Transcript Introduction to computer netw

Basic Computer Networks
L. Budi Handoko, M.Kom.
([email protected])
Dian Nuswantoro University
Course Content (Syllabus)
1. Understanding about basic concept of computer
networks.
2. Understanding about network applications and
utilizations.
3. Understanding about networks benefits and
liability.
4. Understanding about networks structure,
achitecture, devices and topology.
5. Understanding about networks reference or
standardization.
6. Understanding about wireless networking.
7. Understanding about security and the risk.
References
• Andrew S. Tanenbaum, Computer Networks, 4th
Edition, Prentice Hall, 2003
• S.S. Shinde, Computer Network, New Age, 2009
• Libor Dotálek and Alena Kabelová,
Understanding TCP/IP, Packt, 2006
Grading Guidelines
• Middle Exam (20%)
• Final Exam (30%)
• Assignments (50%), consisting :
▫
▫
▫
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Individual Assignment
Group Assignment
Attendance
Project or Challange (If Any...)
Introduction to Computer Networks
(Basic Concept of Computer Networks)
• History (just read the books !!! We’re not on history
lesson !)
• Stand alone (What ???)
• Term for Computer (used to be) or Devices (gadget)
• Connect 2 or more devices or computers
• Functions ? (communications and using
available resources together)
• Location ? (no problem)
• Size ? (whatever)
• Benefits and liablity ? (hmm... let‘s see and break
them down together in the next session)
Introduction to Computer Networks
(Terminology)
• The Unit used on nework
▫ bit (b) smallest unit to describe a bit to flow in the network for binary
data
▫ Byte (B) consisting from 8 bit in a byte
▫ For measurement can be combine with (from smallest to biggest unit) :
Factor
101
102
103
106
109
1012
1015
1018
1021
1024
Name
deka
hecto
kilo
mega
giga
tera
peta
exa
zetta
yotta
Symbol
da
h
k
M
G
T
P
E
Z
Y
Factor
1027
1030
1033
1036
1039
1042
1045
1048
1051
1054
Name
xona
weka
vunda
uda
treda
sorta
rinta
quexa
pepta
ocha
Symbol
X
W
V
U
TD
S
R
Q
PP
O
Factor
1057
1042
1045
1048
1051
1054
1057
1060
1063
Name
nena
sorta
rinta
quexa
pepta
ocha
nena
minga
luma
Symbol
N
S
R
Q
PP
O
N
MI
L
Introduction to Computer Networks
(Terminology Continues)
▫ smallest unit :
Factor
10-1
10-2
10-3
10-6
10-9
10-12
10-15
10-18
10-21
10-24
10-27
10-30
10-33
10-36
Name
deci
centi
milli
micro
nano
pico
femto
atto
zepto
yocto
xonto
wekto
vunkto
unto
Symbol
d
c
m
µ
n
p
f
a
z
y
x
w
v
u
Factor
10-39
10-42
10-45
10-48
10-51
10-54
10-57
10-60
10-63
Name
trekto
sotro
rimto
quekto
pekro
otro
nekto
mikto
lunto
Symbol
td
s
r
q
pk
o
nk
mi
l
Introduction to Computer Networks
(Terminology Continues)
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BandWidth
Transfer Rate
Wi-Fi
Concentrator (Hub, Switch,
Access Point for wireless)
NOS (Network Operating
System)
Autonomous System
Hacking is not cracking
Broadband
WiMax (Worldwide
Interopeability for Microwave
Access)
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ISP (Internet Service Provider)
NAP (Network Access Provider)
Bit is not a byte
IP Address
Proxy
Anonymous
NOC
DataCenter
DRC
Anything else ???
Introduction to Computer Networks
(Advantages)
• In General
▫ Easiness (bussines, education, personal, social life,
informations, communications, entertaintment)
▫ Mobility (anywhere, anytime, high reliability)
▫ Efficiency (time, money, resources sharing)
• Network Administrator
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Good salary (really ???)
Control other peoples (annoyed ??? just kick off...)
Faster than others (conventional)
Relax (enjoy your life, seriously ???)
Introduction to Computer Networks
(Disadvantages)
• In General
▫ Psychology (lack of direct interaction)
▫ Personal information generally available (no more
secret)
▫ Socially (abuse, pornography, bullying, fraud)
▫ Cyberterorism, Cyberwar (please watch Die Hard 4 or
The Net)
• Network Administrator
▫ ERROR !!! (you’re become a fugitive, a lot of people
want to KILL YOU !!!)
Introduction to Computer Networks
(Applications)
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•
•
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•
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Communication (e-mail, chat, im, voip, vicon)
Resource Sharing (hardware and software)
Information Sharing (files, databases)
Cloud Computing (Offices, Bussiness)
Cluster Computing (Super Computer)
GRID Computing (Distributed processing)
SAN (Storage Management)
What do you need ? (Multimedia, Databases,
Security, Appliance, etc)
Introduction to Computer Networks
(Classification – Scale)
• NFC (Near Field Communication)
Super small area were covered for this type. It’s about 1 meter persquare.
• PAN (Personal Area Network)
Very small geographical area. Usually using bluetooth for the connection less
than 25 metres per square (open space).
• LAN (Local Area Network)
Small geographical area (Room, Building or limited area like Campus) within
10 km to a few hundreds km.
• MAN (Metropolitan Area Network)
Medium geographical area (City size).
• WAN (Wide Area Network)
Large geographical area (country, continent, entire planet)
• IPN (InterPlanetary Network)
Very Large geographical area, just like what it sound, it’s inter planet network.
(Seriouslly ??? Is the lecturer have a day dream ???)
Introduction to Computer Networks
(Classification - Type)
• Intranet
Closed group network with limited scale.
• Extranet
Semi closed group network with medium scale.
• Internet
Publicy open network with large scale.
Introduction to Computer Networks
(Topology - Diagram)
Network topology is
about how to define s
the way in which
computer, printer, and
others device are
connected.
A network topology
describes the layout of the
wire (or wireless) and
devices as well as the paths
used by data transmissions.
Introduction to Computer Networks
(Topology – Type -> Bus)
• Commonly referred to as a linear bus, all the
device on a bus topology are connected by one
single cable. (coaxial cable with BNC connector
and terminator)
• Allows information to be directed from one
computer to the other. Lots of binary collision.
Introduction to Computer Networks
(Topology – Type -> Star (or Tree ?)
• The most commonly used achitecture
in Ethernet LAN(s). Less collisions
and most efficient. Using twisted pair
cable and RJ45 connectort.
• Larger networks use the extended star
topology also known as tree topology.
• When used with network device that
filter frames or packets, like bridges,
switches, and routers, this topology
significantly reduces the traffic on the
wires by sending packets only to the
wires of the destination host.
Introduction to Computer Networks
(Topology – Type -> Ring)
• A frame travels around the ring,
stopping at each node. If a node wants
to transmit data, it adds the data as well
as the destination address to the frame.
• The frame then continues around the
ring until it finds the destination node,
which takes the data out of the frames.
▫ Single ring – All the devices on the
network share a single cable. (upper
figure)
▫ Dual ring – The dual ring topology allows
data to be sent in both direction. (lower
figure)
• Disadvantage ? (use you logic !)
Introduction to Computer Networks
(Topology – Type -> Mesh )
• The mesh topology connects all
devices (nodes) to each other for
redundancy and fault tolerance.
• It is used in WANs to interconnect
LANs and for mission critical
networks like those used by banks
and financial institutions.
• Implementing the mesh topology
is expensive and difficult.
Introduction to Computer Networks
(Standardization)
• There are 2 important network architecture :
▫ the OSI (Open System Interconnection) reference
model, and
▫ the DoD reference model which known as TCP/IP
reference.
• TCP/IP reference is a simplification of OSI
reference.
• OSI models are widely use for discusing a
compter network.
Introduction to Computer Networks
(Comparison of TCP/IP and OSI)
Introduction to Computer Networks
(OSI Model)
• A model defines the stages or tasks of a protocol
as it prepares to send data
▫ Open meaning standards available to all.
• The model is devided into seven distinct layers
• Each subsequent layer should perform a welldefined function and the layer boundaries are
designed to minimize the information flow
across the interfaces
Data Units and Function
Introduction to Computer Networks
(Layer 7 - Application)
• Defines the format in which data should be
received from or handed over to the applications
• Main function is to provides a user interface
(example : web browsers, e-mail clients)
• Includes file, print, database, app. services
• Contains a variety of protocols that are
commonly needed (examples : HTTP, SMTP)
Introduction to Computer Networks
(Layer 6 - Presentation)
• Main function is to present the data (example :
image, audio, video)
• Includes encryption, compression and
translation services
• Contains a variety of file types (examples : JPG,
AVI, MID)
Introduction to Computer Networks
(Layer 5 - Session)
• Main function is to facilitates exchange of data
between two (or more) applications (it serves as
a checkpoint and is involved in synchronizing
transaction, correctly closing files, handle
session, etc.)
• Keeps different applications data separated
• Protocols that functioning on this layer are NFS,
RPC, etc.
Introduction to Computer Networks
(Layer 4 - Transport)
• The basic function is to accept data from the session
layer, split it up into smaller units if needed, pass
these to the network layer and ensure that the pieces
all arrive correctly at the other end
• Provides reliable delivery of data transmissions
• Performs error detection
• Includes end to end connection
• There are 2 kind of connection at this layer which is
▫ TCP (Transmission Control Protocol)
▫ UDP (User Datagram Protocol)
Introduction to Computer Networks
(Layer 3 - Network)
• Main function is to ensures the data transfer
between two remote computers within a
particular WAN
• The basic unit of transfer is a datagram that is
wrapped (encapsulated) in a frame.
• Provides logical addressing
• Routing layer
Introduction to Computer Networks
(Layer 2 – Data Link)
• Main function or task is to take a raw transmission
facility and transform it into a line that appears free
of undetected transmission errors to the network
layer (read the book please !)
• Combines packets into bytes then into frames
• Performs error detection (not correction)
• Provides media access adressing (point-to-point)
• MAC (Media Access Control) and DLC (Data Link
Control)
Introduction to Computer Networks
(Layer 1 - Physical)
The responsibility is transmitting raw bits over
communication channel through hubs, wires,
modems, NICs (Network Interface Card) 
basically anything that is physical to the network
Introduction to Computer Networks
(Encapsulation)
User data
Appl header
User data
TCP header
Application data
IP header
TCP header
Application data
Ethernet header IP header
TCP header
Application data
Ethernet tailer
Introduction to Computer Networks
(OSI Upper Layer - Application)
• DNS (Domain Name System)
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DNS Server also known as Name Server
Provide translation domain name to IP vice versa
Domain name consist a strings separated by dot
TLDs consist of gTLD and ccTLD
Stored in name servers as RR (Resource Records)
Using UDP Transport for query on port 53
Using TCP Transport for zone transfer on port 53
Introduction to Computer Networks
(OSI Upper Layer - Application)
• WWW (World Wide Web)
▫ Consisting various of informations
▫ Using tools or application known as ‘Browser’
▫ Using HTTP (HyperText Transfer Protocol) as the
protocol
▫ Using HTML (HyperText Markup Language) as
the primary session
▫ Using TCP as the transport on port 80
▫ Support for SSL Extension for secure connection
Introduction to Computer Networks
(OSI Upper Layer - Application)
• E-Mail (Electronic Mail)
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▫
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Communication device for personals or groups
Support MIME (Multipurpose Internet Mail Extensions)
Using tools or applications known as Mail Client or WebMail
Consisting from :
 MUA (Mail User Agent)
 MTA (Mail Transfer Agent)
 MDA (Mail Delivery Agent)
▫ Using TCP for the transport
▫ Protocol can be used are :
 Incoming (To receive the mail)
 POP3 (Post Office Protocol) operational on port 110
 IMAP4 (Internet Message Access Protocol) operational on port 143
 Outgouing (To send the email)
 SMTP (Simple Mail Transfer Protocol) operational on port 25
Introduction to Computer Networks
(OSI Upper Layer - Application)
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FTP (File Transfer Protocol)
Remote Access (TELNET, SSH, RHOST, etc)
SNMP (Simple Network Management Protocol)
File Sharing (SMB, NFS, etc)
Storage (NAS, SAN exclude for DAS)
AAA (RADIUS)
Authentication Server (LDAP, KERBEROS, NIS,
etc)
• NNTP, SIP, SMPP, DHCP, RTP, etc. (Can you
mention at least 25 others applications ???)
Introduction to Computer Networks
(OSI Upper Layer - Presentation)
• Nothing more to be discuss in here
• Just a bunch of file(s) format
(.txt, .html, .jpg, .avi, etc)
• Security and extension (MIME, TLS, SSL, etc)
• Merged with Application layer
Introduction to Computer Networks
(OSI Upper Layer - Session)
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iSNS (Internet Storage Name Service)
L2TP (Layer 2 Tunneling Protocol)
PPTP (Point-to-Point Tunneling Protocol)
NetBIOS (Network Basic Input Output System)
SAP (Session Announcement Protocol)
SOCKS (Internet Socket)
SMPP (Short Message Peer-to-Peer)
SCP (Session Control Protocol)
ASP, L2F, PAP, RPC, RTCP, SDP, etc
Introduction to Computer Networks
(OSI Upper Layer - Transport)
• TCP (Transmission Control Protocol)
▫ Reliable
▫ Offers a stream service (unit of information is a byte)
• UDP (User Datagram Protocol)
▫ Unreliable
▫ Offers a datagram service to the application (unit of
information is a messages)
•
•
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SCTP (Stream Control Transmission Protocol)
DCCP (Datagram Congestion Control Protocol)
SPX (Sequence Packet Exchange)
ATP, FCP, RDP, etc.
Introduction to Computer Networks
(OSI Lower Layer - Network)
• Provide logical addressing (Internet
Protocol / Internetworking Packet
eXchange)
• Re-route the packets (Routing Information
Protocol, Border Gateway Protocol, etc.)
• ICMP (Internet Control Message Protocol)
• IPSec (Internet Protocol Security)
• IGMP (Internet Group Multicast Protocol)
• etc.
Introduction to Computer Networks
(Internet Protocol Address)
• The principal communication protocol used for
relaying datagrams (packets) across an
internetworking
• Controlling the operation of the subnet
• Responsible for routing packets across network
boundaries, it is the primary protocol that
establishes the Internet
• Versions : IPv4 and IPv6
Computer Networks
(TCP/IP Terminology)
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Network Address / Net ID
Broadcast Address / Broadcast ID
Netmask / Bitmask / Subnet Mask
Host / Host ID / (Useable) IP Address
NAT (Network Address Translation)
NAPT (Network Address and Port Translation)
CIDR (Classless Inter-Domain Routing)
VLSM (Variable Length Subnet Masking)
Computer Networks
(TCP/IP Terminology Continues)
• Binary
base-2 number system, represents numeric values using two symbols,
0 and 1
Example : 11000000. 10101000. 01011000. 00001000
• Decimal
base ten number system has ten symbol for numeral system 0-9
Example : 192.168.88.8
• Hexadecimal
base 16 is a positional numeral system with a radix, or base of 16. It
uses sixteen distinct symbols, most often the symbols 0–9 to
represent values zero to nine, and A, B, C, D, E, F (or alternatively
a–f) to represent values ten to fifteen
Example : C0.A8.58.08
Computer Networks
(TCP/IP Terminology Continues)
• Anycast
a network addressing and routing
methodology in which datagrams
from a single sender are routed to
the topologically nearest node in a
group of potential receivers all
identified by the same destination
address.
• Broadcast
a method of transferring a message to
all recipients simultaneously.
Computer Networks
(TCP/IP Terminology Continues)
• Multicast
the delivery of a message or
information to a group of destination
computers simultaneously in a single
transmission from the source creating
copies automatically in other network
elements, such as routers, only when
the topology of the network requires it.
• Unicast
the sending of messages to a single
network destination identified by a
unique address
Introduction to Computer Networks
(IPv4 Compare To IPv6)
Introduction to Computer Networks
(IPv4 Compare To IPv6)
Introduction to Computer Networks
(IPv6)
Introduction to Computer Networks
(IPv6 - Features)
• Larger Address Space
• Aggregation-based address hierarchy
– Efficient backbone routing
• Efficient and Extensible IP datagram
• Stateless Address Autoconfiguration
• Security (IPsec mandatory)
• Mobility
Introduction to Computer Networks
(IPv6 - Deployment)
• Dual-stack backbone
Both version is used on the network and the
application will select the correct address based on
the type of IP traffic and particular requirements of
the communication.
• IPv6 over IPv4 tunneling
Encapsulating IPv6 traffic within IPv4 packets, to be
sent over an IPv4 backbone.
• NAT-PT (Network Address Translation and Protocol
Translation)
Deprecated due to numerous problems.
Introduction to Computer Networks
(IPv6 – Stateless Autoconfiguration)
• Assign IP Address automaticaly without need of
DHCP Server present
• Get the address from ICMPv6 and Neighbor
Discovery Protocol
• Use MAC Address as the basis of IPv6
addressing
• Using Modified EUI-64 (Convert EUI-48 from
MAC into EUI-64 for IPv6)
Introduction to Computer Networks
(IPv6 – Convert EUI-48 to EUI-64)
• Reference from IEEE
(RFC 2373)
• Conver 48-bit MAC into
64-bit MAC by inserting
FF FE in the middle of
MAC Address
• Invert the universal/local
(U/L) flag (bit 7) in the
OUI portion of the
address
Introduction to Computer Networks
(IPv6 – Modified EUI-64)
Introduction to Computer Networks
(IPv6 – Address Space)
IP
Prefix
Allocation
Reference
IP
Prefix
Allocation
Reference
0000::/8
Reserved by IETF
RFC 4291
A000::/3
Reserved by IETF
RFC 4291
0100::/8
Reserved by IETF
RFC 4291
C000::/3
Reserved by IETF
RFC 4291
0200::/7
Reserved by IETF
RFC 4048
E000::/4
Reserved by IETF
RFC 4291
0400::/6
Reserved by IETF
RFC 4291
F000::/5
Reserved by IETF
RFC 4291
0800::/5
Reserved by IETF
RFC 4291
F800::/6
Reserved by IETF
RFC 4291
1000::/4
Reserved by IETF
RFC 4291
FC00::/7
Unique Local Unicast
RFC 4193
2000::/3
Global Unicast
RFC 4291
FE00::/9
Reserved by IETF
RFC 4291
4000::/3
Reserved by IETF
RFC 4291
FE80::/10
Link Local Unicast
RFC 4291
6000::/3
Reserved by IETF
RFC 4291
FEC0::/10
Reserved by IETF
RFC 3879
8000::/3
Reserved by IETF
RFC 4291
FF00::/8
Multicast
RFC 4291
Introduction to Computer Networks
(IPv6 – Allocation)
• 2000::/3 — Only one eighth of the total address space is currently allocated
for use on the Internet.
• ::/128 — The address with all zero bits is called the unspecified address
(corresponding to 0.0.0.0/32 in IPv4)
• ::/0 — The default unicast route (default route) address (corresponding
to 0.0.0.0/0 in IPv4)
• ::1/128 — The loopback address is a unicast localhost address. If an
application in a host sends packets to this address, the IPv6 stack will loop
these packets back on the same virtual interface (corresponding to
127.0.0.0/8 in IPv4)
• fe80::/10 — Addresses in the link-local prefix are only valid and unique
on a single link. Within this prefix only one subnet is allocated (54 zero bits),
yielding an effective format of fe80::/64. The least significant 64 bits are
usually chosen as the interface hardware address constructed in modified
EUI-64 format. A link-local address is required on every IPv6-enabled
interface, in other words, applications may rely on the existence of a linklocal address even when there is no IPv6 routing. These addresses are
comparable to the auto-configuration addresses 169.254.0.0/16 of IPv4.
Introduction to Computer Networks
(IPv6 – Allocation Continues)
• fc00::/7 — Unique local addresses (ULAs) are intended for local
communication. They are routable only within a set of cooperating
sites (analogous to the private address ranges 10.0.0.0/8,
172.16.0.0/12, and 192.168.0.0/16 of IPv4)
• Transition from IPv4
▫ ::ffff:0:0/96 — This prefix designated an IPv4-mapped IPv6 address.
With a few exceptions, this address type allows the transparent use of the
Transport Layer protocols over IPv4 through the IPv6 networking
application programming interface
▫ ::ffff:0:0:0/96 — A prefix used for IPv4-translated addresses which are
used by the Stateless IP/ICMP Translation (SIIT) protocol
▫ 64:ff9b::/96 — The "Well-Known" Prefix. Addresses with this prefix are
used for automatic IPv4/IPv6 translation
▫ 2002::/16 — This prefix is used for 6to4 addressing. Here, an address
from the IPv4 network 192.88.99.0/24 is also used
Introduction to Computer Networks
(IPv6 – Allocation Continues)
• Special-purpose addresses
▫ 2001::/32 — Used for Teredo tunneling (which also falls
into the category of IPv6 transition mechanisms)
▫ 2001:2::/48 — Assigned to the Benchmarking Methodology
Working Group (BMWG) for benchmarking IPv6
(corresponding to 198.18.0.0/15 for benchmarking IPv4)
▫ 2001:10::/28 — ORCHID (Overlay Routable Cryptographic
Hash Identifiers)
• 2001:db8::/32 — This prefix is used in documentation.
The addresses should be used anywhere an example IPv6
address is given or model networking scenarios are
described (corresponding to 192.0.2.0/24,
198.51.100.0/24, and 203.0.113.0/24 in IPv4)
Introduction to Computer Networks
(IPv4)
• Classful addressing
• Have limited number of IP Address
• Have techniques to reduce addressing shortage
using :
▫ Subnetting
▫ CIDR
▫ NAT
Introduction to Computer Networks
(IPv4)
Introduction to Computer Networks
(IP Address Classification)
• Classification by class :
▫ Class A
 Range 0 – 127
 Publicly available
▫ Class B
 Range 128 – 191
 Publicly available
▫ Class C
 Range 192 – 223
 Publicly available
▫ Class D
 Range 224 – 239
 Reserved for
Multicasting
▫ Class E
 Range 240 – 255
 Experimental (used
for research)
Introduction to Computer Networks
(IP Address Classification Continues)
• Classification by usages rules :
▫ Private
 Allocated for individual, research or NAT
 Can be used freely but not recognized in the internet
 Allocated IP’s or network’s are :





10.0.0.0/8 (Class A)
127.0.0.0/8 ( Class A and known as local loopback)
169.254.0.0/16 (Class B and known as NetZeroConf)
172.16.0.0/12 (Class B)
192.168.0.0/16 (Class C)
▫ Public
 Allocated for publicly usage address on internet
 “Can not” be used freely and recognized in the internet
 Usage rugulation by IANA (AfriNIC, APNIC, ARIN, LACNIC,
RIPE and NCC)
Introduction to Computer Networks
(IP Address Classification)
• Netmask or network class :
▫ Class A
 Netmask : 255.0.0.0 (/8)
 Number of host 224 - 2 (16.777.214)
▫ Class B
 Netmask : 255.255.0.0 (/16)
 Number of host 216 – 2 (65.534)
▫ Class C
 Netmask : 255.255.255.0 (/24)
 Number of host 28 – 2 (254)
▫ Class D
 Netmask : 255.255.255.255 (/32)
 Number of host is 1
 Known as point-to-point
Computer Networks
(IPv4 Subnetting and Supernetting)
• Subnetting
▫
▫
▫
▫
▫
Devide one large network into a few smaller network(s)
Reducing broadcast domain
Optimizing network performance
Easy to manage
Effective for large goegraphical scale network
• Supernetting
▫ Contain a few smaller network (subnets)
▫ Known as Classless Network (CIDR -> developed to provide
more granularity than legacy classful addressing; CIDR notation
is expressed as /XX)
▫ Used for large scale of network
▫ Using VLSM (an arbitrary length between 0 and 32 bits) for
deviding the addresses
Computer Networks
(Illustration Subnet and Supernet)
Computer Networks
(Subnetting)
192.168.0.0 – 192.168.0.255
•Subnet mask : 255.255.255.0
•Bitmask : /24
•Binary : 11111111.11111111.11111111.00000000
•Network ID : 192.168.0.0
•Broadcast Address : 192.168.0.255
•Number of IP (2n) : 28 = 256
•Number of host (2n - 2) : 28 – 2 = 254
Computer Networks
(Subnet)
Subnet Mask
Bitmask
Number of IP
255.255.255.255
/32
1 (P2P)
255.255.255.254
/31
2 (Invalid)
255.255.255.252
/30
4
255.255.255.248
/29
8
255.255.255.240
/28
16
255.255.255.224
/27
32
255.255.255.192
/26
64
255.255.255.128
/25
128
255.255.255.0
/24
256
Computer Networks
(Subnet – VLSM Table)
Computer Networks
(Subnetting - Exercise)
• Specify for the netmask, network address,
broadcast address, host, and number of IP and
useable IP, block of subnet for the following
address :
▫
▫
▫
▫
▫
192.168.23.37/28
172.16.123.109/19
192.168.23.5/26
10.30.2.1/22
183.91.86.92/26
Computer Networks
(Network Address Translation)
• NAT is a way to conserve IP addresses
• Hide a number of hosts behind a single IP
address
• Needed configuration for host :
▫
▫
▫
▫
IP Address
Subnet Mask / Netmask
Network Address / Broadcast Address
Gateway Address
Computer Networks
(NAT - Translation Modes)
• Dynamic Translation (IP Masquerading)
large number of internal users share a single external address
• Static Translation
a block external addresses are translated to a same size block of
internal addresses
• Load Balancing Translation
a single incoming IP address is distributed across a number of
internal servers
• Network Redundancy Translation
multiple internet connections are attached to a NAT Firewall that it
chooses and uses based on bandwidth, congestion and availability.
Computer Networks
(NAT - Topology)
Computer Networks
(Terminology)
Computer Networks
(Routing)
How do packets get from A to B in the Internet?
Internet
A
B
Routing is (refering to) a process of selecting
paths in a network along which to send network
traffic.
Computer Networks
(Routing – Packet Route Illustration)
Computer Networks
(Routing Continues)
• Static Routing
It is the type of routing characterized by the absence of
communication between routers regarding the current
topology of the network. This is achieved by manually
adding routes to the routing table.
• Dynamic Routing (aka. Adaptive Routing)
The capability of a system, through which routes are
characterized by their destination, to alter the path that the
route takes through the system in response to a change in
conditions. The adaptation is intended to allow as many
routes as possible to remain valid (that is, have destinations
that can be reached) in response to the change.
Computer Networks
(Routing Protocols)
• A protocol that specifies how routers communicate with
each other, disseminating information that enables them
to select routes between any two nodes on a computer
network, the choice of the route being done by routing
algorithms.
• 3 major classes in widespread use on IP networks are :
▫ Interior gateway routing via link-state routing
protocols, such as OSPF and IS-IS
▫ Interior gateway routing via path vector or distance
vector protocols, such as RIP, IGRP and EIGRP
▫ Exterior gateway routing. BGP v4 is the routing protocol
used by the public Internet.
Computer Networks
(Routing Protocols Illustration)
Exterior routing
Interior routing
Customer routing
Computer Networks
(Link-state Routing Protocol)
• The basic concept is that every node constructs a map of
the connectivity to the network, in the form of a graph,
showing which nodes are connected to which other
nodes. Each node then independently calculates the next
best logical path from it to every possible destination in
the network. The collection of best paths will then form
the node's routing table.
• The algorithm :
▫ Each link, the connected nodes and the metric is flooded to
all routers
▫ Each link up/down status change is incrementally flooded
▫ Each router re-computes the routing table in parallel using
the common link state database
Computer Networks
(Distance Vector Routing Protocol)
• Use the Bellman-Ford algorithm, Ford–Fulkerson
algorithm, or DUAL FSM to calculate paths.
• Requires that a router informs its neighbors of
topology changes periodically.
• The algorithm :
▫ Each node sends its routing table (destination distance)
to all neighbors every 30 seconds
▫ Lower distances are updated with the neighbor as next
hop
▫ cannot scale
▫ cannot resolve routing loops quickly
Introduction to Computer Networks
(OSI Lower Layer – Data Link)
• The data link layer has two sublayers :
▫ LLC (Logical Link Control)
The uppermost sublayer, LLC, multiplexes protocols running atop the data
link layer, and optionally provides flow control, acknowledgment, and error
notification. The LLC provides addressing and control of the data link. It
specifies which mechanisms are to be used for addressing stations over the
transmission medium and for controlling the data exchanged between the
originator and recipient machines.
▫ MAC (Media Access Control)
MAC may refer to the sublayer that determines who is allowed to access the
media at any one time (usually CSMA/CD). Other times it refers to a frame
structure with MAC addresses inside.
• Protocols
ATM, SDLC, HDLC, ARP, MPLS, LAPD, CSLIP, SLIP, GFP, PLIP, IEEE
802.3, Frame Relay, ITU-T G.hn DLL, PPP, X.25, Network switch, etc.
Introduction to Computer Networks
(OSI Lower Layer – Data Link Services)
•
Encapsulation of network layer data packets into frames
•
Frame synchronization
•
LLC :
▫
▫
•
Error control (automatic repeat request,ARQ), in addition to ARQ provided by some transport-layer protocols,
to forward error correction (FEC) techniques provided on the physical layer, and to error-detection and
packet canceling provided at all layers, including the network layer. Data-link-layer error control (i.e.
retransmission of erroneous packets) is provided in wireless networks and V.42 telephone network modems,
but not in LAN protocols such as Ethernet, since bit errors are so uncommon in short wires. In that case, only
error detection and canceling of erroneous packets are provided.
Flow control, in addition to the one provided on the transport layer. Data-link-layer error control is not used
in LAN protocols such as Ethernet, but in modems and wireless networks.
MAC :
▫
▫
▫
▫
▫
▫
▫
Multiple access protocols for channel-access control, for example CSMA/CD protocols for collision detection
and retransmission in Ethernet bus networks and hub networks, or the CSMA/CA protocol for collision
avoidance in wireless networks.
Physical addressing (MAC addressing)
LAN switching (packet switching) including MAC filtering and spanning tree protocol
Data packet queueing or scheduling
Store-and-forward switching or cut-through switching
Quality of Service (QoS) control
Virtual LANs (VLAN)
Introduction to Computer Networks
(OSI Lower Layer - Physical)
• Interfaces with the data link layer's medium
access control (MAC) sublayer.
• Performs character encoding, transmission,
reception and decoding.
• Performs mandatory isolation functions.
• Protocols :
Modems, USB, Bluetooth, DSL, ISDN, IEEE 802.11,
Ethernet, ITU, etc.
Introduction to Computer Networks
(OSI Lower Layer – Physical Services)
• Bit-by-bit or symbol-by-symbol delivery
• Providing a standardized interface to physical transmission media, including
▫
▫
▫
▫
•
•
•
•
•
•
•
•
Mechanical specification of electrical connectors and cables, for example maximum cable
length
Electrical specification of transmission line signal level and impedance
Radio interface, including electromagnetic spectrum frequency allocation and specification of
signal strength, analog bandwidth, etc.
Specifications for IR over optical fiber or a wireless IR communication link
Modulation
Line coding
Bit synchronization in synchronous serial communication
Start-stop signalling and flow control in asynchronous serial communication
Circuit switching
Multiplexing (Establishment and termination of circuit switched connections)
Carrier sense and collision detection utilized by some level 2 multiple access protocols
Equalization filtering, training sequences, pulse shaping and other signal processing of
physical signals
• Forward error correction
• Bit-interleaving and other channel coding
Introduction to Computer Networks
(OSI Lower Layer – Physical Concern With)
• Bit rate
• Point-to-point, multipoint or point-tomultipoint line configuration
• Physical network topology, for example bus, ring,
mesh or star network
• Serial or parallel communication
• Simplex, half duplex or full duplex transmission
mode
• Autonegotiation
Introduction to Computer Networks
(Twisted Pair Cables)
• Twisted pair cabling is a type of wiring in which two conductors (the forward and return
conductors of a single circuit) are twisted together for the purposes of canceling out
electromagnetic interference (EMI) from external sources invented by Alexander Graham
Bell
• For network (ethernet) usage there are 2 kind of cables we use, which is :
▫
▫
UTP (Unshielded Twisted Pair)
STP (Shielded Twisted Pair)
• The cable category for ethernet cables usually we use : Cat3, Cat4, Cat5, Cat5e, Cat6, Cat6a,
Cat 7a
• There are 8 core in one cable with a different unique color for each core (brown, white
brown, green, white green, blue, white blue, orange, white orange)
• The connector we use called RJ45
• We need a crimper to create a network cable(s)
• Network cables order commonly use are known as straight thru, crossover and rollover.
Introduction to Computer Networks
(Network Cable Order)
• Straight thru and crossover cables use
for data communication
• Rollover is use for console cable
commonly use to configure cisco
devices.
• The order for each cable are :
Introduction to Computer Networks
(Wireless Networking Terminology)
• Wi-Fi is a mechanism for wirelessly connecting
electronic devices. It is a trademark of the Wi-Fi
Alliance and the brand name for products using
the IEEE 802.11 family of standards.
Introduction to Computer Networks
(Wireless Networking Terminology)
• Fresnel Zone is one of a (theoretically infinite)
number of concentric ellipsoids which define
volumes in the radiation pattern of a (usually)
circular aperture. Fresnel zones result from
diffraction by the circular aperture.
Introduction to Computer Networks
(Wireless Networking)
• A wireless LAN or WLAN is a wireless local area
network that uses radio waves as its carrier.
• The last link with the users is wireless, to give a
network connection to all users in a building or
campus.
• The backbone network usually uses cables.
• There is a need of an access point that bridges
wireless LAN traffic into the wired LAN.
• The access point (AP) can also act as a repeater for
wireless nodes, effectively doubling the maximum
possible distance between nodes.
Introduction to Computer Networks
(WLAN Common Topology)
Introduction to Computer Networks
(WLAN Standard – IEEE 802.11)
• A family of wireless LAN (WLAN) specifications
developed by a working group at the Institute of
Electrical and Electronic Engineers (IEEE)
• Defines standard for WLANs using the following
four technologies
▫
▫
▫
▫
Frequency Hopping Spread Spectrum (FHSS)
Direct Sequence Spread Spectrum (DSSS)
Infrared (IR)
Orthogonal Frequency Division Multiplexing (OFDM)
• Versions : 802.11a, 802.11b, 802.11g, 802.11e,
802.11f, 802.11i
Introduction to Computer Networks
(WLAN Standard 802.11a and 802.11b)
Introduction to Computer Networks
(WLAN Standard – IEEE 802.11)
Introduction to Computer Networks
(WLAN Frequency Bands ISM)
• Industrial, Scientific, and Medical (ISM) bands
• Unlicensed, 22 MHz channel bandwidth
Audio
AM Broadcast
Infrared wireless LAN
Television
Cellular (840MHz)
NPCS (1.9GHz)
ExtremelyVery Low MediumHigh VeryUltra Super InfraredVisible Ultra- X-Rays
Low
Low
High High High
Light violet
902 - 928 MHz
26 MHz
2.4 - 2.4835
GHz
83.5 MHz
(IEEE 802.11)
5 GHz
(IEEE 802.11)
HyperLAN
HyperLAN2
Introduction to Computer Networks
(WLAN Operation Modes)
• Infrastructure mode
▫ Associates with an access point
▫ All communication goes through the access point
▫ Used for wireless access at a company or campus
• Peer-to-Peer (Ad Hoc) Mode
▫ If two nodes are within range of each other they
can communicate directly with no access point
▫ A few users in a room could quickly exchange files
with no access point required