network protocols handbook.pdf

101Protocols GuideNetwork Security Technologies and ProtocolsDescriptionNetwork security covers such issues as network communication privacy,information confidentiality and integrity over network, controlled access torestricted network domains and sensitive information, and using the publicnetwork such as Internet for private communications. To address theseissues, various network and information security technologies have beendeveloped by various organizations and technology vendors. Here is a summaryof the technologies:AAA: Authorization, Authentication and Accounting is a technology for intelligentlycontrolling access to network resources, enforcing policies, auditingusage, and providing the information necessary to bill for services. Authenticationprovides a way of identifying a user, typically by having the user entera valid user name and valid password before access is granted. The authorizationprocess determines whether the user has the authority to accesscertain information or some network sub-domains. Accounting measuresthe resources a user consumes while using the network, which includesthe amount of system time or the amount of data a user has sent and/orreceived during a session, which could be used for authorization control,billing, trend analysis, resource utilization, and capacity planning activities.A dedicated AAA server or a program that performs these functions oftenprovides authentication, authorization, and accounting services.VPN: Virtual Private Network is a technology allowing private communicationsby business and individuals, such as remote access to a corporatenetwork or using a public telecommunication infrastructure, such as the Internet.A virtual private network can also be a specially configured networkover the public network infrastructure that is only used by one organization.Various network-tunneling technologies such as L2TP have been developedto reach this goal. Using encryption technologies such as IPsec could furtherenhance information privacy over network and virtual private networks.Firewall: Firewall is a software program or hardware device that filters theinformation coming through the Internet connection into a private networkor computer system. Firewalls use one or more of three methods to controltraffic flowing in and out the network:• Packet filtering - Packets are analyzed against a set of filters. Packetsthat make it through the filters are sent to the requesting systemand all others are discarded.• Proxy service - Information from the Internet is retrieved by the firewalland then sent to the requesting system and vice versa.• Stateful inspection - compares certain key parts of packets passingthrough with a database of trusted information. Outgoing informationfrom inside the firewall is monitored for specific defining characteristics,and incoming information is then compared with these characteristics.If the comparison yields a reasonable match, the informationis allowed through. Otherwise it is discarded.