15.3 ILS Networking

This topic describes the ILS networking components and their functions.

Main ILS and GDPR Functions

Component Description
ILS networking Joins clusters into a network. Provides discovery of ILS services that are available on remote clusters. Allows dynamic exchange of information among participating clusters.
URI exchange A function of GDPR that exchanges URIs and associated route strings.
Number exchange A function of GDPR that exchanges numbers and associated route strings.

ILS consists of three main components.

ILS Networking

ILS networking joins clusters into a network. ILS networking provides a discovery of ILS services that are available on remote clusters. ILS services can use the ILS network to propagate service-specific information across clusters.

Exchange of Directory URIs

Each cluster can propagate and learn URIs and their associated route strings from the members of an ILS network. Each cluster advertises all locally configured URIs and the route string of the cluster to all other clusters. Each cluster listens to the advertisements that are sent by other clusters and builds a table of learned URIs and their associated route strings.

Exchange of Numbers and Patterns

Similar to the exchange of directory URIs, this function exchanges numbered call-routing information over an ILS network. The call-routing information that is advertised includes the route string of the advertising cluster.

Note

While ILS is a general service that allows the discovery of remote ILS services and provides the framework to exchange any kind of information between clusters, GDPR is an ILS application that uses the ILS network to exchange call-routing information.

Cisco documentation and the Cisco Unified Communications Manager Administration GUI often do not differentiate between ILS and GDPR and use the term ILS also in the context of GDPR.

ILS Network Topology

This section describes the main characteristics of an ILS network, including ILS cluster roles and how synchronization is performed within an ILS network.

  • Clusters can be joined to form an ILS network.
  • Each cluster in an ILS network has a hub or spoke role.
  • Each hub syncs directly with all other hubs (full mesh between hubs) and with its own spokes.
  • A hub can have no spokes, one spoke, or more than one spoke.
  • Each spoke has one hub, and it syncs directly with that hub only.

Cisco Unified Communications Manager clusters can be joined to form an ILS network. Each cluster in an ILS network has one of the following roles: hub or spoke.

Each hub synchronizes information directly with all other hubs and with its own spokes. A hub can have no spoke, one spoke, or more than one spoke. Each spoke has one hub and synchronizes information with this hub only.

In summary, hubs are fully meshed, and spokes form a star topology with their hub. Any combination is possible: a single hub with associated spokes, multiple hubs with no spokes, or a mixed topology, as shown in the figure.

By default, each cluster is in standalone mode. This situation means that the cluster is not part of an ILS network.

ILS Synchronization

Synchronization in an ILS network is pull-based, which means that each cluster requests information from its connected clusters.

Per synchronization interval, the cluster pulls in information from every other cluster that is directly associated.

  • Hubs fetch information from all other hubs.
  • Spokes fetch information from their own hub.
  • Sync interval is configured independently per cluster (default: 10 minutes).

Convergence time depends on the synchronization path (number of hops) and configured sync intervals.

  • Maximum distance in an ILS network is three hops: spoke–hub–hub–spoke.
  • Maximum convergence time is the total of sync intervals along the synchronization path (default: 30 minutes).

Spokes pull information only from their hub. Hubs pull information from all other hubs. The synchronization interval can be configured independently at each cluster. The default is 10 minutes, and the configurable range is from 1 minute to 1440 minutes (24 hours).

Because each cluster can be configured with different synchronization intervals, update times can also be different. The maximum update time is the total of all synchronization intervals along the synchronization path. The maximum synchronization path is determined by the ILS network topology.

Because all hubs are fully meshed, the maximum number of hops in every ILS network is three.

The figure shows an example of an ILS topology with four clusters. Spoke 1 is connected to hub 1. Hub 1 is connected to hub 2, which is connected to spoke 2. When calculating the maximum update time for updates that occur in spoke 2 to be seen at spoke 1, the synchronization intervals of spoke 1, hub 1, and hub 2 are relevant. The synchronization interval of spoke 2 is not applicable in this case.

Note

Although the synchronization interval can be configured independently per cluster, it is recommended that you configure the same synchronization interval for all members within an ILS network.

ILS Networking: Intercluster Communication

This section describes how information is exchanged between clusters within an ILS network.

ILS runs on the publisher of each cluster.

  • Learned information is stored in a database.
  • Database updates are replicated to all subscribers.

ILS is a feature service that must be activated on the publisher server of each participating cluster.

The publisher server manages the communication to other clusters. The publisher stores learned information in the configuration database. The learned information is therefore distributed within the cluster through database replication.

ILS Networking Characteristics

This section describes the main characteristics of an ILS network.

  • ILS exchange is secured by TLS based on one of these options:
    1. Password
      • Same shared password on all participating publishers
      • Configured at the ILS Configuration pages
    2. Certificate
      • Tomcat certificates of all participating publishers must be exchanged
      • Bulk Certificate Management tool in Cisco Unified Operating System Administration can be used
  • Each participating cluster must have a unique enterprise cluster ID.
  • Each participating cluster advertises its call-routing information (URIs and numbers) with a unique route string.

ILS relies on TLS for secure information exchange. TLS endpoint authentication can be based on certificates or a shared password that is configured at all clusters that participate in the ILS network. In the case of certificates, each publisher server must trust the Tomcat certificate of all other publisher servers. The simplest way to exchange the certificates is to use the Bulk Certificate Management tool.

Each cluster that is a member of an ILS network must have a unique cluster ID.

Each cluster advertises its call-routing information (URIs, numbers, and patterns) with a unique route string.

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