Robust Header Compression

Robust Header Compression

Last updated: May 21, 2009

This section is only applicable to the lab applications.

The Robust Header Compression (ROHC) is one of the efficient header compression algorithms that can save bandwidth dramatically. For example, in case of GSM coded VOIP transmission, the payload is only 33 bytes (13.2 kbps x 20 ms) long and the header of IPv4 accounts for 55% of the packet. But with the help of ROHC, more than 90% of the size of these headers can be saved. For IPv6 this ratio is even larger.

This document describes the various ROHC negotiable parameters available for an active PDP context in the test set and when they takes effect.

ROHC Parameters

The figure below shows the configured ROHC parameters and status information for the active PDP contexts of the selected DUT IP address.

Configurable Parameters (shown as `ROHC Parameters')

The ROHC configuration is performed for each of the PDP contexts in the test set. Up to 4 DUT IP addresses are supported and for each address one primary and up to three secondary PDP contexts are available. See DUT PDP Setup for more information.

Negotiated parameters (shown as `ROHC Status')

Since the negotiation between the test set and the DUT may be different from what are configured in the test set, the negotiated parameters indicates the actual ROHC status. The corresponding information is shown as following:

How to set the ROHC parameters?

The following procedure details how to access and configure the Header Compression parameters.

  1. Press CALL SETUP .
  2. Press the More key on the lower left corner to select the Protocol Control(2 of 4).
  3. Press the More key then select SNDCP ( F2 ) key to display the SNDCP softkey menu. Use the knob to select the parameter that you want to set.
  4. Press the Header Compression ( F1 ) key to display the Header Compression softkey menu.
  5. Select the parameter that you want to set and set the value.

Operating Considerations

The ROHC mode is only available in Active Cell(GPRS/EGPRS) operating mode.

The measured IP data throughput may increase for the application over IP/UDP/RTP, IP/UDP/RTP or IP/ESP.

When a PDP context is active and an external handover occurs on two boxes, the SNDCP XID parameters will be re-negotiated with the ROHC parameters for the new box. This will have an impact on throughput even if both boxes have the same parameters.

Related Topics


DUT PDP Setup