inleiding computersystemen en netwerken deel 2 hogeschool van utrecht / institute for computer,...

Hogeschool van Utrecht / Institute for Computer, Communication and Media Technology

5.1Inleiding computersystemen en netwerken deel 2



Mogelijkheden van netwerken

• Fileserver-systems• Remote execution / log-on• Distributed systems• Resource sharing (printer, scanner)• Document sharing (WWW)• Mail• News• Voice



Protocollen

• The Point-to-Point Protocol (PPP) • Telnet TCP/IP• IPX/SPX• Novell• NFS• RPC• X-25• X-window• Apple talk• Netbeui

An agreed-upon format for transmitting data between two devices.



Novell, IPX / SPX

IPX : Internetworking Packet Exchange

SPX : Sequence Packet Exchange

SPX ligt bovenop IPX en wordt dus ingekapseld in IPX!



IPX-header



SPX-header



Eenvoudig MS-DOS netwerk (LAN)



TCP / IP

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.

IP : Internet Protocol.

IP specifies the format of packets, also called datagrams (soort brievenpost), and the addressing scheme. (de iplaag verzorgt de routering)



IP-header



IP-adres



IP-adres op het internet

• 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

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



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



TCP-header

Het poort nummer is gekoppeld aan een bepaalde applicatie.

Poort 80 wordt bijv. gebruikt voor http verkeer.



UDP (Universal Datagram Protocol)



Protocol stack voor TCP/IPFTP 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)



Voorbeeld van ping <de default gateway> bekeken met Ethereal



En een ping wat verder weg naar 145.89.166.36



En nu als ping www.expa.hvu.nl



Eenvoudig netwerk met router

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.

ethernet, MAC address



IP versie 6

Internet Protocol next generation adres 128 bits = 16 bytes bijv. 2001:07b8:0:0:0:0:0:1 = 2001:7b8::1poort 80 op dit adres schrijf je als [2001:7b8::1]:80



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.



RPC : Remote Procedure Call



DCE : Distributed Computing Environmernt

Suite of technology services developed by The Open Group for creating distributed applications that run on different platforms.



COM, DCOM, CORBA, RMI

• 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.



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.



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)



Internet en intranet (achter firewall)

• E-mail

• FTP

• Telnet

• News

• WWW

• SSH

Bovenop TCP/IP:

A global network connecting millions of computers. More than 100 countries are linked into exchanges of data, news and

opinions.



Opdracht

• bestudeer 15.8 t/m 15.10

• Practicum Ethereal

inleiding computersystemen en netwerken deel 2 hogeschool van utrecht / institute for computer,...

Documents

media technology

ipheader slide

ipadres slide

ipxheader slide

routering slide

spxheader slide

node address slide

ip protocol