Setting up your IPTV network with Nebula

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IGMP Overview

To provide real-time transmission of IP-based video streaming and other multimedia applications, such as IPTV and digital signage, is challenging yet necessary for hospitality services. To address these needs, the ability to provide infrastructure with decent scalability, performance, and stability to deal with high-bandwidth network applications is the first priority for small to medium size hotels.

NEBULA ADVANCED IGMP

Since day 1, the Nebula Control Center provides the option to easily enable the IGMP snooping in all the switches. With this feature enabled, the switch can passively snoop on the IGMP packets transferred between IP multicast routers/switches and multicast clients to learn the multicast group membership and configure the multicast entries, without having to manually configure them. IGMP snooping generates no additional network traffic, allowing to significantly reduce multicast traffic passing through your switch.

Nebula Professional pack now includes the “Advanced IGMP” features, in which customer can set settings such as switch roles, modes and timers, for an effective bandwidth utilization design in an IPTV environment. The following sections introduce the configuration of these settings in the Nebula Control Center.

Pre-requisite: devices need to be upgraded to the latest firmware available on NCC; otherwise the settings won’t take effect.

Once logged in to NCC, Advanced IGMP can be found in the path Site-wide > Configure > Switches > Advanced IGMP. The page (Figure 3) can be breakdown into 5 main sections, explained as follow:

The IGMP snooping button is located on the top of the page; it acts as a global setting to enables and disables the IGMP snooping in all the switches registered in the site. Turning it ON will allow the configuration of the other sections with more granular settings.

IGMP-snooping VLAN consists of 2 options to set the VLAN(s) in which IGMP-snooping will run:

Figure 1 IGMP-snooping VLAN settings

Auto-detect – allows the switch to learn any IGMP report from multicast clients across 16 VLANs.

User Assign VLANs – allows the switch to only learn IGMP reports from multicast clients in VLAN list manually input by the user. It is recommended to use this option in case the switch is bridging more than 16 VLANs.

Unknown multicast drop by turning it ON, multicast traffic are not sent out of ports without multicast clients watching that channel. It is highly recommended to turn ON in live IPTV environment. By turning it OFF (default value), multicast traffic are sent out all ports regardless if any multicast client is watching.

Figure 2 Unknown multicast drop helps to deliver the traffic to joined devices only

Figure 3 Advanced IGMP in Nebula Control Center

IGMP Filtering Profiles can be used to create a whitelist of multicast groups allowed to pass through the switch port, for a better IPTV report accuracy. The profiles can be bound to all the switch ports as explained in section number 5. Ports bound with IGMP filtering profile may only stream traffic in the whitelisted multicast groups as long as unknown multicast drop is turned ON.

Figure 4 IGMP address range filtering

The IPTV Topology setup provides the options to configure each device based on the role or need according to the network topology and end devices connected.
Here, it is possible to enable/disable IGMP snooping for specific devices, define the role according to the network topology and configure the leave mode, timers, IGMP filtering profile and maximum group number that will be used by all the ports on that specific switch device.

Figure 5 IPTV topology setup

Note that, turning OFF IGMP snooping for all the switches will automatically disable the global IGMP snooping button introduced in section number 1.
As the IGMP snooping ON/OFF button simply works to enable or disable the IGMP function in the device, let’s focus on the details for Role and Port setting columns.
Selecting the right role is crucial for IPTV deployments, NCC includes a description of each role, which can be easily accessed by clicking on the question mark (?) next to “Role”:

Querier: should be assigned to the switch that is closest to the server. The querier will send periodic IGMP queries to the smart TV or IP STB.

Aggregator: serves as uplink of the IGMP enabled switch. In small network, the aggregator can be directly connected to both, the Access switch and smart TV.

Access: set the access role to the switches that have directly connected smart TV or IP STB devices and it does not serve as uplink for other IGMP enabled switch.

Figure 6 Topology tips to set up the right role

When a device is set as Querier role, it is necessary to define the querier IP interface for the VLANs running the IPTV service and from which the switch will send the periodic requests to the multicast clients. By default, NCC will get the switch IP of the management VLAN and auto-fill it in. Up to 16 VLANs can be configured with querier IP interface, same limitation as the IGMP-snooping VLANs in section number 2. Note that if IGMP-snooping VLAN is user assigned, only those VLANs can be configured with querier IP interface.

Figure 7 Querier IP interface settings

Note: not having a querier in the network and using only the default values might result in multicast being flooded across all the switches.

Roles are also important to determine the correct settings in the ports advanced setup, having different default values according to the role selected (Figure 8).

Leave mode: defines how long the switch waits (200 to 6348800 milliseconds) for an IGMP report before removing an IGMP snooping membership entry when an IGMP leave is received on the port from a multicast client.

3 different types of modes can be selected:

Normal Leave: when the port receives an IGMP leave report message from a multicast client, the switch forwards the message to the querier switch which sends out an IGMP Group-Specific Query (GSQ) message to determine whether other clients connected to the port should remain in the specific multicast group. The switch forwards the query message to all clients connected to the port and waits for IGMP reports to update its forwarding

Fast Leave: when the port receives an IGMP leave report message, in order to speed up the leave process, the switch itself sends out an IGMP Group-Specific Query (GSQ) message to determine whether other clients connected to the port should remain in the specific multicast group, and waits for IGMP reports to update its forwarding

Immediate Leave: when the port receives an IGMP leave report message, the switch will remove the port from its multicast forwarding table immediately, without a GSQ message or IGMP reports waiting time. It is strongly recommended to select this mode when there is only one client connected to the port.

Shorter leave timer means more efficient bandwidth utilization, but if set too short, then IPTVs may start to experience service loss. Based on our field experience, 20000 ms and 4000 ms are recommended for the querier and aggregator roles respectively.

Maximum group: if enabled, it is possible to enter the maximum number (range is 1~255) of multicast groups the ports are allowed to join. Upon reaching the upper limit, the earliest group entry will be replaced by the new IGMP join report request. Select Disable to turn off multicast group limits for the switch ports.

For the access role, it is recommended to keep the setting ON and to set a low value to avoid devices that do not implement IGMP protocol correctly joining too many channel groups at a time affecting the network bandwidth.

IGMP Filtering Profile: select an IGMP filtering profile created as pointed out in section 4, to bind it to all the switch ports. Otherwise, select No Select to let the ports join any multicast group that is being used by the multicast clients

Leave mode and timers, Maximum group and IGMP filtering profile settings in the Advanced IGMP page will apply to all the ports of the switch device that is being configured. However, per port settings can also be modified in the Switch port settings as explained below.

Figure 8 Default IGMP ports settings according to role set

SWITCH PORT: IPTV SETTINGS

A switch port or a group of switch ports can be set up with a customized IGMP setting if needed, instead of following the device global configuration set up in Advance IGMP page. The per-port basis configuration can be applied on Site-wide > Configure > Switches > Switch ports > Edit. In this page, it is necessary to first turn ON the option Overwrite advanced IGMP settings in order to display the setting fields*,* since by default, all the switch ports will be configured by Port settings-Advanced setup in Advanced IGMP page.

Leave mode and its timer, Maximum group and IGMP Filtering page are exactly the same settings as explained in Advanced IGMP page, section 5 (Figure 8).

Fixed router port: only configurable in this page, it determines where IGMP reports are sent:

Auto – default value; the switch forwards IGMP reports on the port leading to IGMP

Fixed – the switch sends IGMP reports out of this port, regardless of whether the port leads to a querier or This helps prevent IGMP network topology changes when query packets losses occur.

Use Fixed router ports in installations where streamers are located across different switches.

Figure 9 Per-port IPTV settings

IGMP MONITORING ON NEBULA CONTROL CENTER

Besides providing the Advanced IGMP settings, Nebula Control Center has included monitoring information that gives insights about the status of the Nebula IPTV network, including a completely new report tool to be further introduced.

IGMP status

Nebula Control Center also provides a quick insight about the status of the IGMP settings in a given device. Select the device from the list on Site-wide >Devices > Switches > Switch detail and check the IGMP status information in the device details page.

Figure 10 IGMP status in switch device details page

IGMP switch port counters

Per-port IGMP counters can be found by looking into the details page of the port on the path Site-wide >Devices > Switches > Switch detail > Port detail.

Figure 11 IGMP V2&3 per-port counters

IPTV Report

As part of its Nebula Professional Pack, the NCC introduces a powerful monitoring tool that will help customers, in the hospitality section especially, to quickly gather key information from their IPTV environment, such as channel utilization, alerts and multicast groups or channels’ client statistics and behavior. IPTV Report can determine:

Which channels are the most popular

What time IPTV’s users most often watch channels

Issues that may or are impacting IPTV services

The report can be found on Site-wide > Monitor > Switches > IPTV Report. Keep in mind the IGMP snooping must be enabled and there should be multicast traffic generated and going through the switch devices. Similar to Advanced IGMP, we will breakdown the content of the IPTV Report page for a better explanation (Figure 13).

The top of the page provides a channeloverview. The Total channels value indicates the number of learned multicast address within the set time frame. Channel in use indicates the number of channels currently being watched on the IPTVs. The value of current viewers indicates the number of unique viewers that are currently watching the channels. Therefore, if an IPTV can display 2 channels at the same time, the channel summary will count this as +2 for Channel in use and as +1 Current viewer.

Below the channel overview, the user can set different time period that will update the data displayed in the Total Channels in Channel overview, the Channel summary section (#2) and the Channel information section (#4). User can opt to use the before filter or the range filter.

The Channel summary provides the information of the channel share rate based on the set time frame. A sorting option is available to display either the most or less popular channels, as well as manually input up top 10 desired channels to review.

Figure 12 Channel summary chart elements

Figure 13 IPTV report on Nebula Control Center

Per-Channel share rate is counted by the aggregated time of all IPTVs displaying this channel (at the time frame) divided by the aggregated time of all IPTVs displaying any channel (at time frame).
Take the following example:

• Time Frame = Last
• 2x IPTVs displaying “Channel 1” for 12 hours = 24 hours aggregated time.
• 1x IPTV displaying “Channel 2” for 24
• Aggregated time of all the IPTVs displaying any channel = 48 hours

Results:

• Channel 1 ratio = 50% & Channel 2 ratio = 50%

Note: IPTVs must be displaying a channel for more than 5 minutes to count into the statistics of the IPTV report.

The Network analytic alert logs outstanding events that may impact IPTV service and suggest user to take actions to avoid the degradation or total loss of service.
Currently, 3 different analytics alert that are based on real IPTV issues will be raised on NCC:

UPnP packets detected: the presence of UPnP packets might cause pixilation within the IPTV network. User can click on “Update filter rules” which redirects to switch IP filtering settings and automatically populates the information needed to block these packets.

Joined group request exceed: it is raised when a port tries to learn more than the maximum multicast groups configured for the port (as explained in Advanced IGMP settings). User can click on “port configuration page” to review the settings of the port that reported this

Exceptional bandwidth utilization: when a switch port that has IPTV enabled reaches bandwidth utilization over 80%, NCC will display the alert to let user know that this might affect the streaming User can check topology or switch port settings to mitigate the issue.

When an alert has been raised, the switch list on Site-wide > Devices > Switches will also show an icon alert next to the device status, including a brief description.

Figure 14 Alert icon in switch list indicating an event that affects IPTV

These alerts can be removed at any time when the user considers it appropriate by clicking on the trash bin icon in the IPTV report page.

The Channel information displays the client details of the channel such as client IP, viewing time, switch and port to which the client is connected and VLAN used. It is necessary to first click the arrow on the right of the screen to expand the client information for a specific channel. The channel name can also be changed by clicking on the pen icon placed right beside the channel name.

Figure 15 Channel information details

It is also possible to look into more details for each channel or multicast group to check the current viewers’ statistics. By clicking on a channel name, the channel detail page will be displayed as shown in Figure 16.

Figure 16 Channel detail page showing current viewers information

ZYXEL RECOMMENDS

Deployment strategies

It has been mentioned that the network topology is crucial to determine the settings for each of the devices installed. This topology might be directly related to the size of the network, for which the following arrangements are suggested to keep in mind while building the network up:

Figure 17 Topology design strategies

Fast Leave ports recommendation

IGMP Leave-Proxy (enabled by default in Nebula IGMP implementation) is a mechanism that prevents IGMP enabled switches from sending leave reports while there are other ports that are using the same stream.

Given the following scenario in Figure 18:

Figure 18 Scenario for Fast leave recommendation

The IPTVs in Room-A and Room-B are connected under the same physical port of the Aggregator switch, both displaying the same channel 225.0.0.1. At the same time, another IPTV in Room-C is also displaying the same channel, but connected under a different port of the Aggregator switch. When IPTV in Room-A stops displaying 225.0.0.1, an IGMP leave report should be ideally sent to the IGMP querier having Normal leave enabled. However, because of Leave-proxy, this leave report is never sent to the querier as long as the IPTV in Room-C continues to display 225.0.0.1. As a GSQ is never sent back to Room-B, the Aggregator switch no longer streams 225.0.0.1 down this port.

Consider configuring Fast Leave mode in deployments when IPTVs are connected under switch/bridges without IGMP support, to ensure the sending of GSQ messages by the switches themselves and prevent service interruption.

IPTV devices connected to Querier or Aggregator

It is recommended to configure the individual switch ports to which IPTVs are directly connected on Querier or Aggregator switches:

Leave mode – Immediate leave

Maximum Group – Enable , 3

Figure 19 IPTV connected to Querier or Aggregator

Bandwidth/Storm Control Considerations

In an IPTV network, the bandwidth increases the closer it gets to the Querier switch, by which it is recommended to consider setting up a link aggregation or 10-Gigabit SFP links. It is also recommended to disable Storm Control on the uplink switch ports to avoid packet loss of multicast streams.

Figure 20 Link aggregation and storm control considerations

IGMP filtering profile and IPTV report

Some devices such as printer, IP camera, IP phone or even PC may utilize IGMP for some of their proprietary functions that are non-IPTV related. By sending these IGMP packets (such as for mDNS and LLMNR), the Nebula switch sees this as a legitimate multicast member and will send this information to NCC. The use of IGMP Filtering guarantees IPTV Report to only display IPTV stream channels.

LLDP and IPTV report

Nebula Control Center collects IGMP statistics from the Nebula switch ports that do not connect to another Nebula switch, to avoid double-counting data.

Figure 21 non-Nebula switches might cause inaccurate report

As in Figure 21, NCC will collect statistics from the Nebula switches to which the IPTVs are directly connected. However, having a non-Nebula switch connected in-between will also cause the collection of the data again from the other Nebula switch. For the most accurate report, avoid installing non-Nebula switches between Nebula switches.

NCC is able to determine if downlink ports are connected to another Nebula switch by using LLDP, therefore, LLDP must be enabled on ports between Nebula devices while having an IPTV environment running.

IGMP in Nebula Free

Advanced IGMP settings and IPTV report are part of premium features available in the Nebula Professional Pack.

While IGMP snooping global button can also be activated in Nebula free version, it does not provide the benefits of setting up roles, timers, leave modes and other settings introduced above. Moreover, the IPTV report cannot be accessed at all.