Cisco Certified ExpertCalled and Calling Party lEs
The calling and called number IEs specify the originating and destination numbers associated with the call. The numbers can be a variety of coding structures but are generally seen as ITU E.164 numbers, which mimic telephone numbers. Figure 8-19 shows the formats associated with the calling and called party IEs.
Figure 8-19 Calling and Called Party IE Format Called Party Number
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0 |
1 1 1 0 0 0 0 |
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Length of Called Party Number |
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1 |
Type of Number |
Numbering Plan Identification |
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0/1 |
Number Digits |
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0 |
1 1 |
0 |
1 1 |
0 0 |
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Length of Called Party Number |
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1 |
Type of Number |
Numbering Plan Identification |
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0/1 |
Presentation Indicator |
Spare |
Screening Indicator |
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1 |
Number Digits |
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The called party IE contains several significant fields. The type of number field describes what kind of number the called party is (LSB first):
• Network Specific Number = 110
• Subscriber Number = 001
• Abbreviated Number = 011
Only unknown, international, national, and subscriber numbers are supported under the numbering plan field. The numbering plan identification field identifies what type of numbering plan is being used for the ISDN number (LSB first):
• National Numbering Plan = 0001
• Private Numbering Plan = 1001
The most common numbering plan type you will see is the E.164 numbering plan. The number digits field identifies the actual digits dialed.
The calling party IE has many of the same fields but adds the screening indicator and the presentation indicator. Screening allows the ISDN device to decide on whether the user is allowed to connect. In other words, if the called party has a call screening application in place they can deny calls from specific ISDN numbers.
In the case of an unsuccessful call setup in ISDN, there is a cause code given. The cause code specifies why the call was not able to complete. The cause codes, when given in IOS, are specified in hexadecimal along with a brief description.
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