Network Chapter 3 – Flashcards
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AD
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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 admin when another protocol takes precedence over a previously higher-rated one.
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ARP cache
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A database of records that maps MAC addresses to IP addresses. Stroed 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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ARP table
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A database of records that maps MAC addresses to IP addresses. Stroed 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
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A group of networks, often on the same domain, that are operated by the same organization.
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ASN
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A globally unique number that identifies an autonomous system. Works similarly to IP addresses that identify individual nodes on a network. Assigned by IANA and consists of 32 bits.
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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. The best path is usually the direct path between two points.
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BGP
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Also known as 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 router that connects an autonomous system with an outside network. Ex: 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 boradcast transmissions.Switches and repeating devices by default extend these domains and routers and Layer 3 switches separate them.
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checksum
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A method of error checking that determines 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 several types of 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 recognize a best path in the event of a change or network outage.
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default route
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A backup route, usually to another router, used when a router cannot determine a path to a message's destination.
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distance-vector routing protocol
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The simplest type of routing protocols; used to determine the best route for data based on the distance to a destination. Some only factor the number of hops, others take into account thins like latency and other network traffic characteristics.
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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 in 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. This can reroute data on a failure or congestion in the network.
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EGP
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A type of protocol used by border routers and exterior routers to distribute data outside of autonomous systems. This is the only modern example of an exterior gateway protocol.
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exterior router
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A router that directs data between autonomous systems. Ex: 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 this information to ensure packets belonging to the same transmission arrive together.
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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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gateway router
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A router that connects an autonomous system with an outside network. Ex: The router that connects a business to its ISP.
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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, is used for router-to-router communication.
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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
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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 groups, and nodes use this to leave or join a multicast group.
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IGP
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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 connection between a node and network is malfunctioning. Can be prompted by any number of problems even 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 traverse more than one LAN segment and more than one type of network through a router.
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IS-IS
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A link-state routing protocol that uses a best-path algorithm similar to OSPF's. Designed for interior routers only and was originally codified by ISO.
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ISN
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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 OS.
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jumbo frame
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A setting on Ethernet network devices 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,a nd 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 ping, traceroute, tracert, or BGP to remotely 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
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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. Router returns and ICMP error message to sender, although, the sender sees messages being lost for no reason.
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Nbtstat
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A TCP/IP troubleshooting utility that provies 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 netwofks, this process is managed by ARP with help from ICMP. On IPv6 networks, NDP automatically detects neighborign devices and adjusts to failures.
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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.
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OSPF
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An IGP and link-state routing protocol that makes up for some of the limitations of RIP and 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 network issues along a route; similar to UNIX's mtr command.
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probe
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A repeated trial message transmitted by the tracert and traceroute utilities to trigger routers along a route to return specific information about the route.
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RIP
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The oldest routing protocol that is still widely used. A distance-vector protocol that uses hop count as it's routing metric and allows up to only 15 hops.
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RIPv2
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An updated version of the original protocol. It generates less broadcast traffic and functions more securely than the previous one. Packet forwarding is still limited to 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 specifications.
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routing cost
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A value assigned to a particular route as judged by the network admin; 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. Routing metrics may be calculated using any of several variables, 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. This determines 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 them.
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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, record 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. These remain the same until someone manually modifies them with the ARP utility.
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static routing
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A technique in which a network admin programs a router to use specific paths between networks. It does not account for network congestion, failed connections, device moves, and manual configuration. This is not optimal.
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three-way handshake
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A three-step process in which Transport layer protocols establish a connection between nodes. Uses a SYN packet to a node, the node responds with a SYN-ACK packet, and the next response is an ACK packet.
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traceroute
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A TCP/IP troubleshooying 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 networked node to another. Identifies all intermediate hops.
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tracert
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A windows utility that uses ICMP echo requests to trace the path from one networked node to another. Identifying all intermediate hops.
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TTL
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Indicates the maximum duration that an IPv4 packet can remain on the network before it is discarded. Although this field was originally meant to represent units of time, on mondern networks it represents the number of times a packet can be forwarded by a router, or the maximum router hops remaining.
