Lightware VINX-120-HDMI-ENC User Manual page 101

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10. Appendix
Switch Setup for Dante® Audio Signal Transmission
You can configure the QoS settings to ensure good system
performance in a busy network. QoS (Quality of Service) refers to
technologyforprioritizingthetransferofspecificdata.Byconfiguring
the QoS settings recommended by Dante® on a network switch,
youcanprioritizethetransferofDante®clocksynchronizationdata
and audio data over background data traffic. This will ensure good
system performance when you need to transfer non-Dante® data
overthesamenetwork.QoSisrequiredwhenusingDanteinnetworks
that have 100Mbps devices and is optional in networks with Gigabit
devices.WerecommendthatQoSbeenabledinallDante®networks
in order to ensure proper operation under all possible conditions.
The table below shows how Dante uses various Diffserv Code Points
*
(DSCP) packet priority values:
DSCP
Priority Usage
Label
Time critical
High CS7
PTP events
Medium Audio, PTP EF
Low (reserved) CS1
None Othertraffic BestEffort
Green Ethernet in the Network
EEE (Energy Efficient Ethernet) is a technology that reduces switch
power consumption during periods of low network traffic. It is also
sometimesknownasGreenEthernetandIEEE802.3az.
Although power management should be negotiated automatically in
switches that support EEE, it is a relatively new technology, and some
switches do not perform the negotiation properly. This may cause EEE
to be enabled in Dante networks when it is not appropriate, resulting in
poor synchronisation performance and occasional dropouts.
Managed Switch Properties in Details
IGMPv2
IGMPv2 is version 2 of the Internet Group Management Protocol. This
protocol is used by end-point devices to signal their interest in receiving
* source: https://www.audinate.com/learning/faqs
a specific multicast content via subscribing to the multicast group
corresponding to the content. Using IGMPv2 packets, the end-point
devices can send a leave message to indicate that they are no longer
interested in receiving the stream of the multicast group. Moreover, a
multicast capable router can periodically poll the end-point devices on
its interfaces which multicast streams they are interested to receive.
The answer to such a query is called a membership report. IGMPv2
must be supported by the managed switch.
IGMP Snooping
IGMP snooping is a feature which allows the switch to monitor
IGMPtrafficwhenenabled.TheinformationcollectedfromtheIGMP
packets is used by the managed switch to determine which interfaces
the multicast traffic should be forwarded to. In other words, IGMP
snooping is used to conserve bandwidth by allowing the switch to
forwardmulticasttraffictothoseinterfaceswhereitisreallyrequired.
Hex Decimal Binary
IGMP Fast Leave
IGMP fast leave (or immediate leave), when configured, reduces
0x38 56 111000
the amount of time it takes for the managed switch to stop sending
multicast traffic (corresponding to a multicast group defined by a
multicast address) to an interface, where all end-point devices that
0x2E 46 101110
used to be interested in a stream have sent a IGMP leave message.
Withoutfastleavebeingenabledthemanagedswitchwouldfirstsend
0x08 8 001000
out a query message and then would stop forwarding when no end-
points answered within a pre-specified time interval. If fast leave is
enabled, the switch stops forwarding the traffic without sending a
0x00 0 000000
query message.
IGMP Querier
In order for IGMP snooping to work properly, IGMP messages must
traverse in the subnet between managed switches. However, if there
is no multicast capable router present periodically sending out query
messages and receiving answers to those queries, IGMP messages
are usually not forwarded upstream from one switch to another. By
enabling the IGMP querier feature in a managed switch, the managed
switch will act like a router and periodically query the devices in the
subnet (even other managed switches) to send their membership
reports. From those report all the listening switches with IGMP
snooping enabled will be able to determine where multicast traffic
should be sent to.
Multicast Filtering
Some control information from VINX devices is transmitted via
multicast packets. However, these packets are not registered during
certain startup intervals or not registered at all. In order for all VINX
Appliedfirmwarepackage:v2.0.2b4 | LDCsoftware:v2.5.2b3
VINX-1x0-HDMI Extenders – User's Manual
devices in the subnet to receive such control information, multicast
filteringmustbesetup,sothatunregisteredgroupsareforwardedto
all interfaces on the managed switch.
Jumbo/Giant Frames
Ethernet frames consist of a header and a payload. Since the header
hasafixedlength(20or26bytes)thebiggerthepayload,thehigher
the useful bandwidth is. Similarly, the higher the useful bandwidth,
the better the picture quality of the encoded video stream will be. To
maximizepicturequality,theEthernetframesize(andconsequently,
the payload) should be as high as possible. In a normal Ethernet
frame, the payload can be at most 1500 bytes. An Ethernet jumbo
frame,however,cancarryupto9000bytesofpayload.Sincethegoal
of the transmission is to provide the best possible picture quality in
all circumstances, the VINX Encoder device produces Ethernet jumbo
frames. Thus, the handling of jumbo frames has to be enabled in the
managed switches.
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