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CCNA Vocabulary -- Cloned from: CCNA Vocabulary
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Enterprise Network


Network that integrates all systems within a company or organization. An enterprise network differs from a WAN because it is privately owned and maintained.


Converged Network


A network capable of carrying voice, video and digital data.


NOC


An enterprise centralizes network management in a Network Operations Center.


Failover


Occurrence of a redundant network device performing the load or function of another device automatically if the initial device fails. The failover scheme creates a backup system for mission-critical hardware and software. The objective is to reduce the impact of system failure to a minimum by actively monitoring and identifying system failure.


Mission-critical


Type of network or computing process that is vital to an organization. Mission-critical applications that are halted often or for too long may have negative consequences.


Hierarchical Design Model


Representation of a network featuring an access layer, a distribution layer, and core layer.


Access Layer


Level of the hierarchical Cisco internetworking model that encompass the hosts that are the point of entry into the network. Access Layer devices include switches, hubs, workstations, servers, IP phones, web cameras, and access points.


Distribution Layer


Layer in a hierarchical design between the Access layer and Core layer. The Distribution layer interconnects access layer hosts and switches, and provides security and traffic management for the Core Layer.


Core Layer


Layer in a three-layer hierarchical design with the Access Layer and Distribution Layer. The Core Layer is a high-speed backbone layer between geographically dispersed end networks.


ECNM


Enterprise Composite Network Model Cisco network design that divides the network into functional components while still maintaining the concept of Core, Distribution, and Access layers. The functional components are the Enterprise Campus, Enterprise Edge, and Service Provider Edge.


Enterprise Campus


Consists of the campus infrastructure with: Building Access, Building Distribution, Campus Core, Server Farms, and Network Management


Enterprise Edge


Consists of the Internet, VPN, and WAN modules connecting the enterprise with the service provider's network The module extends the enterprise services to remote sites and enables the enterprise to use Internet and partner resources. It provides QoS, policy enforcement, service levels, and security


Service Provider Edge


Provides Internet, Public Switched Telephone Network (PSTN), and WAN services


Edge device


Filter on the perimeter of an enterprise network where incoming packets are passed. Examples of edge devices include firewall and DMZ. Edge devices may be equipped with IDS and IPS to examine and block unwanted traffic.


IDS


Intrusion Detection System Combination of a sensor, console, and central engine in a single device installed on a network to protect against attacks missed by a conventional firewall. IDS inspects all inbound and outbound network activity and identifies suspicious patterns that may indicate a network or system attack. It is configured to send an alarm to network administrators when such attack is encountered.


IPS


Intrusion Prevention System Active device in the traffic path that monitors network traffic and permits or denies flows and packets into the network. All traffic passes through an IPS for inspection. When the IPS detects malicious traffic, it sends an alert to the management station and blocks the malicious traffic immediately. IPS proactively prevents attacks by blocking the original and subsequent malicious traffic.


DMZ


Demilitarized Zone Area in a network design that is located between the internal network and external network, usually the Internet. The DMZ is accessible to devices on the Internet, such as a web server, FTP server, SMTP server, and DNS.


Failure Domain


Area of a network that is affected when a networking device malfunctions or fails. A properly designed network minimizes the size of failure domains.


Downtime


Percentage of time in which a network is unavailable because of administrative shutdown or equipment failure.


Back end


Application that performs final or hidden functions in a process.


POP


Point of Presence Physical connection between a communication facility provided by an ISP or local telephone company , and an organization’s main distribution facility.


HDLC


High-Level Data Link Control Bit-oriented synchronous Data Link Layer protocol developed by ISO. HDLC specifies a data encapsulation method on synchronous serial links using frame characters and checksums.


PPP


Point-to-point Protocol Standard that provides router-to-router and host-to-network connections over synchronous and asynchronous circuits.


Frame Relay


Industry-standard, switched, WAN standard that operates at the Physical Layer and Data Link Layer of the OSI Reference Model. Frame Relay handles multiple virtual circuits using HDLC encapsulation between connected devices. It is more efficient than the X.25 protocol that it replaced.


ATM


Asynchronous transfer mode International standard for the cell relay of service types, such as voice, video, or data. In ATM, the services are conveyed in fixed-length, 53-byte cells. Fixed-length cells reduce transit delays because cell processing occurs in the hardware. ATM is designed for high-speed transmission media such as E3, SONET, and T3.


Intranet


Networks accessible internal users of an organization. An intranet is used to share internal information and computing resources


Extranet


Network that provides access to information or operations of an organization to suppliers, vendors, partners, customers, or other businesses. Extranet is a private network using Internet protocols and the public telecommunication system to share internal resources. It may be considered an extension of an intranet.


External Traffic


Data communication to and from a private network. External Traffic is traffic that originates from or is destined to the Internet. VPN and Internet traffic is considered external traffic flow.


Packet Sniffer


Tool that analyzes traffic flows based on the source and destination of the traffic as well as the type of traffic being sent. Packet sniffer analysis can be used to make decisions on how to manage the traffic more efficiently.


UDP


User Datagram Protocol Standard for connectionless transmission of voice and video traffic. Transmissions using UDP are not affected by the delays caused from acknowledgements and retransmitting lost packets.


TCP


Transmission Control Protocol
TCP provides services that ensure accurate and timely delivery of network communications between two hosts. TCP provides the following services to ensure message delivery:
· Sequencing of data packets · Flow control · Error checking While the use of acknowledgements makes TCP a more reliable delivery protocol, it also incurs a delay.


Latency


1) Delay between the time when a device receives a frame and the time that frame is forwarded out the destination port. 2) Data latency is the time between a query and the results displaying on the screen.


Jitter


Analog communication line distortion. Jitter can be caused by the variation of a signal from the reference timing positions, network congestion, or route changes. It can cause data loss, particularly at high speeds.


QoS


Quality of Service Standard for monitoring and maintaining a level of transmission performance and service, such as available data transmission bandwidth and error rate.


Teleworking


Employee that works at a location other than the centralized office location.


Telecommuting


Working from a location other than the centralized office


Teleworker


Employee that works at a location other than the centralized office


Teleconferencing


Method for a group of people to communicate in real time online


VoIP


Voice Over Internet Protocol Standard for transmitting voice data encapsulated in an IP packet on an already implemented IP network without needing its own network infrastructure. In VoIP, the digital signal processor divides the voice signal into frames which are paired in groups of two and stored in voice packets. The voice packets are transported using IP in compliance with ITU-T specification H.323.


FTP


File Transfer Protocol
20 & 21 TCP
FTP provides a generic method of transferring files. It can include file security through usernames and passwords, and it allows file transfer between dissimilar computer systems. FTP can transfer both binary and text files, including HTML, to another host. FTP URLs are preceded by ftp:// followed by the DNS name of the FTP server. To log in to an FTP server, use: ftp://username@servername. Uses ports 20 & 21. Port 20 it the port the FTP server opens to send information back to the FTP client. 21 is the actual port that all FTP servers bind to by default. Defined in RFC959.


Telnet


Remote Terminal Emulation
Telnet allows an attached computer to act as a dumb terminal, with data processing taking place on the TCP/IP host computer. It is still widely used to provide connectivity between dissimilar systems. Telnet can also be used to test a service by the use of HTTP commands.
Uses port 23 TCP


VPN


Virtual Private Network Network through which data is sent through a public telecommunication infrastructure while maintaining the privacy of the data by creating a tunnel through the public telecommunication infrastructure.


TLS


Transport Layer Security
TLS ensures that messages being transmitted on the Internet are private and tamper proof. TLS is implemented through two protocols: •TLS Record--Can provide connection security with encryption (with DES for example).
•TLS Handshake--Provides mutual authentication and choice of encryption
method.


IPSec


IP Security A suite of protocols that provide many services including:
  • ·         Data encryption
  • ·         Integrity validation
  • ·         Peer authentication
  • ·         Key management
IPSec provides security services at the IP layer. IPSec uses IKE to handle the negotiation of protocols and algorithms based on local policy and to generate the encryption and authentication keys to be used by IPSec. IPSec can protect one or more data flows between a pair of hosts, between a pair of security gateways, or between a security gateway and a host.


Network Infrastructure Diagram


Illustration of the topology of a network that shows the location, function, and status of devices. A network infrastructure diagram may represent either a physical or logical network.


Topology


Map of the arrangement of network nodes and media within an enterprise networking infrastructure. Topology can be physical or logical.


Physical Topology


Layout of devices on a network. The physical topology shows the way that the devices are connected through the cabling and how cables are arranged.


Logical Topology


Map of the flow of data on a network that shows how devices communicate with each other.


Control Plane


Collection of processes that run at the process level on the route processor. Control plane processes collectively provide high-level control for most Cisco IOS functions. Control plane information describes failure domains and defines the interfaces where different network technologies intersect.


CSU/DSU


Channel service unit/data service unit Network devices that connect an organization to a digital circuit.














CSU


Channel Service Unit Digital interface device that connects end-user equipment to the local digital telephone loop. Often referred to with DSU, as CSU/DSU


DSU


Data Service Unit Digital Transmission device that adapts the physical interface on a DTE to a transmission facility such as T1 or E1. The DSU is also responsible for functions such as signal timing. Often referred to with CSU, as CSU/DSU.


Redlined


Marks on blueprints showing changes in the design


as-built


Diagram that shows the original design and any changes that have been made to a network topology.


BCP


Business Continuity Plan Steps to be taken to continue business operations when there is a natural or man-made disaster.


BSP


Business Security Plan Physical, system, and organizational control measures to be taken to protect network and information assets.


NMP


Network Maintenance Plan Ensures business continuity by keeping the network running efficiently. Network maintenance must be scheduled during specific time periods, usually nights and weekends, to minimize the impact on business operations.


SLA


Service Level Agreement Binding contract between a network service provider and the end user who requires a certain level of service.


Data Center


Central management location that monitors all network resources.
  • ·         Also known as the NOC
  • ·         usually has:
o   Raised floors (allow for cabling to run under the floor to equipment) o   High performance UPS systems and air conditioning equipment to provide a safe operating environment for equipment o   Fire suppression systems integrated into the ceiling o   Network monitoring stations, servers, backup systems, and data storage o   Access layer switches and distribution layer routers, if it serves as a Main Distribution Facility (MDF) for the building or campus where it is located


Server Farm


Collection of servers located in a central facility and maintained by the central group to provide server needs for organizations. A server farm usually has primary and backup server hardware for load balancing, redundancy, and fault tolerance purposes. Server farm architecture provides the operation and maintenance of servers.






















































































































































































CSU


Channel Service Unit Digital interface device that connects end-user equipment to the local digital telephone loop. Often referred to with DSU, as CSU/DSU


DSU


Data Service Unit Digital Transmission device that adapts the physical interface on a DTE to a transmission facility such as T1 or E1. The DSU is also responsible for functions such as signal timing. Often referred to with CSU, as CSU/DSU.


Redlined


Marks on blueprints showing changes in the design


as-built


Diagram that shows the original design and any changes that have been made to a network topology.


BCP


Business Continuity Plan Steps to be taken to continue business operations when there is a natural or man-made disaster.


BSP


Business Security Plan Physical, system, and organizational control measures to be taken to protect network and information assets.


NMP


Network Maintenance Plan Ensures business continuity by keeping the network running efficiently. Network maintenance must be scheduled during specific time periods, usually nights and weekends, to minimize the impact on business operations.


SLA


Service Level Agreement Binding contract between a network service provider and the end user who requires a certain level of service.


Data Center


Central management location that monitors all network resources.
  • ·         Also known as the NOC
  • ·         usually has:
o   Raised floors (allow for cabling to run under the floor to equipment) o   High performance UPS systems and air conditioning equipment to provide a safe operating environment for equipment o   Fire suppression systems integrated into the ceiling o   Network monitoring stations, servers, backup systems, and data storage o   Access layer switches and distribution layer routers, if it serves as a Main Distribution Facility (MDF) for the building or campus where it is located


Server Farm


Collection of servers located in a central facility and maintained by the central group to provide server needs for organizations. A server farm usually has primary and backup server hardware for load balancing, redundancy, and fault tolerance purposes. Server farm architecture provides the operation and maintenance of servers.


Load Balancing


Ability of a router to distribute traffic over all network interfaces that are the same distance from the destination address. Load balancing increases the use of network segments which improves bandwidth. A load-balancing algorithm may use both line speed and reliability information.


NAS


Network Attached Storage High-speed, high-capacity data storage that groups large numbers of disk drives that are directly attached to the network and can be used by any server. A NAS    device is typically attached to an Ethernet network and is assigned its own IP address


SAN


Storage Area Network Data communication platform that interconnects servers and storage at Gigabaud speeds. By combining LAN networking models with server performance and mass storage capacity, SAN eliminates bandwidth issues and scalability limitations created by previous SCSI bus-based architectures


RU


Rack Unit Standard form factor measurement for the vertical space that equipment occupies. A rack unit is equal to the height of 1.75 inches (4.4cm). A device is measured in RUs. If a device is 1.75 inches tall, it is 1RU. If it is 3.5 inches tall, it is 2RU.


Structured Cabling


Using an internationally recognized standard to implement a physical network cabling design, this is easily understood by installers, network administrators, and any other technicians who work with cables.


EMI


Disturbance in an electronic circuit from an external electrical source.


Telecommunications Room


Facility that contains network and telecommunications equipment, vertical and horizontal cable terminations, and cross-connect cables. Also known as a riser, a distribution facility, or a wiring closet.


IDF


Intermediate Distribution Facility Secondary communications room for a building that uses a star networking topology. An IDF has a frame that cross-connects the user cable media to individual user line circuits and may serve as a distribution point for multi-pair cables from the main distribution frame. The IDF is dependent on the MDF


MDF


Main Distribution Facility Primary communications room for a building. An MDF is the central point of a star networking topology where patch panels, hubs, and routers are located. It is used to connect public or private lines coming into the building to internal networks.


AP


Access Point Access Layer device that connects to a wired network and relays data between wireless and wired devices. An AP connects wireless communication devices to form a wireless network to allow roaming.


PoE


Power over Ethernet Powering standard of network devices over Ethernet cable. IEEE 802.3af and cisco specify two different PoE methods. Cisco power sourcing equipment and powered devices support both PoE methods.


POP


Point of Presence Physical connection between a communication facility provided by an ISP or local telephone company, and an organization’s main distribution facility.


Demarc


Indicated point between carrier equipment and CPE The demarc provides a boundary that designates responsibility for equipment between the service provider (SP) and customer. Equipment from the service provider up to the point of demarcation is the responsibility of the provider; anything past the demarc point is the responsibility of the customer.


SP


Service Provider Organization, such as the local phone or cable company, that provides Internet service.


DoS


Denial of Service Attack by a single system on a network that floods the bandwidth or resources of a targeted system, such as a web server, with the purpose of shutting it down.


Firewall


One or more router or access servers designated as a buffer between any connected public networks and a private network. A firewall router uses access lists and other methods to ensure the security of the private network.


T1


Digital WAN carrier facility that transmits DS-1-formatted data at 1.544 Mbps through the telephone-switching network, with the use of AMI or binary 8-zero substitution coding.


E1


Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 2.048 Mbps. E1 lines can be leased for private use from common carriers.


Punchdown block


A device that connects telephone or data lines to each other. The solid copper wires are punched down into short open-ended slots to establish connectivity.


  CPE


Customer Premise Equipment Terminating equi0pment, such as terminals, telephones, and modems, supplied by the telephone company, installed at a customer site, and connected to the telephone company network.


Interface


1) Connection between two systems or devices. 2) In routing terminology, a network connection. 3) In telephony, a shared boundary devined by common physical interconnection characteristics, signal characteristics, and meanings of interchanged signals. 4) the boundary between adjacent layers of the OSI model


Default Gateway


Path of a packet on a network used by default, or as the gateway of last resort, when the destination hosts are not listed in the routing table.


Form Factor


Physical size and shape of computer components. Components that share the same form factor are physically interchangeable.


Out-of-band


Transmission using frequencies or channels outside the frequencies or channels normally used for information transfer. Out-of-band signaling is often used for error reporting in situations in which in-band signaling can be affected by whatever problems the network might be experiencing.


In-band


Management technique for connecting a computer to a network device. In-band management is used to monitor and make configuration changes to a network device over a network connection.


Port density


Amount of ports per RU on a switch


Wire speed


Rate that packets are forwarded on a network.


VLAN


Virtual Local Area Network Group of devices on a network, typically end-user stations, that communicate as if attached to the same network segment even though they may be on different segments. VLANs are configured on workgroup switches. Switches with VLANs may interconnect using VLAN trunking protocols.


CAM


Content Addressable Memory MAC address table maintained by a switch. A CAM is recreated every time a switch is activated.


Aging timer


Period of time in which an entry must be used before a switch deletes it from the MAC address table.


Unicast


Type of message sent to a single network destination.


Floods


Technique used by switches to pass traffic that is received on an interface to all other interfaces of the device except the interface on which the information was originally received.


Broadcast


Set of devices that receive broadcast frames originating from any of the devices within the set. A broadcast domain is typically bounded by routers because routers do not forward broadcast frames.


Collision Domain


Network area in Ethernet where frames that have collided are propagated. Repeaters and hubs have collision domains. LAN switches, bridges, and routers do not.


Microsegmentation


Division of a network into smaller segments, usually with the intention of increasing aggregate bandwidth to network devices.


VC


Virtual Circuit Logical relationship created to ensure reliable communication between two network devices. A virtual circuit is defined by a virtual path identifier/virtual channel identifier pair, and can be either a permanent virtual circuit or switched virtual circuit. Virtual circuits are used in Frame Relay and X.25. In ATM, a virtual circuit is called a virtual channel.


Asymmetric


When one function on a network takes a greater length of time than the reverse function. An example of an asymmetric function is the compression and decompression of data.


Uplink Ports


High-speed port that connects to areas that have a higher demand for bandwidth, such as another switch, a server farm, or other networks.


Microprocessor


Chip that contains the central processing unit for the device.


Multilayer Switching


Device that filters and forwards packets based on MAC addresses and network addresses. A layer 2/ layer 3 switch is a multilayer switch.


ASIC


Application-specific Integrated circuit Circuit that gives precise instructions for the functionality of a device during Layer 3 switching.


Cache


Act of storing data, or the location of stored data.


Store and forward Packet Switching


Technique in which frames are completely processed before being forwarded out of the appropriate port. Store and forward packet switching is a process that includes the calculation of the cyclic redundancy check and the verification of the destination address.


Cut-through switching


Process where data is streamed through a switch so that the leading edge of a packet exits the switch at the output port before the packet finishes entering the input port. Cut-through packet switching enables a device to read, process, and forward packets as soon as the destination address is looked up, and the outgoing port determined. Cut-through packet switching is also known as on-the-fly packet switching. Contrast with store and forward packet switching.


CRC


Cyclic Redundancy Check Store and Forward error checking technique that counts the number of packets the checksum generates by far end device and compares it to the checksum calculated from the data received. A CRC error may indicate noise, gain hits, or transmission problems on the data link or interface.


FCS


Frame Check Sequence Characters added to a frame for error control purposes. FCS is used in HDLC, Frame Relay, and other Data Link Layer protocols


Fast-forward


Cut-through switching method where the switch forwards the frame before all of frame is received. Using the fast-forward method, the switch forwards the frame out of the destination port immediately when the destination MAC address is read. The switch does not calculate or check the CRC value. The fast-forward method has lowest latency but may forward collision fragments and damaged frames. This method of switching works best in a stable network with few errors.


Fragment-free


A switching technique that forwards a frame after the first 64 bytes are received. Fragment-free switching has a higher latency than fast-forward switching.


Runt


Frame that is less than 64 bytes, usually the result of a collision. In fragment-free switching, the switch reads the first 64 bytes of the frame before it begins to forward it out the destination port. Checkign the first 64 bytes ensures that the switch does not forward collision fragments.


Threshold value


Maximum number of errors that a switch allows before it will go into store and forwarding switching to slow traffic and correct the problem.


Adaptive Cut-through


Type of switching when the flow reverts back to fast-forward mode when the number of errors drops below the threshold value to an acceptable level.


Redundancy


1) Duplication of components on a network, such as devices, services, or connections, for the purpose of maintaining operability if any tools fails. 2) Portion of the total information contained in a message that can be eliminated without losing the contest.


Congestion


Traffic in excess of network capacity.


Availability


Condition of accessibility.


Switching loops


Causes duplicate frames to be sent throughout a network. A switching loop occurs when there is more than one path between two switches.


Broadcast storm


Undersirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and typically causes network time-outs.


Unicast Frames


Data packet that is addressed to a single destination


STP


Spanning Tree Protocol Bridge standards that use the spanning-tree algorithm and enable a bridge to dynamically work around loops in a network topology by creating a spanning tree. A bridge exchanges BPDU messages with other bridges to detect loops, and then removes the loops by shutting down bridge interfaces.


BPDU


Bridge Protocol Data Units STP hello packets that is sent out at configurable intervals to exchange information among bridges ni the network


Blocking


1) Condition in a switching system in which no paths are available to complete a circuit. 2) Condition when one activity cannot begin until another has been completed.


Listening


One of four states that a port cycles through when a switch powers on an STP network. The switch listens for BPDUs from neighboring switches.


Learning


One of four states that a port cycles through when a switch powers on an STP network. The switch uses information learned to forward a packet.


Forwarding


Process of sending a frame out of a port toward the destination by way of an internetworking device. Examples of devices that forward frames are hosts, repeaters, bridges, and routers.


Root Bridge


Also known as Root Switch Designated packet forwarding device in a spanning-tree implementation that receive topology information and notifies all other bridges in the network when topology changes are required. A root bridge prevents loops and provides a measure of defense against link failure.


Root Switch


Also known as Root Bridge Designated packet forwarding device in a spanning-tree implementation that receive topology information and notifies all other bridges in the network when topology changes are required. A root bridge prevents loops and provides a measure of defense against link failure.


BID


Bridge ID Identification of the root bridge which is the focal point in an STP network.