IP Phone Test-Testing Index and Method (Chapter 2)

2 Advanced Functions of IP Phone-BLF and Multi-Functional Key

BLF is shorted for Busy Lamp Field. This function is mainly designed for the front desk secretary, the front desk secretary can check the status of each extension through the LED status when the LEDs are configured properly. The explanation of LED status is as following:

LED Indicator


Green Solid

The extension is idle.

Red Blinking

The extension is ringing.

Red Solid

The extension is busy, generally in the call.

Table 4 BLF Indicator

Suppose the following situation: when the front desk secretary receives an incoming call and is required to transfer the call to some extension, he/she can confirm whether the extension is busy or not by checking the LED status; or after he/she transfers the call, he/she can confirm whether the extension is ringing and no one picks up the call, if it does, he can picks up the call again and tell the caller that the person he is looking for is not at the desk, he can call him some time later. These are all done via the BLF function.

For IP phones, keys used to realize the BLF function are usually called multi-functional key. The key is usually a button with LED, on one hand, it is a button, on the other hand, it is a LED indicator, which indicates the key status using red and green two colors. When the multi-functional key is used as BLF, each key itypely corresponds to an extension number. Well, we all know that the size of the telephone are generally not large, usuallt 20 multi-functional keys has been a lot, however, the extension quantity of most offices is larger than 20, what to do at this time?

Simply, the answer is to use expansion modules, general business IP phones can support expansion modules, for example, IP652 can support six expansion modules and a maximum of 260 multi-functional keys, (in the folloing picture3, IP652 is connected to1 extension module, and support 60 multi-functional keys), this is already sufficient for the general office applications.

Picture 3 IP652 with one extension module

Multi-functional key supports not only BLF, but also a series of value-added functions, such as shortcut keys, speed dial keys and so on. The clever configuration multi-functional keys, generally make IP phones more convenient and efficient.

3 Network functions, VPN and QoS

IP phone is a kind of network device, which is connected to the Internet through local area network. To make IP phone work stablely, QoS configuration is critical. Simply, user should be able to make SIP signaling packets and RTP packets to be a higher priority, so as to allow routers and other network equipment to handle voice call-related data in priority, thus ensure phone's connection and voice quality.

IP phone is required to configure 2 layer QoS(IEEE802.1p) and 3 layer QoS(TOS field of the IP packer). What's more, it is generally required to configure SIP signaling and RTP packets separately, like the following picture4.

Picture 4 QoS

User needs to trace the packets to confirm if whether the QoS function is performed correctly to take effect. You need packet trace tools, such as WireShark(open source tool, referring to www.wireshark.org), crawl IP phone's packets and analyze if the corresponding field is consistent with the configuration phase.

4 Dial Plan-Very important

Dial Plan, which is often used with the term Dial Rule, or Digit Map, means to control user's dialing behavior via some configurations, such as automatically dial(without  pressing "send" key or "#" key0, automatic abbreviated, automatic added bit, automatical replace,delay, play dial tone for outgoing calls and so on.

Each company has different  methods to realize secific Dial Plan, user can check if the phone's Dial Plan ability is strong enough by testing the functions which are described in the following chat.

Configuration of Dial  Plan

User's Input

Destination Address
(Get from the SIP packets)

Desired dial tone in local place





Play outgoing call dial tone after user presses 1 and stop after user presses 2.





Play outgoing call dial tone after user presses 1 and stop after user presses 3.





Play outgoing call dial tone after user presses 7 and keep on playing after user presses 5 and stop afer user presses 6.





Play outgoing call dial tone after user presses 6 and stop after user presses 7.





Play outgoing call dial tone after user presses 8 and keep on playing after user presses 6 and 2, but stop after user presses 1.





play outgoing call dial tone after user presses 1 and stop after user presses 4.





play outgoing call dial tone after user presses 8 and stop after user presses 9.

Table 5 Dial Plan Test
Notice: Different company has different ways to test Dial Plan, not all are the same as Table 5.

5 Phonebook and Blacklist

Phonebook and blacklist is another test item for IP phone. "Blacklist" , as the name implies, is used to block some unwelcome callers' numbers(usually some mass advertising phone or malicious disturb telephone). IP phone wil automatically rejects the calls from these numbers.

Like the blacklist or MSN or QQ, the recorded numbers in the phonebook and blacklist are exclusive, a number in the phonebook can not exist in the blacklist at the same time. These two configurations, are convenient  to removed, like in the following picture 5, configurations are easy enough.

Picture 5 Phonebook and Blacklist

6 Call History

Usually, user can searc
h the call history on phone's LCD, and sometimes check on phone's WEB GUI.
Assessment of this feature, 
it should be not only easy to use the interface, but also contains enough items of reccord. Generally, incoming and outgoing call list should be at least 60 messages and missed calls should be 40 messages.

7 Remote Maint
enance and Support characteristics

This includes system l
og(the syslog), configuration file upload and download,Provision, SNMP, TR069 and so on. More detials will be described in "4.Bulk deployment and management".

8 Security and Certificate 

If an IP phone claims to support TLS/SRTP security features, or to support
 the TR069 or HTTPS provision, generally it also needs to support the management of the certificate, including the CA's certicificate and private key certicificate. Certicificate management interface is generally shown as the following Picture 6.

Picture 6 Certicificate Management