0x27B1 RTP Payload Size

Use this TLV in the NPDI Universal ICB (0x0033) to configure the RTP Payload Size.

By changing the multiple of the payload size, you can configure how much encoded PCM data a packet contains.

Example: For G.711 on the VDAC-ONE card, a 160-byte payload of encoded PCM data is sent at the G.711 Basic Packet Rate of every 20 milliseconds. But if you change the multiple for G.711 to 2x, then a 320-byte payload is sent every 40 milliseconds.

In effect, changing the multiple also changes the throughput available over an Ethernet network. Larger packets create greater network delay overall, but they use the Ethernet bandwidth more efficiently. Smaller packets may use the Ethernet bandwidth less efficiently, but they may provide better voice quality.

Used in:
0x0033 NPDI Universal ICB in:
Request for Service with Data message
Route Control message
Outseize Control message

Important! Do not confuse this TLV with 0x0101 which is the regular resource attribute TLV for RTP Payload Size. Tag 0x27B1 is the RTP Payload Size in NPDI format.

Byte | Description
0, 1 | Tag: RTP Payload Size (0x27B1)
2, 3 | Length: 0x0002
4 | Value [0] Direction 0x00 Ingress 0x01 Egress
5 | Value [1]: Multiple of the Basic Packet Rate (Default = 0x01)

Tag-Length-Value block. A standardized block that allows data to inserted in a standard way into API messages.
Network Protocol Data Intelligence. Also called “Interworking,” it is a software product that operates within Excel’s Call Control (Layer 4) and Services (Layer 5) call processing layers. NPDI is meant to enhance Excel’s call processing product offering by allowing call processing layers (specifically Layers 4 and 5) to perform advanced analysis, generation, and conversion of Network Signaling (NS) Layer 3 information.
See Information Control Block.
Real-Time Transport Protocol. Supports transport of real-time data like interactive voice and video over packet-switched networks.
See Pulse Code Modulation.
The protocol used in most local area PC networks. Typically, most Ethernet networks support data transmission speeds up to 10 Mbps, but 100 Mbps is also possible.
Outgoing call setup during real-time call processing on a specific channel.