Mino – The UC Guy

Microsoft Unified Communications Blog

Setting up the Cisco Call Manager 4.2.1 with Ofice Communication Server 2007 “Part One – Cisco Side”

Posted by Mino on October 7, 2008

 configuration of Direct SIP with Cisco Call Manager 4.2.1.

1)      Main assumptions for the example

Here are the main assumptions for this example:

·         This is a single site, located in Paris, France (country code 33, local code 1).

·         All PSTN calls, incoming and outgoing, from and to Cisco Call Manager and Office Communications Server, use the preexisting PSTN interconnection trunks that are connected to and managed by the Cisco Call Manager. All calls to and from Office Communications Server go across the SIP trunk between Cisco Call Manager and Mediation Server.
As discussed before, it is also possible (and eventually more effective, especially at large scale and for example with the use of SIP Trunking to Carrier) to have direct PSTN-out routes from Office Communications Server to the PSTN without going through the Cisco Call Manager. Also, in this example, we do not implement redundant routes between Cisco Call Manager and Office Communications Server; that is of course possible but exceeds the scope of this simple example.

·         All users are assigned a unique, externally routable DID from a local range and a unique 4 digits extension that matches their DID’s last 4 digits.

·         Specifically all DID for users on both the Cisco Call Manager and Office Communications Server are of the format +3316986xxxx where xxxx is their extension.

·         Users on the Cisco Call Manager are accustomed to dialing 4 digits for internal users, and we want to maintain that pattern when they dial out to users on Office Communications Server.

·         Users on the Cisco Call Manager need dial 0 as prefix to exit to the PSTN.

·         In the first part of this example, the extension range 4xxx to 5xxx is allocated to Office Communications Server; in the advanced section, we will provide a configuration for situations where there are exceptions to the range allocation.
We do not assume that all numbers in the range are actually allocated on Office Communications Server; calls to unallocated numbers will be routed by Cisco Call Manager to Office Communications Server which will answer 503 (service unavailable) and reject the call, which will receive a “fast busy” dial tone.

·         All other numbers are allocated to the Cisco Call Manager; it is of course possible, but beyond the scope of this example, to create more complex, granular route patterns.

We are also making the following assumptions for the formatting of the FROM and TO fields of calls:

The local PSTN carrier requires the following:

·         The FROM field must be formatted as a 9-digit dial string xxxxxxxxx

·         The TO field:

o   For domestic (i.e. destined to a DID in France) calls: the TO field must be formatted as a full 10-digit local French number (which is not an E.164 number): 0xxxxxxxxx

o   For international calls (i.e. destined to a DID outside of France): the TO field must be formatted as a 00 (the prefix for international dialing in France) followed by the E.164 dial string for the caller, for example 0014255551212

·         Please note that this may vary by locale, carrier or even on the basis of the type of trunk used; please check appropriately.

For calls from a Cisco Call Manager extension xxxx to an Office Communications Server extension yyyy sent across the SIP trunk:

·         The FROM field is the dial string xxxx

·         The TO field is the dial string yyyy.

For calls from the PSTN to an Office Communications Server extension yyyy:

·         The FROM field has already been formatted by Cisco Call Manager into a dial string that enables immediate dial back to the PSTN in France:

o   For domestic (i.e. originated from a DID in France) calls: the “outside line prefix” 0 followed by the full ten-digit local French number (which is not an E.164 number): 00xxxxxxxxx

o   For international calls (i.e. originated from a DID outside of France): the “outside line” prefix 0 followed by 00 (the prefix for international dialing in France) and by the E.164 dial string for the caller, for example 00014255551212

·         The TO field is the dial string yyyy.

 

2)      Creating a partition on Cisco Call Manager

First we will create a partition, which we name “OCSIncoming”.

A Cisco Call Manager partition contains a list of route patterns. Partitions facilitate call routing by dividing the route plan into logical subsets that are based on organization, location, and call type. For more information about partitions, please refer to “Partitions and Calling Search Spaces” in the Cisco Call Manager System Guide.

This partition will enable us to apply specific rules (route patterns and translation patterns) specific to the incoming traffic into the Cisco Call Manager from the Mediation Server across the SIP trunk

Note: whether a partition is required or not in a particular environment may depend on the rules required. Please verify with your Cisco Call Manager administrator.

3)      Creating a Calling Search Space on Cisco Call Manager

A Cisco Call Manager calling search space is an ordered list of route partitions. Calling search spaces determine which partition(s) (and in which order) are searched when Cisco Call Manager is attempting to complete a call.

In this case, we create a calling search space which we call “OCSIncoming”, and to which we assign the “OCSIncoming” partition created above.

4)      Setting up Translation Patterns for the Partition on Cisco Call Manager

Next we create translation patterns for the partition. The translation patterns will be used for inbound calls to the Cisco Call Manager from Office Communications Server. Translation patterns manipulate dial strings before routing a call.

The first translation pattern (called [^33]!, which means TO strings that do not start with 33) will handle all calls from Office Communications Server that are destined to an international PSTN number. Note that the translation pattern is assigned to the “OCSIncoming” partition.

For the FROM field: the pattern retains the last 9 digits; therefore it strips the country prefix (which is always 33 in this case) from the E.164 calling party dial string, and presents it to the PSTN in the required format. In this case it transforms 3316986xxxx into 16986xxxx.

For the TO field: the pattern simply adds 000 as a prefix to the called party dial string. For example it transforms 14255551212 into 00014255551212.

The reason it translates dial strings sent by the Mediation Server in a different manner for the TO and the FROM is the need for the TO field to start with the outside line prefix (in this example “0”) to obtain an outside line on the Cisco Call Manager, then the international prefix 00, and then the full E.164 dial string.

The second translation pattern (called 33.xxxxxxxxx, which means TO strings starting with 33 followed by 9 digits) will handle all calls from Office Communications Server that are destined to a domestic PSTN number. Here too the translation pattern is assigned to the “OCSIncoming” partition.

For the FROM field: as for the previous translation pattern, we retain the last 9 digits, stripping the country prefix (which is always 33 in this case) from the E.164 calling party dial string, and presenting it to the PSTN in the required format. In this case it transforms 3316986xxxx into 16986xxxx.

For the TO field: the pattern strips the leading 33 (i.e. the digits prior to the dot) and adds 00 as a prefix to the remaining string. It transforms 33xxxxxxxxx into 00xxxxxxxxx, where the first 0 is the outside line prefix needed to obtain an outside line on the Cisco Call Manager

The third translation pattern (called 3316986xxxx) will handle all calls from Office Communications Server that are destined to a Cisco Call Manager assigned number. Here again the translation pattern is assigned to the “OCSIncoming” partition. This pattern will be applied to calls where the TO field is of the form 3316986xxxx, rather than the second translation pattern, because it represents a longer match. Cisco Call Manager selects translation patterns from a list on the basis of the longest match.

The translation pattern translates dial strings for calls sent by the Mediation Server where the TO field matches the pattern. It strips all leading digits from TO and FROM fields to retain the last 4 digits of both. Dial strings of the pattern 3316986xxxx will be translated to dial strings of the form xxxx that match the internal Cisco Call Manager dial plan. As can be seen below, this translation will be performed on both the called number and the caller number.

Other translation patterns could be set up if appropriate, for example for normalization of emergency number, but are outside the scope of this example.

5)      Provisioning the SIP trunk on Cisco Call Manager

At this time we will set up a SIP trunk on the Cisco Call Manager, and assign the Calling Search Space for incoming traffic we created previously, “OCSIncoming”.

The trunk name in this example is “Trunk_to_OCS”. The Mediation Server’s external edge IP address here is 192.168.0.105. Please note the selection of TCP for transport, and the port selection:

6)      Setting up a Route Pattern for the SIP trunk on Cisco Call Manager

Route Patterns are used for outbound calls from Cisco Call Manager to Mediation Server. They define what calls are sent to the SIP trunk based on matching the number in the TO field with a specific pattern. Route Patterns can also perform transformations of the dial strings in both the TO and the FROM field.

We now create a route pattern [4-5]xxx to handle outgoing calls from Cisco Call Manager to Office Communications Server, associated with the “Trunk_to_OCS” SIP trunk. This Route Pattern instructs Cisco Call Manager to route to Mediation Server all calls destined to Office Communicator users (from both the PSTN and Cisco Call Manager users), on the basis of the match of the TO string with the pattern [4-5]xxx. In this case we do not need any transformation of the strings in the TO and the FROM fields.

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