This document discusses servers and services in a network. It describes domain controllers, file and print servers, and server roles like Windows Internet Name Service (WINS) and Domain Name System (DNS). It also discusses Windows Server 2008 editions, reasons for using servers over desktops, best practices for running servers, and provides a case study of Nottingham Trent University's network infrastructure.

1. Lecture 3:
More on Servers &
Services
Network Design & Administration

2. “Domain” Controller
• A Domain Controller provides centralised control
of users and access control to resources (e.g.
shares, printers, etc)
• Microsoft Server systems can be promoted to be
Network Design & Administration
domain controllers – in Active Directory Domain
Services (AD DS) they hold a copy of the AD DS
database.
• They are so important, there should be
redundant ones!
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• We will cover AD DS in more detail in a future
lecture.

3. Server Roles: File & Print
Servers
• Some servers may simply provide file storage.
• Some may be used to ease latency in printing (covered in
a later session)
• Question:
Network Design & Administration
• Are there any other operating systems which could be
found within a corporate network?
• SAMBA allows Linux server to provide these services to
Windows or Linux clients.
• “Samba is an open source / free software suite that
provides file and print services to SMB/CIFS clients”[1]
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4. Server Role: Windows Internet
Name Service (WINS)
• Provides resolution of names to IP address.
• Works on NetBIOS names (flat namespace).
• Needed if Microsoft machines prior to Windows 2000 on network.
Since then, DNS preferred and best not to install WINS.
• However, some apps, e.g. SQL Server 2000, Exchange Server 2003
Network Design & Administration
still need WINS.
• Recommended to have redundant WINS servers – a primary and
multiple secondary servers.
• No difference between servers – clients just choose to query to
query in specific order.
• Clients use secondary's only when primary is:
• Unavailable on the network when the service request is made, or
• Unable to resolve a name for the client (in the case of a name 4
query)[2]

5. Domain Name System (DNS)
• Originally networks were very small – even ARPANET – so
used a (manually modified) list of machines and
addresses on each host and then a central list file at a
particular server.
Network Design & Administration
• The manual list still exists as etc/hosts on both Linux and
Windows (mine just contains: 127.0.0.1 localhost).
• Unrealistic for large dynamic nets (e.g. the internet).
• Needs servers to work out the IP addresses given a
human memorable symbolic name for a machine.
• If name servers are not available, small networks can
survive by broadcast queries. 5

6. Domain Name Service (DNS)
• Software to resolve names against addresses has been
around since 1983.
• Tree structure of domain names allows client to find out
address by sending request up the tree.
Network Design & Administration
• DNS servers try to resolve a request from a client (though
client apps may have their own cache of recently
resolved names). If they cannot deal with it directly, then
pass it on.
• Bind is a standard open source implementation of this
software.
• DNS and DHCP together link MAC, IP and names. 6

7. Dynamic DNS & DHCP
• In this, client hosts tell DHCP server their hostname & DHCP server
tells DNS server.
• In theory, means DNS information always correct for host whatever
subnet it is plugged into.
• But only need to know hostname if it is running services – so it
Network Design & Administration
should have permanent lease anyway!
• Also, security risk – could have host claiming same name as a critical
server.
• Dynamic DNS is an essential part of MS Active Directory, since AD DS
Domain Controllers register themselves to let other machines in AD
DS see them.
• Within the Internet, dynamic DNS updates have to encrypted to
avoid attempted security breaches but dynamic is necessary to allow 7
users to be assigned IP addresses from pool provided by ISP.

8. Windows Server 2008
Editions[3]
• Standard
• Enterprise
• Datacentre
• Web Server
Network Design & Administration
• HPC Server
• Itanium
• Foundation
• Editions are not the same as versions (which normally
denote releases).
• Editions relate to expected usage. 8

9. Windows Server Differences[4]
Network Design & Administration
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10. Windows Server Differences[4]
Network Design & Administration
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11. Why a Server? (Revisited &
extended)
Why not a desktop machine running Windows 7?
Hardware Reasons:
• Server hardware needs to be more reliable:
Network Design & Administration
• Potentially want redundant power supplies,
redundant disks (including disk controllers), hot
swap memory (not just hot-plug)
• Server hardware needs to be extensible:
• Need room for more disks, more cards, more
memory, more fans …
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12. Why a Server?
• Servers need more performance:
• Tend to have leading edge CPU’s, higher spec
network interfaces and associated upgrade
options.
Network Design & Administration
• Servers need to be supported:
• Usually business-critical, so need maintenance
contracts
• Servers need to last longer:
• Maintenance contracts, upgrades, spares have to
be available for longer 12

13. Why a Server?
• Software is the main reason.
• Although desktop operating system has support for most
features but normally curtailed in some way.
• E.g. Internet Information Services
Network Design & Administration
• On XP was limited to 10 concurrent connections (it would block
HTTP connections)
• With Windows 7 / Vista, IIS version 7.5 will queue requests for a
limited number of connections at the same time, but connections
can be from more machines.
• Microsoft Terminal Services limited to one connection at
a time (although 3rd party tools provide more
connections). 13

14. Running Servers
• Preferably have a clean, lockable environment to
keep them in (no dust or coffee in the works and
basic security).
• Use remote methods to control / monitor (see
Network Design & Administration
later sessions) but provide local screen /
keyboard in case.
• Preferably use rack-mount system even if only 1
server in rack) to allow for easy extensibility /
replacement.
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• Consider provision of spares pack for quick
repair.

15. Case Study: NTU infrastructure
Network Design & Administration
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16. Clifton Distribution
Network Design & Administration
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17. Summary of NTU Intranet
• 700 Switches and Routers
• 400 Servers
• 14,000 PC’s
Network Design & Administration
(approximately)
• This is a very big system! Such a system tends to
have ‘grown’ and then been occasionally re-
engineered rather than built from scratch.
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18. Next time & References
• Client machines and their relationships to servers.
[1] www.samba.org
[2] http://technet.microsoft.com/en-
Network Design & Administration
us/library/cc781189%28WS.10%29.aspx (Windows Server 2003
article)
[3] http://www.microsoft.com/en-us/server-cloud/windows-
server/2008-r2-editions.aspx
[4] http://download.microsoft.com/download/F/C/6/FC6006B5-
866E-42C1-88F8-9AC4B8BC610D/WS%20Brand%20Pages%20-
%20Editions%20Comparison%20Guide.pdf
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