Class of Service for Shared Line Across Sites#
Class of Service (CoS) refers to a Calling Search Space (CSS) that is specifically used to define call routing and feature processing for a line or a phone. There are a number of CSSs defined when a customer and site dial plan are deployed, and some of the CSSs are only used internally and should not be selected in the CSS drop-down list on a line or phone configuration page.
The Class of Service CSSs are listed in the Dial Plan Management > Site > Class of Service menu item. A few example CoSs are predefined when a site dial plan is deployed, but the intent is for the administrator to create their own CoSs to meet the desired call routing and feature processing behavior. Below is a summary of Class of Service as it pertains to Shared Lines Across Sites feature.
COS is used in two places:
Line Calling Search Space - which appears in VOSS Automate at Subscriber Management > Lines > Directory Number Basic Information tab > Calling Search Space
Device Calling Search Space - which appears in VOSS Automate at
Subscriber Management > Phones > Phone tab > Calling Search Space Name
Subscriber Management > Subscribers > Phones tab > Calling Search Space Name
Additionally, CoS can provide line-based routing (LBR) or device-based routing (DBR). For each call made from a phone, the device CSS of the phone is combined with the line CSS of the line from which the call is being made, and the features and routing for the call are processed based on the combined list of partitions of these two CSSs. The default set of CoSs provided when a site dial plan is deployed includes a device CoS for emergency dialing only, and several line CoSs for feature processing, national dialing, and international dialing and that support either DBR and LBR. The following table shows the default allocation of feature and routing duties between the two sets of CoSs.
Feature |
Default Device CoS |
Default Line CoS |
|---|---|---|
Emergency call routing |
yes* |
- |
Intrasite routing |
- |
yes |
Intersite routing |
- |
yes |
Local PSTN call routing |
- |
yes** |
National PSTN call routing |
- |
yes |
International PSTN call routing |
- |
yes |
Feature processing |
- |
yes |
Table: Default Class of Service for Shared Line Across Sites Feature
* Emergency call routing is dependent on the country configured for the site. The country is used to route to the correct emergency number for that country (for example, 911 routes to 112 in the United Kingdom). Emergency call routing is assigned to the Device CoS because it is location-dependent, and must be tied to the site where the phone/user actually resides.
** Local call routing is dependent on local area codes defined in the site dial plan. The local area codes configured in the site dial plan allow dialing local dialing (for example 7-digit dialing in the United States).
As shown in the table above, routing is weighted heavily toward the line CoS because when the CoS is assigned to the line, it applies equally to the phone, extension mobility, and single number reach, which all typically share the same line configuration and provide similar dialing behavior for a given user. However, this assumes that the lines and devices are all constrained to individual sites. When we open up lines to be shared across sites, the site-specific configuration becomes more important in order to determine what to put in the device CoS versus the line CoS.
Class of Service (CoS) management for Shared Lines Across Sites is heavily dependent on the customer’s specific deployment scenario. The distribution of work between the device CoS and the line CoS depends on the type of country dial plan, and the dialing behavior the customer wants.
For example, if the country dial plan is flat and closed like the Swiss dial plan, meaning that the subscriber numbers are not variable length and there is no site-specific area codes (only national dialing), then most of the routing can occur in the line CoS because there is not much site-specific dialing behavior.
However, if the country dial plan uses area codes and the customer wants a local dialing experience (ability to dial a shorter number such as 7-digit dialing in the United States, and relying on the dial plan to fill in the local area code), then local call routing must be in the device CoS because the device context is needed to determine which area codes to apply to the dialed number. Feature processing partitions can almost always stay with the line CoS since there is usually no geographic dependencies for the feature processing. The exception to this is Time of Day (TOD) routing which may vary depending on the site.
In order to decide how to distribute routing and feature processing between the line COS and the device CoS, refer to the table that follows.
Feature |
Line CoS |
Device CoS |
|---|---|---|
Emergency call routing |
- |
Emergency routing should always be location-specific |
Intrasite routing |
Always using the PrelSR route partition |
- |
Intersite routing |
Always using the PrelSR route partition |
- |
Local call routing |
When full E.164 number is always dialed for offnet calls, for example, national dial plans with no local call routing |
When site-specific area codes and/or variable length subscriber numbers (local dialing behavior) are defined |
National call routing |
If local dialing is line-specific, national dialing should be line-specific. |
If local dialing is device-specific, national dialing should be device-specific. |
Toll-free call routing |
If local dialing is line-specific, toll-free dialing should be line-specific. |
If local dialing is device-specific, toll-free dialing should be device-specific. |
International call routing |
If local dialing is line-specific, international dialing should be line-specific. |
If local dialing is device-specific, international dialing should be device-specific. |
Service call routing |
If local dialing is line-specific, service number dialing should be line-specific. |
If local dialing is device-specific, service number dialing should be device-specific. |
Table: Routing and Feature Processing between Line CoS and Device CoS
To speed up the process of configuring lines and phones when you create new Classes of Service, set the site-specific default line CSS and site-specific default device CSS (Site Management > Defaults). These fields appear in the following tabs:
Device Defaults > Default CUCM Device CSS
Line Defaults > Default CUCM Line CSS