VIAVI TestCenter: What are the VIAVI TestCenter signature fields?

VIAVI TestCenter: What are the VIAVI TestCenter signature fields?

  • The Stream ID is defined by each application.   • Each port’s stream IDs will be different (the upper 16 bits), but they don’t necessarily relate to a chassis/module/port number. • They are NOT assigned sequentially from 01 to 10 to 11 to 100, etc. Rather they are assigned arbitrarily to each port and can vary from one test to the next even with the same configuration opened back up. • Regarding the composition of the 32-bit Stream ID: • The top 16 bits of the Stream ID is related to the chassis/slot/port so that they will be cause uniqueness within a configuration (but not between configurations - i.e., different configurations can generate the same stream IDs). • The bottom 16 bits is usually the generator’s test stream number. • Sequence Number - its use by the Analyzer • Enhanced Detection Mode (default) • To improve the VIAVI Signature detection circuitry by using byte locations 5 and 6 of the sequence number as the inverted sequence of bytes 2 and 3.  • This lessons the chance of the analyzer detecting random data as a signature frame.  • This is useful if an application is intermixing a lot of user-defined or cut thru packets into the data stream. • Sequence Mode • A 6-byte Sequence Number is inserted into the frame.  • The LSB of the sequence number is inverted and inserted into the first byte of the test signature for two reasons:  • as detection of the Signature’s existence in the frame; and • as a seed for a scrambler.  • Timestamp field • 38-bits • Each increment represents 2.5ns resolution. So, modules that support 10 ns timestamp resolution, increment by 4. • It depicts the time when the frame is passed "over the line." • The timestamp can be configured to mark the time of the first byte of the frame being passed or the last byte of the frame being passed. • this location is indicated by the Timestamp Location Reference Bit • PRBS bit • If the fill is PRBS, then the PRBS bit is set. • 1st bit after the Timestamp filed. • Timestamp Location Reference Bit • 0 indicates Start of Frame (defaul) • 1 indicates End of Frame • 2nd bit after the Timestamp field • CRC16 • uses the CRC-CCITT polynomial used in PPP, but it’s used big endian instead of little endian. • TCP/UDP checksum cheater  • see FAQ11140