Transcript Network

Motivation
• Providing basic knowledge about conception,
implementation and functioning of computer
networks.
• Configuration of a network in order to gain
experience in that subject.
Computer Net Lab/
Praktikum Datenverarbeitung 2
1
History
• 1969 the resarch network „ARPANET“ was introduced. It consists of 4
connected computers.
• 1976 Queen Elizabeth II. sent an Email from England to America.
• 1980 (27th of Oktober) the ARPANET was stopped by a virus.
• 1983 the servers got names. Since that time it is not longer neccessary
to know the exact path to another system.
• 1984 DNS (Domain name services) was established.
• 1990 300000 Computers were connected to the Internet. A text oriented
search-system (archie) was created.
• 1991 Tim Berners-Lee developed the hypertext sytem. The Birthday of
HTML.
• Today it is assumed that more than one billion (1.000.000.000)
computers are connected.
Computer Net Lab/
Praktikum Datenverarbeitung 2
2
What is LAN
• A local area network is used for the bit seriell transmission
among connected but independent devices. A LAN is located
within a limited area and belongs completly to the operating
company.
• LAN is an acronym for „local area network“. A LAN is a group of
computers and peripherals in a close area that are connected to
share information and resources.
Computer Net Lab/
Praktikum Datenverarbeitung 2
3
LAN jobs (1)
• Message exchange
mail systems
• Access to central/shared devices
printer, scanner
• Access to rescources of other computers
distributed programming/calculation
• Access to central data
shareable Data
data bases
user administration
Computer Net Lab/
Praktikum Datenverarbeitung 2
4
LAN jobs (2)
Shared use of
information
Centralization of
administration and
support
Shared use of hardware and
Software
Computer Net Lab/
Praktikum Datenverarbeitung 2
5
LAN Modelling
• Network size, number of clients, area of the network
• Reliability, redundance
• Security, avoidance of unauthorized access, firewalls
• Costs (purchase, maintenance, administration)
• Functionality
Computer Net Lab/
Praktikum Datenverarbeitung 2
6
Functions in a LAN
Mail
server
Mailserver
Mail
server
Fax
server
Faxserver
Fax
server
Database server
Databaser
server
Datenbank
Database
File-Fileandand
printprint
server
server
Directory Serviceserver
Client computer
Computer Net Lab/
Praktikum Datenverarbeitung 2
7
Network types
Peer-to-Peer Network
Client-/Server Network
Computer Net Lab/
Praktikum Datenverarbeitung 2
8
Network topology
Hub
BUS
STAR
Computer Net Lab/
Praktikum Datenverarbeitung 2
RING
9
Network technology (Ethernet)
Signal transmission
Signal detection
CSMA (Carrier Sense Multiple Access)
Attributes
Access method
transfer rate
Detect collision
CD (Collision Detection)
Description
CSMA/CD
Standard-Ethernet - 10 Mbit/s
Fast Ethernet - 100 Mbit/s
Gigabit Ethernet - 1 Gbit/s (1.000 Mbit/s)
Computer Net Lab/
Praktikum Datenverarbeitung 2
10
Network technology (Token Ring)
Logical
Physical
Attributes
Description
Access method
Tokenpassing
transfer rate
4 bis 16 Mbit/s for all cable types
Computer Net Lab/
Praktikum Datenverarbeitung 2
11
Network components
• Repeater
amplifies electrical signals
• Hub
delivers all packages to all connected stations
• Bridge
allows the segmentation of a network
• Switch
delivers packages only to the target computer
• Router
determines the best route between sender and receiver
• Gateway
data transfer management from one net into another one
Computer Net Lab/
Praktikum Datenverarbeitung 2
12
Protocols
Protocol = data transmission language
A communication between 2 computers requires that both computers understand the
same protocol
• NetBeui
fast, not routeable, only in Microsoft environment
• IPX/SPX
Protocol collection for Novell, routeable
• Apple Talk
Kommunication protokoll for Apple-Network, routeable
• TCP/IP
Protocol collection for different computer types, routeable
Computer Net Lab/
Praktikum Datenverarbeitung 2
13
TCP/IP
•
•
•
TCP and IP are two different protocols
They build a protocol family with other protocols like UDP and ICMP
Only the combination of these protocols offers the well known functionality of a network
routeable
Windows-Client
Segment 1
Windows-Client
Segment 2
TCP/IP
TCP/IP
Router
Computer Net Lab/
Praktikum Datenverarbeitung 2
14
IP
IP (Internet Protocol) has 3 main tasks:
1.
2.
3.
It carries the transport protocols TCP and UDP.
It builds IP-Packages out of the data which have to be transmitted
It adds additional information, the IP-Header. It contains source and destination
address.
Computer Net Lab/
Praktikum Datenverarbeitung 2
15
TCP
•
•
•
TCP (Transmission Control Protocol) confirms every received data package
TCP repeats each data package until its receiving is confirmed
TCP is reliable, that means the transmission is guaranteed
32 BIT
Computer Net Lab/
Praktikum Datenverarbeitung 2
16
IP-Addresses (1)
• The addressing within TCP/IP Networks is realised by use of IPAdresses
• 32 Bit Value (IP
Byte
V4):
Byte
Byte
Byte
• Each node (IP-Address) in the Internet is unique
• IP-Addresses are divided in Classes
• IP-Addresses are divided in Network part (Network-ID) and Host
part (Host-ID)
• Certain IP-Addresses have special meanings
Computer Net Lab/
Praktikum Datenverarbeitung 2
17
IP Address classes
Class A
1.Byte(1-126)
Network-ID
0xxxxxxx
Network-ID
Class B
1.Byte(128-191) 10xxxxxx
Network-ID
Class C
1.Byte(192-223) 110xxxxx
Host-ID
Host-ID
xxxxxxxx
Host-ID
xxxxxxxx
xxxxxxxx
Klasse A : 126 nets each with 16777214 devices
Klasse B : 16382 nets each with 65534 devices
Klasse C : 2097150 nets each with 254 devices.
Computer Net Lab/
Praktikum Datenverarbeitung 2
18
Address guidelines
• Network ID 127 ist not allowed
- 127 is reserved for loopback function (localhost)
• Network -ID and Host-ID can‘t be 255
- 255 is the Broadcast Adress
• Network -ID and Host-ID can‘t be 0
- 0 means only that network
• Host ID must be unique
Computer Net Lab/
Praktikum Datenverarbeitung 2
19
IP-Addresses (2)
192.168.2.100
IPAdresse
192.168.3.100
192.168.1.100
192.168.1.0
192.168.2.0
192.168.3.0
Network-Address
(Host-ID = 0)
192.168.1.100
192.168.2.101
Computer Net Lab/
Praktikum Datenverarbeitung 2
Host-ID
20
Subnetmask (1)
• Seperates Network-ID and Host-ID
• Is used in order to decide if the target host is located in the own
network or in an external (remote) one
• lokal: Net-ID of sender is equal to receivers Net-ID
• remote: Net-ID of sender differs from receivers Net-ID
IP-Address
10.50.100.
200
Subnetmask
255.255.255.
0
Network- ID
10.50.100.
0
Computer Net Lab/
Praktikum Datenverarbeitung 2
21
Subnetmask (2)
Sender-IP
10.50.100.
200
Subnetmask
255.255.255.
0
Network-ID
Sender
10.50.100.
0
Receiver-IP
10.50.101.
220
Subnetmask
255.255.255.
0
Network- ID
Receiver
10.50.101.
0
Network-ID of sender differs from network-ID of receiver
=> Receiver IP ist not in the same network
Computer Net Lab/
Praktikum Datenverarbeitung 2
22
Private IP-Addresses
• There are IP-Ranges which are exclusivly used for private
purposes.
• Therefore addresses of this range will never be found in the
WWW.
• There are following private IP-Ranges:
10.0.0.0
10.255.255.255 (A)
172.16.0.0 172.31.255.255 (B)
192.168.0.0 192.168.255.255 (C)
Computer Net Lab/
Praktikum Datenverarbeitung 2
23
DHCP
• DHCP (Dynamic Host Configuration Protocol)
• Enables the automatically configuration of client-devices
• Requires a DHCP-Servers which distributes the settings
automatically to the clients
• Client devices receive an IP-Address, address of the gateway,
subnetmask and address of the DNS server
• Benefit: manual configuration of the client device installation is
not longer necessary
Computer Net Lab/
Praktikum Datenverarbeitung 2
24
DNS
• DNS = Domain Name Service
• Unique host names are used
• DNS allows the assignment: IP-Addresses Host name
• Each host which should be accessible via its name needs an
entry within the database of a name server. Otherwise this
machine is only accessible via ist IP-Address
• Example: nslookup www.uni-duisburg.de  134.91.4.169
Computer Net Lab/
Praktikum Datenverarbeitung 2
25
IP-Adresses used in our lab
Privates Class C-Netz
Gateway-IP
HUB
Client-IP
Server-IP
Computer Net Lab/
Praktikum Datenverarbeitung 2
26
NAT
• Nat = Network Address Translation
• Enables the assignment between private IP-Addresses and
offical IP-Addresses => Hosts with a private IP-Address have
access to the internet.
192.168.0.10
Webserver
Webbrowser
w2.x2.y2.z2
w1.x1.y1.z1
Internet
NAT
Computer Net Lab/
Praktikum Datenverarbeitung 2
27
Little exercise
1.
2.
What do you think? What kind of IP-Network does our university have?
www.uni-due.de = 132.252.184.87
In our lab we will use six (netnumber 1-6) private class C-Nets. Following rules should
be used for the setup of the net:
Private Class C-Net: 192.168.<netnumber>.xxx
The server should get the first IP-Address from the available IP-Adress-Range.
The gateway should get the last IP-Address from the available IP-Adress-Range.
Clients should get the rest from the available IP-Adress-Range.
What are the IP-addresses of server and gateway?
What is the IP-Adress-range of the clients?
What is the subnetmask?
Computer Net Lab/
Praktikum Datenverarbeitung 2
28
Short answer
1. The network of our university is a class B net because the first
byte (132) lies in the range between 128-191
Z.B. www.uni-due.de = 132.252.184.87
2. netnumber is 1=>
Address of the subnet:
Address of the server:
Client-Addresses:
Gateway address:
Broadcast-Address:
192.168.1.0
192.168.1.1
192.168.1.2 - 192.168.1. 253
192.168.1.254
192.168.1.255
Computer Net Lab/
Praktikum Datenverarbeitung 2
29
Netzwerktechnologien (Ethernet 2)
Computer Net Lab/
Praktikum Datenverarbeitung 2
30