User manual POLYCOM SOUNDSTATION EX

[. . . ] It also allows locking down access to configuration and signaling servers to only allow access from phones. Using VLANs also allows placing IP phones on the public Internet while the connected PCs remain on a corporate intranet; this can facilitate using IP Centrex-type services from third parties without the complications of NAT between the phones and the Internet. [. . . ] Since phones have a very limited set of ports required for operation, the additional risk of having them exposed to the Internet can be more easily mitigated. QoS Benefits of using VLANs Typically, QoS is used to reduce the packet loss, latency, and jitter (variation in latency) that realtime traffic, such as VoIP, experiences in the network. Packets are marked at the source to indicate that they are real-time traffic, and network devices such as routers and switches can be configured to use that marking (or other factors) to determine which packets need special treatment. Many network administrators are concerned that devices other than phones will try to abuse QoS policies to achieve better performance. Segregating IP phones into a different VLAN allows the administrator to configure their devices to ignore or un-mark packets coming from non-phone VLANs to defeat these attempts. Some administrators find it easier to base the treatment of packets on the source or destination IP address rather than use packet markings; having phones in particular VLANs makes identifying the IP addresses of phones much easier. Background on 802. 1q/p Tagging The IEEE has defined an optional tag for 802. x networks which can convey additional Layer 2 information. It defaults to null, which means that the phone will be on the native VLAN specified in the Ethernet switch. Because this setting must be known before the phone can obtain an IP address or retrieve its configuration files from its boot server, there is no way to specify the VLAN ID in either those configuration files or via the web configuration interface. Automatic Configuration of VLAN ID In the Network Settings menu, there is another field called "CDP"; this controls whether the phone supports the Cisco Discovery Protocol. Among many other things, CDP allows the Ethernet switch to inform an IP phone what VLAN ID it should use without requiring manual configuration of each phone. 3 If CDP is enabled and a VLAN ID is also manually configured, any value received via CDP will override the manual configuration. If no VLAN ID is received via CDP, the phone will fall back to the configured value, if present, or to the native VLAN. QoS Configuration By default, the phone sends all audio packets with 802. 1p tag and IP Precedence values of 5, which is the highest priority level available for user traffic. This can be adjusted via the qos. ethernet. rtp. user_priority and qos. ip. rtp. precedence values in the configuration files. [. . . ] If no VLAN ID is received via CDP, the phone will fall back to the configured value, if present, or to the native VLAN. QoS Configuration By default, the phone sends all audio packets with 802. 1p tag and IP Precedence values of 5, which is the highest priority level available for user traffic. This can be adjusted via the qos. ethernet. rtp. user_priority and qos. ip. rtp. precedence values in the configuration files. [. . . ]