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 - ITU -T (CCITT original) - for computers communication (ISDN,…) ISO (International Organization for Standardization) - IEEE (Institute of Electrical and Electronics Engineers) - 147countries - IEEE802 - standard. for LAN tech. (IEEE 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. ( 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 -server peer-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 service start-end of connection non-connected service without connection (posted packet) entity 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 N Communication protocol

TCP/IPISO/OSI application applicationpresentation relationtransportnetwork network interfacelink physic Four layers TCP/IP Application - application interface Transport - direct connection Network - routing Network interface - transfer of bits Protocols TCP/IP

ALAL TLTL NLNL PHLPHL IGMP transfer medium HTTP 80 HTTP 80 FTP TELNET SMTPPOP3DNSNFSRPC other 20/ TCP UDP IP ARP RARP ICMPRIPOSPF 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) IP address = logic address (network layer) 32 bits MAC address = physic (real) address (net inteface) 48 bits Each node in the network has its own unique address TCP/IP Communication TCP/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: novell www net augustana com org nasa vutbr cz fee fce Unnamed root edugov mil indy de int czech only USA

IP address IP version 4 32bits integer expressed as four dot separated numbers logic (abstract) address Finite number of addresses: 2 32 Example of IP address: new IP protocol (IP version 6) 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 mask A p q.r.s B p.q r.s C p.q.r s IP address (p.q.r.s) contains two parts (for routing) - netid - hostid Example: IP network address

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 netnode 110 net node 10 net node A B C Subnet mask netnode net subnet node

Examples: determining of net and node parts of IP address = = = network part of IP address = IP address = , subnet mask = = = = network part of IP address = IP address = , subnet mask =

Special IP addresses subnet address - symbolic address of the subnet - hostid contains only 0 bits: broadcast - message to all nodes in LAN - group IP address (hostid contains only 1 bits) example: = multicast - message to some group of nodes in LAN IP address = subnet mask = = = = network part of IP address = Examples: determining of net and node parts of IP address

Subnetting One net representation Gateway net x.x net x net x

Applicat. layer Transport layer Network layer Physic interface layer physic transport frame Application data Applicat. layer Transport layer Network layer Physic interface layer datagram packet message TCP data TCP header IP header IP data Frame data Frame header Node X Node Y Each 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 bridge repeater 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 Layer TCP Layer Ports of well-known services (WWW - port no. 80) Other services - dynamic generated ports Port = number of the service Socket = IP address + port

Ports and protocols of some services Transport medium HTTP 80 HTTP 80 FTP TELNET SMTP POP3DNSNFSRPC 20/ IP TCPUDP 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 communication Server 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 (

Network is inaccessible ipconfig - default gateway determining ping to IP address - answer of gateway Useful commands

nslookup addressdomain and IP address resolving tracert addressprop. of the trace to the node