Network Services

Peer-to-Peer Networks Workstations share files or printers among themselves. Best suited to smaller networks (<= 10 users)‏ Advantages include low cost, ease of installation and users directly manage resource sharing. Main disadvantages Lack of central control possibilities of security weaknesses due to mismanagement of sharable resources.

Client-Server Architecture Computer servers provide services File storage, databases, printing services, login services, web services Client computers Execute programs in its own memory Access files either locally or can request files from a server

Client / server architecture Major benefit is centralisation. Server provides a central control point for network provision, security and management. Disadvantages include higher cost of dedicated servers large amount of administration effort.

Directory Services Used to manage users & devices on larger (client server) networks Consists of Domain control Account management Users Groups Authentication management

Domains 2 main types Internet domains Organisation domains

Internet domain names IP addresses are 32 bit binary e.g. 62.73.175.70 is “human friendly” version of 00111110010010011010111101110110 Humans prefer words =>Domain names e.g. llandrillo.ac.uk Early ARPAnet used a central list called hosts.txt to map names to numbers Changes emailed out!

Domain names Now distributed database called Domain Name System (DNS) used “Root” is administered by Internet Assigned Numbers Authority (IANA)‏ “Root” consists of several networks but logically is a single point Top Level Domains (TLDs) are next level down from “Root” TLDs may be country based (e.g. uk, jp) or generic (e.g. com, org)‏

Domain names Each TLD has a sponsoring organisation responsible for allocating domain names within their TLD running master name servers for their TLD UK’s is Nominet UK (www.nic.uk)‏ Most domain name registration delegated to “registration agents” Cheaper to register small numbers of domain names through an agent Domain details through whois query

Whois query for cadburys.co.uk

Domain name resolution If a host doesn’t know the address for a domain name it will send a query to a defined DNS server DNS server normally run by the ISP If DNS server doesn’t know the address it will send a query to a higher level DNS server. Process is repeated until the address is found.

Organisation domains Often refers to Windows based network Logical group of computers which share a central directory database Each user has a single unique username for use across the domain One major difference between Home & Pro versions of Windows XP was ability to join a domain.

Windows domains Servers e.g. Clients e.g. Windows Server 2003 Windows XP Pro Windows Vista

Account Management User account contain info like... User name Password Password expiry date Personal details e.g. real name Email address Groups you are member of File / directory access rights Server /printer access rights Web access rights / restrictions

User groups User rights / restrictions are rarely assigned to individuals Too time consuming Complex Possibility of error Rights / restrictions assigned to groups Users made members of groups Users inherit group rights / restrictions

Authentication Occurs in many different ways User authentication normally by username & password Account may be locked if wrong password attempted too many times

Other types of authentication Internet ecommerce & secure webpages Secure Wide Area Network connections Routers, servers etc Wireless systems WEP, WPA etc.