Network Routing and its Protocols

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Virtual Private Networks 

Introduction 

 Virtual Private Network (VPN) is a private communications network widely used by several companies or organizations or within a particular company to communicate confidentially over a non-private network. VPNs are implemented with a wide range of technologies and as such can be self-implemented or managed by a service provider thus allowing the end customers to realize the cost advantages of a shared network, while enjoying its benefits of security, quality of service (QoS), reliability and manageability. A VPN uses virtual connections routed through the internet from the company’s private network to the remote site or employee. It is also worth knowing that VPN traffic can be carried over a public networking infrastructure like the internet but has to be on top of standard protocols or over a service provider’s private network with a defined service level agreement in place. Virtual Private Networks using the internet have the potential to solve many of today’s business networking problems e.g. businesses today are finding that past solutions to wide are networking between the main corporate network and branch offices, such as dedicated leased lines or frame relay circuits, do no provide the flexibility required for quickly creating new partner links or supporting project teams in the field. VPNs therefore allow many network managers to connect remote branch offices and project teams to the main corporate network economically and provide remote access to employees while also reducing the internal requirements for equipment and support. VPNs also offer direct cost savings over other communications methods such as leased lines and long distance calls and also offer other advantages including indirect cost savings as a result of reduced training requirements and equipment, increased flexibility and scalability.

    A well designed VPN should be able to have the following features in order to achieve its aim: Security, Scalability, Policy management, network management and reliability. In addition also, VPNs are mostly not limited to corporate sites and branch offices but it rather has an advantage also of providing secure connectivity for mobile workers. There are various types of VPN that will be discussed here and they include: Internet Protocol (IP VPN), IPSec VPN, and Secure socket layer (SSL VPN), MPLS VPN etc

 Internet Protocol VPNs (IP VPNs) 

 IP-based VPNs enable enterprises to take advantage to the flexibility of both the internet and service provider IP networks to create-to-any WAN communications. IP VPNs require publicly addressed IP routing across shared network infrastructures. The major goal of IP VPN is to adequately provide IP connectivity over a shared IP infrastructure while still maintaining the security and service features of a dedicated private network. 

There are a number of essential attributes of VPNs that can extend the capabilities of a private network and they include: 

1. Quality of Service (QoS): They typically allow the prioritization of voice, data and video applications traveling across the networks. 

 2. Security: Privacy for network traffic moving across public networks both in the core and network edges are provided by using such security technology as IP security (IPSec). 

 3. Scalability: provisioning times are decreased and access speed enhanced when there is access to a variety of broadband network connection types such as point-to-point protocol (PPP), ATM, Frame Relay, DSL etc. 

 4. Ease of Management: Service providers today, have more network management points and IP visibility through which to monitor and report on data traversing their networks. 

5. High availability: Network availability is increased because the carrier network contains equipment and core link redundancy, broadband backbones, access links and a twenty four hours everyday management.

There are three basic classes of IP VPNs and they include Access VPNs, Intranet VPNs and Extranet VPNs.

Access Virtual Private networks (VPNs) 

 An access VPN can be defined as a scheme that allows secure remote access to an internal corporate server. They allow remote corporate users to have on-demand connectivity into their corporate intranets through ad hoc tunnels. Access VPNs actually allows companies to take work to the worker, wherever they are. There are some certain requirements that need to be fulfilled by such a scheme and they include:

 a) User authentication and authorization: The scheme should be able to identify the user and to verify that this user is authorized to access the contacted internal server. 

b) Data Privacy: The scheme should be able to guarantee that the exchanged data is encrypted and authentication at least when it is sent over the public internet. 

 c.) Private addressing: The access VPN scheme should be able to assign the remote user a private IP address taken from the same range since many corporations use private IP addresses in their intranets. The main reason for the wide variety of access VPN solutions and their complexity is that up to five entities can be actively involved as tunnel endpoints; the end host (i.e. the user’s PC), the broadband modem, the operator access gateway, the ISP access gateway and the corporate access gateway. 

MPLS VPNs for Remote Access 

 MPLS VPN is a technology that allows service providers to have complete control over parameters that are critical to offering its customers service guarantees with regard to bandwidth throughputs, latencies and availability. The technology enables secure VPNs to be built and allows scalability that will make it possible for service providers to offer assured growth to its customers without having to make significant investments. Service providers would now be geared to provide bandwidth on demand, video conferencing, Voice over IP (VoIP), multimedia services and a host of other value added services that could revolutionize the way a corporate business works.

MPLS based VPNs reduces customer networking complexity, costs and totally do away with the requirement of in-house technical workforce. Rather than setting up and managing individual point-to-point circuits between each office using a pair of leased lines, MPLS VPN customers need to provide only one connection from their office router to a service provider edge router. MPLS VPNs allows service providers to deploy scalable VPNs and build the foundation to deliver value added services