Does SD-WAN offer any value to WebRTC services?
The promise of SD-WAN (Software Defined WAN) is reliable high quality enterprise WAN using low cost access (e.g. broadband) instead of expensive MPLS.
SD-WAN is a collection of several technologies with centralized management on top. These include:
- WAN Optimization – An end to end technology to optimize the traffic sent over a specific link using technologies such as compression and error correction
- Hybrid WAN – Utilize more than one type access interface simultaneously
- Dynamic path selection – Dynamic packet by packet network route selection based on quality, application priority and other policies
- Resiliency – Active-Active network connections
- Application specific optimization – Prioritize one application over another or specific traffic or users of an application
- Security – Encryption
SD-WAN solutions include an on premise device, a smart router, and a cloud based management that controls the on premise devices.
SD-WAN is used between enterprise branches but in some cases, solution also includes POPs (Points of Presence) in close proximity to main cloud hubs and data centers in order to improve connectivity with critical cloud applications. An aggregation GW that receives and aggregates traffic coming from the on premise devices is deployed in those POPs.
Hosted UC connectivity common practice
Hosted UC is provided by one of the following 2 types of providers:
- Operators – those that own the network
- OTT – those that don’t own the network
In the case of operators, they typically bundle with their hosted UC a dedicated network link to their data center for UC traffic and ensure network quality, thus quality of service.
In the case of OTT, many recommend/require the enterprise to connect to their data center with an MPLS line. Microsoft offers their ExpressRoute for enterprises that use their Skype for Business service (or for any other reason require a direct link to Azur).
SD-WAN brings enhanced competitiveness to the OTT vs. the operator as OTTs can more easily retire their requirement for MPLS, hence reduce overall cost of their service to the enterprise. Yet, since bringing up and provisioning an MPLS link is a time consuming hassle it also functions as an anti-churn tool for the OTTs.
For the operator, SD-WAN does have the promise of reducing cost but as it gives the enterprise more agility for switching providers while reducing cost of OTT hosted UC it is also a threat.
WebRTC has quality & security built into it
I listed above the main benefits and capabilities of SD-WAN, now let’s see which of these are relevant for WebRTC. Before touching this it is important to note that WebRTC, similar to any VoIP solution, includes 2 areas that take care of overall call quality:
- Pre-post processing algorithms
This is important because the same logic detailed hereunder may apply to other VoIP solutions that utilize the same codecs and similar quality and resilience technologies.
WebRTC based services typically offer good quality of service. This is due to usage of codecs built for error prone networks as the Internet. Opus, the voice codec of WebRTC has error resiliency built into it and it supports a wide bit rate allowing to optimize quality given bandwidth and network conditions.
Some applications decide to default to G.711, which is a very bad choice for sending voice traffic over the Internet. We see G.711 being used mainly in cases where WebRTC is connected with another network (VoIP, PSTN) and due to cost considerations limiting the usage of transcoding from Opus to other codecs such as G.711 and G.729.
On the video side, WebRTC uses VP8 or in some cases H.264 but it includes algorithms for resiliency and optimization of resolution, frame-rate and compression, based on network conditions. WebRTC is also starting to make use of VP9 to which Google is also adding SVC (Scalable Video Coding) through their partnership with Vidyo hence offering even better quality for a given bandwidth with enhanced resiliency.
Another important point to remember is that WebRTC encrypts all media. Additionally, Google already mandates the use of HTTPS instead of HTTP in Chrome hence signaling is also encrypted in many cases.
Where SD-WAN brings no value for WebRTC
This renders VOID some of the SD-WAN functionality when it comes to WebRTC. Specifically, the WAN optimization and anything that tries to perform application specific enhancements such as media resiliency and optimization. It also doesn’t allow for any transcoding (for example from G.711 to Opus) as media is encrypted and decryption of the media requires being a B2BUA. Encryption is also not required as WebRTC already handles this by default and further encryption is a waste of resources and increases delay.
SD-WAN value for WebRTC
Given the above some attempts to “enhance” WebRTC traffic may cause more harm than value but there are some areas where SD-WAN still brings value to WebRTC.
Dynamic path selection and hybrid WAN
Deciding based on network conditions of each path and network interface how to route WebRTC media.
Having a single network interface for an enterprise would be problematic when that network interface fails. Some resiliency solutions offer an active-standby resiliency mode, which is simpler but not efficient. SD-WAN typically offers an active-active resiliency mode where multiple network interfaces are used simultaneously through dynamic path selection offering better utilization of available network resources as well as network resiliency.
Application specific optimization
In this the only valuable decision SD-WAN solutions can offer is routing of WebRTC media through the better network path thus, the one with lower delay and lower packet loss.
Cloud aggregation POPs
Hosted UC providers (UCaaS) that offer a WebRTC interface and other hosted WebRTC service providers can eliminate the requirement for MPLS between the enterprise and the provider’s data center by placing an SD-WAN aggregation GW at the edge of their data center.
Why this is important
SD-WAN is gaining popularity in enterprise networks. Gartner sees significant growth in adoption of this technology from only 1% of US enterprises in 2015 to 10% in 2018 with continued growth thereafter.
When selecting and deploying your SD-WAN solution of choice it is important to give special attention to the most delay and network sensitive application which is real-time communication and given the above, specifically to WebRTC as it includes some special cases compared to other VoIP applications.