SecurityArena

Networking Services

NOS - Networking operations system It is designed to control network resource access and provide the necessary services to enable a device to interact with the surrounding network.
DNS - Domain Name service It is a service for resolving hostnames to ip addresses. The DNS System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains. This mechanism has made the DNS distributed, fault tolerant, and helped avoid the need for a single central register to be continually consulted and updated.
Directory Service A network service that identifies all resources on a network and makes them accessible to users and applications. Resources include e-mail addresses, computers, and peripheral devices such as printers. Ideally, the directory service should make the physical network topology and protocols transparent so that a user on a network can access any resource without knowing where or how it is physically connected.
There are a number of directory services that are used widely. Two of the most important ones are LDAP, which is used primarily for e-mail addresses, and Netware Directory Service (NDS), which is used on Novell Netware networks. Virtually all directory services are based on the X.500 ITU standard, although the standard is so large and complex that no vendor complies with it fully.

Extranets It refers to an intranet that is partially accessible to authorized outsiders. Whereas an intranet resides behind a firewall and is accessible only to people who are members of the same company or organization, an extranet provides various levels of accessibility to outsiders. You can access an extranet only if you have a valid username and password, and your identity determines which parts of the extranet you can view.
Extranets are becoming a very popular means for business partners to exchange information.

NAT Network Address Translation NAT enables a LAN to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT device located at the boundry of internet and LAN makes all necessary IP address translations. It serves three main purposes:

• Provides a type of firewall by hiding internal IP addresses.
• Enables a company to use multiple private internal IP addresses. While using a single or small set of public ip addresses to communicate with rest of world.
• Allows sharing of single internet connection by multiple intranet users.