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Inleiding computersystemen en netwerken deel 2
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.1
Inleiding computersystemen en netwerken deel 2
Mogelijkheden van netwerken
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Fileserver-systems
Remote execution / log-on
Distributed systems
Resource sharing (printer, scanner)
Document sharing (WWW)
Mail
News
Voice
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.2
Inleiding computersystemen en netwerken deel 2
Protocollen
An agreed-upon format for transmitting data between two devices.
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The Point-to-Point Protocol (PPP)
Telnet TCP/IP
IPX/SPX
Novell
NFS
RPC
X-25
X-window
Apple talk
Netbeui
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.3
Inleiding computersystemen en netwerken deel 2
Novell, IPX / SPX
IPX : Internetworking Packet Exchange
SPX : Sequence Packet Exchange
SPX ligt bovenop IPX en wordt
dus ingekapseld in IPX!
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.4
Inleiding computersystemen en netwerken deel 2
IPX-header
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.5
Inleiding computersystemen en netwerken deel 2
SPX-header
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.6
Inleiding computersystemen en netwerken deel 2
Eenvoudig MS-DOS netwerk (LAN)
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.7
Inleiding computersystemen en netwerken deel 2
5.8
TCP / IP
IP : Internet Protocol.
IP specifies the format of packets, also called datagrams (soort
brievenpost), and the addressing scheme. (de iplaag verzorgt
de routering)
TCP : Transmission Control Protocol
Whereas the IP protocol deals only with packets, TCP enables
two hosts to establish a connection and exchange streams of data.
TCP guarantees delivery of data and also guarantees that packets
will be delivered in the same order in which they were sent.
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
Inleiding computersystemen en netwerken deel 2
IP-header
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.9
Inleiding computersystemen en netwerken deel 2
IP-adres
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.10
Inleiding computersystemen en netwerken deel 2
IP-adres op het internet
An IP address consists of two parts, one identifying the
network and one identifying the node, or host. The Class of
the address determines which part belongs to the network
address and which part belongs to the node address
• Class A - supports 16 million hosts on each of 126 networks
• Class B - supports 65,000 hosts on each of 16,000 networks
• Class C - supports 254 hosts on each of 2 million networks
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.11
Inleiding computersystemen en netwerken deel 2
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.12
Inleiding computersystemen en netwerken deel 2
5.13
Niet routeerbare adressen
Beginadres
Eindadres
10.0.0.0
10.255.255.255
172.16.0.0
172.31.255.255
192.168.0.0
192.168.255.255
127.0.0.0
127.255.255.255
loopback
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
Inleiding computersystemen en netwerken deel 2
TCP-header
Het poort nummer is gekoppeld aan een bepaalde applicatie.
Poort 80 wordt bijv. gebruikt voor http verkeer.
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.14
Inleiding computersystemen en netwerken deel 2
UDP (Universal Datagram Protocol)
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.15
Inleiding computersystemen en netwerken deel 2
Protocol stack voor TCP/IP
FTP via poort 21, HTTP via 80, telnet via 23, NNTP via 119, SMTP via 25
(zie /etc/services op een linuxmachine voor een lijst met standaard poortnummers )
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.16
Inleiding computersystemen en netwerken deel 2
Voorbeeld van ping <de default gateway>
bekeken met Ethereal
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
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Inleiding computersystemen en netwerken deel 2
En een ping wat verder weg naar 145.89.166.36
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.18
Inleiding computersystemen en netwerken deel 2
En nu als ping www.expa.hvu.nl
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
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Inleiding computersystemen en netwerken deel 2
5.20
Eenvoudig netwerk met router
ethernet,
MAC address
ARP : Address Resolution Protocol, a network layer protocol
used to convert an IP address into a physical address (Data Link
Control address or MAC address).
DHCP : Dynamic Host Configuration Protocol, a protocol for
assigning dynamic IP addresses to devices on a network.
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
Inleiding computersystemen en netwerken deel 2
IP versie 6
Internet Protocol next generation
adres 128 bits = 16 bytes bijv. 2001:07b8:0:0:0:0:0:1 = 2001:7b8::1
poort 80 op dit adres schrijf je als [2001:7b8::1]:80
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
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Inleiding computersystemen en netwerken deel 2
5.22
V: 4-bit Internet Protocol version number = 6.
Prio: 4-bit Priority value.
Flow Label: 24-bit field, Quality of Service.
Payload Length: 16-bit unsigned integer. Length of payload, i.e., the rest of
the packet following the IPng header, in octets.
Next Hdr: 8-bit selector. Identifies the type of header immediately
following the IPng header.
Hop Limit: 8-bit unsigned integer. Decremented by 1 by each node that
forwards the packet. The packet is discarded if Hop Limit is decremented to
zero.
Source Address: 128 bits.
Destination Address: 128 bits.
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
Inleiding computersystemen en netwerken deel 2
RPC : Remote Procedure Call
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.23
Inleiding computersystemen en netwerken deel 2
5.24
DCE : Distributed Computing Environmernt
Suite of technology services developed by The Open Group for
creating distributed applications that run on different platforms.
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
Inleiding computersystemen en netwerken deel 2
COM, DCOM, CORBA, RMI
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COM : Component Object Model, DCOM : Distributed COM
(Microsoft)
CORBA : Common Object Request Broker Archticture (Open Source)
RMI: Remote Method Invocation (Java)
The COM software architecture is developed by Microsoft to build
component-based applications. COM objects are discrete components,
each with a unique identity, which expose interfaces that allow
applications and other components to access their features.
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.25
Inleiding computersystemen en netwerken deel 2
LDAP
LDAP : Lightweight Directory Access Protocol, a set
of protocols for accessing information directories.
OpenLDAP is the Open Source Version of LDAP
LDAP should eventually make it possible for almost
any application running on virtually any computer
platform to obtain directory information, such as
email addresses and public keys.
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
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Inleiding computersystemen en netwerken deel 2
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Security by Encryption
(not by Obscurity!)
Encryption techniques are based on public and private
key’s. Examples:
GPG (GNU Pretty Good privacy for files and email)
SSL (Secure Socket Layer - on application level)
TLS (Transport Layer Security - on application level)
IPSec (IP Secure – on IP level)
SSH (Secure Shell protocol)
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
Inleiding computersystemen en netwerken deel 2
Internet en intranet (achter firewall)
A global network connecting millions of computers. More than
100 countries are linked into exchanges of data, news and
opinions.
Bovenop TCP/IP:
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E-mail
FTP
Telnet
News
WWW
SSH
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.28
Inleiding computersystemen en netwerken deel 2
Opdracht
• bestudeer 15.8 t/m 15.10
• Practicum Ethereal
Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology
5.29