# IP Networking/XNET Compression

## Description

MiVoice Business uses G.729a audio compression codecs instead of the higher audio quaility G.722.1 codec to reduce the bandwidth required for an IP call. Compression is optional. Whether or not it's applied depends on the following:

- the Zone and Zone Group of the originating and terminating endpoints (as explained below)

- the compression handling capabilities of the endpoints

- the compression setting of the IP Trunking route used to route the call

### Zones for Compression

IP telephones are grouped into zones. The default zone (1) has intra-zone compression turned off. Other zones are created to allow for intra-zone compression at different settings (i.e., compression ON or compression OFF). If a call originates and terminates in different zone, compression is used when both endpoints are capable of handling it. If a call originates and terminates within the same zone, the configuration parameters determine whether or not compression is applied.

NOTE: For 3300 ICP Release 8.0 software and later, you can manage bandwidth through Call Admission Control. See Bandwidth Management Description for more information.

IP devices can be moved to different locations as long as they stay within the same network segment. If it is moved into a different compression zone, configuration must be modified or the incorrect compression settings may be used.

If an IP device is on the same LAN as the 3300 ICP/MiVoice Business system it is normally placed in the default zone and calls between these IP devices are not compressed. Occasionally, it is necessary to compress calls between IP phones within the same zone. To do this, zones can be configured for intra-zone compression. If the IP device is located on a remote LAN segment and must connect over a WAN link to the system, it should be placed in a compression zone created for IP devices on that specific remote LAN.

Non-IP endpoints include any device on the system capable of originating or terminating a call, but does not support IP streaming (for example, analog telephones, TDM based digital telephones, ISDN trunks, voice mail ports, Music On Hold, Recorded Announcement Device, etc.). These devices are placed in the default compression zone (1). Calls made between IP phones in the default zone and a non-IP telephones/trunks are not compressed. Calls made between non-IP telephones/trunks and IP devices in other compression zones are compressed when possible.

IP trunk routes can be configured to control whether calls using a specific route should be compressed. IP trunks between co-located systems would normally be configured for no compression while those between systems connected through a WAN would be configured for compression.

When a call is placed, the originating system determines if compression should be used based on the compression zone of the originating device and the compression setting of the IP trunk. When the destination system receives a compression request, it will attempt compression if it is not in the default compression zone. If compression is not possible the call will still be connected but without compression.

### Zone Groups for Voice Quality (no compression)

As explained above, calls between endpoints in different zones are compressed. When voice quality is more important than bandwidth usage, you can override inter-zone compression by assigning zones to a Zone Group.

The following diagram illustrates a typical use case for Zone Groups:

Typical Zone Group Usage

Calls between endpoints within Zone Group 2 (zones 2, 3, and 4) will use higher quality audio codecs (G.722.1). The same for endpoints calling each other within Zone Group 3.

Calls between endpoints in Zone Group 2 and Zone Group 3 will use G.729 compression codecs.

NOTES

- IP Trunking route compression (ARS Routes form) overrides the Zone Group Number. If route compression between Zone Groups 2 and 3 in the example above is set to ON, compression codec (G.729a) selection will occur on calls between these zones. To use G.722.1 codecs, change the route compression setting to Auto.

- Intra-zone compression can be used for calls within the zone boundary—for example, between endpoints in Zone 4—if the intra-zone compression is set to Yes. If you want endpoints in Zone 4 to compress when communicating with endpoints in Zone 2 and Zone 3, remove Zone 4 from the Zone Group.

## Conditions and Feature Interactions

- See IP Networking/XNET Planning for IP Networking/XNET conditions

## Exceptions

Condition | Result
Link to 3300 ICP/MiVoice Business system in the route is down | Caller hears reorder tone, display shown as DPNSS leased line would
No compression resource | Call is connected without compression
No TDM to IP resource | Caller hears reorder tone
Packet loss during call | Low quality audio is experienced
DPNSS timeout | Call hears reorder tone, "ERROR" is displayed on telephone
A call comes from Node 1, through Node 2, to Node 3, where: Node 1: 3300 ICP Release 5.0 or later with compression OFF. Node 2: 3300 ICP Release 4.1 or before with compression ON. Node 3: 3300 ICP Release 5.0 or later. | The call is not compressed when going through Node 2.
IP calls between MiVoice Business 7.2 and systems running older software. | Bi-direction codec selection (G722.1 one direction, G729 the other direction) resulting in low quality audio on one leg of call. NOTE: SIP sets, older MiNET sets, and OASIS sets which do not support bi-direction codecs will experience one-way audio.

## Programming

To program compression zones and configure IP devices for compression:

1. Plan the appropriate compression zones required for your networked system.

2. Station Attributes form

- Enter the appropriate compression zone number in the Compression Zone ID field (1 = default, no compression).

3. Network Zones form

- Set the Intra-zone Compression field to "Yes" when compression is preferred for calls within that zone.

- Enter a descriptive label in the Label field.

Related Topics

- IP Networking/XNET Description

- IP Networking/XNET Call Processing

- IP Networking/XNET Planning

- XNET Programming

- IP Networking Programming