Call Routing

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Call Routing
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Three Responsibilities

• The Call Routing Components of Cisco CallManager
  has three main responsibilities
• To determine which endpoint CallManager should
  ring based on the digits you dial.
• To perform address translation
• To support individualized routing

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Determining End Points

• End points are often other IP phones
• Or, numbers controlled by other system. Such as
  the public switched telephone network, other
  PBXs. Or other CM clusters
• There are cases when the digits you dial do not
  correspond to a physical device.
• Call Park codes
• Meet-Me conference code

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Performing Address Translation

• Address translation allows you to modify the
  dialed digits and the calling number as the call
  propagated through the network.
• Address Translation is important when a network
  must pass a call from a private network with its
  private numbering plan to the PSTN with a
  standardized numbering plan.
• Example Most PBXs require users to dial an
  access code to place a call to the PSTN . If CM
  does not first remove the access code before
  offering the call to PSTN, the PSTN will reject
  the call
• Address Translation reconciles Private Numbering
  Plan against PSTNs numbering plan

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Supporting Individualized Routing

• The destination you reach when you dial a number
  might differ completely form the destination your
  neighbor reaches when your neighbor dials the
  same number.
• This capability is useful to support routing by
  class of calling user, by organization, or by
  geographic location.
• Example routing by class of calling user permits
  you to restrict calls made from lobby phones
  while allowing your executives full access to
  international numbers.
• Example routing by organization means that
  calls from different departments can be routed
  differently. Also, routing by organization is
  used to control two different enterprises using
  one CallManager
• Example Routing by geographic location allows
  a CM in one location to control phones in two
  different locations this ensures that emergency
  calls from a particular location route to the
  appropriate emergency response center.

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The Seven Fundamentals of Call Routing

• Route Patterns
• Route Filters
• Dialing Transformations
• Translation Patterns
• Route Lists
• Calling Search Spaces
• Partitions

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Route Patterns and Route Filters

• Route patterns and route filters permit
  CallManger to fulfill its primary responsibility
  of locating a destination.
• Route patterns are the addresses you assign to
  devices.
• Example Associating the route pattern 8xxx with
  a gateway means that when you dial a number
  between 8000 and 8999, your call routes out that
  gateway.
• Route filters are used in conjunction with the
  special route pattern wildcard _at_. Route filters
  restrict the scope of the _at_ wildcard.

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Route Patterns and Route Filters

• By including a non-numeric characters called
  wildcards in a route pattern, you tell CM to ring
  the associated device for a range of dialed
  numbers.
• Route filters are a special range-refining
  mechanism. You use route filters with route
  patterns that contain the special _at_ wildcard.
  The _at_ wildcard allows you to represent the PSTN
  with a single route pattern.
• When you must limit the types of PSTN calls that
  users can place, route filters limit the scope of
  the _at_ wildcard.

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Wildcards
Route patterns use wildcards, which are digit
placeholders that permit you to specify quickly a
range of matching digits.

• What are the possible matches for the following
  route patterns
• 1234
• 11X
• 12XX
• 1325-86
• 133-96
• 15!

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Dialing Behavior

• In collecting the users digits, the call routing
  component goes through the following steps
• Compare the current sequence of dialed digits
  against the list of all route patterns and
  determine which route patterns currently match.
  This is known as the set of Current Matches.
• If current matches is empty, the users dialed
  digit string does not currently correspond with a
  destination.
• If current matches contains one of more member,
  the call routing component determines the closest
  match. The closest match s the route pattern in
  the current matches that matches the fewest
  number of route patterns.
• Example The dialed digit string 2000 matches
  both route pattern 2xxx and 20xx. However, there
  are 1000 different dialed digit strings that
  match 2xxx, and only 100 dialed digit strings
  match 20xx 20xx is therefore the closest match.

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Example 1 Dialed Destination 1100
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Example 2 Dialed Destination 1200
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Example 3 Dialed Destination 1300
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Example 3 Continued Dialed Destination 1300

• The ! wild card at the end of a route pattern
  means that condition potential matches always
  holds true.
• The system interdigit timeout default to 10
  seconds.
• When a route pattern ends with a wildcard that
  matches multiple digits, CM must wait for the
  system interdigit timeout to expire before it can
  route the call.
• This scenario is needed in non-North American
  Numbering Plans where many countries have
  variable-length national dialing plans.

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Dialing Behavior Refinements

• Urgent Route Patterns Describes how to
  interrupt interdigit timing when CM must route a
  call immediately.
• Outside Dial Tone Describes the logic that
  determines when CM applies outside dial tone.

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Dialing Behavior Refinements

• By marking the 9.911 route pattern as urgent, you
  tell CM to route the call to the emergency center
  the instant that a user dials 9911
• Outside dial tone is an indication that users
  expect when CM routes their calls off of the
  local network

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_at_ Wildcard

• _at_ pattern matches any number that you can dial
  from your North American home phone
• CM interprets _at_ as a macro expansion.
• Four different route patterns in the North
  American numbering plan

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_at_ Wildcard Example

• When a user dials 555 1212 both route patterns
  match however the _at_ route pattern is more
  specific and the call will be routed out gateway
  1.
• To configure a certain route pattern to take
  precedence over the _at_ pattern, you have to use
  route filters (explained soon)

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The . wildcard

• The . Wildcard does not match digits at all.
• The . Wildcard function solely as a delimiter
  It divides the dial string into PreDot and
  PostDot sections
• The . Wildcard is used in conjunction with digit
  discarding instructions.
• Example 9._at_ is used to discard the access code
  section from the dialed string

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Building a Route Plan

• Building a route plan is a four-step process
• Add Gateway devices
• Build route groups from available devices
• Build route lists from available route groups
• Build a route pattern from available route lists

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Next Week

• Route Filters