Cisco Cisco Agent Desktop 8.5 Guia Da Instalação
31-Mar-06
77
Testing Ethernet Cards for
Silent Monitoring
Silent Monitoring
Overview
On a site where IP telephony is deployed, the Cisco CallManager and the IP phones
are normally configured to use a Virtual Local Area Network (VLAN) so that voice is
logically separated from data. Although both traffic types are carried on the same
physical channel, they are transmitted on different VLAN, one for voice and another
for data. This configuration allows voice to be transmitted with higher priority than
data.
are normally configured to use a Virtual Local Area Network (VLAN) so that voice is
logically separated from data. Although both traffic types are carried on the same
physical channel, they are transmitted on different VLAN, one for voice and another
for data. This configuration allows voice to be transmitted with higher priority than
data.
In a contact center that uses silent monitoring, the agent desktop system is required
to be connected to the PC port on the back of the IP phone so that voice packets
reaching the phone can be collected by the silent monitor subsystem and then be
forwarded to the supervisor workstation. In this case, the agent desktop system will
then be using one single physical channel to interact with two different VLANs.
to be connected to the PC port on the back of the IP phone so that voice packets
reaching the phone can be collected by the silent monitor subsystem and then be
forwarded to the supervisor workstation. In this case, the agent desktop system will
then be using one single physical channel to interact with two different VLANs.
The agent desktop system accesses the physical channel via an Ethernet Network
Interface Controller (NIC). The NIC watches the channel and collects Ethernet
frames addressed to the agent’s computer. The NIC then runs a pre-processing step
to extract IP packets from the Ethernet frames and delivers them to the TCP/IP stack
on the operating system.
Interface Controller (NIC). The NIC watches the channel and collects Ethernet
frames addressed to the agent’s computer. The NIC then runs a pre-processing step
to extract IP packets from the Ethernet frames and delivers them to the TCP/IP stack
on the operating system.
During internal testing, Cisco identified that some Ethernet NIC card drivers are not
capable of pre-processing Ethernet frames that have an IP packet encapsulated in a
VLAN frame. That is, the NIC card driver discards the Ethernet frame altogether if the
IP packet is encapsulated in an 802.1Q frame. Some vendors can provide a
configuration setting that allows their NIC card driver to forward VLAN traffic to the
TCP/IP stack.
capable of pre-processing Ethernet frames that have an IP packet encapsulated in a
VLAN frame. That is, the NIC card driver discards the Ethernet frame altogether if the
IP packet is encapsulated in an 802.1Q frame. Some vendors can provide a
configuration setting that allows their NIC card driver to forward VLAN traffic to the
TCP/IP stack.
If an agent desktop’s NIC card driver discards VLAN traffic, then the silent monitor
subsystem on that desktop will not be able to collect and forward voice packets to
the supervisor workstation and silent monitoring will not function properly.
subsystem on that desktop will not be able to collect and forward voice packets to
the supervisor workstation and silent monitoring will not function properly.
Cisco has developed a procedure to determine if a particular Ethernet NIC card
driver will work with CAD silent monitoring. The procedure is described in the
following section.
driver will work with CAD silent monitoring. The procedure is described in the
following section.