Unified Device Mobility, Part 1

An exciting bit of programming that can be done on Cisco Communication Manager Version 6 and above is to configure a feature called Device Mobility. The idea of device mobility is that people are generally mobile and move their devices around from one location to another.

For instance, say you have configured IP Softphones for the IT or sales and marketing department employees who tend to travel from headquarters to remote offices. The question is, if they make calls, do you want them to use the local gateway or the gateway currently configured back at headquarters? Most likely you would prefer them to use the gateway closest to their current location.

Other things come to mind as well: how about using local media resources? Or if the WAN goes down, being able to still get service from a router running SRST operations. So it is much more than just making sure I use a local gateway, especially when dialing 911 numbers!

There are two types of Phone Settings that can be applied by the device mobility feature:

1) Roaming Sensitive settings – deal with parameters you would normally configure always based upon the phones physical location. The roaming sensitive settings that can be changed when moving from one physical location to another would be:

  • DTG (Date Time Groups)
  • Regions – Deal with codec selection
  • Location – goes hand in hand with Region since the region determines your per call bandwidth requirements and location deals with maximum bandwidth when calling from one location to another
  • Connection Monitor Duration – if the phone registers to SRST, how long does the phone wait when the WAN is restored to fall back to its Communications Manager
  • Network Locale – Phone cadence based upon country selection
  • SRST Reference – IP address of gateway to fall to when the WAN goes down
  • MRGL (Media Resource Group List) – selects local media resources
  • Physical Location – Helps determine if device is roaming between locations
  • Device Mobility Group – Helps determine if Device Mobility-Related settings will be used

2) Device Mobility-Related Settings

  • Device Mobility Calling Search Space – This will replace the Device Calling search space which deals with routes and gateway selection
  • AAR Calling Search space – Gateway selection when not enough bandwidth to make a call
  • AAR Group – what must be prefixed in order to select a route within the AAR Calling Search Space

The settings listed above in blue can be configured either at the Device Pool level or Device level. If configured at both levels, the Device level wins. Therefore it is imperative that you do only the configurations at the device pool level if you want the device mobility feature to change them.

Next post I will continue explaining how a physical location is tied to an IP subnet and how the device mobility is able to change settings dynamically.

Author: Joe Parlas

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1 comment

  1. Dennis Reply

    Thanks for this.
    Today i was asking myself how mobility worked.
    Thanks for the explanation.

    One question is can this also be applied using extension mobility?

    Hence i have a user who travels between sites using extension mobility and i want the user to continue to use the resources as if he is in his bace location.