^ Platform Requirements

Sharpen is architected to allow for a simple and easy connection through a web browser. While most users will have no issues connecting and using Sharpen, it is important to understand that some configurations oriented toward supporting other solutions (especially legacy on-premise solutions) can cause interruptions. Some items are simple configuration items, while others are unsupported configurations. This guide provides our perspective and recommendations regarding some configurations which can commonly cause service disruption.

Unsupported Configurations

• SIP ALG

  • Perhaps contrary to its name, SIP ALG is not compatible with most enterprise VoIP solutions, such as Sharpen. Depending on the manufacturer, network device configurations will show up as “SIP ALG”, “SIP”, “VoIP”, or something similar. Intermittent disconnection, dropped calls, one-way audio, and the inability to register are common symptoms when SIP ALG is enabled.

  • Depending on your device manufacturer or ISP, it may be difficult to get a straight answer on confirming this setting is off. Commonly, ISPs will have this setting enabled, because it supports their own options for VoIP solutions. It is not uncommon to have to work through a couple layers of support or technical team members to validate the proper setting is turned off. 

Not Recommended

• Virtual Desktop Infrastructure (VDI)

  • Utilizing VDI is a common way to centralize the administration and use of a collection of desktop applications across a a similar set of users. The benefits of this technology are significant (ease of central administration, virtualize and scale desktop applications with minimal hardware, improved risk management, workflow standardization, etc.). Even so, the use of VDI can have risks, complicating the use of a web app such as Sharpen, which is already virtualized through our cloud infrastructure. The infrastructure and functionality layers supporting a VDI environment introduces potential points of failure, particularly with voice traffic, which Sharpen has limited ability to support. There is nothing inherently incompatible between VDIs and voice. However, it is important that the environment is architected in a way which optimizes Sharpen traffic and respects its expectation of having real-time data available when it needs it.

  • If the accountability and risk of utilizing VDI is understood, it is recommended that the VDI provider documentation be consulted for optimal configuration for voice platforms. Here is some example documentation from common VDI providers which Sharpen customers may find useful.

    • VMWare

    • Citrix

    • Amazon Workspaces

• VPN

  • VPNs have many valid use cases, especially for work from home users. However, VPNs are not always configured to be optimal for voice traffic. Adding the additional virtual layer to the network, in most situations, will cause a recognizable degradation in network performance. Voice requires low latency, with minimal packet loss. As a result, if the VPN configuration introduces too much interruption, your quality of service will be impacted. If VPN is necessary, it is recommended to configure it so Sharpen traffic can be omitted through the use of split tunneling.

• MPLS

  • Similar to VDI and VPN, an MPLS has understood value. However, the use of an MPLS with Sharpen is not recommended as it undermines our intended connection path from the user to our cloud through the public internet. Most commonly, customers will have had MPLS configurations remaining from previous on-premise or direct to data center VoIP solutions. This is understandable because there are narrowly identified VoIP endpoints which you can create a specific path to through the MPLS. Your users then connect to your corporate network and then their traffic tunnels through that optimal connection. However, this architecture actually causes problems for a more universally available cloud-based solution such as Sharpen. Sharpen expects the lowest latency path over the internet to the most proximate availability zone.

  • The best solution is a solid internet connection with standalone network equipment. This allows for the lowest latency path to our resources, and the best experience.

• Stateful Packet Inspection (SPI)

  • Similar to SIP ALG, SPI is a setting which has its benefits, but can conflict with the proper operation of voice traffic. Stateful Packet Inspection is a dynamic packet filtering technology for firewalls which inspects the state of packets to determine whether packets should be blocked or allowed. WebRTC traffic is stateless, and thus you may experience issues with the inability to establish a connection or 2 way audio if it is enabled. This happens because SPI may not recognize webRTC and thus treat it as unapproved UDP traffic.

• ISP provided “combination” network equipment

  • Especially if you’re working from home on your residential internet connection, be weary of the Internet Service Provider (ISP) controlled settings which may exist on these managed devices. “Combination” devices are typically those which integrate modem, router, and wifi into one device. While in principle, the integration of these functions problematic, they can sometimes come with configuration hurdles which are difficult to overcome since you, as the borrower of the device, do not have administration access to the devices. It is not uncommon for settings like SIP ALG to be enabled but invisible to you as the user. These situations require that you work with your ISP’s support team to change a setting. 

  • As a result, Sharpen discourages the use of combination network equipment. Instead we recommend purchasing a stand alone modem which is compatible with your ISP, and connecting a router of choice to it. This allows you full control of any potentially conflicting setting. Most self-managed devices have these problematic settings disabled by default.

  • If you can not acquire a stand-alone modem and router, we recommend reaching out to your ISP to see if they can place your combination device in “bridge” mode, then purchasing and connecting a 3rd party router to handle the local networking. 

Common interruptions

• NAT misconfigurations

  • NAT (Network Address Translation) exists to provide security and preserve local IPv4 addresses. NATs associate or bind private IP:port addresses to public IP:port addresses. Hosts outside the local network will only see and know of the bound outside IP:Port.  Hosts directing traffic to this bound IP:port will first arrive at the NAT before being translated and sent to the actual destination IP:Port.

  • With VoIP and webRTC, NAT can cause challenges if not configured optimally. Though the STUN protocol exists to overcome this challenge through its participation with ICE candidate negotiation. Some NAT configurations can still get in the way. For instance, utilizing a Sonicwall firewall without the use of its “Consistent NAT” feature, will result in 1-way audio. Consistent NAT uses an MD5 hashing method to consistently assign the same mapped public IP address and UDP Port pair to each internal private IP address and port pair.

• UDP timeout is set less than 240 seconds

  • Sharpen’s expected SIP registration interval is 4 minutes (240 seconds). If your network is set to “timeout” UDP connections at less than that, it will disconnect an active registration. Depending on when this happens, you’ll see the following symptoms.

    • Dropped calls

    • Inability to be reached on the phone which has lost its connection. 

    • You’ll be able to dial outbound without issue, since registration is established on an attempted outbound call, if it does not already exist. 

    • You’re probably seeing a sawtooth pattern in your latency graphs.