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The TCP/IP protocol suite operates at four layers and has many protocols at each layer
what are the layers


what does the application layer do

Supports the communication between operating system supported applications (email, chat, web browser), which depend on user interaction. The protocols are diverse and are continuously developed.

what does the Transport layer do

Manages the 'end-to-end' reliability of each communication. .
tcp udp

The TCP protocol supports

resending of traffic

UDP (User Datagram Protocol) is based on

'best effort' and is designed for communication which does not benefit from resends, such as voice or video traffic.

what does the Internet layer do

Provides the unique address for each system and supports the internetwork routing of packets

what does the link layer do

Looks after the physical network connection, this may be the Ethernet cable, wireless connection, 3G or Bluetooth amongst many other systems.

At this layer each 'interface' or connection has a unique physically encoded address (called a MAC address).

application layer examples

SMTP (email)

transfer layer examples



Scalable TCP

internet layer examples

IP (Internet Protocol) and IPv6
ICMP (used by the ping utility)
many routing protocols including RIP, OSPF and BGP


Internet Control Message Protocol

link layer examples

wireless (802.11a, b, g, n)

Ethernet (802.3)

displays settings on the 'first' Ethernet card, eth0

ifconfig eth0

displays information on all active and inactive interfaces on system

ifconfig -a

starts up the eth0 interface

ifconfig eth0 up

shuts down the eth0 interface

ifconfig eth0 down

sets up an IP address with subnet mask and broadcast address

ifconfig eth0 netmask broadcast

ifconfig (in english)

interface configuration

DHCP (Dynamic Host Configuration Protocol) and DNS (Domain Name System)

both manage the allocation and the association of IP addresses to devices and domains.

DHCP request the client will In most cases (your local operating system) will receive:

a unique, currently unused IP address
the subnet mask
the default gateway (the address of the local router)
the address of the DNS server (or servers).

command to renew the IP address


quickly obtain the IP address to domain name


a program to query Internet domain name servers


nslookup (in english)

name servers look up

IPv4 how many bit


IPv6 how many bits


IPv4 address are divided into what classes, and what are they used for

Classes A, B, and C are used to allocate addresses on public and private networks. Class D is used for multicast communication traffic (such as routing protocols) and Class E is reserved.

IPv4 address is divided into four

octets to, to to
reserved for what

private use.

IPv6 3FFE:0000:0000:0000:0200:f8FF:FE21:67CF
can be shortened , how ?


IPv6 address is hexadecimal and uses

16 digits from 0 to F (0123456789ABCDEF).


feature of IPv4 where the IP address is followed by a binary mask which is used by routers as well as Linux systems to describe what network an IP address may be a member of.

port 7

Echo (ping)

port 20 ,21

File Transfer Protocol (FTP)

port 25

Simple Mail Transfer Protocol (SMTP)

port 53

Domain Name System (DNS)

port 80

Hypertext Transfer Protocol (HTTP)

port 443

Secure Sockets Layer (SSL)


Uncomplicated Firewall

start,stop ufw

ufw enable, ufw disable

Allow a port,block a port

ufw allow 80,ufw deny 80

Allow remote entry to system or computer

ufw allow proto tcp from to any port 80

lspci -(in english )

list all PCI devices


Ethernet 0 wired or wireless network interface


wireless local area network 0 wireless network interface


Atheros 0 wireless network interface that uses the Atheros chipset


personal area network 0 allows Bluetooth devices to form an ad hoc network


loopback 0 internal logical interface used by TCP/IP

make permanent changes to your network interfaces by

modify the contents of the /etc/network/interface file

start theNetworkManager Tool from cli



Media Access Control

command to apply wireless-specific settings to the card


manually configure a default gateway

route add default gw {IP address of gateway device}{network card}
route del default gw ath0

remove the default gateway,

route del default gw ath0

DNS server addresses can be manually configured by using a text editor

the /etc/resolv.conf

eg add

display the kernel IP routing table

route -n

The Dynamic Host Configuration Protocol (DHCP) was developed to

provide network address information to host devices

force your system's network interface to contact the DHCP server and renew its IP address

ifconfig eth0 down
dhclient eth0

ping three times

ping -c 3
c = count

what is ping

an Internet Control Message Protocol (ICMP): it is a combination of an ICMP echo request, and an ICMP echo reply

a command displays each step (router) along the path



network address translation


Interactive Colorful IP LAN Monitor

A combination of an IP address and a port number is known as a

a socket uniquely identifies an application on a specific system

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