IPTV slows down your network? IGMP Snooping helps.

On a Sunday night, you were browsing a website on your PC. Everything was lovely until it took too long to load a webpage. You walked around, anxious to find out what went wrong. As you saw your mom watching the IPTV programs, everything was fairly explained. All the network devices were busy handling the IPTV traffic and delayed transmitting your web data. Quite reasonable, right? Well, it’s not always the case. Let’s look into what takes place behind the scenes.

Browsing Webpages vs. Watching IPTV Programs

Suppose you and your neighbor are browsing the same website simultaneously. As Figure 1 shows, the web server sends the same traffic to both PCs, respectively. This method is called “unicast” – the traffic goes directly from the source to the destination each time and every device along the path knows exactly where to send the traffic.

Figure 1  Unicast

However, the “unicast” method wouldn’t work well for IPTV. Unlike web browsing, watching IPTV programs requires vast bandwidth. Chances are that hundreds of users watch a channel at the same time. If the IPTV source used unicast, it should send one copy of the traffic to each user, and that heavy burden would cause intolerable delay.

In fact, the network functions in a different way called “multicast”. As Figure 2 shows, rather than send the traffic to the users one by one, the IPTV source sends it to a particular group. If you want to watch the channel, your TV requests to join the group and then receives the traffic. When your neighbor or anyone else wants to watch the same channel, his TV also joins that group. The benefit is that no matter how many people are watching it, the IPTV source only sends one copy of the traffic.

Figure 2  Multicast Without IGMP Snooping

But this method can cause another problem. A switch (with no IGMP Snooping feature) typically copies and floods multicast traffic to all connected devices, including PCs, set-top boxes, and anything else, because it doesn’t know exactly which device belongs to that multicast group. Irrelevant devices (like the PC in this case) discard the traffic after receiving it, thus part of the bandwidth is wasted.

What does IGMP Snooping do?

IGMP Snooping allows the switch to listen to the conversation when the TV requests to join an IGMP group, and record the membership of that group. Then when the IPTV source sends the multicast traffic, the switch intelligently tells where to transport the traffic and no longer floods it. Therefore, the overall network efficiency is improved.

Figure 3  Multicast With IGMP Snooping

How to Configure IGMP Snooping

The configuration steps are simple. Let’s take TL-SG105E as an example. In the web management page, choose the menu Switching > IGMP Snooping to load the following page and enable IGMP Snooping (By default, this feature is already enabled). Click Apply.

Tip: All the TP-Link Managed/Smart/Easy Smart Switch models support IGMP Snooping. Some of TP-Link Unmanaged Switch models also support the feature, which is enabled by default. To check whether your product supports the feature, refer to the specifications of the model on our website. For further configuration details, refer to the user guide on the Support page.
https://www.tp-link.com/support