10 Networking Tips to Manage Video Traffic

As video is added to a client's network traffic, integrators need to offer strategies to keep the systems running smoothly.

Everyone is aware of the increasing overlap of AV with IT by now. We are adding video to our clients network switches through the use of HD over IP, IP surveillance cameras, and video teleconferencing (VTC) and telepresence systems.

As we add video to our clients network traffic, we need to be able to advise them on some strategies to keep things moving and to avoid bottlenecks.

Here are 10 things to consider when adding video to a client’s network.

Segmentation
This advice is given quite often. Keep distributed video on a separate network switch. For example, if you have a distributed digital signage network that uses IP to distribute content, put those signs on one switch, while keeping the computers on another to make sure video traffic doesn’t impede employee productivity. This separate video switch will typically have one port connected to the PC network switch or to the incoming data circuit to grant Internet access as needed for updates to the signage server.

Distribution
Is the video being distributed within the facility, such as a hotel with signage throughout for room scheduling, event announcements, and canned media, or is the video being pushed out to another location? If the video is leaving the facility, segmentation may not be enough to assure your video data is not impeded as it travels to its end point, nor that your PC bandwidth is not eaten up with video traffic.

Bandwidth
Obviously total bandwidth of the Internet service connection greatly affects video on the network when it needs to leave the premises as it does from a signage server serving remote locations, a Network Video Recorder being monitored remotely, or in a video teleconferencing system. Even as far back as four years ago, it was recommended to have 2-4 MB of free bandwidth for a VTC system serving up video and data content in an office. A standard 1.5 MB T1 falls short of that.

Circuit Architecture and Infrastructure
What kind of service does the facility have? Even if you segment switches within the facility, and keep video separate from normal PC network traffic, in most cases you are building a pyramid of switches that eventually culminate in a pyramid crown that is the inbound circuit connected to a modem that feeds the top switch. This is the only entry/exit point for any kind of data from any of the segmented switches. You will be limited by the data transfer rate of that last wire leaving the building. T1s have set limits on bandwidth, but can be bonded to create more broadband service has high potential bandwidth that varies greatly based on how many other users are on the system, and FiOS obviously has the least potential for issues due to the capacity of fiber to carry data.

Each end point on the network is also connected to the switch by a piece of wire. Make sure that wire and the associated connectors are capable of supporting the data rate needed for video transmission. 10G over Cat5/6, Cat 5e, Cat6, fiber, etc.

Video Quality
The size of the file affects the amount of traffic as well. File size commonly hinges on two things which are resolution (pixel data) and frame rate. Production quality video frame rates are typically 60fps while surveillance and VTC frame rates are typically 30fps. A third consideration can arise, but does so rarely, which is color bit depth. Most content we distribute is 8 bit (or 24 bit if you multiply it by the three colors). However DCI content for digital movie theaters is 12 bit, and deep color is 10 bit and technically supported by Blu-ray etc, although I have seen many equate the potential of Deep Color in that compression strategy to the mythical Unicorn.

Packet Size
Here is a hard one to control, as there are several packet standards and redundant packet strategies employed for data, even within a single standard like H.264 video compression used in Blu-ray and in surveillance and VTC video transmission. Large packets take up more bandwidth, but in shorter bursts. However if the packet is not received on the other end, there will be a larger gap in the transmission.

Smaller packet sizes can minimize the gaps in transmission, but result in more consistent traffic on the network. Think of it like rush hour. There are large masses of traffic spread out, (stop and go) letting you go 60 mph at times and 0 mph at others when traffic all converges. In the second scenario, there are smaller amounts of traffic all over the road that keep you moving, but at an average speed of 30 mph.

Depending on the frequency of convergence in the first scenario, the later may be faster or slower.

Protocol
Network protocol makes a difference in your video transmission as well. TCP protocol sends a return packet for every sent packet to verify the packet was received. As you can see, this increases the traffic on the network with the return packets going back. The advantage is that getting a receipt mitigates gaps in transmission, as if a packet is not received it can be resent. This is very important in video, especially if the packets are large.

UDP protocol is used a lot in IP telephony. It reduces traffic on the network by eliminating return packets. However, this means packets do not have the opportunity to be resent as there is no communication as to whether they were received or not. This is why in high traffic periods, IP phones have a tendency to cut in and out if not managed properly. The way that this type of system reduces gaps, is by reducing packet size of the data in its transmissions.

Switch Fabric
A 24-port gigabit switch doesn’t necessarily have the ability to pass 24 gigabits at once. Make sure you look at the total switch throughput or switch fabric to assure the switch can handle your demands. Switches, like Cisco Catalyst, are more costly but have 32 gigabit switch fabrics and management features.

Switch Management Features
If you have a complex network of mixed devices, or devices with differing priority of operation, a managed switch is most-likely a must. These switches allow you to create VLANs or virtual networks within the switch itself to limit access of one VLAN to another, or to set data ceilings and floor on the ports in the switch. In this case, you can predetermine what devices get more available bandwidth than others by limiting the throughput on that port of the switch itself. For example, the executive boardroom may always have a higher priority and more bandwidth than a middle management conference space.

Another great feature on some newer switches is VLAN by MAC address. If the CEO has a VTC client on his laptop, his VLAN can be given more priority or VLAN based on the MAC address of his machine. No matter where he plugs in at the facility, the port his machine is plugged into will be given that VLAN and those preferential settings. Now, the CEO can move around to different locations and have a jitter free videoconference call with his distributor in China.

Bursts vs Streaming
Placing a small PC or networked video player device at each screen, or close by, can decrease the consistence of network traffic.

The most simple example is trying to watch You Tube on a slow connection. Watching it real time as it is streaming is futile. You wait until it downloads, then you watch it and there are no issues. Once the data is in local memory, it is not dependent on the network to get it up on the screen.

This is why many signage players are not technically streaming content. The devices receive updated data from a signage server in a large chunk, taking up traffic for a fixed period of time. After the data received, that content is played from local storage to the screen, limited by bus and processor speed, not by the network or ISP. NetStreams uses this method, making their name a misnomer as the data really isn’t streaming. Each endpoint gets the data, they all wait to make sure everyone has it, and then they all start to play at the same time. This eliminates time delay in more traditional systems due to the varying distances.

If you need real time access, streaming is the best option. It can also be optimized to available bandwidth, like Netflix does, to evaluate the bandwidth and adjust the video quality to mitigate the instances of gaps in the data.

At the end of the day, to be a true resource to your clients, ask for introductions to their IT staff and start asking all the right questions to find out the info above. You will become their ally in the process, and you will have all the info to deliver an outstanding system which will ultimately produce a happy customer.