P1: IML/FFX P2: IML/FFX QC: IML/FFX T1: IML
Thompson2 WL040/Bidgolio-Vol I WL040-Sample.cls June 19, 2003 17:7 Char Count= 0
168 PUBLICNETWORKScause data to be delayed or even lost. A VPN uses a public
network for site-to-site communication and added tech-
nology to solve the problems of security and congestion
(Panko, 2001).
A public network provider has a value-added network
if it owns the packet-switching nodes and leases trans-
mission capacity from an interexchange carrier such as
AT&T (Stallings, 2001). It is called a value-added network
because the leased lines add value to the packet switching
nodes. A network provider that provides a value-added
network is sometimes called a value-added carrier. In
many cases a public network provider will partner with
companies that provide services that require network con-
nectivity such as Web hosting and give discounts to them
for using their network. A business which bundles a ser-
vice with a particular public network provider is called a
value-added reseller.
Public network providers often offer services such
as Web hosting to subscribers in addition to connectiv-
ity between sites. These additional services are called
value-added services. These services include asset man-
agement, configuration control, fault management, moni-
toring, Web-based reporting, Web hosting, e-mail services,
and content delivery networks.
Asset management is keeping inventory of devices that
are connected to the network. As devices are added or
taken off the network the asset management system will
keep an up-to-date log of the assets. Configuration control
is about maintaining and keeping records of the configu-
ration of networked devices. The network provider typi-
cally maintains the configuration of the packet switching
node that connects each of the subscriber locations to the
network. A provider will also monitor devices to detect
faults and either fix them or notify the appropriate on-site
personnel. This is called fault management. A provider
can invest in large network operation centers for moni-
toring their subscribers’ network devices. This includes
maintaining a firewall to prevent unwanted users into
the network and intrusion detection systems for detect-
ing activity that is consistent with common hacker tech-
niques. With Web-based reporting the provider gives the
subscriber reports about the status of their network and
a history of its downtime and performance.
One of the most popular value-added services is Web
hosting. The provider maintains one or more servers and
allocates space on them for the subscriber’s Web site. The
provider maintains the server and performs backups. Sub-
scribers are given access to their portions of the server to
post their Web sites and control their content. An advan-
tage to using this value-added service is that it is likely
that the subscriber has other sites that are connected to
the same public network. If the server is connected to the
same public network, it provides faster response times to
the end users.
Medium to large users who have high volumes of
content serving a distributed set of users may consider
a value-added service called a content delivery network
(CDN). A CDN intelligently distributes the content to mul-
tiple locations and closer to the end user. By moving the
customized content closer to the end user the end user
receives faster response times (Allen, 2001). Queries to
the main server or group of servers are routed to thelocation that can best respond to the query. Content is
cached at each of the locations and future requests are
serviced more quickly because the information traverses
fewer links in the network. There are three main advan-
tages to a CDN. First, end users receive faster response
times. Second, it relieves congestion on the original server
that maintains the master copy of the content. Finally,
it reduces the amount of data transmission capacity re-
quired on the network since the content is distributed
to multiple locations and does not have to come from
the original server. Some of the popular CDN providers
are Akamai (http://www.akamai.com) and Mirror Image
(http://www.mirror-image.com).STRUCTURE OF THE PUBLIC
SWITCHED TELEPHONE
NETWORK SYSTEM
The public switched telephone network system is often
used to provide the technology that a business uses to
access a public network or is the technology of the public
or private lines. The structure of the PSTN in the U.S.
has evolved from one that was almost entirely controlled
by a single company to one that allows competition in a
free market. Before January 1, 1984, AT&T (also known
as the Bell System) controlled 80% of the PSTN in the
U.S. (Bellamy, 2000). A Justice Department antitrust suit
filed in 1974 and a private antitrust case by MCI resulted
in a breakup of AT&T (Noam, 2001). The suit argued that
AT&T used its control of the local operation as an unfair
advantage against competing long distance carriers.
On January 1, 1984, AT&T was divided into smaller
companies. The breakup involved the divestiture of seven
Bell operating companies (BOCs) from AT&T. The seven
regional BOCs were known as “Baby Bells” or regional
BOCs (RBOCs) and initially carried only regional tele-
phone and mobile service. The network was partitioned
into two levels (Bellamy, 2000), and the remaining part of
AT&T retained the transport of long distance telephone
service.
The U.S. was divided into local access and transport
areas (LATAs), which are controlled by local exchange car-
riers (LECs). LECs can transport telephone calls within a
LATA, also called intra-LATA traffic, but are not permitted
to transport traffic between different LATAs, also called
inter-LATA traffic, even though the same BOC may con-
trol both LATAs. The inter-LATA traffic is transported by
interexchange carriers (IXCs), commonly known as long
distance carriers. Each IXC interfaces at a single point
in the LATA called a point of presence. At divestiture,
AT&T became an IXC and it opened the door to competi-
tion for other companies’ long distance service. The ma-
jor IXCs in the U.S. include AT&T, MCI–WorldCom, and
Sprint.
The divestiture decree was supervised by District Judge
Harold Greene and known as the modified final judgment
(Noam, 2001). LECs had to grant equal access to all IXCs.
The service offered by the LECs to the IXCs had to be
equal in type, quality, and price (Bellamy, 2000). Also,
users could specify their “primary” IXC to transport their
long distance and international calls (Noam, 2001). Or,