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Essentials of the Internet Protocol and TCP/IP Architecture. Prepared by: Ignac Lovrek, Maja Matijašević, Gordan Gledec, Gordan Ježić, Josip Gracin, Domagoj Mikac, Ognjen Dobrijević, Vedran Podobnik University of Zagreb Faculty of Electrical Engineering and Computing

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essentials of the internet protocol and tcp ip architecture

Essentials of the Internet Protocoland TCP/IP Architecture

Prepared by:

Ignac Lovrek, Maja Matijašević, Gordan Gledec, Gordan Ježić,

Josip Gracin, Domagoj Mikac, Ognjen Dobrijević, Vedran Podobnik

University of Zagreb

Faculty of Electrical Engineering and Computing

Department of Telecommunications

introduction

Introduction

History and size of the Internet

Internet hierarchy

Standards organizations

Request for Comments series

size of the internet
Size of the Internet

University of Zagreb, FER

internet hierarchy
Internet hierarchy

Legend:ISP - Internet Service Provider

IXP - Internet Exchange Point

POP - Internet Point of Presence

ISP

ISP

ISP

Tier 1

peering

IXP

transit

ISP

peering

Tier 2

ISP

ISP

ISP

POP

POP

POP

POP

IXP

transit

ISP

ISP

Tier 3

ISP

POP

POP

corporate user

(LAN)

home user

xDSL, cable access

University of Zagreb, FER

tier 1 isps
Tier-1 ISPs

Wikipedia, Jan. 2014.

University of Zagreb, FER

tier 1 isps1
Tier 1 ISPs

Internet Health Report

http://scoreboard.keynote.com/scoreboard/Main.aspx?Login=Y&Username=public&Password=public

University of Zagreb, FER

internet standards organizations
Internet standards organizations

administration

collaboration

University of Zagreb, FER

requests for comment rfc series
Requests for Comment (RFC) series
  • RFC documents are a series of memoranda encompassing new research, innovations, and methodologies applicable to Internet technologies
  • RFC Editor (team) edits and publishes RFCs online
      • RFC Index http://www.rfc-editor.org/rfc-index.html
    • RFC Editor issues each RFC document with a unique serial number
    • once published, RFCs never change – errata are published separately
    • RFC subseries
      • Internet Standard (STD), For Your Information (FYI), Best Current Practice (BCP)
    • also important: RFC status – may be “standards track” (proposed standard, draft standard, Internet standard), or other (informational, experimental, BCP, or historic)
  • the IETF adopts some of the proposals published in RFCs as Internet standards - not all RFCs are/become Internet standards; only ~70 STDs out of 7000+ (as of Jan 2014) RFCs

University of Zagreb, FER

structure of the internet

Structure of the Internet

Logical and physical view

Autonomous System

logical vs ph y s i cal view
Logical vs. physical view

Internet

physical view -network of networks

logical view -one global network

Legend:

SN – subnet

University of Zagreb, FER

autonomous system
Autonomous system
  • Autonomous system (AS)
    • collection of IP networks and routers under the control of one entity (or sometimes more) that presents a common routing policy to the Internet
  • a unique AS number (ASN) is assigned by IANA
      • for example, AS2108 CARNET-AS Croatian Academic and Research Network

routing view - collection of ASs

Legend:

SN -subnet

AS – autonomous system

University of Zagreb, FER

protocol stack and the role of tcp ip

Protocol stack and the role of TCP/IP

Reference networking model

Comparison of OSI and Internet TCP/IP model

TCP/IP functionality

reference networking model
Reference Networking Model
  • provides an abstract view of network architecture
  • concept of layering
    • each layer implements a set of well-defined functionalities
    • each layer provides the foundation and the services required by the layer above
    • each layer-n entity interacts directly only with the layer immediately beneath it, and provides facilities for use by the layer above it
  • protocol suite = collection of protocolsorganized into layers
    • protocol is a “language” that enables an entity in one host to interact with a cooresponding entity (peer) at the same layer in a remote host
    • standardized interfaces

University of Zagreb, FER

comparison between osi and tcp ip architecture

TCP/IP (Internet)

Open Systems Interconnection

Application layer

Application layer

Presentation layer

Session layer

Transport layer

Transport layer

Network layer

Network layer

Link layer

Data Link layer

Physical layer

Comparison between OSI and TCP/IP architecture

Application layer

Application layer

Presentation layer

Session layer

Transport layer

Transport layer

Network layer

Network layer

Data Link layer

Link layer

Physical layer

(Physical layer)

University of Zagreb, FER

tcp ip protocol stack

WWW

SMTP - Simple Mail Transfer Protocol

HTTP - HyperText Transfer Protocol

DNS - Domain Name System

TFTP - Trivial File Transfer Protocol

SNMP - Simple Network Management Protocol

RTP - Real-time Transport Protocol

IP - Internet Protocol

ICMP - Internet Control Message Protocol

ARP - Address Resolution Protocol

RARP - Reverse Address Resolution Protocol

TCP - Transmission Control Protocol

UDP - User Datagram Protocol

FTP - File Transfer Protocol

TCP/IP protocol stack

Telnet

HTTP

SNMP

SMTP

TFTP

Application layer

FTP

RTP

DNS

Transport layer

TCP

UDP

routing

(RIP, OSPF, BGP)

Network layer

IP

control (ICMP, IGMP)

RARP

ARP

Link layer

Ethernet/IEEE802.x, PPP, ATM,...

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how tcp ip works encapsulation example

HTTP

data

HTTP

data

TCP

data

TCP

HTTP

data

IP

TCP

data

IP

TCP

HTTP

data

F

IP

TCP

data

20 byte

20 byte

14 byte

4 byte

46-1500 byte

How TCP/IP works – encapsulation example

data

HTTP

data

Application layer

(web appl.)

TCP

Transport layer

IP

Network layer

F

Link layer

(Ethernet/IEEE802.3)

University of Zagreb, FER

network layer functionality

Network Layer functionality

Internet Protocol – IPv4

Control Protocols

Routing Protocols

internet protocol v4

Internet Protocol v4

IP features

Datagram format

Fragmentation and reassembly

IP addressing and naming

internet protocol
Internet Protocol
  • IP, version 4
  • connectionless unreliable transfer of datagrams
  • specified in RFC 791, STD-5
  • defines the Internet addressingscheme
    • unique address space
    • each host has one unique IP addresses per interface
    • a host may also use other special addresses (e.g. localhost, multicast, broadcast ,…)
    • if source and destination are located in different networks, IP datagrams are routed through one or more IP routers
  • defines how to handle fragmentation
    • a datagram must fit inthe frame of specific lower layer protocol
    • datagram bigger than the frame must be fragmented
    • receiving side reassembles the fragments

University of Zagreb, FER

ip datagram format

32 bits

F

IP

TCP

data

version

Hdr. Len

Type of Service

Total Length

Identification

Flags

Fragment Offset

Time to Live

Protocol

Header Checksum

Source IP address

Destination IP address

header,

20 octets

Options

Padding

Higher layer data

max. 60 octets

IP datagram format

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ip datagram size fragmentation and reassembly
IP datagram size - fragmentation and reassembly
  • datagram must be small enough to fit into the frame of the lower layer protocol
    • MTU - Maximum Transmission Unit
      • media dependent
      • for example, Ethernet/IEEE 802.3: 1500 bytes
  • otherwise, the datagram must be split or fragmented into several datagrams
  • fragments are sent independently and reassembled into the original message at the destination

source

destination

MTU=576

MTU=1500

MTU=1500

reassembly

fragmentation

University of Zagreb, FER

ip addressing and naming

IP addressing and naming

IP address structure

Types of IP addresses

Domain Name System

Address Resolution Protocol

Internet Control Message Protocol

ip addressing

161

.

53

.

19

.

201

IP addressing
  • IP address provides unique identification of the network interface
    • a device can have more than one interface
    • different from the physical (MAC) addresses
  • IP address is required to ensure that the IP datagram is delivered to the correct recipient
  • Address representation
    • 32 bit binary number
      • hard to read and remember

10100001

00110101

00010011

11001001

  • Dotted-decimal notation
    • easier to remember
  • Symbolic address or name (hosts.txt)

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ip address structure

.

.

.

161

201

53

19

1010000100110101 00010011 11001001

IP address structure
  • IP address has two parts:
    • Network Identifier (Net ID)
      • a certain number of bits (starting from the left-most bit), used to identify the network where the network interface is located
      • network prefix
    • Host Identifier (Host ID)
      • the remainder of the bits used to identify the network interface in the network specified with Net ID
  • type of IP address
    • unicast, broadcast, multicast

Net ID

Host ID

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classes of ip adresses
Classes of IP adresses

Class A: 0.0.0.0 - 127.255.255.255

0

Net ID

Host ID

Class B: 128.0.0.0 - 191.255.255.255

1

0

Net ID

Host ID

Class C: 192.0.0.0 - 223.255.255.255

1

1

0

Net ID

Host ID

Class D: 224.0.0.0 - 239.255.255.255

1

1

1

0

multicast

Class E: 240.0.0.0 - 247.255.255.255

1

1

1

1

0

reserved

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classless addressing scheme
Classless addressing scheme
  • prefix-based representation of IP address
  • partitioning between the NetID and HostID can occur at any bit boundary in the address
  • length of Net ID is specified with the network prefix following the IP address

195.24.0.0/13

11000011.00011000.00000000.00000000

network prefix

  • introduced for the purposes of Classless Inter-Domain Routing (CIDR)
    • network part (NetID) of the IP address is not determined by address class
    • eliminates the significance of address classes for route aggregation(that’s why CIDR is termed classless)

University of Zagreb, FER

types of ip addresses
Types of IP addresses

IPv4 Address Space

(RFC 5735, BCP0153)

Public address space

  • for use in public Internet
  • IP address must beglobally unique
    • two devices connected to the public Internet cannot have the same IP address
  • routing must be possible
  • IANA, ICANN, RIPE...

Reserved address space

  • “this” network 0.0.0.0/8
  • loopback 127.0.0.0/8
  • multicast 224.0.0.0/4
  • broadcast - Host ID all 1s
  • blocks reserved by IANA, some subject to allocation, some not

IP Network Address Translator (NAT)

Private address space

  • for use in private internets
  • organization manages the entire private address space
  • IP addresses within the private network must be unique
  • blocks of IP address space for private internets specified by IANA: 10/8, 172.16/12, 192.168/16

University of Zagreb, FER

slide28

private Internet

(address space 10/8)

public Internet

The role of NAT – example

A: 10.0.0.1

B: 161.53.19.201

X: 139.130.1.1(public IP address space )

NAT

NAT binding:

10.0.0.1 ↔ 139.130.1.1

datagram A->B

source: 10.0.0.1

destination: 161.53.19.201

source: 139.130.1.1

destination: 161.53.19.201

datagram B->A

source: 161.53.19.201

destination: 10.0.0.1

source: 161.53.19.201

destination: 139.130.1.1

University of Zagreb, FER

obtaining an ip ad d res s
Obtaining an IP address
  • static address assignment
    • IP address is manually configured for a network device (i.e. IP phone)
    • acceptable for small networks, complicated for large networks
    • usually applied for network servers, routers and other devices that never change their IP addresses
  • dynamic address assignment
    • IP address and other network settings received from a server
    • simplifies address assignment in large networks (e.g. corporation, ISP)
    • DHCP – Dynamic Host Configuration Protocol (RFC 2131)
      • successor to BOOTP – Bootstrap Protocol
      • DHCP server leases an IP address from a previously configured address range to a device for a specific time (allows serial reassignment of IP address)
      • DHCP server provides entire TCP/IP configuration (IP address, subnet mask, default gateway)

University of Zagreb, FER

d omain n ame s ystem dns
Domain Name System (DNS)
  • numerical IP adresses are hard to remember – a name may be assigned for easier reference
  • Domain Name System
    • “(...) the idea of a hierarchical name space, with the hierarchy roughly corresponding to organizational structure, and names using ‘.’ as the character to mark the boundary between hierarchy levels.” (RFC 1034)
    • a “directory service” for the Internet
    • domain– a group of computers most commonly associated by the organization they belong to
      • top level domain (generic, country)
      • subdomains, for example: .hr, fer.hr, tel.fer.hr
    • Fully Qualified Domain Nameuniquely identifies the host on the Internet
      • for example, www.tel.fer.hr
    • maintained as the hierarchical database distributed on the Internet
      • root DNS server on the top of the hierarchy
      • other DNS servers have authority over their zones/domains

University of Zagreb, FER

d omain n ame s ystem dns1
Domain Name System (DNS)

novac

php

nautika

ivoivic

www

ip6

grunf

smiley

. (root)

generic Top Level Domains (gTLD)

country code Top level Domains (ccTLD)

gTLD

ccTLD

big seven,1980s

org

(new gTLD s– 2000s

ac

zw

cat

aero

mil

biz

top level

domain: .hr

hr

com

museum

mobi

edu

info

(ISO 3166)

gov

jobs

asia

int

coop

name

travel

net

pro

tel

subdomain: fer.hr

itu

dell

cnn

com

from

fer

srce

mit

google

(sub)domain

eecs

ietf

tel

zemris

hosts

www

www

mail

www

www

www

www

mail

FQDN: www.fer.hr

*TLD - Top Level Domain

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domain name servers
Domain name servers

Root DNS server

13 servers (a to m, e.g., k.root-servers.net) with several identical instances

http://www.root-servers.org/

Approximate position of root DNS servers, end of 2006.

Izvor: Matthäus Wander, 2006. Wikipedia Commons.

University of Zagreb, FER

dns example

2.

3.

hr

at

fi

4.

fer

foi

5.

161.53.19.221

www.tel.fer.hr?

tel

zesoi

zpm

1.

6.

www

oluja

DNS Example

root DNS

128.9.0.107

www.tel.fer.hr?

.

DNS for .hr

local

DNS

server

www.tel.fer.hr?

DNS for .hr161.53.3.7

DNS for fer.hr

www.tel.fer.hr?

DNS for .fer.hr

161.53.72.21

DNS for tel.fer.hr

www.tel.fer.hr?

DNS for tel.fer.hr

161.53.19.203

161.53.19.221

application

resolver

query for www.tel.fer.hr

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routing protocols

Routing protocols

Classless Interdomain Routing

Routing Information Protocol

Open Shortest Path First

Border Gateway Protocol

ip routing
IP Routing
  • Internet is a packet-switching network
  • Classless Inter-Domain Routing – CIDR (RFC 4632)
    • destination IP address is matched based on NetID
    • packets (IP datagrams) are routed independently of each other
  • no end-to-end connection
    • hop-by-hop routing
  • each router contains a routing table which contains its information on the topology of the network
    • used for matching a destination address to the outgoing network interface
      • entries (i.e. rows) in routing table contain:
        • destination address
        • IP address of the next-hop router on the way to the destination
      • default route – special entry in routing table
        • matches all destinations – 0.0.0.0/0
        • considered when no other more specific routes are found
        • used, for example, in leaf networks

University of Zagreb, FER

routing protocols classification
Routing Protocols Classification

EGPExterior Gateway Protocol

Border Gateway Protocol – BGP ◄

Exterior Gateway Protocol - EGP

AS1

AS2

IGP

IGP

EGP

IGP

Interior GatewayProtocol

Open Shortest Path First - OSPF◄

Routing Information Protocol – RIP ◄

Interior Gateway Routing Protocol -IGRP

Intermediate System to Intermediate System (IS-IS)

IGP

AS – Autonomous System

AS3

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transport layer

Transport Layer

Transport layer functionality

User Datagram Protocol

Transmission Control Protocol

transport layer protocols in the internet tcp and udp
User Datagram Protocol

connectionless protocol

unreliable transfer

order not guaranteed

no flow control

no congestion control

applications:

audio, video, internet telephony, teleconferencing (RTP)

dynamic address allocation (BOOTP, DHCP)

Transmission Control Protocol

connection-oriented protocol

reliable transfer

ordered delivery

flow control

congestion control

applications:

web (HTTP)

e-mail (SMTP, POP, IMAP)

file transfer (FTP)

remote terminal (TELNET)

Transport Layer Protocols in the Internet: TCP and UDP

TCP

UDP

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transmission control protocol tcp

TCP segment structure

header,20 octets

source port

destination port

sequence number

acknowledgment number

length

rsvd.

control bits

window size

max. 60 octets

checksum

urgency pointer

TCP options (optional)

padding

higher layer data

32 bits

Transmission Control Protocol (TCP)
  • specified in RFC 793
  • functionality of TCP
    • accepts higher layer data, divides the octet stream into segments, and passes them down to the IP layer
    • provides ordered, reliable delivery of stream of octets
    • provides transport layer addressing/multiplexing (ports)

F

IP

TCP

data

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t cp mechanisms
TCP mechanisms
  • three phases of a connection: connection establishment, data transfer, connection termination
  • ordered, reliable data delivery over IP
    • delivers data as a stream of octets
    • divides the octet stream into appropriately sized segments
    • Maximum Segment Size (MSS) is determined by the link-layer frame size
    • each segments is numbered
  • reliability mechanisms
    • acknowledgments
    • retransmission
  • sliding window flow control
  • congestion avoidance
    • slow start, fast retransmit and fast recovery algorithms
    • doing congestion avoidance in TCP is an important design decision of the Internet network

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how www works general idea
How WWW works, general idea

Go to:http://www.fer.hr/

local DNS

server

IP www.fer.hr ?

161.53.72.111

browser

disk

www.fer.hr

161.53.72.111

HTTP request for root index document

web

server

HTTP server responds with HTML source

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example fer home page

form

image

text

active element - menu

Example: FER Home page

(css)

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processing of the source html code
Processing of the source HTML code

in this example, HTML code contains references to:

CSS layout

images

Javascript

text

text control elements (formatting, hyperlinks, etc.)

all page elements are fetched from the server by using HTTP

the client may start a new HTTP connection, or use the existing one to get the files from the server

<link href="/_themes/metallish/platinum/style.css" rel="stylesheet" type="text/css">

<img src="/shared/images/spacer.gif" height="6" width="1" alt="">

<script type="text/javascript" src="/lib/v1treeview.js"></script>

<p>Svečana promocija pristupnika koji su diplomirali u veljači i ožujku...<p>

<a title="Pročitaj obavijest" href="/[email protected]=1dhtp#news_8980">Više...</a>

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client application requests the image element
Client application requests the image element…

image on the home page must be fetched from the server (HTTP request)

the size of the image file is 16,711 bytes

  • to be transported over TCP, the image file must be broken into smaller pieces (<=MSS)
    • transport layer breaks initial 17 kB into 12 TCP segments
      • MSS = MTU - size of {IP, TCP} headers = 1500 – 20 – 20 = 1460 bytes
      • each segment is sent to network layer and routed independently

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the server application generates the http response

HTTP

HTTP

data

MSS

MSS

*

MSS

TCP

HTTP

data

IP

TCP

HTTP

data

The server application generates the HTTP response…

Application layer

(HTTP response)

... image data ...

TCP

TCP

IP

IP

F

Ethernet

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containing the image being delivered to the client

HTTP

Application layer

(HTTP response)

... image data ...

HTTP

data

TCP

TCP

TCP

HTTP

data

IP

IP

IP

TCP

HTTP

data

F

... containing the image being delivered to the client ...

…………….

Ethernet

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