Transcript Session_2__FoundationChapter1PDx

Foundations
 Connectivity
 Cost-effective resource sharing
 Support for common services
 Layering/ Encapsulation
 OSI model; TCP/IP model
Requirements from
1
[1.2.1; P&D]
Point to Point Link
Multiple-access Link
Point to Point Link
Multiple-access Link
Links connect computers through physical medium
Wide variety of transmission links:
1)
2)
3)
4)
5)
Magnetic media (transported)
Copper twisted pair
Coaxial cable
Optical fiber
Wireless media
For reference, see [Chapter 2, Tanen]
Direct Link
Multiple-access Link
Switches/ Routers
Hosts, PCs
A network can be defined
recursively as two or more
nodes connected by a
physical link, by two or
more networks connected
by one or more nodes.
Net 2
Net 1
Net 3
1. Addressing
2. Routing messages
3. Support for unicast/ multicast/ broadcast
2
[1.2.2; P&D]
Source
(Caller)
Call establishment
Data transfer
Connection
close
(before data transfer)
Destination
(Callee)
 Message is broken down in packets
 Each packet is addressed is separately routed
 Packet switches use
paradigm
 More
(which is
 Service like a
(snail-mail) service
unlike the telephone-like service of circuit
switching
)
Source
1
2
Message
1 2
Packets
Destination
Source
1
2
Message
1 2
Packets
Destination
Source
1
2
Message
1 2
Packets
Destination
23
3
[1.2.3; P&D]
 Typically due to power surge, lightning,
interference, etc.
 Typically low: 1 in 106/107 for Cu Cable;
1 in 1012/1014 for Optical fiber
 Uncorrectable bit error;
 Lack of buffer space; buggy software
 Difficult to distinguish between
packets
 Buggy software
 Power failure
 Misconfiguration of a network device
Architecture of
FTP
HTTP
DNS
TFTP
…
…
TCP
UDP
Applications
UDP
TCP
Narrow Waist
IP
Data Link
NET1
NET2
…
NETn
Physical
The Hourglass Model
FTP
HTTP
TFTP
TCP
UDP
Network
IP
TCP/UDP
IP
NET1
NET2
…
NETn
Type
Field
Protocol Port No.
Field
Study how internet principles
(encapsulation/ layering) work
through a practical example
Accessing
www.seecs.edu.pk
on the Internet
through a browser
[P&D]