Inbound Call
Softphone (SIP based) is no doubt the most important tool for your remote agents. Comparing with other ways, installing softphones on computers is easier, and technicians can help on this procedure via remote desktop tools. Prepare an installation guide for the remote agents and also some patience.
The desktop IP Phones can also be sent to agents’ locations, but make sure the configurations are already done on these phones as agents are not technical professionals. Now main SIP servers or IP PBXs support auto provisioning feature, which might make things easier than before.
These softphones or IP phones usually can be registered as remote SIP extensions to your main SIP server in headquarter of call center via VPN or DDNS (Dynamic Domain Name System). The agents can keep their original extensions and user habits. Meanwhile, a few settings need to be done on your firewall/router like port forwarding etc., which inevitably bring some security threats, an issue can’t be ignored.
To facilitate inbound remote soft phone and IP Phone access, Session border controller (SBC) is a key component of this system, be deployed at the edge of the call center network. When an SBC is deployed, all VoIP-related traffic (both signaling and media) can be routed from the softphones or IP phones over the public Internet to the SBC, which ensures all incoming / outgoing VoIP traffic is carefully controlled by the call center.
Key functions performed by SBC include
Manage SIP endpoints: SBC acts as a proxy server of UC/IPPBXs, all SIP related signaling message has to be accepted and forwarded by SBC. For example, while a softphone tries to register to remote IPPBX, illegal IP/domain name or SIP account may include in SIP header, so SIP register request won’t be forwarded to IPPBX and add illegal IP/domain to blacklist.
NAT traversal, to perform mapping between the private IP addressing space and the public Internet.
Quality of Service, including prioritizing of traffic flows based on ToS/DSCP settings and bandwidth management. SBC QoS is ability to prioritize, limit and optimize sessions in real time.
Also, SBC offers various features to ensure security like DoS/DDoS protection, topology hiding, SIP TLS / SRTP encryption etc., protects the call centers from attacks. Furthermore, SBC offers SIP interoperability, transcoding and media manipulation capabilities to increase the connectivity of the call center system.
For call center not wanting to deploy SBCs, the alternative is to rely on VPN connections between the home and remote call center. This approach reduces the capacity of the VPN server, but may be adequate in some scenarios; while the VPN server performs security and NAT traversal functions, it does not allow for prioritization of VoIP traffic and is typically costlier to manage.
