Lecture 28: Internet Protocols

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Lecture 28: Internet Protocols

15-110 Principles of Computing, Spring 2016

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Reminder: Exam 2

• Exam 2 will take place next Monday, on April 4.

• Further details will be provided in next class.

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This unit

Internet fundamentals

• Computer networks

• Important ideas:

• Abstraction and protocols

• Connection-oriented vs connectionless

• Current issues: network neutrality

Internet protocols

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This unit

Internet fundamentals

• Computer networks

• Important ideas:

• Abstraction and protocols

• Connection-oriented vs connectionless

• Current issues: network neutrality

Internet protocols

• IP, TCP, UDP, domain names, world wide web

Internet security

• encryption

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This unit

Internet fundamentals

Internet protocols

• Internet networking architecture (TCP/IP model)

• Layer-specific protocols of TCP/IP model:

• Network/Internet: IP

• Transport: TCP and UDP

• Application:

• Client-server: HTTP, DNS

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Recap

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Recap: abstraction for networking software

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physical medium layer 1

computer 1

[A. S. Tanenbaum. Computer Networks. 5th Edition.]

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Recap: abstraction for networking software

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computer 1

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Recap: abstraction for networking software

computer 1 layer 2 layer 3 layer 4 computer 2 layer 2 layer 3 layer 4 interface interface interface layer 3 carries out a conversation

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Recap: abstraction for networking software

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computer 1

layer 2 layer 3 layer 4 layer 1 computer 2 layer 2 layer 3 layer 4 interface interface interface layer 3 carries out a conversation

with peer layer 3

protocol protocol

protocol

the rules are governed by implemented

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Recap: abstraction for networking software

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computer 1

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Recap: abstraction for networking software

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computer 1

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Recap: service offered by layer: two kinds

Connection-oriented (circuit switching)

• Connection is established, used, and then released.

• Like a tube where sender pushes objects in at one end and receiver takes them out.

• Real-world example: telephone system

Connectionless (packet switching)

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Internet networking architecture:

TCP/IP model

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A model networking architecture

Application Transport

Network

sending of finite-length messages between routing of messages within entire network, congestion handling (e.g., IP)

source-to-destination communication (e.g., TCP, UDP)

programs that make use of internet (e.g., HTTP, SMTP, DNS)

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A model networking architecture

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Network Link

Physical transmission of bits as signals across _{different physical media}

sending of finite-length messages between directly connected computers

routing of messages within entire network, congestion handling (e.g., IP)

Tasks:

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A model networking architecture

Network

sending of finite-length messages between routing of messages within entire network, congestion handling (e.g., IP)

Tasks:

textbook networking architecture

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Other networking architectures

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Network Data Link Physical Transport Session Presentation Application ISO OSI

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Other networking architectures

Network Transport Session Presentation Application ISO OSI

(Open Systems Interconnection)

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Other networking architectures

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model developed by ISO to serve as reference for networking architectures

separate standards for layer-specific protocols available, but not used in

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Other networking architectures

model developed by ISO to serve as reference for networking architectures

separate standards for layer-specific protocols available, but not used in

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Other networking architectures

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Other networking architectures

Internet Transport Application

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Other networking architectures

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Internet Link Transport Application TCP/IP model architecture of the

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Other networking architectures

TCP/IP model

architecture of the

internet, named after its two primary protocols

protocols were developed first, then model as a description of

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Other networking architectures

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Internet Link

Transport Application

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Other networking architectures

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Other networking architectures

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Internet Link Transport Application TCP/IP model Network Link Physical Transport Application “textbook” architecture

OSI model without

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Other networking architectures

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TCP/IP model

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Internet Link

Transport Application

TCP/IP model Protocols:

HTTP, DNS, SMTP, RTP, POP, IMAP, FTP, and many more (see Wikipedia)

TCP, UDP, and many more (see Wikipedia) IP, ICP, and many more (see Wikipedia)

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TCP/IP model

TCP/IP model Protocols:

HTTP, DNS, SMTP, RTP, POP, IMAP, FTP, and many more (see Wikipedia)

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Protocols of TCP/IP model

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Internet Layer: IP (Internet Protocol)

• Transports fixed-length

packages

from source to

destination.

• Abstracts network boundaries: delivery irregardless of

whether machines are on same network or whether there

are other networks in between.

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IP addresses

• Network address of a host or router on the internet, used

in source and destination address fields in IP packets.

• An IP address refers to the network interface, not the

physical machine. E.g., a router has an IP address for

each network it is part of.

• IP addresses are hierarchical, with a network portion and

a host portion. Network portion is the same for all hosts

on a single network.

• Hierarchical routing allows routers to ignore host part,

resulting in smaller routing tables.

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IP addresses

• Originally, IP addresses were 32-bit long. They are

defined by the IP Version 4 (IPv4) protocol.

• IPv4 limits the address space to roughly 4.3 billions.

• To prevent expected address exhaustion, IPv6 has been

developed.

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Transport layer

• Transport

data

from process on source machine to

process on destination machine.

• Provides abstraction that applications need to use the

network. Assigns port number to application.

• Splits up application data into packages.

• Note: transport-layer software runs entirely on user’s

machine, network-layer software runs on routers too.

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Transport layer protocols: TCP vs UDP

TCP (Transmission Control Protocol)

• connection-oriented protocol

• reliable, end-to-end byte stream over unreliable network

• predominantly used

UDP (User Datagram Protocol)

• connection-less protocol

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Application layer

• Actual internet applications and supporting protocols

• Client-server

architecture (predominant)

• distinguishes provider (server) of a shared resource from its clients

• clients send requests to server, server responds with service

• Examples: HTTP, DNS

• Peer-to-peer

architecture

• many computers pool their resources to form a content distribution system

• computers are peers because they both act as clients and servers

• Examples: BitTorrent, Skype, Bitcoin

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Application layer protocols: HTTP and DNS

HTTP (HyperText Transfer Protocol)

• Defines interaction between web client application (e.g., Firefox, Safari) and web server application (e.g., Apache).

• Agreement on how to ask for a web page, on how to send data entered into a form, on how to report errors, etc.

DNS (Domain Name System)

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This unit

Internet fundamentals

Internet protocols

• Internet networking architecture (TCP/IP model)

• Layer-specific protocols of TCP/IP model:

• Network/Internet: IP

• Transport: TCP and UDP

• Application:

• Client-server: HTTP, DNS

• Peer-to-peer: BitTorrent, Skype, Bitcoin

Internet security

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