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Effnet ROHC™

Effnet provides a highly portable, efficient and fully compliant software implementation of RObust Header Compression (ROHC) technology which is based on IETF standard RFC 3095 published in 2001. It is has been designed and standardized to address the need for high compression efficiency even in the presence of high bit error rates and long round trip times typically observed in wireless networks e.g. cellular and satellite.

Effnet ROHC™ supports compression of the following header chains:


Effnet ROHC™ is an enabler of VoIP and a substantially increases the capacity on networks such as HSPA, EV-DO, WiMAX and LTE. The ROHC scheme has been adopted by standardization bodies such as 3GPP and 3GPP2 for efficient use of radio resources. 3GPP has recommended the use of ROHC since the Release 4 version of the specifications which include GPRS, WCDMA(UMTS), HSPA and now from release 8, LTE. In Release 5, ROHC is considered an essential part of the IP-based Multimedia Subsystem, IMS. 3GPP2 has recommended the use of ROHC in CDMA2000 1xEV-DO specifications. It is also being adopted by satellite modem manufacturers to attain better performance over satellite links.


Effnet scientists participated as authors of the IETF standard ROHC (RFC 3095). Effnet's research and development team is actively involved in the standardization process including interoperability and field tests as well as further developments.

General features

  • Fully compliant with IETF standards RFC3095 & RFC4815
  • Lightweight implementation including all features suitable for low-end devices
  • Highly portable ANSI-C implementation
  • Platform, endianness and byte-order independent
  • Highly configurable with compile and run-time options
  • Highly modular with external memory management
  • Multi-threading support
  • Extensively tested, in-house as well as during interoperability and field tests.

Standards based functions:

  • All profiles: Uncompressed (0x0000), RTP (0x0001), UDP (0x0002) and ESP (0x0003)
  • Compression of IPv4 and IPv6 with extension headers
  • All states and modes including mode transitions
  • All ROHC packet types, including all extensions: 0, 1, 2, and 3
  • Both interspersed and piggyback feedback and feedback options
  • All encoding mechanisms: LSB, W-LSB, scaled RTP timestamp, timer-based RTP timestamp
  • Local repair mechanisms with enhancements
  • List compression
  • ROHC Segmentation and Reassembly
  • Packet Size Limitation Enforcements
  • Reverse Decompression

Additional features for improved efficiency and operation:

  • Full featured and efficient classifier and context manager module
  • Efficient VoIP flow compression using:
    • Improved field pattern detection algorithm
    • Link layer information
    • Effective use of feedback channel using a rate control mechanism
  • Support for running and switching between multiple instances for redundancy and fail safe operation (Used in large systems)
  • Support for 3GPP2 C.S0085-0 standard recommendations for header compression.
  • Support for MBMS as defined in 3GPP Rel 6 standard for PDCP layer.

Effnet Classifier and Context Manager (EFFRCCM™)

The classification and context management is an essential component of header compression function. Even though RFC 3095 and RFC 3843 do not standardize it, Effnet provides this component together with Effnet ROHC™ . The classifier and context manager does the following functions:

  • Performs exact matching on all required header fields for ROHC, including IP version (IPv4 or IPv6), Source address, Source port, Destination address, Destination port, RTP SSRC (in special case).
  • Handles AH, GRE and MINE headers.
  • Handles IPv6 extension headers (sometimes used within IPv4, if tunneled).
  • Detects and avoids fragmentation and IPv4 options.
  • Provides profile hint for a packet based on header chain present.
  • Provides context associated with a packet via context management.


Effnet provides support and maintenance services covering problem reporting, bug fixes, updates, training, consulting and integration. A sample application code together with detailed documentation covering well defined and easy to use API is provided to speed up the process of integration


Effnet ROHC™ v2.4

The focus of the latest release of Effnet ROHC™ has been improved compression efficiency and addition of new features. The release supports MBMS (Multimedia Broadcast Multicast Service) as defined in 3GPP Rel 6 standard. Mobile terminals supporting MBMS and ROHC will benefit from this feature. The release will enable users of the 3GPP2 standards to follow the recommendations for VoIP over EV-DO networks. Other Effnet ROHC™ features and optimizations focus on improving compression efficiency in order to maximize the gains of using ROHC technology in the network. For details, please contact info@effnet.com.

Effnet ROHC™ 2.4 works seamlessly with other Effnet header compression products. Thus, using more than one product a broad range of protocol headers can be compressed.

Effnet ROHC™ is continuously tested on various platforms such as Nucleus, VxWorks, Linux, FreeBSD, Windows and Solaris. The results of performance testing on x86, ARM, MIPS and PowerPC processors are available to interested parties.

Effnet ROHC-LLA™ version 1.0

Zero byte compression - A 100% reduction of packet header overhead for VoIP packets is implemented in the new product release: Effnet ROHC-LLA™ 1.0.

The ROHC Link-Layer assisted profile (ROHC LLA), defined in IETF RFC 3242, uses functionality of the lower layers to be able to compress headers of RTP packets to as small as 0 bytes under normal operational conditions. This profile is suitable to be used on air interfaces based on technologies such as IS-95 or GSM. The ROHC LLA profile is included in the 3GPP2 standard IS-835, where the LLA profile is used as service option 61 (SO61).

The ROHC LLA profile is now available as an add-on to the Effnet ROHC™ version 2.1 and later. The Effnet ROHC-LLA™ includes full adaptation towards 3GPP2 and includes the functionality of the HRU (Header Reduction Upper) Layer for use together with SO61. The Effnet ROHC-LLA™ contains all the functionality needed to perform HRU operations in a PDSN or in a mobile terminal. The Effnet ROHC-LLA™ is fully compatible with the other profiles offered by the Effnet ROHC™ and contains all configuration options offered by the RFC 3242 and SO61 specifications.

For testing, integration and evaluations by Effnet's customers, the LLA profile can also optionally be delivered with an adaptation of Effnet HC-Sim™ that makes it possible to simulate a synchronized link where the LLA profile can be used.

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Effnet EthHC™
Effnet ROHC™
Effnet ROHC-TCP™
Effnet ROHC-IP™
Effnet ROHCv2™
Effnet IPHC™
Effnet CRTP™
Effnet HC-Sim™

Learn more about IP header compression from our white papers:

Performance on Intel® CoreEMicroarchitecture-Based Processors

An introduction to IP header compression

The concept of robust header compression, ROHC

Data sheet

Effnet ROHC™

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