Core Issue
This issue is addressed in Cisco bug ID CSCdz79165.
The issue occurs because DISPLAY IE is not a recognized IE for 4ESS/5ESS switch types and any un-recognized information element (IE) in codeset_0 is dropped by the PSTN switch. So, the DISPLAY text never appears on a phone connected to the PBX. But, the switch forwards any codeset_6 un-recognized IEs transparently to the PBX.
In order to send the display information to the PBX, ISDN has to shift the codeset of a DISPLAY IE to codeset_6 before you send a message to the PSTN switch. Once the CLI is enabled, a DISPLAY IE is shifted to codeset_6 in an outgoing message. This CLI has no effect on the incoming messages to gateway. Note that 4ESS and 5ESS does not officially support DISPLAY IE. But these switches and the Avaya PBXs provide the DISPLAY IE support in codeset_6.
Resolution
The isdn outgoing ie display codeset_0 shiftcodeset codeset_6 command is chosen to meet this requirement. This CLI is hidden and can be configured for PRI interfaces with 4ESS/5ESS switchtypes only.
Instead of the use of the normal Q.931 calling number information element (IE), verify if your PBXes uses the Codeset 6 IE 0x28 to display the name of the caller on the called phone.
According to the Q.931 spec: Codeset 6 is reserved for information elements specific to the local network (either public or private). Use the debug isdn q931 trace in order to check this.
This CLI works only for 4ESS and 5ESS switch-type. If this does not work for your switch config, then you need to work with Avaya to handle Q.931 calling number IE.
