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A partition is a group of dialable patterns with similar accessibility. Any dialable pattern
can be assigned to a partition. All phone numbers are in the null partition by default, and
all devices have access to the null partition. As soon as a phone number is assigned to a
different partition, the devices in the network will not be able to access that phone number
without the configuration of a calling search space (CSS).
Long Distance Internal
Emergency
Local PSTN
Long-distance PSTN
International Internal
Emergency
Local PSTN
Long-distance PSTN
International PSTN
Table 13-2 Call-Privileges Configuration Elements
Element Characteristic
Partition Group of numbers with similar reachability characteristics (including route
patterns, directory numbers, translation patterns, and so on)
Calling search space Ordered list of accessible partitions applied to device to restrict call privileges
Time periods Static days or recurring time intervals
Time schedules Ordered list of time periods
CMCs Used to track calls to certain destinations
FACs Restrict outgoing calls to certain numbers
Table 13-1 Class of Service Example (Continued)
Class of Service Allowed Destinations
308 Chapter 13: Calling Privileges
A CSS defines which partitions are accessible to a particular device. A device can call only
those call-routing table entries located in partitions that are part of the CSS assigned to the
device.
Partitions are assigned to call-routing targets. Any entry of the call-routing table, including
voice-mail ports, directory numbers (DN), route patterns, translation patterns, meet-me
conference numbers, and so on can be assigned to a partition.
CSSs are assigned to devices, which are the source of a call-routing request (phones, phone
lines, gateways, trunks, voice-mail ports, and computer telephony integration [CTI] ports).
Calls that come into the network from a gateway or trunk inherit the CSS assigned to the
gateway or trunk.
By default, all entities that can be configured with a partition are in partition <None> (null
partition), all entities that can be configured with a CSS are assigned with CSS <None>
(null CSS).
Members of partition <None> are always accessible by sources of a call-routing request,
regardless of the CSS applied to the calling party. Entities that do not have a CSS assigned
can only access numbers that are in partition <None>. Partition <None> is commonly
referred to as the null partition.
In Figure 13-1, various partitions and CSSs have been created. An easier way of understanding
partitions and CSSs is to use an analogy of locks and key rings. If each house on
a block has a different lock (partition), your key ring (CSS) would have to include many
keys (to unlock different doors).
In Figure 13-1, DN 1 of Phone 1 has been configured in the lobby partition, and DN 1 of
Phone 2 is in the employee partition, while Phone 3 and Phone 5 are both in the manager
partition. Phone 4 has not been assigned to a partition. Following the analogy with locks
and keys, there are three different types of locks (lobby, employee, and manager). Phone 4
does not have a lock. Phone 4 is therefore in the null partition, and everyone has access to
call Phone 4.
When approaching CSSs from the perspective of key rings, Phone 1 has a key ring with the
lobby and employee key on it. Phone 2 has a key ring with keys for the lobby, employee,
and manager key ring. Phone 3 has a key ring with the lobby, employee, manager, and
executive keys. The executive key is not seen in the example, but it will be used in the
system for executive management. The key ring of Phone 4 contains only the lobby key.
Phone 5 does not have any keys, which restricts Phone 5 to call only other DNs in the null
partition.
Partitions and Calling Search Spaces 309
As a result of this implementation of locks and keys, the following effective permissions
apply:
■ Phone 1: Like all other phones, this phone has access to all devices that do not have a
lock applied (Phone 4 in this example). Phone 1 can access DN 1 on Phone 2 and Phone
4. Devices cannot access DNs in the same partition unless their CSS gives explicit
permission to that partition.
■ Phone 2: Phone 2 can access Phone 1, Phone 3, Phone 4, and Phone 5.
■ Phone 3: Phone 3 can access Phone 1, Phone 2, Phone 4, and Phone 5.
■ Phone 4: Phone 4 can access Phone 1 only, because the CSS has access only to the
lobby partition.
■ Phone 5: Like all other phones, this phone has access to all devices that do not have a
lock applied (Phone 4 in this example). Phone 5 cannot unlock any locks because it
does not have any keys. That means that Phone 4 can access only Phone 1.
Figure 13-1 Calling Privileges: Partitions and Calling Search Spaces
Figure 13-2 illustrates a phone with a CSS that contains two partitions: Chicago and San
Jose. A third partition, Atlanta, exists in the system but is not included in the CSS of the
phone. Phone DNs are assigned to partitions as follows:
■ DN 3001 (Phone 2-1) is assigned to partition Chicago.
■ DN 2001 (Phone 1-1) is assigned to partition San Jose.
■ DN 4001 (Phone 3-1) is assigned to partition Atlanta.
IP IP IP IP IP
Partitions: Lobby_PT Employee_PT Manager_PT
No Partition
Assigned Manager_PT
Phones Phone 1 Phone 2 Phone 3 Phone 4 Phone 5
CSSs: Lobby_PT
Employee_PT
Lobby_PT
Employee_PT
Manager_PT
Lobby_PT
Employee_PT
Manager_PT
Executive_PT
Lobby_PT No CSS
Assigned
310 Chapter 13: Calling Privileges
The user at the phone dials 3001, which is the DN of Phone 2-1. CUCM performs digit
analysis against the dialed digits of 3001. The call-routing lookup will search only through
the partitions configured in the CSS of the calling phone (Chicago and San Jose). CUCM
finds a match in partition Chicago, because the DN of 3001 of Phone 2-1 is assigned to this
partition. Because no other matches exist, routing is complete, and Phone 2-1 rings.
Figure 13-2 Partition and CSS Example
A CSS is an ordered list of partitions with the highest-priority partitions listed first.
Multiple identical entities can exist in the call-routing table, but they have to be in different
partitions. It is advisable to route emergency calls through a local gateway in multisite
centralized call-processing deployments. If 911 is the emergency number, there will be
many iterations of the 911 route pattern in the system, but they must each be in a separate
partition. Local call routing in a centralized call-processing approach will result in the
creation of site-specific partitions and CSSs to guarantee that local PSTN resources are
used.
CSS
Partition Chicago
3001 Phone 2-1
Partition San Jose
2001 Phone 1-1
Partition Atlanta
4001 Phone 3-1
Phone CSS
contains two
partitions.
Phone 2-1 DN
3001 lies in
partition Chicago.
Phone 3-1 DN
4001 lies in
partition Atlanta.
Not included in
routing decision.
2
Phone 2-1 will ring.
IP 3
User dials 3001.
1
Partitions and Calling Search Spaces 311
Figure 13-3 Multiple Best Matches Example
Figure 13-3 displays a CSS scenario in which the same dialed pattern matches multiple
partitions. The CSS processing is based on the following order:
1. Best match is searched.
2. If multiple equally qualified matches exist (no single best match), the call routes
through the partition in the CSS that is highest in the list. Many sources of call-routing
requests (trunks, gateways, and translation patterns) have only one CSS. On IP phones,
a different CSS can be applied per line and at the device level. If a CSS is specified only
at the device level, each DN inherits the CSS of the device.
If CSSs are configured at both device and line level, the line from which the call is placed
is considered first in the call-processing logic. CUCM concatenates the two CSSs and
processes them in a top-down manner with the line CSS at the top of the list, as shown in
Figure 13-4.
CSS
Partition Chicago
3001 Phone 2-1
Partition San Jose
3001 Phone 1-1
Partition Atlanta
3001 Phone 3-1
Phone CSS
contains two
partitions.
Phone 2-1 DN
3001 lies in
partition Chicago.
Phone 1-1 DN
3001 lies in
partition San Jose.
Phone 3-1 DN
3001 lies in
partition Atlanta.
Not included in
routing decision.
Phone 2-1 and
Phone 1-1 match
equally well. Phone 2-1
is used because its
partition is listed first
in calling phone’s
CSS.
2
IP
User dials 3001.
1
312 Chapter 13: Calling Privileges
Figure 13-4 Device and Line CSS Example
In Figure 13-5, the line CSS of the calling party includes partitions San Jose and Chicago.
The device CSS of the calling phone includes partition Atlanta.
Figure 13-5 CSS Partition Order Example
NOTE On CTI ports, the line and device CSS are processed in reverse order; the
partitions of the device CSS are processed before the partitions of the line CSS.
Line
Line CSS
Partition L1
Partition L2
Partition L3
Device
Device CSS
Partition D1
Partition D2
Partition D3
Resulting CSS
Partition L1
Partition L2
Partition L3
Partition D1
Partition D2
Partition D3
IP
Line CSS
Device CSS
Partition San Jose
300X Route Pattern
Partition Chicago
3001 Phone 2-1
Partition Atlanta
3001 Phone 3-1
Partitions and Calling Search Spaces 313
Route pattern 300X is in the San Jose partition, with DN 3001 assigned to both Phone 2-1
in the Chicago partition and Phone 3-1 in the Atlanta partition.
When the phone dials 3001, the following will happen:
CUCM interprets the dialed digits and searches for the closest match. The two DN entries
in the call-routing table are more specific than the route pattern of 300X. Phone 2-1 is
chosen because its partition is listed first in the concatenated CSS.
Figure 13-5 illustrates the line CSS having higher priority than the device CSS. If the line
CSS and device CSS were reversed, the call would be sent to Phone 3-1. Notice that the
CSS subsequently performs closest-match routing against all partitions in the CSS at the
same time. If the CSS had been strictly processed on the San Jose partition before
considering the Chicago or Atlanta partitions, 300X would have been the match. Instead,
CUCM was aware of the closest match of 3001 in the other partitions. The partition order
is used as a tiebreaker if there are multiple closest matches.
Figure 13-6 is using partitions and CSS to implement four different classes of service:
■ Internal: Allows internal calls only
■ Local: Allows internal and local PSTN calls
■ Long Distance: Allows internal, local PSTN, and long-distance PSTN calls
■ International: Allows internal, local PSTN, long distance, and international PSTN calls
The following partitions are applied as described:
■ Phones: This partition is applied to all phone lines.
■ Local-PSTN: This partition is applied to route pattern 9.[2–9]XXXXXX
■ LD-PSTN: This partition is applied to route pattern 9.1[2–9]XX[2–9]XX XXXX
■ Intl-PSTN: This partition is applied to route pattern 9.011! and 9.011!#.
NOTE It is a common misunderstanding that the first matching pattern (regardless of
the quality of the match) that is found when searching through the partitions in the order
specified in the CSS is used for call routing. If this were true, subsequent partitions of the
CSS would only be looked at, if no match (of any kind) were found in the earlier
partitions. This is not the case. All partitions are immediately considered for the bestmatch
logic, and only if multiple best matches exist does the partition order become
relevant.
314 Chapter 13: Calling Privileges
The following CSSs are configured, each implementing the corresponding service class:
■ CSS-Internal: Containing partition Phones
■ CSS-Local: Containing partitions Phones and Local-PSTN
■ CSS-LD: Containing partitions Phones, Local-PSTN, and LD-PSTN
■ CSS-International: Containing partitions Phones, Local PSTN, LD-PSTN, and
Intl-PSTN
Figure 13-6 CSS Example
NOTE CSSs take on an inverted logical approach when assigned to devices such as
Session Initiation Protocol (SIP) trunks, intercluster trunks, and gateways. Calls that are
routed through a trunk or gateway take on the CSS applied at the device. In a multicluster
distributed call-processing environment, it is not advised to allow emergency call routing
across trunk links. Most organizations locally route emergency calls to the local public
safety answering point (PSAP). It is common practice to restrict emergency call routing
in the CSS applied to trunks.
CSS Internal CSS Local CSS LD CSS
International
Partition Phones
(All Phone DNs)
Partition Local-PSTN
9[2-9]XXXXXX
Partition LD-PSTN
91[2-9]XX[2-9]XXXXXX
Partition
Intl-PSTN
9011!#
X
X
X
X
X X
Internal Calls
Local Calls
Long-Distance
Calls
International
Calls
IP
Assigned CSS determines
calling privilege.
Partitions and Calling Search Spaces 315
Configuration of partitions and CSSs includes the following steps:
Step 1 Create partitions.
Step 2 Assign partitions to the DN, route-translation patterns, CTI ports, voicemail
ports, meet-me conference bridge numbers, call-park ranges, and
any other number in the system.
Step 3 Create CSSs.
Step 4 Add partitions in the desired order into each newly created CSS.
Step 5 Assign CSSs to entities that can request lookups to the call-routing table
to route a call; examples for such entities are phones and phone lines,
trunks, gateways, and translation patterns.
To add partitions in CUCM Administration, navigate to Call Routing > Class of Control
> Partition and click the Add New button. Figure 13-7 shows the Partition Configuration
page in CUCM. You can add up to 75 partitions in one insertion of partitions with a
character limitation of 1475 characters. If more than 75 partitions are required, you may
perform multiple insertions.
Partition names should not be lengthy because the CSS has a maximum length restriction
of 1024 characters. A CSS is a string of partition names. The 1024-character limit includes
separator characters between each partition name. (For example, the string
“partition_1:partition_2:partition_3” contains 35 characters.) The maximum number of
partitions in a CSS varies, depending on the length of the partition names and number of
partitions. If individual CSSs are used on both the device and line level, the maximum
character limit for the individual CSS is 512 (half the combined CSS clause limit of 1024
characters).
Figures 13-8 and 13-9 show the application of partitions, respectively, to a DN and route
pattern.
NOTE A translation pattern is a dialable pattern in the call-routing table. When a
translation pattern is matched, it invokes a new call-routing request for the translated
pattern. Which partition the translation pattern is in limits the devices that can access the
translation pattern. The CSS of the translation pattern specifies the entries of the callrouting
table that the translation pattern is allowed to see for the new call-routing request
when it is trying to find the translated pattern in the call-routing table.
316 Chapter 13: Calling Privileges
Figure 13-7 Partition Configuration
Figure 13-8 Partition Application: Directory Number
Partitions and Calling Search Spaces 317
Figure 13-9 Partition Application: Route Pattern
Figure 13-10 shows the Calling Search Space Configuration page. This page is accessible
by navigating to the following CUCM Administration menu: Call Routing > Class of
Control > Calling Search Space. Click the Add New button to add a new CSS. The CSS
should be given a name that is descriptive of the desired functionality. LD_Calling Search
Space would be descriptive of a CSS that allows long-distance, local, emergency, and
internal dialing. Click a partition in the Available Partitions section of the configuration
page and use the down arrow to move the partition to the Selected Partitions section. You
can use the up and down arrows to the right of the Selected Partitions section to move the
priority of the selected partition. The top of the list is the highest priority. The emergency
partition should normally be at the top of the list.
Figure 13-11 displays the phone configuration page with a CSS applied. CSSs can be
assigned to phones, phone lines, gateways, trunks, voice-mail pilots, voice-mail ports, CTI
route points, CTI ports, translation patterns, and any other source of a call-routing request.
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