Server

This section tells you how to set up the server side of things.  I figured that this should go first since without a server, your client is kind of useless.

Security − keeping people out
Security is very important for a VPN.  That's why you're building one in the first place, isn't it?  You need to keep a few things in mind while setting up your server.

What is a VPN?

What is a VPN?
VPN stands for Virtual Private Network.  A VPN uses the Internet as it's transport mechanism, while maintaining the security of the data on the VPN.

But really, what IS a VPN?
There are several answers to that question.  It really depends on your network layout.  The most common configuration is to have a single main internal network with remote nodes using VPN to gain full access to the central net.  The remote nodes are commonly remote offices or employees working from home.  You can also link two small (or  large) networks to form an even larger single network.

the ISDN transport

Work on developing ISDN began in the  1970s but  would  not  be sold  to the  bandwidth-hungry customer until the  early  to mid 1990s. Many said it was too  little too  late, and  the  consumer market for ISDN never took  off. After the  news  of the  first VoIP telephony call over  the Internet spread in 1995, a renewed interest in ISDN emerged for a short while. But by this  time our attention was turned to the  emerging DSL technology first deployed in 1998.

The eventual ISDN standard provided for two flavors of ISDN: Basic Rate Interface (BRI) and  Primary Rate Interface (PRI). The ISDN standard defines the  basic unit of bandwidth as a B channel, which provides 64 Kbps of band-  width. B stands for bearer channel, which is another name for the  channel that carries POTS calls over  the  PSTN.

The POTS transport

As you already know, POTS is a transport that runs through the  circuit- switched PSTN. All transport lines  in the  PSTN have  a circuit-identification number, which is either all numeric or alphanumeric. For example, a POTS telephone number has  an area  code, a prefix, and  a suffix that correspond to the  physical circuit and  the  lines that make up that circuit.

Understanding How the PSTN Supports VoIP

No other network in the  world can compare to the  reliability of the  U.S. switched network. (Granted, a handful of disasters have  disrupted PSTN services in specific regions, but  these are the  exceptions, not  the  rule.) Such reliability, however, comes at a high price: The cost of the  switched network, particularly recurring (per-minute) charges, is the  highest in the world. Regional  toll and  international calling  using  the  PSTN are the  most highly  reg- ulated switched network services. This means high regulatory fees in addi- tion to recurring usage charges. But VoIP greatly reduces and may eliminate these types of charges.

How VoIP and the Internet Fit the CSI Picture

To understand how the  Internet relates to the  five CSIs, it helps to first recog- nize what  the  Internet is. No doubt Bell would  be captivated by the enormity of what  we call the  Internet. By definition, it is a network of networks. But just  like VoIP can run on any of the  five CSIs in varying  degrees of quality, the  Internet can also  be accessed from any of the  five CSIs in varying degrees of quality and  security.

VoIP over Internet
Yes, the  Internet is a network of networks, and  the  Web is one of its largest applications. But the  Internet is also  a network that is accessible through all five CSIs.

Summing up the CSIs

A CSI is like a highway system that lays out  all the  many  roads that enable people to drive  to their destinations. Within our highway system, we could characterize some roads as being large or wide, some roads as small or narrow, and  some roads as being  between these two extremes. Roads may be further broken  down  by type  of surface, that is, asphalt, concrete, gravel, or dirt.

The wireless CSI

Wireless telecommunications have  been around for more  than eight decades. First we had  the  radio in the  1920s. During World War II, we had the  inception of walkie-talkies. These  led to the development of cell division multiple access (CDMA), one of the  most popular carrier services supporting cell phone net- working  today. In the  1960s, the  first wireless transports connected mobile telephones using  radio telemetry, which connected the  caller (using radio fre- quency channels) to the circuit-switched PSTN.
 

The hybrid fiber-coaxial CSI

When fiber-optic cable began to be deployed widely, the  cable companies started using  fiber to build  out  their infrastructure. But by that time,  much of the  coaxial cable infrastructure supporting localized connections had already been established. This is why a large share of today’s cable customers have  coaxial cable coming into their premises from the  nearby telephone pole.

The optical carrier CSI

The DS carrier service infrastructure gave us two important building blocks that were used to further extend the  capacity for supporting VoIP networks. First and  foremost, the  DS network established that analog signals could be regenerated in digital  format. Second, the  DS network established that digital  signals could be aggregated with other digitally regenerated signals in the  form of DS0 channels. Thus,  the  capability to channelize digital  bandwidth evolved. Dedicated channels have  proven that they  can support VoIP with
the  same if not  better quality of service that we have  come to expect with
POTS over  the  PSTN.

The DS CSI

In 1964, the  carriers began channelizing and  aggregating analog inbound tele- phone calls onto digital,  high-bandwidth transports. The digital service (DS) carrier service infrastructure was born. The type  of wiring used for DS trans- ports was copper, like the  PSTN transport lines  in the PSTN. The DS transport lines,  however, were of a thicker gauge  and  were capable of sustaining higher bandwidth capacities. The carrier often referred to DS type  transport lines  as “high-cap” T1 lines  to distinguish them from other types of copper transport lines  in the  PSTN. Today most T1 transport lines  are provided using  fiber- optic lines.

The PSTN CSI

The public switched telephone network (PSTN) is the  oldest CSI, actually beginning with the work of Alexander Graham  Bell in the late 1800s.

Over the years, carriers have been installing, expanding, improving, and inter- connecting various parts of the  PSTN. Compared to all other carrier service infrastructures, the  PSTN is the  largest.

The Five Golden Rings of CSI

It’s useful  to understand from which CSI a network transport service comes. The CSI to which a transport service belongs affects the  way in which that transport service is implemented. sider the  case of VoIP. An integral part of VoIP is the  concept of transmitting voice  packets over  the  transport. But each CSI, each transport, and  the  VoIP transport service provided therein support voice packets differently. This is because each CSI operates with different underlying protocols.

Choosing a Transport

CSIs are made up of network transports (lines or channels) and  the carrier’s equipment used to terminate these lines.  Each CSI has  multiple carrier trans- ports to offer any customer.

A transport is a physical or wireless channel (or aggregate of contiguous channels) that supports the  transmission of electrical, optical data, telemet- ric data, voice,  or video  signals.

Road Map to VoIP Transports and Services

Let’s face it — telecommunications can be daunting to those who have not given much thought as to how their  voice gets from their  phone’s handset to their  Aunt Matilda  in Dubuque. Be that  as it may, the technology between you and Aunt Matilda  is simply amazing.

This chapter introduces you to the  wonderful world of networks, transports, and transport services. Here you discover what a CSI is (besides a great family of television shows) and  why you should even care. Before you are finished with this  chapter, you’ll have  a good  grasp of things you didn’t  even  know you needed to grasp. (Spooky,  huh?)

Applying VoIP to your situation

The moral of this  story?  If your  company has  facilities distributed across more  than one local calling  area  within the  same LATA, look at your intralata toll charges. If all your  sites switched to VoIP, you’d eliminate most, if not  all, intralata charges you currently incur.

The VoIP solution

I designed a VoIP network that provided a dedicated access line between the  two main locations. These sites were seven miles apart but  in different coun- ties  and  therefore different LATAs. We put  in digital subscriber line (DSL) access at the  other nine locations.

Analyzing the client’s usage

When I came  on the  scene, I analyzed their monthly billings  for the  past three months. I found that their total average monthly billings  for intralata services came to just  under a whopping $11,000 per  month, or a projected annualized billing of $130,000. Intralata recurring charges were about 63 percent of their total monthly telecommunications bill.

VoIP Savings: A Case Study

One of my clients in the  Pittsburgh area  has  eleven locations distributed across several local calling  areas within two Pittsburgh LATAs. Five locations are in the  city itself. The other six are in the  South Hills, with two inside Allegheny County but  outside the  city, and  four located to the south across the  county line in Washington County.  The client spent enormous amounts of money on phone service because an interoffice call between locations often  crossed intralata boundaries.

Add-on recurring costs

Tallying  the  costs of traditional phone service is like adding up the  cost of sending your  kid through college. There just  doesn’t seem to be an end in sight  to the  charges. As if the  access line costs and  recurring carrier service charges weren’t enough, you must deal  with other monthly costs and  regula- tory fees. These payments, which go to various government entities rather than to your  LEC, are based on a percentage of each line’s monthly access cost. Examples include the  Federal line surcharge and the 911 fee.