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![What is a Network?
¡ A
computer
network,
or
simply
a
network,
is
a
collection
of
computers
and
other
hardware
interconnected
by
communication
channels
that
allow
sharing
of
resources
and
information.[1]
Where
at
least
one
process
in
one
device
is
able
to
send/receive
data
to/from
at
least
one
process
residing
in
a
remote
device,
then
the
two
devices
are
said
to
be
in
a
network.
A
network
is
a
group
of
devices
connected
to
each
other.
Networks
may
be
classified
into
a
wide
variety
of
characteristics,
such
as
the
medium
used
to
transport
the
data,
communications
protocol
used,
scale,
topology,
benefit,
and
organizational
scope.
(gotta
love
Wikipedia)
Lynx
Consultants
©
2013](https://image.slidesharecdn.com/networkingdns-130616104855-phpapp02/85/Networking-dns-101-3-320.jpg)
Uploaded byMarc Cluet
Networking & dns 101
This document provides an overview of computer networking concepts including what a network is, common network types like LAN and WAN, how the Internet works using protocols like IPv4 and IPv6, and how basic networking protocols TCP, UDP, and ICMP function. The key topics covered are how networks connect computers and allow sharing of resources, the role of gateways in relaying data between networks, and how protocols ensure reliable or unreliable delivery of data packets.
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- 1. Marc Cluet – Lynx Consultants
- 2. What we’ll cover? ¡ Understand how networking works ¡ Understand all the basic networking protocols ¡ Understand how DNS works ¡ Be more awesome! Lynx Consultants © 2013
- 3. What is aNetwork? ¡ A computer network, or simply a network, is a collection of computers and other hardware interconnected by communication channels that allow sharing of resources and information.[1] Where at least one process in one device is able to send/receive data to/from at least one process residing in a remote device, then the two devices are said to be in a network. A network is a group of devices connected to each other. Networks may be classified into a wide variety of characteristics, such as the medium used to transport the data, communications protocol used, scale, topology, benefit, and organizational scope. (gotta love Wikipedia) Lynx Consultants © 2013
- 4. So in plainwords… ¡ A network connects 2 or more computers together § LAN (Local Area Network) is inside a known location (office, home, etc) § WAN (Wide Area Network) is a network that connects two or more LANs Lynx Consultants © 2013
- 5. The Internet ¡ Internet is a network that connects in a fault tolerant way many networks ¡ Our current version of the Internet works over the protocol IPv4 with the new protocol IPv6 starting to have some presence Lynx Consultants © 2013
- 6. Internet IPv4 ¡ The most common protocol in Internet is right now IPv4 ¡ IPv4 has been the Internet protocol since 1980 (RFC 760) ¡ IPv4 uses 32 bit addresses, having a total space of 4,294,967,296 unique IPs Lynx Consultants © 2013
- 7. IPv4 IP address ¡ An IPv4 IP address is divided in 8 bit chunks (1 byte per number) Lynx Consultants © 2013
- 8. IPv4 IP netmask ¡ A netmask defines what your local network is, anything inside that netmask is considered local to you Lynx Consultants © 2013
- 9. IPv4 Problems ¡ IPv4 is running out of IP addresses (last /8 delivered this year) ¡ IPv4 is not secure for most uses ¡ IPv4 was designed in the 70ies so its up for a review Lynx Consultants © 2013
- 10. IPv6 saves theday! ¡ IPv6 is the new internet protocol ¡ Uses 128 bit addresses ¡ There’s more IP addresses in IPv6 than atoms on planet Earth Lynx Consultants © 2013
- 11. IP gateways ¡ As IP is the Internet Protocol it has to know how to talk to other networks ¡ A gateway server is the one who sits in two networks at the same time, relying packets between those networks Lynx Consultants © 2013
- 12. So then howthe Internet works? ¡ Gateways keep relying your message from network to network until it reaches the destination ¡ The path to reach its destination can change all the time Lynx Consultants © 2013
- 13. IP protocols ¡ IP can run lots of different protocols inside, the most known ones are § TCP (Transmission Control Protocol) § UDP (User Datagram Protocol) § ICMP (Internet Control Message Protocol) Lynx Consultants © 2013
- 14. IP protocol definitions ¡ TCP sends packets with complete assurance that they’ll reach their destination ¡ UDP sends packets without any kind of assurance that they’ll reach their destination ¡ ICMP sends control messages auxiliary to the IP protocol (like ping, traceroute, etc) Lynx Consultants © 2013
- 15. TCP Protocol ¡ Keeps track of all the packets it sends (serial num) ¡ Destination acknowledges (ACK) every packet received ¡ Packets can arrive in any order and they’ll be reordered at destination Lynx Consultants © 2013
- 16. TCP Ports ¡ TCP can listen or talk in several “channels” at the same time ¡ Ports are the channels where TCP (and UDP) talk, there’s a total of 65,536 channels ¡ Most common Ports § 80 http § 443 https § 25 smtp § 110 pop3 § 143 imap Lynx Consultants © 2013
- 17. UDP Protocol ¡ UDP sends packets as TCP to ports, but there’s no guarantee that the packets will reach its destination. ¡ This is ideal for any kind of protocol that doesn’t need all its packets § Video Streaming § Radio Streaming Lynx Consultants © 2013
- 18. ICMP Protocol ¡ ICMP sends auxiliary messages that help Internet routing ¡ Used in all of our common diagnostic tools § PING (icmp echo) § TRACEROUTE (icmp route) Lynx Consultants © 2013
- 19. ICMP - Ping ¡ Ping sends a packet to a destination and reads the reply ¡ Bases itself on ICMP echo ¡ Can be filtered by routers and inbetween policy filters Lynx Consultants © 2013
- 20. ICMP - Traceroute ¡ Traceroute sends requests to every single hop between us and a destination ¡ This is based on one special type of ICMP packet ¡ Some routers can decide to filter traceroute, in that case * will appear instead of the TTL Lynx Consultants © 2013
- 21. What is DNS? ¡ The Internet works with IP addresses ¡ How can we remember always that google is 173.194.67.103? ¡ It’s humanly impossible! Lynx Consultants © 2013
- 22. DNS saves theday ¡ DNS is a service (listens on UDP port 53) ¡ DNS will give you the IP address of any name you want ¡ It can give you more than one address for extra redundancy Lynx Consultants © 2013
- 23. DNS Servers ¡ DNS is also a security risk, you don’t want everyone to know your full DNS structure ¡ Big companies will show you a different DNS “view” based on where you are Lynx Consultants © 2013
- 24. DNS Geo Balanced ¡ DNS is also very useful to be able to send you to the nearest point ¡ Try resolving www.google.com from different parts of the world! Lynx Consultants © 2013 www.google.com is 173.194.41.84 www.google.com is 74.125.26.104
- 25.