Chapter 3 Networking Vocabulary – Flashcards
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AD (administrative distance)
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A number indicating a protocol's reliability, with lower values being given higher priority. This assignment can be changed by a network administrator when one protocol should take precedence over a previously higher-rate protocol on a network.
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ARP table
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(A.K.A ARP cache) A database of records that maps MAC addresses to IP addresses. Is stored on a computer's hard disk where it is used by the ARP utility to supply the MAC addresses of network nodes, given their IP addresses.
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AS (authentication service)
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In Kerberos termonology, the process that runs on a KDC (key distribution center) to initially validate a client that is logging on.
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ASN (autonomous system number)
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A globally unique number identifies an autonomous system. Work similarly to IP addresses that identify individual nodes on a network. Each now consists of 32 bits instead of 16 bits, and they are assigned by IANA.
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Best path
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The most efficient route from one node on a network to another, as calculated by a router. Under optimal network conditions, the best path is the most direct path between two points. However, when traffic congestion, segment failures, and other factors create obstacles, the most direct path might not be the best path.
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BGP (border gateway protocol)
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Dubbled the "protocol of the Internet," this path-vector routing protocol is the only current EGP and is capable of considering many factors in its routing metrics.
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Border router
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(A.K.A gateway router) A router that connects an autonomous system with outside network- for example, the router that connects a business to its ISP.
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Broadcast domain
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Logically grouped network nodes that can communicate directly via broadcast transmission. By default, switches and repeating devices, such as hubs, extend broadcast domains. Routers and other Layer 3 devices separate broadcast domains.
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Checksum
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A method of error checking that determins if the contents of an arriving data unit match the contents of the data unit sent by the source.
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Connectivity device
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One of the several typesof specialized devices that allows two or more networks or multiple parts of one network to connect and exchange data.
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Convergence time
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The time it takes for a router to rcognize a best path in the event of a change or network outage.
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Distance-vector routing protocol
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The simplest type of of routing protocols; used to determine the best route for data based on the distance to a destination. Some only factor in the number of hops to the destination, while others take into account latency and other network traffic characters.
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Dynamic ARP table entry
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A record in an ARP table that is created when a client makes an ARP request that cannot be satisfied by data already on the ARP table.
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Dynamic routing
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A method of routing that automatically calculates the best path between two networks and accumulates this information in a routing table. If congestion or failures affect the network, a router using dynamic routing can detect the problems and reroute data through a different path. Modern networks primarily use this.
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EGP (exterior gateway protocol)
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A type of routing protocol used by border routers and exterior routers to distribute data outside of autonomous systems. BGP is the only modern example of this protocol.
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Exterior router
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A router that directs data between autonomous systems, for example, routers used on the Internet's backbone.
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Flow
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A sequence of packets issued from one source to one or many destinations. Routers interpret flow information to ensure that packets belonging to the same transmission arrive together. May also help with traffic prioritization.
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Flow control
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A method of gauging the appropriate rate of data transmission based on how fast the recipient can accept data.
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Gateway of last resort
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The router on a network that accepts all unroutable messages from other routers.
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Hop
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A term used to describe each trip a unit of data takes from one connectivity device to another. Typically used in the context of router-to-router communications.
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Hop limit
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The number of times that an IPv6 packet can be forwarded by routers on the network; similar to the TTL field in IPv4 packets.
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Hybrid routing protocol
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A routing protocol that exhibits characteristics of both distance-vector and link-state routing protocols.
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IGMP (internet group management protocol or internet group multicast protocol)
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A network layer protocol used on IPv4 networks to manage multicast transmissions. Routers use this to determine which nodes belong to a multicast group, and nodes use this to join or leave a multicast group.
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IGP (interior gateway protocol)
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A type of routing protocol, such as OSPF and IS-IS, used by interior routers and border routers within autonomous systems.
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Interface error
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An error that is reported when a logical (not physical) connection between a node and a network is malfunctioning. They can be prompted by any number of problems, including interface misconfiguration.
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Interior router
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A router that directs data between networks within the same autonomous system.
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Internetwork
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To travers more than one LAN segment and more than one type of network through a router.
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IS-IS (intermediate system to intermediate system)
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A link-state routing protocol that uses a best-path algorithm similar to OSPF's. It was originally codified by ISO, which referred to routers as "intermediate systems," thus the protocol's name. Unlike OSPF, this is designed for use on interior routers only.
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ISN (initial sequence number)
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The sequence number in the first SYN message in a three-way handshake. This appears to be random, but in reality, it is calculated by a specific, clock-based algorithm, which varies by operating systems.
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Jumbo frame
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A setting on Ethernet network device that allows the creation and transmission of extra-large frames, as high as 9198 bytes, depending on the type of Ethernet architecture used.
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Latency
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The delay between the transmission of a signal and its receipt.
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Layer 3 switch
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A switch capable of interpreting Layer 3 data and works much like a router in that it supports the same routing protocols and makes routing decisions.
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Layer 4 switch
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A switch capable of interpreting Layer 4 data, which means it can perform advanced filtering, keep statistics, and provide security functions.
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Link-state routing protocol
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A type of routing protocol that enables routers to share information beyond neighboring routers, after which each router can independently map the network and determine the best path between itself and a message's destination node.
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Looking glass site
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A web site that provides access to a looking glass server, which processes queries generated by by ping, traceroute, tracert, or BGP to femotely report network routing information from its network or Web site.
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MAC address lookup table
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An online database that correlates manufacturers with their respective OUIs.
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MTU (maximum transmission unit)
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The largest IP packet size in bytes allowable by routers in a path without fragmentation and excluding the frame size.
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MTU black hole
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A problem that occurs when a router receives a message that is too large for the next segment's MTU. The router returns an ICMP error message to the sender, but the error message is not returned correctly. From the senders perspective, messages are lost for no apparent reason.
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nbtstat (NetBIOS over TCP/IP Statistics)
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A TCP/IP troubleshooting utility that provides information about NetBIOS names and their IP addresses. If you know the NetBIOS name of a workstation, you can use this to determine its IP address.
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Neighbor discovery
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A process whereby routers learn about all of the devices on their networks. On IPv4 networks, this process is managed by ARP with help from ICMP. On IPv6 networks, NDP ( Neighbor discovery protocol) automatically detects neighboring devices ans automatically adjusts when nodes fail or are removed from the network.
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netstat
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A TCP/IP troubleshooting utility that displays statistics and details about TCP/IP components and connections on a host. It also displays ports, which can signal whether services are using the correct ports.
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OSPF (open shortest pathe first)
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An IGP and link-state routing protocol that makes up for some of the limitations of RIPand can coexist with RIP on a network.
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pathping
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A windows utility that combines the functionality of the tracert and ping utilities to provide deeper information about a network issues along a route; similar to UNIX's mtr command.
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Probe
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(1) A repeated trial message transmitted by the tracert and traceroute utilities to trigger routers along a route to return specific information about the route. (2) In 802.11 wireless networking, a type of frame issued by a station during active scanning to find nearby access points.
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RIP (routing information protocol)
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The oldest routing protocol that is still widely used, it is a distance-vector protocol that uses hop count as its routing metric and allows up to only 15 hops. Compared with other, more modern, routing protocols, it is slower and less secure.
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RIPv2 (routing information protocol version 2)
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An updated version of the original RIP routing protocol that generates less broadcast traffic and functions more securely than its predecessor. However, its packet forwarding is still limited to a maximum of 15 hops.
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route command
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A command-line tool that shows a host's routing table.
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Route redistribution
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A complex, manual process in which route information from one routing protocol is adapted to another routing protocol's specification.
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Routing cost
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A value assigned to a particular route as judged by the network administarator; the more desirable the path, the lower its cost.
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Routing loop
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A problem that happens when a message gets stuck in a loop between a limited number of routers without ever reaching its destination.
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Routing metric
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Properties of a route used by routing protocols to determine the best path to a destination when various paths are available. It may be calculated using any of several variables, including hop count, bandwidth, delay, MTU, cost, and reliability.
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Routing protocol
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The means by which routers communicate with each other about network status. Routing protocols determine the best path for data to take between networks.
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Routing table
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A database stored in a router's memory that maintains information about the location of hosts and best paths for forwarding packets to determine.
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Sequence number
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A chronological number that TCP attaches to each segment so the destination host can, if necessary, recorder segments as they arrive.
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Static ARP table entry
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A record in an ARP table that someone has manually entered using the ARP utility. Static ARP table entries remain the same until someone manually modefies them with the ARP utility.
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Static routing
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A technique in which a network administartor programs a router to use specific parhs between networks. Because it does not account for occasional network congestion, failed connections, or device moves, and requires manual configuration, static routing is not optimal.
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Three-way handshake
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A three-stap process in which Transport layer protocols establish a connection between nodes. The three steps are: Node A issues a SYN packet to node B, node B responds with SYN-ACK, and node A responds with ACK.
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Traceroute
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A TCP/IP troubleshooting utility available in Linux, UNIX, and OS X systems that sends UDP messages to a random port on the destination node to trace the path from one network node to another, identifying all intermediate hops between the two nodes.
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Tracert
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A Windows utility that uses ICMP echo requests to trace the path from one network node to another, identifying all intermediate hops between the two nodes.
