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Intermittent Audio Distortion in AVB Stream with SNTP Client enabled

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TitleIntermittent Audio Distortion in AVB Stream with SNTP Client enabled
  • Audio Distortion on AVB stream
  • gPTP messages not being transmitted by switch port
  • SNTP client enabled on AVB switch
  • Summit
  • EXOS version 15.3.X and up
  • Audio Video Bridging (AVB)
  • Simple Network Time Protocol (SNTP)
When SNTP and AVB are enabled on the same switch the gPTP protocol may enter a faulty state causing gPTP enabled ports to operate incorrectly.  This is due to a conflict when both protocols are attempting to access the system clock.  The result of this failure is audio distortion on the AVB endpoints.  

SNTP can be disabled on switches participating in AVB networks.  To disable SNTP enter the following command:

disable sntp-client


CR xos0058050 was created to resolve this issue.

Fixed releases:
EXOS 15.6.1
EXOS 15.7.1 patch 1-2
EXOS 15.5.2 patch 1-5

Additional notes
This issue can be confirmed by checking the gPTP port counters.  When in the faulty state the transmit counters will not increment.  Example output below:

L3L_K1_U33(65.44).12 #show network-clock gptp ports 2,22 counters 

Port number                                      : 2
gPTP port status                                 : Enabled
Parameter                             Receive       Transmit
Announce                                 1603              0
Sync                                    13357              0
Follow Up                               13357              0
Peer Delay Request                       1603           1601
Peer Delay Response                      1601           1603
Peer Delay Response Follow Up            1601           1603
gPTP packet discards                        0              -



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