APN makes VoIP reliable over any combination of networks

Enterprise class Voice-over-IP (VoIP) is a challenging application to run over a wide area network (WAN). End to end quality of service (QoS) must be provided to ensure that whenever congestion occurs, VoIP packets can jump to the head of the queue. On top of that there needs to be sufficient bandwidth to support the appropriate number of concurrent calls alongside other business applications on the network. With each call taking up 24 to 80kbps of bandwidth, depending on the CODEC, it is easy to eat up a significant fraction of an expensive T1 MPLS circuit just with voice.

Adaptive Private Networking addresses the challenging requirements of voice in a number of ways:

Abundant Bandwidth

Bandwidth using APN is 30 to 100 times cheaper than private WAN bandwidth, so businesses can afford to provision much more bandwidth for any given application. Existing bandwidth provisioned only for VPN-based backup or local Internet access can be used, and of course additional inexpensive broadband links can easily be added. This immediately removes the problem of too many applications competing for too little bandwidth.

Ingress QoS

An APN Conduit between two sites can have up to 10 classes of service which allows VoIP packets to be assigned the appropriate priority relative to e-mail or file transfers for instance. This guarantees that VoIP packets are not delayed in getting on to the WAN. To determine which traffic is VoIP and deserves real-time priority, Talari’s Mercury appliances can be configured to honor IPTOS and DSCP markings or can be configured to make this classification decision based on flow characteristics such as port number and/or source or destination IP address.

Congestion Avoidance

At the start of a call, APN will pick the path which currently has the best characteristics for a voice call. Since APN continually monitors these characteristics of a path it can quickly reroute VoIP packets, within a fraction of a second, to a new path with minimum disruption in call quality.

Optional Packet Replication

To offer the highest possible call quality it is possible to trade additional — and thanks to APN, inexpensive — bandwidth for ‘platinum’ quality voice. By replicating voice packets over two disparate paths across the network, suppressing duplicates at the receiving appliance, APN can always pick from the most timely of two VoIP packets and be able to hide packet loss or excessive delay on either of the paths.

Destination Traffic Shaping / Egress QoS

As traffic leaves the Internet or private WAN, APN ensures that the sum total of traffic heading for a destination matches the link bandwidth to avoid “self-induced” congestion at the entry to the last mile link.

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