The Effnet ROHC product portfolio includes Effnet header compression software products based on RFCs which define RObust Header Compression (ROHC). ROHC is a header compression algorithm and protocol standardized by the IETF. The Effnet ROHC product portfolio will provide significant improvements in link efficiency for TCP traffic e.g. web, file transfers etc., RTP and UDP traffic e.g. real time, interactive and streaming applications and ESP traffic e.g. secure traffic over high BER, long RTT links.
ROHC supports both unidirectional and bidirectional modes of operation. The unidirectional mode of operation is suitable for broadcast and multicast applications and the bidirectional mode of operation is suitable for interactive applications including web, email, file transfer, Voice over IP and Video over IP.
There are many advantages of using Effnet ROHC on satellite links:
The following table shows some examples of bandwidth savings for various voice codecs:
|Codec||Sample size (bytes)||Packet size (w/o ROHC) (bytes)||Bandwidth (w/o ROHC) (Kbps)||Packet size (w ROHC) (bytes)||Bandwidth (w ROHC) (Kbps)||Savings (%)|
|GSM FR (13.2 Kbps)||33||73||29||36||14||51|
|GSM EFR/AMR (12.2Kbps)||30.5||70.5||28||33.5||13||52|
ROHC framework and profiles implemented in the form of various Effnet products are as follows:
|Effnet ROHC™||Uncompressed, RTP/UDP/IP, UDP/IP, ESP/IP||RFC 3095, RFC 4815|
|Effnet ROHC-IP™||IP||RFC 3843, RFC 4815|
|Effnet ROHC-TCP™||TCP/IP||RFC 4996|
The Effnet ROHC product portfolio can be optionally complemented with a test environment, Effnet HC-Sim™, which can simulate IP traffic with configurable link conditions, e.g. bit errors, packet loss, reordering etc.
Packet classification and context management is essential to header compression. Effnet provides this additional module together with the Effnet ROHC product family.
The VoIP enabler on wireless networks! Effnet ROHC™ is an important component to efficiently run VoIP services over wireless networks. Most of the RTP applications use UDP for signaling purposes and there are also many stand-alone UDP applications, so the support for IP/UDP compression adds further to the efficiency. There is significant demand for secure exchange of information which leads to increased header overhead. The capability to compress IP/ESP, the header overhead in secure connections, makes it possible to run secure networks without additional bandwidth.
As more and more networks are moving to support IP based communications, the number of nodes that require an IP address are increasing rapidly. The introduction of IPv6 should address this concern but at least during transition time, a lot of traffic will be sent via tunnels across networks. Effnet ROHC-IP™ is capable of compressing layers of IP headers thus making it possible to run tunneled traffic without need for additional bandwidth.
Multiple Internet packet size studies* are in agreement that at least 40% of all IPv4 packets carry no or only a few bytes of payload i.e. packet sizes are at or very near to header size (IPv4+TCP). One study of IPv6 packets shows the same trend. Even more remarkable in that study is that for IPv6, 60-80% of the packets carry more header data than packet data. Effnet ROHC-TCP™ would be very beneficial in these cases.
|Average packet size (w/o ROHC) (bytes)||Average packet size (w ROHC) (bytes)||Savings (%)|
|TCP Ack (w/o options)||40||10||75|
|TCP Ack (Timestamp)||52||13||75|
*Packet size studies at www.caida.org