Unsupported features are in red.

Limitations are in orange.

Main features

• ROHC compression
• ROHC decompression
• ROHC channels: small and large Channel IDs (CIDs)
• ROHC modes:
  • Unidirectional mode (U-mode)
  • Bidirectional Optimistic mode (O-mode)
  • Bidirectional Reliable mode (R-mode)
• ROHC states:
  • Initialization & Refresh (IR)
  • First Order (FO)
  • Second Order (SO)
• Feedback:
  • Feedback packets
  • Piggy-backed feedbacks
  • Negative ACKs
• ROHC packets:
  • Feedback packets (RFC 3095, §5.2.1 and §5.2.2)
  • IR packet (RFC 3095, §5.2.3)
    • Optional dynamic part is always sent
  • IR-DYN packet (RFC 3095, §5.2.3)
  • Packet type 0 (RFC 3095, §5.7.1)
    • UO-0
    • R-0
    • R-0-CRC
  • Packet type 1 for R-mode (RFC 3095, §5.7.2)
    • R-1
    • R-1-TS
    • R-1-ID
  • Packet type 1 for U/O-mode (RFC 3095, §5.7.3)
    • UO-1
    • UO-1-ID
    • UO-1-TS
  • Packet type 2 (RFC 3095, §5.7.4)
    • UOR-2
• Actions upon CRC failure (RFC 3095, §5.3.2.2.3, §5.3.2.2.4 and §5.3.2.2.5)

ROHC profiles

• Uncompressed (0x0000)
• RTP (0x0001)
• UDP (0x0002)
• ESP (0x0003)
• IP-only (0x0004)
• TCP (0x0006)
• UDP-Light (0x0008)

Features shared by all supported profiles

• Compression of up to two IPv4/IPv6 headers
• Compressed IPv4 Header Extension List (RFC 3095, §5.8.4.1 & §5.8.5.1)
• Compressed IPv6 Header Extension List (RFC 3095, §5.8.4.1 & §5.8.5.1)
• Authentication Header (AH) Compression (RFC 3095, §5.8.4.2)
• Encapsulating Security Payload Header (ESP) Compression (RFC 3095, §5.8.4.3)
• GRE Header Compression (RFC 3095, §5.8.4.4)
• Forced context reinitialization controled by the user
• Fixed sizes parameters in order to specify the size of ROHC packets
• Optional Reverse decompression (RFC 3095, §6.1)
• ROHC segmentation (RFC 3095, §5.2.5)

Profile-specific features

Encoding methods

• Least Significant Bits (LSB) encoding (RFC 3095, §4.5.1)
• Window-based LSB (W-LSB) encoding (RFC 3095, §4.5.2)
• Scaled RTP Timestamp encoding (RFC 3095, §4.5.3)
• Timer-based compression of RTP Timestamp (RFC 3095, §4.5.4)
• Offset IP-ID encoding (RFC 3095, §4.5.5)
• Self-describing variable-length (SDVL) values (RFC 3095, §4.5.6)
• Encoded values across several fields in compressed headers (RFC 3095, §4.5.7)
  • Not fully respected: if more bits than stricly necessary are available, more bits are sent

Non-standard ROHC enhancements

• Use of encapsulation padding for sending larger packets
  • Padding not used with Compressed IPv6 Header Extension List
• Optional simplification of UOR-2-TS / UOR-2-ID packets to help distinguish them at decompressor