Affinity Naming Function

The affinity naming function simplifies the configuration of tunnel affinities and link administrative group attributes. Using this function, you can query whether a tunnel affinity matches a link administrative group attribute.

Background

A tunnel affinity and a link administrative group attribute are 8-bit hexadecimal numbers. An IGP (IS-IS or OSPF) advertises the administrative group attribute to devices in the same IGP area. RSVP-TE advertises the tunnel affinity to downstream devices. CSPF on the ingress checks whether administrative group bits match affinity bits to determine whether a link can be used to establish an LSP.

Hexadecimal calculations are complex, and maintaining and querying tunnels established using hexadecimal calculations are difficult. To address this issue, the NetEngine 8000 F allows you to assign different names (such as colors) for the 128 bits in the affinity attribute. Naming affinity bits help verify that tunnel affinity bits match link administrative group bits, facilitating network planning and deployment.

Implementation

An affinity name template can be configured to manage the mapping between affinity bits and names. Configuring the same template on all nodes on an MPLS network is recommended. Inconsistent configuration may cause a service deployment failure. As shown in Figure 1, the affinity bits are named using colors. The first affinity bit is named "red", the fourth bit "blue", and the sixth bit "brown." You can name each of the 128 affinity bits differently.

Figure 1 Affinity naming example

Bits in a link administrative group must also be configured with the same names as the affinity bits.

Once affinity bits are named, you can then determine which links a CR-LSP can include or exclude on the ingress. Rules for selecting links are as follows:

IncludeAny: CSPF includes a link when calculating a path, if any link administrative group bit has the same name as an affinity bit.
ExcludeAny: CSPF excludes a link when calculating a path, if any link administrative group bit has the same name as an affinity bit.
IncludeAll: CSPF includes a link when calculating a path, only if each link administrative group bit has the same name as each affinity bit.

Usage Scenarios

The affinity naming function is used when CSPF calculates paths over which RSVP-TE establishes CR-LSPs.

Benefits

The affinity naming function allows you to easily and rapidly use affinity bits to control paths over which CR-LSPs are established.