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
(SNTP).
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 15.3.5.3 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 http://www.boulder.nist.gov/timefreq/service/time-servers.html
Name IP Address Location
time-a.nist.gov 129.6.15.28 NIST, Gaithersburg, Maryland
time-b.nist.gov 129.6.15.29 NIST, Gaithersburg, Maryland
time-a.timefreq.bldrdoc.gov 132.163.4.101 NIST, Boulder, Colorado
time-b.timefreq.bldrdoc.gov 132.163.4.102 NIST, Boulder, Colorado
time-c.timefreq.bldrdoc.gov 132.163.4.103 NIST, Boulder, Colorado
utcnist.colorado.edu 128.138.140.44 University of Colorado, Boulder
time.nist.gov 192.43.244.18 NCAR, Boulder, Colorado
time-nw.nist.gov 131.107.1.10 Microsoft, Redmond, Washington
nist1.symmetricom.com 69.25.96.13 Symmetricom, San Jose, California
nist1-dc.glassey.com 216.200.93.8 Abovenet, Virginia
nist1-ny.glassey.com 208.184.49.9 Abovenet, New York City
nist1-sj.glassey.com 207.126.98.204 Abovenet, San Jose, California
nist1.aol-ca.truetime.com 207.200.81.113 TrueTime, AOL facility, Sunnyvale, California
nist1.aol-va.truetime.com 64.236.96.53 TrueTime, AOL facility, Virginia
Table 9-14 NTP Time Servers
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