Specifications

Network Requirements and Preparation
Planning and Installation Guide 9 – 9
Local Area Network
To manage bandwidth in the local area network (intra-site) and meet the requirements
for toll-quality voice, use Ethernet switching. Ethernet switching is cost effective and
simple to provision. Your LAN configuration requirements will vary depending on your
infrastructure and whether your network includes IP phones.
IP phones sample the user’s voice and convert the voice signal to IP packets using the
Real Time Protocol (RTP). These packets must be tagged for higher prioritization in the
network. ShoreTel IP phones are Ethernet switches, so the voice traffic travels ahead of
any data traffic coming from daisy-chained personal computers (for example, large files
transfers and email).
On the local area network, there are three methods to prioritize voice packets:
• IP Precedence = 5 (configurable, recommendation is 5)
• DiffServ/ToS = EF (configurable, recommendation is EF)
• UDP = 5004
The Ethernet switch infrastructure needs to be configured to prioritize traffic using one
of the three methods. This allows the voice traffic arriving at the switch to travel ahead
of the data traffic.
NOTE ShoreTel customers typically choose to prioritize UDP 5004 since this
configuration is easy to set up on smart Ethernet switches.
When IP phones are used, the desktop connection to the user’s computer and phone
must also be part of your switched Ethernet network. The user’s phone is connected to
the port of the Ethernet switch, and the user’s computer or other data device is
connected to the integrated two-port Ethernet switch inside the IP phone. In this
configuration, the switch port connected to the phone must be configured to prioritize
the voice packets from the phone above the data packets. With ShoreTel 6.1, the voice
packets are always sent from the phone on UDP port 5004, so you should prioritize this
UDP port within the switch and in your network’s routers.
NOTE PCs connected through IP phones lose their connection to the network if the IP
phone loses power.
Voice quality can be guaranteed by putting each of the ShoreGear voice switches and
the ShoreWare server on its own Ethernet switch port. A network with this topology
meets the bandwidth, jitter, and latency requirements for toll-quality voice without the
additional need for special prioritization of voice packets.
NOTE You can use a 100M Ethernet hub to connect up to four ShoreGear-120/24 or
ShoreGear-T1/E1 voice switches, or up to eight ShoreGear-60/12 voice switches,
to a single 100M Ethernet switch port. It is important that no other devices use
the hub, since it will need to be dedicated to voice communications.
Virtual LANs
An alternative method to prioritize voice over data is to create a separate virtual LAN
strictly for your voice traffic. The ShoreTel IP phone as well as the ShoreGear voice
switches can be configured on a specific VLAN.
Set the voice VLAN for prioritization higher in the network. The Ethernet switch
infrastructure needs to be configured to prioritize the voice VLAN. This allows the
voice traffic arriving at the switch to travel ahead of the data traffic.