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Feature Description - MPLS 01

NE05E and NE08E V300R003C10SPC500

This is NE05E and NE08E V300R003C10SPC500 Feature Description - MPLS
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Information Advertisement Component

Information Advertisement Component

The information advertisement component advertises network resource information over an MPLS TE network. TE is used to control network traffic distribution, which optimizes network resource usage. All nodes, especially ingress nodes on an MPLS TE network, must obtain information about link resources to determine the paths and nodes for MPLS TE tunnels.

Related Concepts

Information Advertisement Component involves the following concepts:
Table 4-4 Related concepts

Concept

Description

Total link bandwidth

Manually set for a physical link.

Maximum reservable bandwidth

Maximum bandwidth that a link can reserve for an MPLS TE tunnel to be established.

The maximum reservable bandwidth must be lower than or equal to the total link bandwidth. The maximum reservable bandwidth can be manually set.

TE metric

A TE metric is used in TE tunnel path calculation, allowing the calculation process to be independent from IGP route-based path calculation.

The IGP metric is used for MPLS TE tunnels by default.

SRLG

A shared risk link group (SRLG) is a set of links which are likely to fail concurrently when sharing a physical resource (for example, an optical fiber).

Links in an SRLG share the same risk of faults. If one link fails, other links in the SRLG also fail.

An SRLG enhances CR-LSP reliability on an MPLS TE network enabled with CR-LSP hot standby or TE FRR. For more information about the SRLG, see SRLG.

Link administrative group

Link administrative group is also called link color.

A link administrative group is a 32-bit vector, with each bit set to a specified value that is associated with a desired meaning. For example, a link administrative group attribute can be configured to describe link bandwidth, a performance parameter (such as the delay time) or a management policy. The policy can be a traffic type (multicast for example) or a flag indicating that an MPLS TE tunnel passes over the link. The link administrative group attribute is used together with affinities to control the paths for tunnels.

Contents to Be Advertised

The network resource information to be advertised includes the following items:
  • Link status information: interface IP addresses, link types, and link metric values, which are collected by an Interior Gateway Protocol (IGP)

  • Bandwidth information, such as maximum link bandwidth and maximum reservable bandwidth

  • TE metric: TE link metric, which is the same as the IGP metric by default

  • Administrative group

  • SRLG

Advertisement Methods

Either of the following link status protocol extensions can be used to advertise TE information:
  • OSPF TE

  • IS-IS TE

Open Shortest Path First (OSPF) TE and Intermediate System to Intermediate System (IS-IS) TE automatically collect TE information and flood it to MPLS TE nodes.

When to Advertise Information

OSPF TE or IS-IS TE floods link information so that each node can save area-wide link information in a traffic engineering database (TEDB). Information flooding is triggered by the establishment of an MPLS TE tunnel, or one of the following conditions:

  • A specific IGP TE flooding interval elapses.

  • A link is activated or deactivated.

  • A CR-LSP in an MPLS TE tunnel fails to be established because of insufficient bandwidth.

  • Link attributes, such as the administrative group attribute or affinity attribute change.

  • The link bandwidth changes.

    When the available bandwidth of an MPLS interface changes, the system automatically updates information in the TEDB and floods it. When a lot of tunnels are to be established on a node, the node reserves bandwidth and frequently updates information in the TEDB and floods it. For example, the bandwidth of a link is 100 Mbit/s. If 100 TE tunnels, each with bandwidth of 1 Mbit/s, are established, the system floods link information 100 times.

    To help suppress the frequency at which TEDB information is updated and flooded, the flooding is triggered based on either of the following conditions:

    • The proportion of the bandwidth reserved for an MPLS TE tunnel to the available bandwidth in the TEDB is greater than or equal to a specific threshold.

    • The proportion of the bandwidth released by an MPLS TE tunnel to the available bandwidth in the TEDB is greater than or equal to a specific threshold.

    If either of the preceding conditions is met, an IGP floods link bandwidth information, and constraint shortest path first (CSPF) updates the TEDB.

    For example, the available bandwidth of a link is 100 Mbit/s and 100 TE tunnels, each with bandwidth of 1 Mbit/s, are established over the link. The flooding threshold is 10%. The Figure 4-4 shows the proportion of the bandwidth reserved for each MPLS TE tunnel to the available bandwidth in the TEDB.

    Bandwidth flooding is not performed when tunnels 1 to 9 are created. After tunnel 10 is created, the bandwidth information (10 Mbit/s in total) on tunnels 1 to 10 is flooded. The available bandwidth is 90 Mbit/s. Similarly, no bandwidth information is flooded after tunnels 11 to 18 are created. After tunnel 19 is created, bandwidth information on tunnels 11 to 19 is flooded. The process repeats until tunnel 100 is established.

    Figure 4-4 Proportion of the bandwidth reserved for each MPLS TE tunnel to the available bandwidth in the TEDB

Results Obtained After Information Advertisement

Every node creates a TEDB in an MPLS TE area after OSPF TE or IS-IS TE floods bandwidth information.

TE parameters are advertised during the deployment of an MPLS TE network. Every node collects TE link information in the MPLS TE area and saves it in a TEDB. The TEDB contains network link and topology attributes, including information about the constraints and bandwidth usage of each link.

A node calculates the optimal path to another node in the MPLS TE area based on information in the TEDB. MPLS TE then establishes a CR-LSP over this optimal path.

The TEDB and IGP link-state data base (LSDB) are independent of each other. The two types of database both collect routing information flooded by IGPs, but they differ in the following ways:
  • A TEDB contains TE information in addition to all the information in an LSDB.
  • An IGP uses information in an LSDB to calculate the shortest path, while MPLS TE uses information in a TEDB to calculate the optimal path.
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Updated: 2019-01-14

Document ID: EDOC1100058933

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