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Transcript of Computer Networks Department of Computer Science Faculty of Civil Engineering, Brno University of...
Computer Networks
Department of Computer Science
Faculty of Civil Engineering, Brno University of Technology
Computer Technology
• Networking
• Internet Services
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 serviceČSNI (Český normalizační institut) - member of ISOISOC - IAB - IETF, IESG - organizations in InternetIANA, NIC - IP addresses a ports support, top domain admin.
(http://www.nic.com)
Main organization for standardization
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
Bus topology:Ethernet
Topology with structured cabling (star):
Ethernet
Circle topology: Token Ring
HUB
Topology of network (cabling)
client -serverpeer-to-peer
Access method - CSMA with collision detecting (CSMA/CD = Carrier Sense Multiple Access/Collision Detection)
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
•node, host = computer connected to network
•internetworking = communication between networks
•internet = connected networks
•Internet = well-known computer network
•connected servicestart-end of connection
•non-connected servicewithout connection (posted packet)
entityentity
entityentity
•With acknowledge = reliable
•Without acknowledge = non-reliable
Terminology
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
Architecture of networks
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
Layer N
Layer N-1
Layer N+1
Layer NCommunication protocol
TCP/IP ISO/OSI
application
application presentationrelation
transport transportnetwork networknetwork interface link
physic
Four layers TCP/IPApplication - application interfaceTransport - direct connectionNetwork - routingNetwork interface - transfer of bits
Protocols TCP/IP
AL
TL
NL
PHL
Protocols TCP/IP
IGMP
transfer medium
HTTP
80
HTTP
80
FTP TELNET SMTP POP3 DNS NFS RPCother
20/21 23 25 110 53 123 111
TCPUDP
IP
ARP RARP ICMP RIP OSPF
RTP
Ethernet, Token Ring, FDDI, Novel, X.25, ATM, (SLIP, PPP)
Protocols of TCP/IP layers
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
Each node in the network has its own unique address
TCP/IP CommunicationTCP/IP addresses
• 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
(application layer)Domain address in TCP/IP
Domains Hierarchy
Examples:
www.atlas.czwww.rfc-editor.orgwww.altavista.com
novell
www
net
augustana
com org
nasa vutbr
cz
feefce
Unnamed root
edugov mil
indy
deint
czech
only USA
IP address
IP version 4• 32bits integer expressed as four dot separated numbers• logic (abstract) address
1001 0011 1110 0101 0001 1010 0000 10100 7 8 15 16 23 24 31
Finite number of addresses: 2 32
Example of IP address: 147.229.26.10
• 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
Classes of IP addresses and network mask:
class netid hostid nodes max subnet maskA p q.r.s 16777214 255.0.0.0B p.q r.s 65534 255.255.0.0C p.q.r s 254 255.255.255.0
IP address (p.q.r.s) contains two parts (for routing)
- netid- hostid
193 12 99 0
Example: IP network address 193.12.99.0
Subnetting - dividing of the network
• goals: more nodes in the netload 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
0 7 8 15 16 23 24 310 net node
110 net node
10 net node
A
BC
Subnet mask
Subnet mask
net node
net subnet node
Examples: determining of net and node parts of IP address
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
IP address = 193.12.99.18, subnet mask = 255.255.255.0
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
IP address = 147.229.22.85 subnet mask = 255.255.255.192
147.229.22.85 = 1001 0011 1110 0101 0001 0110 0101 0101 255.255.255.192 = 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
Examples: determining of net and node parts of IP address
Subnetting
One net representation
Gatewaynet 193.12.x.x net 193.12.1.x
net 193.12.2.x
193.12.2.3 193.12.2.4
193.12.2.1 193.12.2.2
Applicat. layer
Transport layer
Network layer
Physic interface
layer
physic transport
frame
Application dataApplicat.
layer
Transport layer
Network layer
Physic interface layer
datagram
packet
message
TCP dataTCP header
IP header IP data
Frame dataFrame header
Node X Node YEach submitting layer adds its header (or
removes it in receiving case)
TCP/IP Communication
Passive elements (connectors, cabling, …)
Active elements - electronic equipment for network connection (signal amplifying and transformation)
physic transport
V. síťového rozhraní
node X node Y
Applic.
Transport
Network
Link bridgerepeater
router
Applic.
Transport
Network
Link
gateway
Network connecting - active elements
• 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: ARP, RARP protocols•non-connected, non-reliable
service
Internet (IP) Layer
Router 1
Router 2 Router 3
A B
C D E
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)
Data transfer between two nodes in different networks
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
• 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
Transport LayerTCP Layer
• Ports of well-known services (WWW - port no. 80)
• Other services - dynamic generated ports
Port = number of the serviceSocket = IP address + port
Ports and protocols of some services
Transport medium
HTTP
80
HTTP
80
FTP TELNET SMTP POP3 DNS NFS RPC
20/21 23 25 110 53 123 111
IP
TCP UDP
Network interface
• 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 communicationServer provides the service passively at the client request.
Application Layer
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).
Network is inaccessible
ipconfig - default gateway determining ping to IP address - answer of gateway
Useful commands
nslookup address domain and IP address resolving
tracert address prop. of the trace to the node