Black Box ACR1000A-T Switch User Manual


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ServSwitch Agility and Agility Dual
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Appendix B. Troubleshooting
Problem: The video image of the ServSwitch Agility receiver shows horizontal lines across the screen.
This issue is known as Blinding because the resulting video image looks as though you’re viewing it through a venetian blind.
When video is transmitted by ServSwitch Agility units, the various lines of each screen are divided up and transmitted as separate
data packets. If the reception of those packets is disturbed, then blinding is caused. The lines are displayed in place of the missing
video data packets.
There are several possible causes for the loss of data packets:
• Incorrectswitchconfiguration.Theproblemcouldbecausedbymulticastflooding,whichcausesunnecessarynetworktraffic.
This is what IGMP snooping is designed to combat, however, there can be numerous causes of the flooding.
• Speed/memorybandwidthissueswithinoneormoreswitches.Thespeedandcapabilitiesofdifferentswitchmodelsvaries
greatly. If a switch cannot maintain pace with the quantity of data being sent through it, then it will inevitably start dropping
packets.
• OneormoreServSwitchAgilityunitsmaybeoutputtingJumboframesduetothevideoresolution(2048horizontalpixels)
being used. If jumbo frames are output by a ServSwitch Agility unit, but the network switches have not been configured to use
jumbo frames, the switches will attempt to break the large packets down into standard packets. This process introduces a cer-
tain latency and could be a cause for dropped packets.
• OneormoreServSwitchAgilityunitsmaybeusinganoldfirmwareversion.Firmwareversionspriortov2.1exhibitedanissue
with the timing of IGMP join and leave commands that caused multicast flooding in certain configurations.
Remedies:
• EnsurethatIGMP snooping is enabled on all switches within the subnet.
• WhereeachServSwitchAgilityunitisconnectedasthesoledeviceonaportconnectiontoaswitch,enableIGMP Fast-Leave
(aka Immediate Leave) to reduce unnecessary processing on each switch.
• Checkthevideoresolution(s)beingfedintotheServSwitchAgilitytransmitters.Ifresolutionsusing2048horizontalpixelsare
unavoidable then ensure that Jumbo frames are enabled on all switches.
• Checktheforwarding mode on the switches. If Store and forward is being used, try selecting Cut-through as this mode
causes reduced latency on lesser switch designs.
• EnsurethatonedevicewithinthesubnetiscorrectlyconfiguredasanIGMP Querier, usually a layer 3 switch or multicast rout-
er.
• EnsurethatthefirmwareineveryServSwitchAgilityunitisversion2.1orgreater.
• TryadjustingthetransmittersettingsoneachServSwitchAgilitytomaketheoutputdatastreamasefficientaspossible.See
Agility transmitter video settings for details.
Problem: The audio output of the ServSwitch Agility receiver sounds like a scratched record.
This issue is called Audio crackle and is a symptom of the same problem that produces blinding (see previous page). The issue is
related to missing data packets.
Remedies:
As per blinding discussed above.
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