Internet Architecture and Protocols
Instructor: Engr. Musfara Farooqui
University of Education Township Lahore
Lecture # 01
Introduction and Basic Concepts
University of Education Township Lahore 2
Course Objectives
To understand the design philosophy of the Internet and its basic architectural components.
To provide in-depth knowledge of major Internet technologies. To understand the components of Internet service provider and
its role in Internet architecture. To strengthen the concepts of TCP/IP Protocol Suite. To provide comprehensive knowledge and implementation of
routing protocols. To realize the need of Quality of Service based
communication and to understand various QoS techniques. To introduce the basic concepts of real time communications.
University of Education Township Lahore 3
Lecture - Objectives Introduction What is the Internet?
Nuts and Bolts View Service Oriented View
Network Edge Network Core
Circuit Switched Networks Packet Switched Networks
Datagram Virtual Circuits
Network Access and Physical Media
University of Education Township Lahore 4
Lecture 1: What is the Internet? A Nuts and Bolts Description
End systems Communication Links, Bandwidth Routers, Packet ISPs Protocols, TCP/IP Internet Standards, RFCs
A service Description Distributed Applications Connection Oriented Reliable Service Connectionless Unreliable Service
What is a protocol?University of Education Township Lahore 5
Describing the Internet
Two ways to describe the Internet Nuts and Bolts View
The basic hardware and software components Service Oriented View
The networking infrastructure that provides services to distributed applications
University of Education Township Lahore 6
7
Nuts and Bolts View of the Internet
Hosts or End Systems Computing Devices such as PCs, PDAs (Personal Digital
Assistants), TVs, servers, mobile computers, automobiles, etc. connected to the Internet are called hosts or end systems
University of Education Township Lahore
8
Nuts and Bolts View of the Internet
Communication links End systems are connected together by communication
links. Communication links are made up of different types of
media, including twisted pair, coaxial cable, fiber optics, and radio spectrum.
Bandwidth Different links can transmit data at different rates. The link transmission rate is often called the bandwidth
(i.e., the width of the band) of the link which is measured in bits per second (bps).
University of Education Township Lahore
9
Nuts and Bolts View of the Internet
Routers End systems are not directly connected to each other via a
single communication link. They are indirectly connected to each through intermediate
switching devices known as routers. A router receives chunk of information from one of its
incoming communication link and forwards it to one of its outgoing communication link.
University of Education Township Lahore
10
Nuts and Bolts View of the Internet
Packets The chunk of information is called packet.
Route or Path The path that the packet takes from the sending end system,
through a series of communication links and routers, to the receiving end system is known as a route or path.
Packet switching The Internet uses a technique known as packet switching
that allows multiple communicating end systems to share a path, or parts of path at the same time.
University of Education Township Lahore
11
Nuts and Bolts View of the Internet
Internet Service Providers (ISPs) End systems access the Internet through the Internet
Service Providers (ISPs). The different ISPs provide a variety of different types of
network access to the end systems, including 56Kbps dial up modem access, cable modem or DSL, high speed LAN access, and wireless access.
University of Education Township Lahore
12
Nuts and Bolts View of the Internet
Protocols End systems, routers, and other pieces of the Internet, run
protocols that control the sending and receiving of information within the Internet.
TCP (Transmission Control Protocol) and IP (Internet protocol) are two of the most important protocols in the Internet.
The Internet’s principal protocols are collectively known as TCP/IP Protocol Suite.
University of Education Township Lahore
13
Nuts and Bolts View of the Internet
Intranets There are many private networks, such as many corporate
and government networks, whose hosts cannot exchange messages with hosts outside of the private network (unless the messages pass through so-called firewalls, which restrict the flow of messages to and from the network).
These private networks are often referred to as intranets, as they use the same types of hosts, routers, links, and protocols as the public Internet.
University of Education Township Lahore
14
Nuts and Bolts View of the Internet
Internet Standards At the technical and development level, the Internet is
made possible through creation, testing, and implementation of Internet Standards.
These standards are developed by Internet Engineering Task Force (IETF).
RFCs The IETF standards documents are called RFCs (Request
for comments). RFCs started out as general request for comments (hence
the name) to resolve architecture problems of the Internet. They define protocols such as TCP, IP, HTTP, SMTP
University of Education Township Lahore
15
Some Pieces of the Internet
companynetwork
local ISP
regional ISP
router workstationserver
mobile
University of Education Township Lahore
16
Lecture 2: Service Oriented View of the Internet
Distributed Applications The Internet allows distributed applications running on its
end systems to exchange data with each other. These applications include remote login, electronic mail,
web surfing, instant messaging, audio and video streaming, Internet telephony, distributed games, peer-to-peer (P2P) file sharing, and much more.
Communication Services Connection oriented reliable service Connectionless unreliable service
University of Education Township Lahore
17
Service Oriented View of the Internet
Internet Provides two services to its distributed applications: Connection Oriented Reliable Service• It guarantees that data transmitted from a sender to a
receiver will eventually be delivered to the receiver in order and in its entirety.
Connectionless Unreliable Service• It does not make any guarantees about eventual
delivery. –Note: Distributed applications makes use of one or
the other (but not both) of these two services. Thus, Internet is an infrastructure in which new applications
are being constantly invented and deployed.
University of Education Township Lahore
18
Connection Oriented Service
Reliable Data Transfer• Using acknowledgements & retransmissions
Flow Control• sender won’t overwhelm receiver
Congestion Control• senders “slow down sending rate” when network
congestedTCP• Applications using TCP are:–HTTP (Web), FTP (file transfer), Telnet (remote
login), SMTP (email)
University of Education Township Lahore
19
Connectionless Service
Unreliable Data Transfer• no flow control• no congestion control
Fast• connectionless
UDP• Applications using UDP are:–multimedia, videoconferencing, DNS, Internet
telephony
University of Education Township Lahore
20
TCP vs. UDP
TCP Reliable Protocol Connection Oriented Performs three ways
handshake Provision for error detection
and retransmission Most applications use TCP
for reliable and guaranteed transmission
UDP Unreliable Protocol Connectionless Much faster than TCP No acknowledgement waits No proper sequencing of
data units Suitable for applications
where speed matters more than reliability
University of Education Township Lahore
21
What is a Protocol?
A Human Analogy “Assalam u Alaikum” “What’s the time?”• In human protocols specific messages are sent, and
specific actions are taken in response to messages received, or other events.
Network protocols All activity in the Internet that involves two or more
communicating remote entities is governed by a protocol.
University of Education Township Lahore
22
What is a protocol?
• A human protocol and a computer network protocol
Hi
Hi
Got thetime?
2:00
TCP connection req
TCP connectionresponse
<file>
time
University of Education Township Lahore
23
What is a Protocol?…
A Protocol is a set of rules and regulations that governs the exchange of information between two or more entities.
It takes two (or more) communicating entities running the same protocol in order to accomplish a task.
All communication activity in Internet governed by protocols.
A protocol defines the format, order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.
University of Education Township Lahore
24
The Network Core Mesh of interconnected Routers The fundamental question: how
is data transferred through network? circuit switching• dedicated circuit per call:
telephone net packet-switching• data sent through net in
discrete “chunks”
University of Education Township Lahore
25
Network Core
Long distance transmission is typically done over a network of switched nodes
Nodes not concerned with content of data End devices are stations
Computer, terminal, phone, etc. A collection of nodes and connections is a communications
network Data routed by being switched from node to node Node to node links usually multiplexed
University of Education Township Lahore
26
Network Core: Circuit Switching
End-to-end resources reserved for “call”
link bandwidth, switch capacity dedicated resources: no sharing circuit-like (guaranteed) performance call setup required
University of Education Township Lahore
27
Network Core – Circuit Switching
Switched circuits allow data connections that can be initiated when needed and terminated when communication is complete
Circuit switched network - a network in which a dedicated circuit is established between sender and receiver and all data passes over this circuit.
The telephone system is a common example.
The connection is dedicated until one party or another terminates the connection.
University of Education Township Lahore
28
Circuit Switching
University of Education Township Lahore
29
Network Core – Circuit Switching
Dedicated communication path between two stations Three phases (Establish, Transfer, Disconnect) Inefficient (for data traffic)
Channel capacity dedicated for duration of connection Much of the time a data connection is idle If no data, capacity wasted
Set up (connection) takes time Once connected, transfer is transparent Circuit switching designed for voice Constant Data rate (Both ends must operate at the same
rate)
University of Education Township Lahore
30
Network Core - Circuit Switching
Multiplexing in Circuit Switched Networks Multiplexing is a technique, in which a single transmission
medium is being shared among multiple users. Types of Multiplexing
Frequency Division Multiplexing FDM Time Division Multiplexing TDM
University of Education Township Lahore
31
Circuit Switching: FDM and TDM
University of Education Township Lahore
32University of Education Township Lahore
Output Stream generated by a synchronous time division multiplexer
33
Multiplexer transmission stream with one input device transmitting data.
University of Education Township Lahore
34
Two stations out of four transmitting via a statistical multiplexer
University of Education Township Lahore
35
Network Core: Packet Switching
Packet switched network
A network in which data is transmitted in the form of packets
Multiple users share network resources No dedicated bandwidth is allocated No resources are reserved, resources used as needed Each packet uses full link bandwidth Good for bursty traffic, simpler, no call setup Packets queued and transmitted as fast as possible Packets are accepted even when network is busy, which
causes the delivery to slow down
University of Education Township Lahore
36
Packet Switching: Statistical Multiplexing
• Sequence of A & B packets does not have fixed pattern statistical multiplexing
A
B
C10 Mb/sEthernet
1.5 Mb/s
D E
statistical multiplexing
queue of packetswaiting for output
link
University of Education Township Lahore
37
Network Core: Packet Switching
The goal of packet switching is to move packets through routers from source to destination
Packets sent one at a time to the network Two approaches are used:
Datagram Approach Virtual Circuits Approach
University of Education Township Lahore
38
Packets Forwarding
Two broad classes of packet switched networks are: Datagram Networks• Any network that forwards the packet according to the
destination address is called a datagram network• The routers in the Internet forwards packets according
to host destination addresses; hence the Internet is a datagram network.
Virtual Circuit Networks• Any network that forwards the packet according to the
virtual circuit identifier is called a virtual circuit network• Examples are X.25, Frame Relay, ATM technologies
University of Education Township Lahore
39
Packet Switching - Datagram Datagram Approach:
Each packet is treated independently No reference to packets that have gone before Each node chooses next node on path using destination
address Packets with same destination address may not follow
same route Packets may arrive out of sequence, may be lost It is up to receiver to re-order packets and recover from lost
packets No Call setup For an exchange of a few packets, datagram quicker Analogy: driving, asking directions
University of Education Township Lahore
40
Packet Switching - Datagram
The Internet is a Datagram network
Datagram network is not either connection-oriented or connectionless.
Internet provides both connection-oriented (TCP) and connectionless services (UDP) to applications.
University of Education Township Lahore
41
Datagram Networks
A datagram network is not either a connectionless or a connection oriented network.
It can provide connectionless service to some of its applications and connection-oriented service to other applications.
Example The Internet, which is a datagram network, provides both
connectionless (UDP) and connection oriented (TCP) services to its applications
Networks with Virtual Circuits are, however, always connection-oriented.
University of Education Township Lahore
42
Packet Switching - Datagram
University of Education Township Lahore
43
Packet Switching: Datagram Approach
University of Education Township Lahore
44
Packet Switching – Virtual Circuits
Virtual Circuit Approach: Virtual circuit packet switched network create a logical
path through the subnet Call request and call accept packets establish a virtual
connection Virtual route remains fixed through the call. All packets from one connection follow this path. Each packet contains a virtual circuit identifier instead of
destination address to determines the next hop Not a dedicated path No routing decisions required for each packet
University of Education Township Lahore
45
Switching Technique – Virtual Circuit Preplanned route established before packets sent All packets follow same route Similar to circuit in circuit-switching network
Hence virtual circuit Each packet has virtual circuit identifier
Nodes on route know where to direct packets No routing decisions
Not dedicated path, as in circuit switching Packet still buffered at node and queued for output Routing decision made on before that virtual circuit
Network may provide services related to virtual circuit Sequencing and error control
Packets should transit more rapidly If node fails, all virtual circuits through node lost
University of Education Township Lahore
46
Packet Switching: VC Approach
University of Education Township Lahore
47
Circuit Switching vs. Virtual Circuits
CS Path
A dedicated path is established between two devices for the duration of session.
Reserved Resources The link (multiplexed / not
multiplexed) that makes the path are dedicated, and cannot be used by other connections
constant data rates
VC
Route No dedicated path is
established. Only a route is defined. Each switch creates an entry in its routing table for the duration of virtual circuit
Shared Links The link that makes a route
can be shard by other connections
University of Education Township Lahore
48
Network Taxonomy
University of Education Township Lahore
49
Network Access Network Access:
The physical link that connects an end system to its Edge Router, which is the first router on a path from the end system to any other distant end system.
Classification of Network Access: Residential Access
• Connecting a home end system to an edge router• Dial-up modems, DSL, HFC system
Company Access• Switched Ethernet LANs
Mobile Access• Wireless LAN (802.11b)• Wide Area Wireless Access Networks (GPRS, 3G, WAP)
• Note: these categories are not hard and fast
University of Education Township Lahore
Physical Media
Twisted Pair Cable– UTP Cat 5
Coaxial Cable– Baseband and Broadband Cable
Fiber Optics– Multimode and single mode
Terrestrial Radio Channels– Local Area Radio Channels (Wireless LANs)– Wide Area Radio Channels (WAP, I-mode, 3G)
Satellite Radio Channels– Geostationary Satellites (36000 km)– Low Altitude Satellites
University of Education Township Lahore 50
References Computer Networking; A Top Down Approach Featuring the
Internet– 3rd Edition: Chapter 1, Jim Kurose and Keith Ross
Data and Computer Communications– 7th Edition, William Stallings
Data Communications and Networking– 3rd Edition, Behrouz A. Forouzan
Data Communications and Computer Networks– Curt M. White
Computer Networks– 4th Edition, by Andrew S. Tanenbaum
Note: Slides are adapted from the companion web sites of referenced books.
•
University of Education Township Lahore 51