JUNOS Enterprise Switching

Chapter 10. IP Telephony

This chapter covers IP telephony, which involves using IP to replace the traditional private branch exchange (PBX) architecture, as well as extending IP all the way to the handset. This chapter does not cover Voice over IP (VoIP). This distinction may initially seem contradictory, so let’s define these terms. Voice over IP is the process for digitizing your voice over a WAN connection in order to save costs. IP telephony is actually changing the phone system in order to leverage IP protocols to enhance productivity, usually in the form of IP phones and call managers. So, VoIP is actually a subset of IP telephony, and a full IP telephony system will use VoIP concepts and protocols.

In order to deploy an IP telephony system, you need to configure your routers, switches, phones, and call managers. This chapter focuses on the necessary switch configuration and discusses the process for making a phone call over the LAN, as opposed to a LAN-to-WAN phone call. The standards protocols for EX switches, as well as JUNOS software features, will also be examined.

The topics covered in this chapter include:

• Deployment scenarios

• Power over Ethernet (PoE)

• Link Layer Discovery Protocol (LLDP)

• Link Layer Discovery Protocol-Media Endpoint Discovery (LLDP-MED)

• Voice virtual LANs (VLANs)

• Case studies

Deployment Scenarios

An IP phone can be deployed in several ways. Figure 10-1 shows the most common scenario, in which the end station and phone attach to the same switch port. The ...