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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

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Tier 1 isps

Tier-1 ISPs

Wikipedia, Jan. 2014.

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Tier 1 isps1

Tier 1 ISPs

Internet Health Report

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

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Internet standards organizations

Internet standards organizations

administration

collaboration

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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

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    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

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    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

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    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)

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    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)

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    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

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    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

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    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)

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    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

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    Essentials of the internet protocol and tcp ip architecture

    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

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    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)

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    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

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    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.

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    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

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    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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    Putting it all together how an application uses tcp ip

    Putting it all together... how an application uses TCP/IP

    World Wide Web example


    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="/?@=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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    The client collect all elements and displays the web page

    ... the client collect all elements and displays the Web page.

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