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Section Outcome (TCP/IP Services)
Describe four (4) services that are part of the
TCP/IP protocol suite that would probably be
implemented within a network centre to manage:
• naming within legacy systems
• automated issuing of IP Addresses
• name to IP Address translation
• private IP addressing
Overview
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Dynamic Host Configuration Protocol (DHCP)
Domain Name System (DNS)
Windows Internet Naming System (WINS)
Network Address Translation (NAT)
DHCP
Administering IP Address allocation
- Static configuration (becomes impossible as
network grows in size)
- Dynamic configuration (automated system of
IP address, subnet details and other network
information delivery)
DHCP
Note, not just for delivering the IP Addresses
Simplified but typical infrastructure
Hamilton Network
Centre
IT Div Network
Centre
Telkom
ISP
DHCP Server
Firewall
Free BSD
Diginet Link
To upstream
service provider
East lab etc
DNS Server
Jackall
Gecko
DHCP
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Static VS Dynamic IP Addressing
Pool of IP Addresses known as Scopes
DHCP Renewal Process
DHCP Server per Segment
DHCP Relay Agent
DHCP
DHCPDiscover
DHCPOffer
DHCPRequest
DHCP Client
DHCP Server
DHCPAcknowledgement
DHCP
• Automatic Private IP Addressing (APIPA)
- 10.0.0.0 through 10.255.255.255
169.254.0.0 through 169.254.255.255
172.16.0.0 through 172.31.255.255
192.168.0.0 through 192.168.255.255
- Network Address Translation (NAT)
• Multicast Scopes (224.0.0.0 –
239.255.255.255)
• Scopes and Superscopes
DHCP
Three DHCP Implementations:
• Dynamic allocation
- Leased basis from available pool
• Automatic allocation
- Permanent allocation for duration of
communication. Maintains historical list.
• Static allocation
- MAC/IP address allocation, one MAC address
will have the same IP address all the time
Network Address Translation (NAT)
Office
Telkom
Internal IP
Addresses
Computer running:
Network Address
Translation (NAT)
Diginet Link
A class C IP
Address
Firewalling
DHCP
To upstream service
provider
ISP
DNS
• Host File or DNS Server
• Different Levels of Domain
- Root-level “.”
- Top level domain
(gov / com / org)
- Second level
(Course / Microsoft)
- Subdomain
(sales / marketing)
DNS
• Top Level
- gov (U.S. government agencies)
- com (Commercial organizations)
- mil (U.S. military services)
- edu (Educational institutions)
- net (ISP’s)
- org (Nonprofit organisations)
DNS
• Primary Name Server has DNS zone file.
• Authoritative for Domain means server holds
the main DNS zone file
• Primary name server holds a read / write copy
of zone file
• Incremental Zone Transfers
DNS Query Process
DNS and ISP’s
DNS
• Win2003/7+ provides a full-featured DNS
server integrated with older DNS methods such
as host files
• FreeBSD, UNIX etc
• Primary and Secondary Zones
• Can be primary server for one zone and
secondary for another
• Win 2003/7+ DNS supports Active Directory
• Dynamic DNS, clients can create their own A
records
DNS
• Caching-only servers
• Forward lookup zones
• In-addr.arpa (name given to reverse lookup
zone file)
• Iterative vs recursive
• Secondary name servers (read only copies of
zone file)
• Zone transfers
WINS
• Used for identification in older pre-Windows
2000/3/7 Server versions. Just as DNS
provides IP Addresses for host names,
Windows Internet Name Service (WINS)
provides IP Addresses for NETBIOS computer
names.
WINS
Subnet 1
Subnet 2
No Broadcast Traffic
Router
Other Servers
Other Servers
WINS Server
WINS Server
Proxies
Forward Facing Proxy
Proxies
• Keep machines behind it anonymous.
• To speed up access to resources (using caching).
• To log / audit usage
• To scan transmitted content for malware before delivery.
• To scan outbound content, e.g., for data loss prevention.
• Access enhancement/restriction
Proxies
Open Proxy
Allows users to conceal their IP Address
Proxies
Reverse Proxy
Proxies
1. Security
2. Act as a firewall
3. SSL Encryption
4. Load-balancing
5. Cache static content
6. Compression
7. Spoon-feeding
8. Multiple servers on the same public IP address
Firewalls
Demilitarized Zone (DMZ)
References:
Napier, A., Judd, P.,
Rivers, O., and Adams, A.,
(2003)
E-Business Technologies
Thomson Course Technologies
ISBN: 0-619-06319-x
Panko, R (2005)
Business Data Networks and Communications, 5th
edition, Prentice Hall
ISBN: 0-13-127315-9
Schneider
E-Business, Eighth Edition
ISBN-13: 978-0-324-78807-5
Hogan, F., (2005)
Internet Presentation