Enterprise QoS Solution Reference Network Design Guide

QoS Design Overview
2-12
Enterprise QoS Solution Reference Network Design Guide
Chapter 2 Campus QoS Design
Cisco 7905G—The 7905G is a basic IP phone that addresses the voice communication needs of a
cubicle worker who conducts low to medium telephone traffic. The Cisco 7905G has only a single
10BASE-T Ethernet port on the back of the phone; therefore, there is no hardware support to connect
a PC to it.
Cisco 7910G and 7910G+SW—The 7910G and 7910G+SW IP phones address the
voice-communication needs associated with a reception area, lab, manufacturing floor, or employee
with a minimal amount of telephone traffic. The only difference between the Cisco 7910G and the
Cisco 7910G+SW is that the former has a single 10BASE-T Ethernet port (therefore, there is no
hardware support to connect a PC to it), and the latter has two 10/100BASE-T Ethernet ports, which
allow a PC to be connected to the IP phone.
Cisco 7912G—The 7912G is a basic IP phone that addresses the voice-communication needs of a
cubicle worker who conducts low to medium telephone traffic. The 7912G supports inline power
and an integrated 10/100 Ethernet switch for connecting a PC. The switch used in the 7912G has the
capability to mark CoS and DSCP of Voice and Call Signaling traffic that originates from the IP
phone, but the Cisco 7912G does not have the capability to re-mark CoS values of PC-generated
traffic.
Cisco 7940G—The 7940G IP phone is suited best for an employee in a basic office cubicle
environment—a transaction-type worker, for example—who conducts a medium amount of business
by telephone. The 7940G supports inline power and has an integrated 10/100 Ethernet switch for
connecting a PC.
Cisco 7960G—The 7960G is designed to meet the communication needs of a profes¬sional worker
in an enclosed office environment—an employee who experiences a high amount of phone traffic in
the course of a business day. The 7960G supports inline power and has an integrated 10/100 Ethernet
switch for connecting a PC.
Cisco 7970G—The 7970G not only addresses the needs of the executive or major decision maker,
but also brings network data and applications to users without PCs. This IP phone includes a backlit,
high-resolution color touch-screen display. Cur¬rently, Cisco 7970G is the only Cisco IP phone that
supports both Cisco prestandard Power over Ethernet (PoE) and the IEEE 802.3af PoE. The 7970G
has an integrated 10/100 Ethernet switch for connecting a PC.
All of the IP Phones listed above have the ability to mark 802.1Q/p CoS values for both VoIP and call
signaling (default values are 5 and 3, respectively). Furthermore, they also have the ability to mark DSCP
values for both VoIP and call signaling (current defaults are EF and AF31, respectively; future software
releases will change these values to EF and CS3, respectively).
IP Phone models 7902G, 7905G and 7910G lack the hardware to connecting a PC behind the Cisco IP
Phone. All other IP Phone models listed above (except the 7912G) have the hardware support to connect
a PC behind the IP Phone and also support 802.1Q/p CoS remarking of tagged packets that may originate
from such PCs.
The 10/100 Ethernet switch built into the 7912G does not have the support to re-mark CoS values that
might have been set by a PC, as illustrated in Figure 2-7. This re-marking limitation represents a
potential security hole for enterprises deploying these IP phones. However, this hole can be plugged, for
the most part, with access-edge policers, as will be detailed in this chapter. It is important to note that if
7912G IP phones are deployed to users that move locations, all user switch ports within the enterprise
should have access-edge policers set on them to ensure mobility and security if a 7912G user moves the
phones to another port.
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