Appendix C: Minimum Network Requirements
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N7142 User Manual
Appendix C: Minimum Network Requirements
As you look into an N-Series solution and try to decide what type of network topology and infrastructure will be best suited for your
application, there are some minimum network requirements that must be considered when choosing the hardware to deploy a
Networked AV system. The requirements presented in this guide cover the necessary protocols and features needed to drive an
N-Series stream.
NOTE: Specific configuration recommendations given in this document are based off of the Cisco Catalyst series switch. These
recommendations could vary from manufacturer to manufacturer.
1. Managed Network Switch
2.
Gigabit Ethernet (N1000/N2000 Based Systems)
3.
Internet Group Management Protocol (IGMP) Version 2
a.
IGMP Snooping
i.
Snooping must be enabled on all switches that are communicating with the querier.
b.
IGMP Snooping Querying
i.
Network must include at least one IGMP Querier to maintain stream connections.
1.
It is recommended to have all capable switches with the querier enabled and allow IGMP auto-elect to
determine the Designated Querier (DQ).
a.
DQ is determined by the lowest IP addressed switch, but can be manually assigned. However, this would
need to be manually configured on all switches to bypass the auto-elect.
ii.
Query interval – 30s
1.
Interval between sending IGMP general queries.
iii. Query Response Interval – 10s
1.
The maximum time the system waits for a response to general queries.
iv. Last Member Query Interval – 100ms
1.
The interval to wait for a response to a group specific or group-and-source-specific query message.
v.
Immediate Leave (required for N1000, N2x51 4K, N2300 4K, N2400, and N2x35 [Extreme Quality] Low Latency
Models)
1.
Used to immediately break up multi-cast groups when a leave message is received.
2.
Immediate Leave will break any daisy chaining of multiple units together with a single home run and as such
you will not be able to have both Immediate Leave and daisy chaining in the same VLAN.
3.
Some manufacturers do not have Immediate Leave as an option and use Fast Leave instead.
a.
Fast Leave does not guarantee an immediate leave from the multi-cast group and can affect switching
speeds and performance.
vi. Optional Protocols
1.
IGMP Robustness – Default 2
a.
Robustness can be adjusted generally from 2-10. The higher the value, the more leave latency is added.
b.
This protocol is effectively inactive when Immediate Leave is enabled.
c.
Warnings/Notices
i.
There is a known behavior within IGMP V2 that Encoder streams, whether requested across an uplink or not, will be
requested by the DQ and will be present on the uplinks of all switches between the stream source switch and the DQ.
1.
Essentially this means that even though you may not be routing a stream to another switch, the DQ’s request
will still put the stream on the uplink. Therefore, ensure that you have accounted for all streams forwarding to
the DQ.
2.
A good rule of thumb, when planning for bandwidth considerations on uplinks, is to not exceed 80% of the
uplink’s total bandwidth capacity to give plenty of overhead for spikes and additional traffic.
3.
Multicast routing capabilities on each switch (configured for PIM-SM and with an established rendezvous point)
can be designed to limit or mitigate this behavior.
ii.
When a multicast host leaves a group, it sends an IGMP leave message. When the leave message is received by the
switch, it checks to see if this host is the last to leave the group by sending out an IGMP group-specific or group-
and-source specific query message, and starting a timer. If no reports are received before the timer expires, the
group record is deleted and a report is sent to the upstream multicast router/querier switch. Lower interval times
will increase bandwidth utilization slightly as querying will happen more often.
4.
Protocol Independent Multicast (PIM)
a.
Used to route multicast between VLANs
b.
PIM Sparse Mode (PIM-SM)
i.
Recommended for use with N-Series multicast products.
ii.
PIM-SM uses a pull model to deliver multicast traffic. Only network segments with active receivers that have
explicitly requested the data will receive the traffic.
iii. Requires configuration of a Rendezvous Point (RP).
1.
Must be configured by administrator.
2.
Similar to the DQ in IGMP.
3.
All multicast sources must register with the RP to be able to be routed throughout the network.
c.
Other PIM modes – not recommended for N-Series
i.
Dense Mode (PIM-DM)
ii.
Bidirectional (bidir-PIM)
5.
Jumbo Frames Enabled (For N2300 Series)
