Department of Computer Science
Faculty of Civil Engineering, Brno University of Technology
Computer Technology
Computer Networks
• Networking
• Internet Services
Main organization for standardization
ITU (International Telecommunication Union) - part of OSN
- standards of (tele)connectivity http://www.itu.ch
- ITU -T (CCITT original) - for computers communication (ISDN,…)
ISO (International Organization for Standardization)
- http://www.iso.ch
IEEE (Institute of Electrical and Electronics Engineers) - 147countries
- IEEE802 - standard. for LAN tech. (IEEE802.3 - for Ethernet)
W3C (World Wide Web Consortium) standard of WWW service
ČSNI (Český normalizační institut) - member of ISO
ISOC - IAB - IETF, IESG - organizations in Internet
IANA, NIC - IP addresses a ports support, top domain admin.
(http://www.nic.com)
Classification of networks
• area
– LAN (Local Area Network),
– MAN (Metropolitan Area Network),
– WAN (Wide Area Network)
• topology
– bus (Ethernet),
– circle (Token Ring),
– star (ARCnet)
• access method
– collision (stochastic) - CSMA/ CD - Ethernet,
– non-collision (deterministic) - Token Ring
• node role
– peer to peer, client - server
Topology of network (cabling)
Bus topology:
Ethernet
Topology with structured
cabling (star):
Ethernet
Circle topology:
Token Ring
HUB
Access method - CSMA with collision detecting
(CSMA/CD = Carrier Sense Multiple Access/Collision Detection)
peer-to-peer
client -server
Ethernet today
• Classic – 10 MBit/s
– 10Base-2, 10Base-5, 10Base-T, 10Base-FL
• FastEthernet – 100 MBit/s
– 100Base-TX, 100Base-T4, 100Base-FX
• Gigabit Ethernet – 1000 MBit/s
– 1000Base-SX, 1000Base-LX, 1000Base-T
Terminology
•node, host = computer connected to network
•internetworking = communication between networks
•internet = connected networks
•Internet = well-known computer network
•connected service
start-end of connection
•non-connected service
without connection (posted
packet)
entity
entity
•With acknowledge = reliable
•Without acknowledge = non-reliable
entity
entity
Architecture of networks
Layer model (what and where to do)
• decomposition to the tasks maintained by separated layers
• layer interface definitions
Protocol (how to do)
• set of rules and technologies for communication
• each layer has its own protocol
• format of the data definition
LAN Microsoft: NetBEUI (non-routable)
NetWare: IPX/SPX (routable)
heterogeneous networks (WAN, LAN): TCP/IP
Layer
• Each layer uses the service of the lower layer
• offers its service to the higher layer
• communication partner of the n-th layer is only
the n-th layer
• communication between the partners (the same
layer) is controlled by the protocol
Layer N+1
Layer N+1
Communication protocol
Layer N
Layer N
Layer N-1
Layer N-1
Protocols TCP/IP
Four layers TCP/IP
Application
- application interface
Transport
- direct connection
Network
- routing
Network interface
- transfer of bits
TCP/IP
application
transport
network
network interface
ISO/OSI
application
presentation
relation
transport
network
link
physic
Protocols TCP/IP
Protocols of TCP/IP layers
A HTTP
HTTP FTP TELNET SMTP
L
80
20/21
T
L
23
POP3
DNS
NFS
RPC
110
53
123
111
25
other
UDP
TCP
RTP
N
L
P
H
L
IP
ARP
RARP
ICMP
RIP
IGMP
OSPF
Ethernet, Token Ring, FDDI, Novel, X.25, ATM, (SLIP, PPP)
transfer medium
TCP/IP Communication
TCP/IP addresses
Each node in the network has its own unique address
Layers has its address format
• Domain address = text address (application layer)
www.seznam.cz
• IP address = logic address (network layer)
32 bits - 195.119.180.19
• MAC address = physic (real) address (net inteface)
48 bits - 00-00-64-65-73-74
Domain address in TCP/IP
(application layer)
• DNS (Domain Name System) service
domain address - IP address mapping
• name servers = nodes providing DNS service
• domain address example:
hp832.fce.vutbr.cz
node name . subdomain . subdomain . top level domain
• domain – specification where node is placed
– top level domain:
COM, EDU, GOV, MIL, NET, ORG – v USA
Non-US country code – (cz, sk, at, de, …)
– subdomain
Domains Hierarchy
Unnamed root
only USA
gov
mil
nasa
edu
augustana
com
net
novell
czech
org
int
cz
vutbr
fce
Examples:
www.atlas.cz
www.rfc-editor.org
www.altavista.com
de
www
indy
fee
IP address
IP version 4
• 32bits integer expressed as four dot separated numbers
• logic (abstract) address
Example of IP address:
0
7 8
1001 0011
147.229.26.10
15 16
23 24
31
1110 0101
0001 1010
0000 1010
Finite number of addresses: 2 32
•
new IP protocol (IP version 6) - 128 bits address
- eight hexadecimal numbers colon separated
CA32:F123:C210:1234:0000:0000:0000:1A11
Structure of IP address
IP address (p.q.r.s) contains two parts (for routing)
- netid
- hostid
Example: IP network address 193.12.99.0
193
12
99
0
Classes of IP addresses and network mask:
class
A
B
C
netid hostid
p
q.r.s
p.q
r.s
p.q.r
s
nodes max
16777214
65534
254
subnet mask
255.0.0.0
255.255.0.0
255.255.255.0
Subnetting - dividing of the network
• goals:
more nodes in the net
load balancing
• hostid of IP address is divided to the two parts - subnet num
- node num
• subnet mask
• 32 bits integer expressed as four dot separated numbers
• first continuous part of bits contain 1 - defines network part
of the IP address
C
Classes of IP addresses
A
B
C
0
0
7 8
15 16
net
23 24
31
node
10
net
110
node
net
node
Subnet mask
net
node
Subnet mask
net
subnet
node
Examples: determining of net and node parts of IP address
IP address = 193.12.99.18, subnet mask = 255.255.255.0
193.12.99.18
= 11000001 00001100 01100011 00010010
255.255.255.0
= 11111111 11111111 11111111 00000000
193.12.99.0
= 11000001 00001100 01100011 00000000
network part of IP address = 193.12.99.0
IP address = 195.229.26.10, subnet mask = 255.255.255.224
195.229.26.10
= 11000011 11100101 00011010 11101010
255.255.255.224 = 11111111 11111111 11111111 11100000
195.229.26.224 = 11000011 11100101 00011010 11100000
network part of IP address = 195. 229.26.224
Examples: determining of net and node parts of IP address
IP address = 147.229.22.85
subnet mask = 255.255.255.192
147.229.22.85
255.255.255.192
= 1001 0011 1110 0101 0001 0110 0101 0101
= 1111 1111 1111 1111 1111 1111 1100 0000
147.229.22.64
= 1001 0011 1110 0101 0001 0110 0100 0000
network part of IP address = 147.229.22.64
Special IP addresses
subnet address - symbolic address of the subnet
- hostid contains only 0 bits: 136.229.26.0
broadcast - message to all nodes in LAN
- group IP address (hostid contains only 1 bits)
example: 195.229.26.255 = 11000011 11100101 00011010 11111111
multicast - message to some group of nodes in LAN
Subnetting
193.12.2.1
net 193.12.x.x
193.12.2.2
net 193.12.1.x
Gateway
net 193.12.2.x
One net representation
193.12.2.3
193.12.2.4
TCP/IP Communication
Node X
Each submitting layer adds its header (or
removes it in receiving case)
Applicat.
layer
Application data
message
Transport
layer
TCP
header
packet
Network
layer
Physic
interface
layer
TCP data
IP
header
Frame
header
IP data
datagram
Frame data
frame
physic transport
Node Y
Applicat.
layer
Transport
layer
Network
layer
Physic
interface
layer
Network connecting - active elements
Passive elements (connectors, cabling, …)
Active elements - electronic equipment for network connection (signal
amplifying and transformation)
node X
node Y
Applic.
Applic.
Transport
gateway
Transport
Network
router
Network
Link
bridge
repeater
physic transport
Link
V.
síťového
rozhraní
Internet (IP) Layer
• Realized by IP protocol
• Provides
•unified addresses – logic IP addresses
•unified format of transferred data (IP datagrams)
•routing between the LANs via routers
•address mapping:
B
ARP, RARP protocols
A
•non-connected, non-reliable
Router 1
service
Router 2
C
Router 3
D
E
Data transfer between two nodes in different networks
node knows - source (its) and target IP address,
- source (its) and target MAC address (ARP)
- IP address of router of its network
• node send packet to the router if the net part is different
• router send packet to the router or direct to the target node
• IP routing table - subnet mask, target network, gateway (router)
Network layer protocols
IP
Internet Protocol - packet transfer,
without acknowledge, routing support
ARP Address Resolution Protocol - ARP table determining physic address from IP address
RARP Reverse Address Resolution Protocol - automatic
allocation of IP address to the connected node
ICMP Internet Control Message Protocol transfer of reserved service information
Transport Layer
TCP Layer
• Data transfer between the applications
• TCP (Transmission Control Protocol) - provides:
- connected service - makes connections between the nodes
- acknowledging of successful data receiving
• UDP (User Datagram Protocol) - provides:
- non-connected, non-reliable data transfer
Port = number of the service
Socket = IP address + port
• Ports of well-known services (WWW - port no. 80)
• Other services - dynamic generated ports
Ports and protocols of some services
HTTP FTP
HTTP
80
20/21
TELNET SMTP
23
25
POP3
DNS
NFS
RPC
110
53
123
111
TCP
UDP
IP
Network interface
Transport medium
Application Layer
• Applications and services communicate directly with the
transport layer
• Application implements needed mechanisms not
supported in used transport layer
• The main model of TCP/IP communication:
client-server.
Client actively requests the service and starts the communication
Server provides the service passively at the client request.
Protocols of applikation layer
FTP (File Transfer Protocol)
rfc 959
Telnet -
rfc 854
SMTP (Simple Mail Transfer Protocol)
rfc 821
POP3 (Post Office Protocol)
rfc1939
HTTP (Hypertext Transfer Protocol)
rfc 2616
DNS (Domain Name System)
rfc1035
DHCP (Dynamic Host Configuration Protocol)
From 1969 all information about Internet published in
RFC (Request for Comments) web accessible
(http://www.rfc-editor.org).
Useful commands
Network is inaccessible
ipconfig
ping to IP address
- default gateway determining
- answer of gateway
nslookup address
tracert address
domain and IP address resolving
prop. of the trace to the node