GateD Configuration Guide - Glossary

# 6.7.1 Glossary of Terms

Terms used in descriptions throughout this document are defined below:

adjacency
  A relationship formed between selected neighboring routers for the purpose of exchanging routing information. Not every pair of neighboring routers becomes adjacent.
autonomous system
  A set of routers under a single technical administration, using an interior gateway protocol and common metrics to route packets within the AS, and using an exterior gateway protocol to route packets to other ASs. Since this classic definition was developed, it has become common for a single AS to use several interior gateway protocols and sometimes several sets of metrics within an AS. The use of the term Autonomous System stresses that even when multiple IGPs and metrics are used, the administration of an AS appears to other ASs to have a single coherent interior routing plan and to present a consistent picture of what networks are reachable through it. The AS is represented by a number between 1 and 65534, assigned by the Internet Assigned Numbers Authority.
BGP
Border Gateway Protocol
  One of a class of exterior gateway protocols, described in more detail in the BGPsection of the Protocol Overview.
cost
  An OSPF metric. See metric.
delay
  A HELLO metric. Valid values are from zero to 30000 inclusive. The value of 30000 is the maximum metric and means unreachable. See metric.
designated router
  `OSPF:` Each multiaccess network that has at least two attached routers has a designated router. The designated router generates a link state advertisement for the multiaccess network and assists in running the protocol. The designated router is elected by the HELLO protocol.
destination
  Any network or any host.
distance
  An EGP metric. See metric. Valid values are from zero to 255 inclusive.
egp
exterior gateway protocol
exterior routing protocol
  A class of routing protocols used to exchange routing information within an autonomous system. A detailed explanation of exterior gateway protocolsis available in the Protocol Overview.
EGP
Exterior Gateway Protocol
  One of a class of exterior gateway protocols, described in more detail in the EGPsection of the Protocol Overview.

forwarding table

> The table in the kernel that controls the forwarding of packets is a forwarding table, also know in ISO speak as a forwarding information base, or FIB. The forwarding table contains the tuples which help forward the packet of:

- network (or CIDR prefix),
- next-hop(s)
- interface packet goes out

The table that GateD uses internally to store routing information it learns from routing protocols is a routing table, known in ISO speak as a routing information base, or RIB. gateway

An intermediate destination by which packets are delivered to their ultimate destination. A `host` address of another router that is directly reachable via an attached network. As with any host address it may be specified symbolically. gateway_list

A list of one or more `gateway`s separated by white space.

HELLO

> One of a class of interior gateway protocols, described in more detail in the HELLOsection of the Protocol Overview. host

> The IP address of any host. Usually specified as a dotted quad, four values in the range of 0 to 255 inclusive separated by dots (`.`). For example `132.236.199.63` or `10.0.0.51`. It may also be specified as an eight digit hexadecimal string preceded by `0x`. For example `0x????????` or `0x0a000043`. Finally, if `options noresolv` is not specified, a symbolic hostname. For example `gated.cornell.edu`or `nic.ddn.mil`. The numeric forms are much preferred over the symbolic form.

interface

> The `host` address of an attached interface. This is the address of a broadcast, nbma or loopback interface and the remote address of a point-to-point interface. As with any host address it may be specified symbolically.

interface

> The connection between a router and one of its attached networks. A physical interface may be specified by a single IP address, domain name, or interface name. (Unless the network is an unnumbered point-to-point network.) Multiple levels of reference in the configuration language allow identification of interfaces using wildcard, interface type name, or delete word address. Be careful with the use of interface names as future Unix operating systems may allow more than one address per interface. Dynamic interfaces can be added or deleted and indicated as up or down as well as changes to address, netmask and metric parameters.

igp

interior gateway protocol

interior routing protocol

> One of a class of routing protocols used to exchange routing information within an autonomous system. A detailed explanation of interior gateway protocolsis available in the Protocol Overview. interface_list

> A list of one or more interface names including wildcard names (names without a number) and names which may specify more than one interface or address, or the token "all" for all interfaces. See the section on interface lists for more information.

IS-IS

> One of a class of interior gateway protocols, described in more detail in the IS-ISsection of the Protocol Overview. local_address

> The `host` address of an attached interface. This is the address of a broadcast, nbma or loopback interface and the local address of a point-to-point interface. As with any host address it may be specified symbolically.

mask

> A means of subdividing networks using address modification. A mask is a dotted quad specifying which bits of the destination are significant. Except when used in a route filter, GateD only supports contiguous masks.

mask length

> The number of significant bits in the mask.

metric

> One of the units used to help a system determine the best route. Metrics may be based on hop count, routing delay, or an arbitrary value set by the administrator depending on the type of routing protocol. Routing metrics may influence the value of assigned internal preferences. (See preference.)

> This sample table shows the range of possible values for each routing protocol metric and the value used by each protocol (See Protocol Overview.) to reach a destination.

            SAMPLE ROUTING PROTOCOL METRICS
            Protocol  Metric Represents     Range    Unreachable
            --------  -----------------     -----    -----------
            RIP       distance (hop-count)  0-15           16
            HELLO     delay (milliseconds)  0-29999     30000
            OSPF      cost of path          0-?????    Delete
            ISIS      cost of path          0-254      Delete
            EGP       distance (unused)     0-65535       255
            BGP       unspecified           0-65534     65535

multiaccess networks

> Those physical networks that support the attachment of multiple (more than two) routers. Each pair of routers on such a network is assumed to be able to communicate directly. natural mask

> XXX - define

neighbor

> Another router which with implicit or explicit communication is established by a routing protocol. Neighbors are usually on a shared network, but not always. This term is mostly used in OSPF and EGP. Usually synonymous with peer.

neighboring routers

> Two routers that have interfaces to a common network. On multiaccess networks, routers are dynamically discovered by OSPF's HELLO protocol.

network

> Any packet-switched network. A network may be specified by its IP address or network name. The host bits in a network specification must be zero. Default may be used to specify the default network (0.0.0.0).

network

> The IP address of a network. Usually specified as a dotted quad, one to four values, in the range 0 to 255 inclusive, separated by dots (`.`), for example, `132.236.199`, `132.236`or `10`. It may also be specified as a hexadecimal string preceded by `0x` with an even number of digits, of length between two and eight. For example `0xnnnnnn`, `0xnnnn,`or `0x0n`. Also allowed is the symbolic value `default`which has the distinguished value `0.0.0.0`, the default network. If `options noresolv` is not specified a symbolic network name. For example `nr-tech-prod`, `cornellu-net`and `arpanet`. The numeric forms are much preferred over the symbolic form.

number

> A positive integer.

OSPF

Open Shortest Path First

> One of a class of interior gateway protocols, described in more detail in the OSPF section of the Protocol Overview. ospf_area

> XXX - define.

peer

> Another router which with implicit or explicit communication is established by a routing protocol. Peers are usually on a shared network, but not always. This term is mostly used by BGP. Usually synonymous with neighbor.

port

> A UDP or TCP port number. Valid values are from 1 through 65535 inclusive.

preference

> A `preference` is a value between 0 (zero) and 255, used to select between many routes to the same destination. The route with the best (numerically lowest) preference is the active route. The active route is the one installed in the kernel forwarding table and exported to other protocols. Preference zero is usually reserved for routes to directly attached interfaces. A default preference is assigned to each source from which GateD receives routes. (See Preference.)

prefix

> A contiguous mask covering the most significant bits of an address. The prefix length specifies how many bits are covered.

QoS

quality of service

> The OSI equivalent of TOS. RIP

Routing Information Protocol

> One of a class of interior gateway protocols, described in more detail in the RIP section of the Protocol Overview. reject route

> XXX - define.

route filter

> XXX - define.

router id

> A 32-bit number assigned to each router running the OSPF protocol. This number uniquely identifies the router within the autonomous system.

router_id

> An IP address used as unique identifier assigned to represent a specific router. This is usually the address of an attached interface.

RIB

routing information base

routing database

routing table

> The repository of all of GateD's retained routing information , used to make decisions and as a source for routing information which is propagated. simplex

> An interface may be marked as simplex either by the kernel, or by interface configuration. A simplex interface is an interface on a broadcast media that is not capable of receiving packets it broadcasts.

> GateD takes advantage of interfaces that are capable of receiving their own broadcast packets to monitor whether an interface appears to be functioning properly.

time

> A time value, usually a time interval. It may be specified in any one of the following forms:

> number

> > A non-negative decimal number of seconds. For example, `27`, `60` or `3600`.

number: number

> A non-negative decimal number of minutes followed by a seconds value in the range of zero to 59 inclusive. For example, `0:27`, `1:00` or `60:00`. number: number: number

> > A non-negative decimal number of hours followed by a minutes value in the range of zero to 59 inclusive followed by a seconds value in the range of zero to 59 inclusive. For example, `0:00:27`, `0:01:00`or `1:00:00`. time to live

ttl

> The Time To Live (TTL) of an IP packet. Valid values are from one (1) through 255 inclusive.

> TOS

type of service

> The type of service is for internet service quality selection. The type of service is specified along the abstract parameters precedence, delay, throughput, reliability, and cost. These abstract parameters are to be mapped into the actual service parameters of the particular networks the datagram traverses. The vast majority of IP traffic today uses the default type of service.

Last updated April 26, 1997