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Symptom
Outbound ISDN calls are rejected by the switch due to a missing IE (3.1 Extension Bit/Interface Identifier). This behavior is seen with 4ESS ISDN configuration after upgrading to SR5.1.1 SU125 or higher.
Reason for the
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issue
According to AT&T Telco Specifications (TR41459) octet 3.1 (Extension Bit/Interface Id) can be omitted when the "interface identifier present" field in octet 3 indicates "interface implicity identified".
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1: CHANNEL ID(0x18)
2: IE Length(0x03)
3: 1------- Extension Bit
-0------ Interface ID Present
--1----- Interface Type
---0---- Spare
----1--- Preferred/Exclusive
-----0-- D-Channel Indicator
------01 Info. Channel Sel.
3.2: 1------- Extension Bit
-00----- Coding Standard
---0---- Number Map
----0011 Channel/Map Element
Fix / Solution
Try to get the switch Engineer to make the appropriate changes on the switch. If the changes cannot made refer to work around solution below.
Workaround
If the switch requires octet 3.1 to be present for non-NFAS configurations, perform the following configuration changes:
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Step 3. Restart the drivers for the changes to take affect.
Product List
D/240JCT-T1
D/480JCT-2T1
Glossary of Acronyms / Terms
SU = Service Update