8.5 Device Mobility Operation

This topic describes how Cisco Unified Communications Manager Device Mobility works.

When and How Is the Phone Configuration Modified?

  • Each phone is configured with a device pool (that is, the home device pool).
  • IP subnets are associated with device pools.
  • If the IP address of the phone matches a configured IP subnet, one of the associated device pools is selected (load-shared).
  • If the selected device pool is different from the home device pool of the device, these settings of the two device pools are checked:
    1. If the physical locations are not different, the phone configuration is not modified.
    2. If the physical locations are different, the roaming-sensitive settings of the roaming device pool are applied.
    3. Additionally, if the device mobility groups are not different, the Device Mobility-related settings of the roaming device pool are also applied.
  • In all other cases, the home device pool configuration is applied.

Each phone is configured with a device pool. This device pool is the home device pool of the phone.

IP subnets are associated with device pools (by configuring device mobility infos).

If a phone for which Device Mobility is enabled registers with the Cisco Unified Communications Manager and has an IP address that matches an IP subnet that is configured in a device mobility info, these actions occur:

  • The current device pool is chosen.
    1. If the device mobility info is associated with the home device pool of the phone, the phone is considered to be in its home location; Device Mobility will not reconfigure the phone.
    2. If the device mobility info is associated with one or more device pools other than the home device pool of the phone, one of the associated device pools is chosen based on a load-sharing algorithm (round robin).
  • If the current device pool is different from the home device pool, these checks are performed:
    1. If the physical locations are not different, the configuration of the phone is not modified.
    2. If the physical locations are different, the roaming-sensitive parameters of the current (that is, the roaming) device pool are applied.
    3. If (in addition to different physical locations) the device mobility groups are the same, the Device Mobility-related settings are also applied (in addition to the roaming-sensitive parameters).

In summary, the roaming-sensitive parameters are applied when the physical location of the current device pool is different from the physical location of the home device pool (that is, when roaming between physical locations). The Device Mobility-related settings are applied in addition to the roaming-sensitive parameters when the physical locations are different and the device mobility groups are the same (that is, when roaming between physical locations within the same device mobility group).

As a result, physical locations and device mobility groups should be used in two ways:

  • Physical locations: Configure physical locations so that codec choice and CAC truly reflect the current location of the device. Ensure that local Cisco Unified Survivable Remote Site Telephony (SRST) references and local media resources at the roaming site are used instead of SRST references and media sources that are located at the (currently remote) home network. Depending upon the network structure and allocation of services, you may define physical locations that are based on a city, an enterprise campus, or a building.
  • Device mobility groups: A device mobility group should define a group of sites with similar dialing patterns or dialing behavior. Device mobility groups represent the highest-level geographic entities in your network. Depending upon the network size and scope, your device mobility groups could represent countries, regions, states or provinces, cities, or other entities. Because Device Mobility-related settings (which are applied only when roaming within the same device mobility group) affect call routing, different device mobility groups should be set up whenever roaming users should not be forced to adapt their dialing behavior. In this case, as in roaming between different device mobility groups, the phone-configuration parameters that affect call routing (that is, the Device Mobility-related settings) are not modified.
Note

When using globalized call routing and local route groups, device mobility groups are irrelevant. The reason is that there is no need to change the device-level CSS, the AAR CSS, and the device-level AAR group.

Device Mobility Operation: Flowchart

The figure illustrates Device Mobility operation in a flowchart.

A phone registers with Device Mobility as follows:

  1. A device attempts to register with the Cisco Unified Communications Manager.
  2. The Cisco Unified Communications Manager checks if Device Mobility is enabled for the device.
    1. If Device Mobility is not enabled for the device, the default behavior applies (go to Step 10); otherwise continue.
  3. The Cisco Unified Communications Manager checks if the IP address of the IP phone is found in one of the device mobility groups.
    1. If the IP address is not found, the default behavior applies (go to Step 10); otherwise continue.
  4. The device pool to be used is chosen.
    1. If the home device pool is associated with the device mobility info in which the IP address of the phone was found, the home device pool is chosen.
    2. If the home device pool is not associated with the device mobility info in which the IP address of the phone was found, the device pool is chosen based on a load-sharing algorithm (if more than one device pool is associated with the device mobility info).
  5. If the chosen device pool is the home device pool, the default behavior applies (go to Step 10); otherwise continue.
  6. If the physical locations of the chosen device pool and the home device pool are the same, the default behavior applies (go to Step 10); otherwise continue.
  7. The roaming-sensitive settings of the chosen device pool (that is, the roaming device pool) are used to update the configuration of the phone.
    Note

    In this case, overlapping settings (that is, settings that exist at the phone as well as at the device pool, namely, MRGL, Location, and Network Locale) of the roaming device pool have priority over the corresponding settings at the phone. This behavior is different from the default behavior (see Step 10).

  8. If the device mobility groups of the chosen device pool and the home device pool are the same, the phone configuration is updated by applying the Device Mobility-related settings; otherwise continue.
    Note

    In this case, all settings are overlapping settings (that is, all Device Mobility-related settings exist at the phone as well as at the device pool), and the parameters of the roaming device pool have priority over the corresponding settings at the phone. This behavior is different from the default behavior (see Step 10).

  9. Where the phone configuration has been updated (either with the roaming-sensitive settings only or with the roaming-sensitive settings and the Device Mobility-related settings), the phone is reset so that the updated configuration is applied to the phone.
    Note

    The process ends here; do not continue to Step 10. Step 10 was directly referenced from previous steps in certain conditions and does not apply after Step 9.

  10. Here is a description of the default behavior. First, the settings of the home device pool (that is, the device pool that is configured at the phone) are applied. Some configuration parameters of the device pool can also be set individually at the phone. These overlapping phone-configuration parameters are MRGL, Location, Network Locale, Device Mobility CSS (which is called simply CSS at the phone), AAR CSS, and AAR Group. If these parameters are configured at the phone (that is, are not set to [None]), the phone-configuration settings have priority over the corresponding setting at the device pool.
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