Chapter 9: Network Requirements and Preparation Time Services
ShoreTel 8 Planning and Installation Guide 117
9.9 Time Services
When IP phones are used, time services must be available to maintain the telephone’s date
and time display. This requires a server that supports the Simple Network Time Protocol
If you do not run an NTP server within your organization, you may use a public accessible
time servers used by the NIST Internet Time Service (ITS), shown in Table 9-14.1
In addition, you must configure your DHCP server to provide the correct GMT offset to the
IP phones at each site. See Section on page 211 for more information.
9.10 Virtual Private Network (VPN)
With the increasing desire to leverage the public Internet, and the concern about security,
IP VPNs (Internet Protocol Virtual Private Networks) are becoming the secure access of
choice. IP VPNs establish secure communications between employees, branches, or
partners by using strong IP-based encryption and authentication techniques for transport
security over the public Internet.
IP VPNs are typically viewed as falling into three major categories: remote access VPNs,
intranets (company site-to-site), and extranets (business-to-business). These services are
being adopted by companies of all sizes as a result of the powerful combination of high-
speed access links and public networks. An example is the use of high-speed, low-cost
broadband DSL connectivity to enable teleworkers or branch offices to link securely with
the company network via the Internet, as if they were accessing the LAN at the office
including all network applications. A sample VPN configuration is shown in Figure 9-1.
IP VPNs can be provided via hardware or software solutions located at the remote facility
(branch office or teleworker’s home) and the customer premises. These devices or solutions
use technologies such as tunneling, encryption, and authentication to guarantee secure
communications across a public infrastructure.
1. This list was obtained at
Name IP Address Location NIST, Gaithersburg, Maryland NIST, Gaithersburg, Maryland NIST, Boulder, Colorado NIST, Boulder, Colorado NIST, Boulder, Colorado University of Colorado, Boulder NCAR, Boulder, Colorado Microsoft, Redmond, Washington Symmetricom, San Jose, California Abovenet, Virginia Abovenet, New York City Abovenet, San Jose, California TrueTime, AOL facility, Sunnyvale, California TrueTime, AOL facility, Virginia
Table 9-14 NTP Time Servers
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