Computer Network Lab 2017 Motivation

31.05.2017
Computer Network Lab 2017
•
Fachgebiet Technische Informatik, Joachim Zumbrägel
Motivation
• Providing basic knowledge about conception,
implementation and functioning of computer networks.
• Configuration of a network in order to gain experience in
that subject.
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
1
31.05.2017
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 System) was established.
• 1990 300000 Computers were connected to the Internet. A text oriented searchsystem (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.
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
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.
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
2
31.05.2017
Lan jobs (1)
• Message exchange
mail systems, messaging systems
• Access to central/shared devices
printer, scanner
• Access to rescources of other computers
distributed programming/calculation
• Access to central data
shareable data, databases, user administration
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
Lan jobs (2)
Shared use of
information
Centralization of
administration and
support
Shared use of hardware and
Software
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
3
31.05.2017
Lan Modelling
• Network size, number of clients, area of the network
• Reliability, redundancy
• Security, avoidance of unauthorized access, firewalls
• Costs (purchase, maintenance, administration)
• Functionality
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
Lan Functions
Database
server
Database
Database server
server
Mail server
Fax
server
Faxserver
Web
server
Datenbank
Database
File-Fileandand
printprint
server
server
Directory Serviceserver
Client computer
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
4
31.05.2017
Network Types
Peer-to-Peer
Network
Peer-to-Peer
Network
Client-/Server
Network
Client-/Server
Network
Client-/Server
Network
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
Network Topology
Hub
BUS
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
STAR
Axel Hunger/Joachim Zumbrägel
RING
Computer Network Lab, SS 2016
5
31.05.2017
Ethernet
Signal transmission
Signal detection
CSMA (Carrier Sense Multiple Access)
Attributes
Access method
transfer rate
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Detect collision
CD (Collision Detection)
Description
CSMA/CD
Standard-Ethernet - 10 Mbit/s
Fast Ethernet 100 Mbit/s
Gigabit Ethernet - 1.000 Mbit/s
10-GB-Ethernet – 10.000 Mbit/s
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
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
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
6
31.05.2017
Protocol
Protocol = data transmission language
• A communication between 2 computers requires that both
computers understand the same protocol
• The computer network protocols are organized in
different layers
• For different services we need different protocols
• Example: TCP/IP
Protocol collection
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
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
Segment 1
Segment 2
TCP/IP
TCP/IP
Router
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
7
31.05.2017
IP
IP (Internet Protocol) has 3 main tasks:
1. It carries the transport protocols TCP and UDP.
2. It builds IP-Packages out of the data which have to be transmitted
3. It adds additional information, the IP-Header. Amongst others the
header contains source and destination address.
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
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
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
8
31.05.2017
IP-Addresses
• The addressing within TCP/IP Networks is realised by
use of IP-Adresses
• 32 Bit Value (IP V4):
Byte
Byte
Byte
Byte
• Each node (IP-Address) in the Internet is unique
• IP-Addresses are divided in Network part (Network-ID)
and Host part (Host-ID)
realised by netmask
• Certain IP-Addresses have special meanings
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
IP Address classes (old)
Class A
1.Byte(1-126)
Network-ID
0xxxxxxx
Host-ID
Class B
1.Byte(128-191)
Network-ID
10xxxxxx
xxxxxxxx
Class C
1.Byte(192-223)
Network-ID
110xxxxx
xxxxxxxx
Host-ID
Host-ID
xxxxxxxx
Class A : 126 nets each with 16777214 devices
Class B : 16382 nets each with 65534 devices
Class C : 2097150 nets each with 254 devices.
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
9
31.05.2017
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
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
IP-Addresses (2)
192.168.2.100
IP-Address
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
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
192.168.2.101
Host-ID
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
10
31.05.2017
Subnetmask
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
local: 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
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
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
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
11
31.05.2017
Subnetmask (3)
• Is used to realize the Classless Inter-Domain-Routing
• Determines the „size of the net“, number of useable Addr.
• Examples:
Netmask
/16
255.255.0.0
Useable Addr.
11111111.11111111.00000000.0000000
max. 65.534
/24 255.255.255.0 11111111.11111111. 11111111.0000000
max. 254
/28 255.255.255.240
11111111.11111111. 11111111.11110000
max. 14
/30 255.255.255.252
11111111.11111111. 11111111.11111100
max. 2
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
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)
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
12
31.05.2017
Computer Name and DNS
• A computer name identifies a computer in a net
•
•
•
•
DNS = Domain Name System
Unique host names are used
DNS allows the assignment: IP-Addresses ÙHost 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 its IP-Address
• Example: nslookup www.uni-due.de Ù 132.252.181.87
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
Network Setting
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
13
31.05.2017
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
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
Workgroup vs. Domain
• A workgroup consists of a group of loosely connected
computers where all computers are considered equal
• It is a peer-to-peer network where each member
(computer) is sustainable on its own.
• A domain consists of a trusted group of computers that
share security, access control, etc.
• The centralized management of the domain is done by a
domain controller (server).
• Under Microsoft the domain controllers are using the
Active Directory in order to store the domain information
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
14
31.05.2017
IP-Addresses in our lab
WWW
6 private networks
(192.168.1-6.xxx)
Gateway-IP
Switch
Client-IP
Server-IP
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
NAT
• NAT = Network Address Translation
• Enables the assignment between private IPAddresses and offical IP-Addresses => Hosts with a
private IP-Address have access to the internet.
192.168.1.3
Webbrowser
Webserver
192.168.1.254
132.252.181.1
134.91.90.69
Internet
NAT
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
15
31.05.2017
Little exercise
1. In our lab we will use six (netnumber 1-6) private Nets
netmask = 255.255.255.0 => Hostrange (0-255)
2. 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 IPAdress-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?
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
Short answer
1. netnumber is 1=>
Address of the subnet:
192.168.1.0
Address of switch:
192.168.1.1
Address of 2 hostmachines carrying Virtualization
software for client & server: 192.168.1.2, 192.168.1.3
Address of the server:
Client-Addresses:
Gateway address:
Broadcast-Address:
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
192.168.1.4
192.168.1.5 - 253
192.168.1.254
192.168.1.255
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
16
31.05.2017
Network technolgies (2)
Fachgebiet Technische Informatik (http://ti.uni‐due.de)
Axel Hunger/Joachim Zumbrägel
Computer Network Lab, SS 2016
17