used for 1000BASE-T networks, which carry data at a rate of 1 Gbps. Cat 5e offers reduced crosstalk, as compared to Cat 5.
BNC (Bayonet Neill-Concelman or British Naval Connector)
common connector used on coax cables and can be used for a variety of applications, including being used as a connector in a 10BASE2 Ethernet network
F-connector
common connector used on coax cables and frequently used for cable TV (including cable modem) connections
Cat 5 cable
commonly used in Ethernet 100BASE-TX networks, which carry data at a rate of 100 Mbps. However, Cat 5 cable can carry ATM traffic at a rate of 155 Mbps. Most Cat 5 cables consist of four pairs of 24 gauge wires. On average, one pair of wires has a twist every 5 cm.
Cat 3 cable
commonly used in Ethernet 10BASE-T networks, which carry data at a rate of 10 Mbps. Cat 3 cable carries data at a max rate of 16 Mbps.
RG prefix
prefix used in coax cables stands for Radio Guide