Network Types - 3

Content Networks

Content networks (CNs) were developed to ease users’ access to Internet resources. CNs are aware of layers 4–7 of the OSI Reference Model and use this information to make intelligent decisions about how to obtain the information for the user or users. CNs come in the following categories: content distribution, content routing, content switching, content management, content delivery, and intelligent network
services, which include QoS, security, multicasting, and virtual private networks (VPNs).

Companies deploy basically two types of CNs:



■ Caching downloaded Internet information
■ Distributing Internet traffic loads across multiple servers

For the first item, CNs are used to reduce the amount of bandwidth that you need for your users’ Internet connections. When users download content, it is cached on a local server. And then when a user make another request, that request is first checked with the local server to determine if the content exists there. If it does, the local server sends the information to the user, thus providing higher data rates, since the client is acquiring its information from the LAN instead of having to download it again from the Internet. If not, the local server will obtain the information from the Internet resource. Because many items, especially GIFs and JPEGs, are included on every page from a web site, this information doesn’t have to be repeatedly downloaded. The main problem with this solution, however, is that all traffic to and from the network must go through a CN device, commonly called a proxy server, which can reduce your throughput.

CNs are also used to reduce the overhead for external users that want to access internal resources in your network. In the old days of networking, if your web server was overwhelmed with requests, your only solution was to upgrade its processor, memory, disk drive, and interface card to larger sizes or faster speeds. And if you
have ever upgraded a server, you know that this is not always an easy process. With the introduction of CNs, you can distribute the traffic load from external users across multiple internal servers, thus reducing network congestion to the servers and reducing the resources required to handle the external users’ requests.

Because of the advantages that CNs provide, they are commonly used in LAN environments. Customers use them to access external resources more efficiently and to provide better throughput and redundancy for local resources. ISPs also commonly use CNs in their LANs to help reduce some congestion by providing caching services for commonly accessed web pages.

Intranets, Extranets, and Internets

Now that you have a basic understanding of various types of networks, let’s discuss some other terms that are used to describe locality: intranet, extranet, and internet. An intranet is basically a network that is local to a company. In other words, users from within this company can find all of their resources without having to go outside of the company. An intranet can include LANs, private WANs and MANs, and SANs.

An extranet is an extended intranet, where certain internal services are made available to known external users or external business partners at remote locations. The connections between these external users and the internal resource are typically secured via a firewall and a VPN, a feature that is briefly discussed in the next section.

An internet is used when unknown external users need to access internal resources in your network.
In other words, your company might have a web site that sells various products, and you want any external user to be able to access this service.

There is a difference between the terms internet and Internet. The lowercase internet refers to any type of network connection where external users access publicly available resources. The Internet is the main public network that most companies and people use when accessing external resources.

Typically, a firewall is used to secure your internal resources from external users.

Virtual Private Networks

A virtual private network (VPN) is a special type of secured network. A VPN is used to provide a secure connection across a public network, such as an internet. Extranets typically use a VPN to provide a secure connection between a company and its known external users or offices.

A VPN typically provides authentication, confidentiality, and integrity to create a secure connection between two sites or devices. Authentication is provided to validate the identities of the two peers. Confidentiality provides encryption of the data to keep it private from prying eyes. And integrity is used to ensure that the data sent between the two devices or sites has not been tampered with.