Peer-to-peer (P2P) networking is one of three core eCDN technologies used to optimize the delivery of video. A P2P eCDN uses personal devices active on a network to share video files with one another. The goal is to save bandwidth by reducing the number of requests traveling to and from a primary video server. But like its eCDN counterparts, P2P has relative strengths and weaknesses.
If any of the following network environments or streaming use cases describe your enterprise, P2P networking might be a good technology to include in your eCDN toolbox.
You have locations without infrastructure
One of the strongest features of a P2P eCDN is that it needs virtually no infrastructure, and in most locations, none at all. The only infrastructure a P2P network typically needs is a centralized controller to coordinate the initiation of the P2P trees. The controller can be deployed in the cloud as easily as anywhere else since video traffic never passes through it.
In a world that has moved from server farms to data centers to the cloud, infrastructure is disappearing from corporate facilities. Outside of the large corporate facilities, servers or spare compute devices are rarely available anymore, so a P2P eCDN can work at these small locations.
Live events are a priority
In most P2P eCDN implementations, peers perform two functions: participating as member of the P2P network and serving content to itself through a local video client. The peers are the personal devices being used by people watching the video.
This dual role of the peers is important when considering what kind of video can be served. When the video is a live stream, such as an executive town hall, most viewers are watching the event at the same time and, in fact, are seeing the same timeframe of video at almost exactly the same time. Therefore, most peers will have the same segments of the same video readily available to share. In this mode, a P2P eCDN is at its most effective.
For on-demand video, viewers are rarely watching the same video at the same time. And even if they are, it is unlikely they will be viewing the same timeframe of the video at the same time. To gain efficiencies, P2P needs more than one person watching the same video at the same time. And it needs a deep enough cache on at least one peer to allow it to meaningfully store past video segments to serve to other peers. So, in the case of video on demand (VOD), the bandwidth optimization with P2P is opportunistic.
You have locations with small numbers of users
P2P eCDNs are best suited for smaller offices and branches where infrastructure does not exist and the number of users is modest. While P2P can scale to build large networks, the WAN impact can rapidly become unnecessarily high when large numbers of users are involved.
In fact, published use cases typically show efficiencies around 80% with P2P trees averaging five nodes. In the context of eCDN, these are modest improvements.
Users are mostly on wired devices
In a Wi-Fi network, all traffic is routed via the core-connected wireless controller. So for a given Wi-Fi connected peer, all traffic from the upstream peer is sent to the core before being sent back to the Wi-Fi connected device—the least efficient journey using double the bandwidth. A low density of Wi-Fi connected peers in a P2P network will not really induce a problem, but once the numbers start to scale up the inefficiencies can have a real impact on the wireless network.
The same effect is true if the Wi-Fi connected peer has downstream peers. However, the problem can become even worse if the peer’s connect speed degrades. Because Wi-Fi is half duplex, the upstream peer must first receive the complete video segment. Then, once it receives a request from a downstream peer that has waited for its turn to transmit, the upstream peer waits for its turn to transmit the segment to the downstream peer. On modern high-speed Wi-Fi, these delays are not too bad, and the segment can be quickly sent. For each downstream peer connected to that same upstream peer, the problem is compounded, and at scale, it can have an impact. Simply put, 100 Wi-Fi connected peers on a P2P network, accessing a 4 Mbps video, will generate 800 Mbps of network traffic, when only 400 Mbps is required.
Therefore, a P2P eCDN is best when the majority of the peers are wired devices.
You need a solution you can deploy and begin using quickly
A P2P eCDN is often a quick solution to deploy for two reasons.
As mentioned earlier, it needs little or no infrastructure, particularly when the controller is provided through a hosted, cloud service.
In addition, P2P has recently experienced a step forward in the area of rapid deployment with the emergence of WebRTC P2P clients. WebRTC relies on inherent capabilities built into HTML5 web browsers that allow the P2P client to be downloaded at the same time the video player is downloaded, making deployment completely automated and invisible to the user. For this reason, WebRTC-based P2P solutions are considered clientless.
Choosing the right eCDN
P2P networking is just one of the three core eCDN technologies on the market. You can also consider multicast, video caching, or a combination of all three eCDN solutions. Each has its own inherent strengths, weaknesses and network considerations.
To learn how each eCDN works, key deployment considerations and pros and cons of each, download Protect Your Network from Streaming Video: Guide to Selecting the Right eCDN.