CSS Line Device Approach

CSS Line Device Approach

Hi All,

  As we start understanding CSS and partitions next confusion we normally have is what is Line and Device CSS. There is a very simple definition of CSS Line/Device Approach

• ·        The Device CSS decides through which gateway/trunk call will go out of our network.
• ·        Line CSS defines (Class of Service) calling privileges.

 For an example you are in City A, and if you want to call and international number Line CSS will decide whether you should dial that number or not and Device CSS will decide that you should use the voice gateway of City A so you are paying correct charges based on your guidelines define by your country law and it shows the correct caller ID if you are sending it. We also have a concept called TEHO which may contradict with this but we will discuss that later in a different post altogether.

How it works:

• ·        It concatenates the Line and Device CSS being partitions in line first and then in device CSS.
• ·        It routes or blocks the call as it matches the pattern, even if we have a similar pattern with a different partition in the list.
• ·       Line CSS is used to define the number that needs to be blocked.
• ·        Everything is allowed on Device CSS.

Design Considerations:

We will take an example for Internal, Local, Long Distance and internal calls. In this example we will consider all phones are in partition PT-Internal and devices has been assigned CSS-Device.

Below is the list of defined Route Patterns and CSS including their partitions:

Route Pattern	Partition		Blocking Pattern	Partition
9.[2-9]XX.XXXX	PT-Local		9.[2-9]XX.XXXX	PT-Local Blocking
9.1.[2-9]XX.[2-9]XX.XXXX	PT-Long Distance		9.1.[2-9]XX.[2-9]XX.XXXX	PT-Long Distance Blocking
9.XXXXXXXXXXX	PT-International		9.XXXXXXXXXXX	PT-International Blocking

CSS	Partition
CSS-Device	PT-Internal, PT-Local, PT-Long Distance, PT-International
CSS-Line Local	PT-Internal, PT-International Blocking ,  PT-Long Distance Blocking
CSS-Line Long Distance	PT-Internal, PT-International Blocking
CSS-Line International	PT-Internal

Route Pattern: For a Route Pattern we define the pattern and select the option “Route this pattern” in Route Pattern.

Blocking Pattern: Similarly for a blocking pattern we can use “Block this Pattern” in Route pattern.

Example:

Line CSS: CSS-Line Local

When a user with CSS-Line Local tries dialing a number his partition list becomes like this in order:

PT-Long Distance Blocking

PT-International Blocking

PT-Local

PT-Long Distance

PT-International

  When he tries dialing a long distance number it matches the pattern 9.1.[2-9]XX.[2-9]XX.XXXX. This pattern is configured with two partitions: PT-Long Distance Blocking & PT-Long Distance. In the partition list PT-Long Distance Blocking comes first so it will match blocking pattern and block the number.

When the same user tries dialing a local number it matches the pattern 9.[2-9]XX.XXXX which has two partitions: PT-Local & PT-Local Blocking, but first and the only match is PT-Local and the call is routed.

We will discuss more on path selection in next post how it selects a site specific gateway.