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Using SigComp in TLS for Efficient Signaling Compression

Explore the use of SigComp in TLS to speed up SIP signaling over cellular networks. Learn about Universal Decompressor Virtual Machine and its optimization for decompression. Consider using SigComp with TLS for instant interoperability and compression efficiency.

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Using SigComp in TLS for Efficient Signaling Compression

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  1. Using SigComp in TLS? Carsten Bormann, 2002-11-20 cabo@tzi.org

  2. SigComp — Signaling compression • Problem: SIP signaling takes too long at cellular bandwidths (e.g., 8K at 1K/s = 8 s) • SIP is highly compressible though • Problem: Compression heavily encumbered • inhibits standardizing one compression scheme • Universal Decompressor Virtual Machine • draft-ietf-rohc-sigcomp-07.txt • Approved by IESG for PS (in RFC ed queue) cabo@tzi.org

  3. UDVM code example (LZSS) • 0f8604a0 c48d00a0 c41e2031 020900a0 ff8e048c bfff0117 508d0f23 06222101 13210123 16e51d04 22e80611 030e2463 14505123 22525116 9fd22300 00bfc086 a08906 (from draft-price-rohc-sigcomp-user-guide-01.txt) • 67 bytes • 13 instructions set (udvm_memory_size, 8192) set (state_length, (udvm_memory_size - 64)) at (32) :index pad (2) set (index_lsb, (index + 1)) :length_value pad (2) :old_pointer pad (2) at (64) :byte_copy_left pad (2) :byte_copy_right pad (2) :input_bit_order pad (2) :decompressed_pointer pad (2) align (64) MULTILOAD (64, 4, circular_buffer, udvm_memory_size, 0, circular_buffer) :decompress_sigcomp_message :next_character INPUT-HUFFMAN (index, end_of_message, 2, 9, 0, 255, 16384, 4, 4096, 8191, 1) COMPARE ($index, 8192, length, end_of_message, literal) :literal OUTPUT (index_lsb, 1) COPY-LITERAL (index_lsb, 1, $decompressed_pointer) JUMP (next_character) :length INPUT-BITS (4, length_value, !) ADD ($length_value, 3) LOAD (old_pointer, $decompressed_pointer) COPY-OFFSET ($index, $length_value, $decompressed_pointer) OUTPUT ($old_pointer, $length_value) JUMP (next_character) :end_of_message END-MESSAGE (0, 0, state_length, 64, decompress_sigcomp_message, 6, 0) :circular_buffer cabo@tzi.org

  4. The UDVM approach • UDVM Code for a decompressor is small • 50–500 B — smaller than a cert • Download it from compressor at start of session • No need to standardize compressors any more • UDVM optimized for decompression • May slow down decompression by factor of 3 • Compression is much slower than that anyway cabo@tzi.org

  5. SigComp and TLS • SigComp runs fine above TLS (or TCP or UDP) • This is one way it is used in SIP • Idea: Allow use of SigComp in TLS • Allows use of compression by existing apps • No need to register/standardize zillions of compressors • Instant interoperability of new compressors • SigComp can use TLS for parameter negotiation cabo@tzi.org

  6. SigComp and TLS: to do • Define details of using SigComp in TLS: • Negotiation of SigComp parameters • UDVM size, cycles per bit, … • Interaction of SigComp with Record Protocol • UDVM startup, block vs. stream mode, … • Bar BOF tbd (come to the front at the end) cabo@tzi.org

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