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Network Fundamentals
Network basics By: Mohand
For: arabhardware
Network Fundamentals Network basics
What is the network?
Is a group of computers that are connected together to communicate and share resources such as a file, printers, data, applications and Email.
What is the networks history?
Floppy desk » mainframe with dump terminal » personal computers What are the network types (LAN, MAN, WAN)? Local area network: Are self –contained networks that are spans a small area, such as a single
building, floor or room. Speed of LAN: 10, 100, 1000 mega. Space: 1 km
Metropolitan area network: which covers an area equivalent to a city?
Space: 1 to10 km Wide area network: is a network that spans multiple geographic locations Not important: CAN and GAN What is the internet? Is the single largest global wan, linking virtually every Country, continent and organizations in the
world What are the host types (server and client)? Server offer services and client to request a service
1- Client to client networks: peer to peer, host to host, all computers are client and server in same time. 2- Client to server
Host: any network device that has ip address
What are the full duplex and half duplex communication?
Full duplex is send and receive data at the same time (Two-direction) Half duplex is send date or receive data at different time What are the server types? file server , print server, web server, applications server, proxy server, mail server, fax server,
remote access server, date base server , domain name server DNS , Wins server, domain controller server DC,
What are the Network Topologies?
Physical topology: is how the devices actually interconnected with wires and cables , is anything physical on the network that you could touch like the cables, switches, hubs, routers and even the end devices.
Logical topology:
Is something you can see on a map, it looks like all the points are a short distance away but in reality they maybe in different parts of the area or maybe in a different country
Bus topology: All computers are connected in one line and all devices sharing same media Problems: collision
Solution: CSMA/CD Reduces the collision and jamming signal Bandwidth: 10 MB/S
Star topology: A star network uses a central server, switch, hub, MAU, access point
To route data between clients Ring topology: Connects computers in a circle of point-to-point connections, with no central server, such as a series
of desktop computers in an office. Each node handles its own applications and also shares resources over the entire network
Bandwidth 45MB/S Pc will load data and load address Wanted pc: match address, copy data, repeat signal, mark taken, and release taken
Logical topology Physical topology with MAU
Hybrid and mesh topology: not important useless
What is the right topology?
Cost, easy installation, easy maintenance, cable fault tolerance What is the building blocks there are used to construct network are? Nods: is any device that can connect to the network and can generate, process, or transfer network
data Backbone: is the highest –speed transmission path that carries the majority of the network data Segment: is any discrete physical subdivision of a network such as hubs, switches and routers
Subnet: is a portion of a network that shares a common network address
What are the network cables?
Coaxial cable: 10 base 2 is a thin coaxial cable connects until 185 m, speed 10 mbps. 10 base 5 is thick 500 m
Unshielded twisted pair (UTP):
Cable connect until 100 m Midi: 1 and 2 for Transmit, 3 and 6 for receive (NIC, router)
Midix: 1 and 2 for receive, 3 and 6 for Transmit (hub, switch) Straight-through cable between midi and midix Cross-over cable between midix and midix, midi and midi
Rolled-over console
10mb Ethernet, 100 fast Ethernet, 100 Giga Ethernet Fiber optic
What are the Network devices? Network interface card NIC: is a device that serves as an intermediary between the computer's
data and the network Mac address = 48 bits Hexadecimal digit = 0—9 a b c d e f
1 hexadecimal digit = 4 bits 00-A1-92-D8-0D-E8
00-A1-92 D8-0D-E8 OUI NIC IEEE Vendor
Repeater: Is a device that regenerates a signal to improve transmission distance Hub: The hub allows each device to talk to the others. Hubs are such simple devices, they require no
configuration, and have no manuals Bridge: It describes connecting two parts of a wireless network separated
Switch:
Is used in a wired network to connect Ethernet cables from a number of devices together. The switch allows each device to talk to the others. Switches aren't used in networks with only wireless connections
Switches allow dozens of devices to connect. Switches keep traffic between the devices
Switches allow you to monitor usage and control access Router: When a router is used, all Internet traffic passes through it to your local network
Open Systems Interconnection model
OSI 7 layers: Application
Presentation Session
Transport Network Data link
Physical Application layer:
User interface HTTP: browsing protocol
FTP: file transfer protocol TFTP: trivial FTP
Telnet: remote access protocol SMTP: simple mail transfer protocol
SNMP: simple network management protocol DNS: domain name system Presentation layer: Data formatting
Compression and decompression of data Encoding and decoding of data
Such as ASCII code (8 bit) Session layer: Establish and main connect
Set a logical connection between different applications Specifies communication mode (Simplex - half duplex - full duplex)
Transport layer: Accurate data Flow control stop
(Buffering congestion avoidance) |_| |_| Windowing go
Error recovery Type of protocols at transport layer
TCP: transmission Control Protocol Connection oriented protocol It must establish session before transmit the data and make recovery and control
UDP: user Datagram Protocol Connectionless protocol no session no recovery no control
Network layer: Routing: find the best path to the destination
Ip addressing: for router every interfaces has ip address For switch one ip address
For pc one ip address each Data link layer: Arbitration: find the best time to send the data by CSMA\CD and taken Error detection:
Parity check: but very weak CRC: cyclic redundancy check Depend on math equation
Data link is divided into two sub layers: 802.3 MAC sub layer (media access control)
802.2 LLC sub layer (logical link control) MAC address: hardware address 48 bit, 24 for vendor NIC, 24 for IEEE LLC: tcp\ip, spx\ipx
Physical layer: Ethernet 802.3
10base2: thin Ethernet 10 base 5: thick Ethernet
10baseT: twisted pair Encapsulation data: 1- Upper layer data Application PDU
2- Upper layer data Presentation PDU 3- Upper layer data Session PDU
4- TCP header | upper data Transport Segment 5- Ip header | data Network Packet
6- LLC header | data | FCS Data link Frame MAC header | data |FCS 7- 0101011101011 Physical Bits
DE-capsulation data: Upper layer data x Application PDU Upper layer data x Presentation PDU
Upper layer data x Session PDU Tcp header x Transport segment
Ip header x Network packet LLC header x Data link frame
Mac header x 0101011101011 Physical bits
Bandwidth: is the describe how much data can be transmitted over a connection Throughput: the Data rate, which pass inside the wire in a particular section, and a certain time Hubs at physical layer:
All devices in the same collision domain All devices in the same broadcast domain
Devices share the same bandwidth Switches at data link layer:
Each segment has its own collision domain All segments are in the same broadcast domain
Router at network layer:
Number of broadcast domains depending on the number of interfaces
The TCP\IP
Application Telnet, T*FTP, SMTP, DNS, RIP, SNMP, NFS, LPD Host to host (transport) TCP, UDP
Internet ARP, IP, IGMP, ICMP Network access (interface) Ethernet, token ring, frame relay, ATM
TCP segment format:
Socket: Ip = Source and destination + TCP or UDP + Source and destination port no.
Port numbers:
TCP ---> HTTP = (80), FTP = (21), Telnet = (23), SMTP = (25), DNS = (53) UDP ---> TFTP = (69), SNMP = (161), RIP = (520)
TCP three ways: handshake / open connection: Host a Host B
1 send SYN seq=100 SYN received SYN received 2 send SYN, ACK seq=300, seq=101
3 Established seq=101, ACK seq=301
Windowing: (window size= 3) Sender Receiver Send 1 Receive 1
Send 2 Receive 2 Send 3 Receive 3
ACK 4 UDP segment format:
IP Header:
FTP TFTP
Slow Fast Organized non- Organized Authentication no Authentication
Secure Unsecured Provides a reliable service its use of TCP does not since it uses UDP
Uses two connections uses one connection (stop and wait) Provides many commands provides only five commands
TCP UDP
Sequenced Un-sequenced Reliable Unreliable
Connection Oriented Connectionless Virtual circuit Low overhead ACK windowing flow control No ACK
Ethernet:
Allows all hosts on the network layer share the same bandwidth CSMA/CD Collisions are eliminated
Easy of installation Operation on layer 1 & 2 on OSI model
Ethernet, Fast Ethernet, Gig Ethernet Half duplex and full duplex
Ethernet addressing: NIC support Ethernet (unique identifier) MAC
Ethernet frame: Dreamble | DA | SA | Type | Data | FCS Dreamble = clocking & lock bit stream
Fast Ethernet frame: Dreamble | DA | SA | Type | length | Data | FCS Dreamble= clocking & end bit
Ethernet cables:
Cable Speed Length Name User Connectors
10 base 2 10 base 5 10 base T
100 base TX 100 base FX
1000 base T
10 mbps 10 mbps 10 mbps
100 mbps 100 mbps
1000 mbps
185 M 500 M 100 M
100 M 412 M
100 M
Thin Thick Cat3\UTP
Cat 5 6 7 Fiber\ multi
Cat 5 6 7
30 1024 1
1 1
1
BNC BNC RJ-45
RJ-45 ST or SC
RJ-45
Straight Through The straight-through cable is used to connect
Host to switch or hub Router to switch or hub
Crossover Cable The crossover cable can be used to connect Switch to switch
Hub to hub Host to host
Hub to switch Router direct to host
Rolled Cable You can use a rolled Ethernet cable to connect a host to a router console serial communication
(com) port.
► Numbering systems:
{Decimal= 0 1 2 3 4 5 6 7 8 9 – binary= 0 1} 00000000 = 0
11111111 = 255
► IP address:
{An identifier for a computer or device on a TCP/IP network}
{32bits – 4bytes – 4 octet – 1octet= 8 bit = 1byte}
{The Dotted Decimal Address – octet 1● octet 2 ● octet 3 ● octet 4}
► Logical and Physical:
{An IP address is a logical address that is assigned by software residing in a server or router (DHCP). In order to locate a device in the network, the logical IP address is converted to a physical address by a function within the TCP/IP protocol software (ARP). The physical address is actually
built into the hardware}
►Static and Dynamic IP:
{Network infrastructure devices such as servers, routers and firewalls are typically assigned permanent "static" IP addresses. The client machines can also be assigned static IPs by a network administrator, but most often are automatically assigned temporary "dynamic" IP addresses via
software that uses the "dynamic host configuration protocol" (Cable and DSL modems typically use dynamic IP with a new IP address assigned to the modem each time it is rebooted}
► IP address components:
{IP= Network + Hosts – A= |N|H|H|H| - B= |N|N|H|H| - C = |N|N|N|H|}
► IP address classes:
{A B C D E - A= 0 to 126 – B= 128 to 191 - C= 192 to 223 D= Multicast 224 to 239 E=
Experimental 240 to 255}
{127.0.0.1= loopback local host}
► Problem of IPv4:
{Temporary solution= private ips and public or real ips - Permanent solution= IPv6}
{Private ips: Class A= 10.0.0.0 to 10.255.255.255 - Class B= 172.16.0.0 to 172.31.255.255 -
Class D= 192.168.0.0 TO 192.168.255.255}
{To connect to the internet with private ip u must use NAT to convert private ip to public ip}
► Subnet mask:
{A mask used to determine what subnet an IP address belongs to network address and host address}
{Bitwise anding} {Network =1 – Host= 0 – in binary language}
{A= 255.0.0.0 – B= 255.255.0.0 – C= 255.255.255.0} {Network ID – broadcast ID – first ip – last ip} (Number of hosts= 2h-2 – h= number of zero's from the right}
(Number of subnets= 2n-2 – n= number of one's from the right} {FLSM= fixed-length subnet mask = Dividing the network into equal parts}
{VLSM= Variable-length subnet mask = Dividing the network into unequal parts}