Glossary

B

backup bandwidth

Maximum bandwidth available for backup tunnels on a link. It is used to constrain backup tunnels. The total bandwidth available to accommodate backup tunnels without interfering with the primary traffic on the link.

backup tunnel

An MPLS Traffic Engineering tunnel used to protect other (primary) tunnel's traffic when a link or node failure occurs.

bandwidth

The available traffic capacity of a link. There are two types of bandwidth: primary and backup.

bandwidth protection

The guarantee that when a single element fails, the backup tunnels associated with that failed element will traverse network links with sufficient bandwidth to support the primary traffic that was traversing the failed element.

BRG

Backup Route Generator. The algorithm component of Tunnel Builder Pro that generates Fast Reroute backup tunnels for elements in a network or checks whether an element is Fast Reroute protected by existing backup tunnels.

D

delay

The time between the initiation of a transaction by a sender and the first response received by the sender. Also, the time required to move a packet from the source to the destination over a given path.

dynamic route

A route that adjusts automatically to network or traffic changes.

E

element

A node, link, or SRLG.

F

Fast Reroute

Fast Reroute (FRR) is a mechanism for protecting MPLS Traffic Engineering (TE) LSPs from link and node failures by locally repairing the LSPs at the point of failure, allowing data to continue to flow on them while their head-end routers attempt to establish new end-to-end LSPs to replace them. FRR locally repairs the protected LSPs by rerouting them over backup tunnels that bypass failed links or nodes.

flow

Protected traffic that uses a network element. When that element fails, all flows are redirected by Fast Reroute backup tunnels protecting that element. In the case of a node, there is at least one flow between each pair of neighbor nodes, depending on the presence of parallel links.

G

global parameters

Parameters that are set for all links and all nodes in the network, rather than on a per-link or per-node basis.

global pool

MPLS traffic engineering allows constraint-based routing (CBR) of IP traffic. One of the constraints satisfied by CBR is the availability of required bandwidth over a selected path. Diff-Serv-aware Traffic Engineering extends MPLS traffic engineering to enable you to perform CBR of "guaranteed" traffic, which satisfies a more restrictive bandwidth constraint than that satisfied by CBR for regular traffic. The more restrictive bandwidth is termed a sub-pool, whereas the regular TE tunnel bandwidth is called the global pool. (The sub-pool is a portion of the global pool.) This ability to satisfy a more restrictive bandwidth constraint translates into an ability to achieve higher quality of service performance (in terms of delay, jitter, or loss) for the guaranteed traffic.

H

head-end

The upstream, transmitting end of a tunnel. This is the first router in the LSP.

hop

Passage of a data packet between two network nodes (for example, between two routers).

I

IGP

Interior Gateway Protocol. Internet protocol used to exchange routing information between routers in the network. Examples of common IGPs include OSPF and RIP.

Interior Gateway Protocol

See IGP.

internetwork

Collection of networks interconnected by routers and other devices that functions (generally) as a single network.

J

jitter

The interpacket delay variance; that is, the difference between interpacket arrival and departure. Jitter is an important metric for voice and video applications.

L

label-switched path

See LSP.

link

Point-to-point connection between adjacent nodes. Links are protected by NHOP backup tunnels.

link speed

Speed at which an interface transmits and receives information.

link speed factor

A global variable in Tunnel Builder Pro that is used to modify the link speed assumed by the Tunnel Builder Pro search algorithm.

load balancing

The distribution of traffic among multiple paths to the same destination in order to use bandwidth efficiently. Load balancing increases the use of network segments, thus increasing the amount of bandwidth that can be routed across a network.

LSP

label-switched path. A sequence of hops (R0...Rn) in which a packet travels from R0 to Rn through label switching mechanisms. A label-switched path can be chosen dynamically, based on normal routing mechanisms, or through configuration.

M

MPLS

Multiprotocol Label Switching. A method for forwarding packets through a network. It enables routers at the edge of a network to apply labels to packets. ATM switches or existing routers in the network core can switch packets according to the labels with minimal lookup overhead.

N

NNHOP backup tunnel

Next-next-hop backup tunnels protect against node failures.

NHOP backup tunnel

Next-hop backup tunnels protect against link and SRLG failures.

node

Endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be interconnected by links, and serve as control points in the network.

P

primary bandwidth

The amount of primary traffic bandwidth on a link that will be backed up by BRG. Tunnel Builder Pro uses the global pool bandwidth or the subpool bandwidth as the primary bandwidth.

primary tunnel

An MPLS tunnel whose LSP can be fast rerouted if there is a failure.

R

route

Path from the sending device to the receiving device.

S

seed router

The Tunnel Builder Pro application references network maps based on a seed router. The seed router provides the MPLS-based topology information.

SRLG

Shared Risk Link Group. Sets of links that are likely to go down together (for example, because they have the same underlying fiber).

static route

User-defined routes that cause packets moving between a source and a destination to take a specified path. It is useful for controlling security and reducing traffic.

subpool

MPLS traffic engineering allows constraint-based routing (CBR) of IP traffic. One of the constraints satisfied by CBR is the availability of required bandwidth over a selected path. Diff-Serv-aware Traffic Engineering extends MPLS traffic engineering to enable you to perform CBR of "guaranteed" traffic, which satisfies a more restrictive bandwidth constraint than that satisfied by CBR for regular traffic. The more restrictive bandwidth is termed a sub-pool, whereas the regular TE tunnel bandwidth is called the global pool. (The sub-pool is a portion of the global pool.) This ability to satisfy a more restrictive bandwidth constraint translates into an ability to achieve higher quality of service performance (in terms of delay, jitter, or loss) for the guaranteed traffic.

T

tail-end

The downstream, receiving end of a tunnel. The router that terminates the traffic engineering LSP.

timeout

Parameter used to limit the calculation time that the Tunnel Builder Pro algorithm spends for each bandwidth protection request.

topology

The physical arrangement of network nodes and media within an enterprise networking structure.

traffic engineering

The techniques and processes used to cause routed traffic to travel through the network on a path other than the one that would have been chosen if standard routing methods had been used.

tunnel

A secure communication between two peers, such as two routers. A traffic engineering tunnel is a label-switched tunnel that is used for traffic engineering. Such a tunnel is set up through means other than normal Layer 3 routing; it is used to direct traffic over a path different from the one that Layer 3 routing could cause the tunnel to take.