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CCNA 1 v3.0 Module 9 TCP/IP Protocol Suite and IP Addressing


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Title: CCNA 1 v3.0 Module 9 TCP/IP Protocol Suite and IP Addressing

CCNA 1 v3.0 Module 9 TCP/IP Protocol Suite and
IP Addressing
  • Introduction to TCP/IP
  • Internet addresses
  • Obtaining an IP address

Introduction to TCP/IP
History and Future of TCP/IP
  • The U.S. Department of Defense (DoD) created the
    TCP/IP reference model because it wanted a
    network that could survive any conditions.
  • Some of the layers in the TCP/IP model have the
    same name as layers in the OSI model.

Application Layer
  • Handles high-level protocols, issues of
    representation, encoding, and dialog control.
  • The TCP/IP protocol suite combines all
    application related issues into one layer and
    ensures this data is properly packaged before
    passing it on to the next layer.

Application Layer Examples
Transport Layer
  • Five basic services
  • Segmenting upper-layer application data
  • Establishing end-to-end operations
  • Sending segments from one end host to another end
  • Ensuring data reliability
  • Providing flow control

  • Relaible/ Unreliable
  • IP is sometimes referred to as an unreliable
    protocol. This does not mean that IP will not
    accurately deliver data across a network. Calling
    IP an unreliable protocol simply means that IP
    does not perform error checking and correction.
    That function is handled by upper layer protocols
    from the transport or application layers.

Transport Layer Protocols
  • TCP and UDP
  • Segmenting upper-layer application data
  • Sending segments from one end device to another
    end device
  • TCP only
  • Establishing end-to-end operations
  • Flow control provided by sliding windows
  • Reliability provided by sequence numbers and

Internet Layer
The purpose of the Internet layer is to send
packets from a network node and have them arrive
at the destination node independent of the path
  • IP performs the following operations
  • Defines a packet and an addressing scheme
  • Transfers data between the Internet layer and
    network access layers
  • Routes packets to remote hosts

Network Access Layer
  • The network access layer is concerned with all of
    the issues that an IP packet requires to actually
    make a physical link to the network media.
  • It includes the LAN and WAN technology details,
    and all the details contained in the OSI physical
    and data link layers.

Comparing the OSI Model and TCP/IP Model
Similarities of the OSI and TCP/IP Models
  • Both have layers.
  • Both have application layers, though they include
    very different services.
  • Both have comparable transport and network
  • Packet-switched, not circuit-switched, technology
    is assumed.
  • Networking professionals need to know both

Differences of the OSI and TCP/IP Models
  • TCP/IP combines the presentation and session
    layer into its application layer.
  • TCP/IP combines the OSI data link and physical
    layers into one layer.
  • TCP/IP appears simpler because it has fewer
  • TCP/IP transport layer using UDP does not always
    guarantee reliable delivery of packets as the
    transport layer in the OSI model does.

Internet Architecture
  • Two computers, anywhere in the world, following
    certain hardware, software, protocol
    specifications, can communicate, reliably even
    when not directly connected.
  • LANs are no longer scalable beyond a certain
    number of stations or geographic separation.

Internet Architecture
  • The OSI models goal is to build the functionality
    of the network in independent modules. This
    allows a diversity of LAN technologies at Layers
    1 and 2 and a diversity of applications
    functioning at Layers 5, 6, and 7.
  • Not all networks are directly connected to one
    another. The router must have some method to
    handle this situation.

  • A router to keep a list of all computers and all
    the paths to them. The router would then decide
    how to forward data packets based on this
    reference table.
  • The forwarding is based on the IP address of the
    destination computer. This option would become
    difficult as the number of users grows.
    Scalability is introduced when the router keeps a
    list of all networks, but leaves the local
    delivery details to the local physical networks.
  • The routers pass messages to other routers. Each
    router shares information about which networks it
    is connected to. This builds the routing table.

Internet Addresses
IP Addressing
  • An IP address is a 32-bit sequence of 1s and 0s.
  • To make the IP address easier to use, the address
    is usually written as four decimal numbers
    separated by periods.
  • This way of writing the address is called the
    dotted decimal format.

IP addressing
  • An IP address is a 32-bit sequence of 1s and 0s.
    The IP address is broken down into two parts the
    network portion and the host portion. IP
    addresses were originally divided into three main
    classes A, B and C. Class A addresses are
    assigned to larger networks. Class B addresses
    are used for medium-sized networks, and Class C
    for small networks

IPv4 Addressing
Class A, B and C
  • In Class A address the fist octet (8 bits)
    defines the network number the other three define
    host ID, this means up to 126 Class A networks
    are possible each hosting up to 16m hosts.
  • Class B addresses, the first and second octets
    are defined as the network number and the third
    and forth as the host number, this means there
    are 16,000 class B addresses which can have 65000
  • In class C addresses only the forth octet is
    assigned to the network number, each of 2,000,000
    class C addresses can host 254 hosts.

Reserved IP Addresses
  • Certain host addresses are reserved and cannot be
    assigned to devices on a network.
  • An IP address that has binary 0s in all host bit
    positions is reserved for the network address.
  • An IP address that has binary 1s in all host bit
    positions is reserved for the network address.

Public and Private IP Addresses
  • No two machines that connect to a public network
    can have the same IP address because public IP
    addresses are global and standardized.
  • However, private networks that are not connected
    to the Internet may use any host addresses, as
    long as each host within the private network is
  • RFC 1918 sets aside three blocks of IP addresses
    for private, internal use.
  • Connecting a network using private addresses to
    the Internet requires translation of the private
    addresses to public addresses using Network
    Address Translation (NAT).

Introduction to Subnetting
  • To create a subnet address, a network
    administrator borrows bits from the host field
    and designates them as the subnet field.

IPv4 versus IPv6
  • IP version 6 (IPv6) has been defined and
  • IPv6 uses 128 bits rather than the 32 bits
    currently used in IPv4.
  • IPv6 uses hexadecimal numbers to represent the
    128 bits.

Obtaining an IP Address
Obtaining an Internet Address
  • Static addressing
  • Each individual device must be configured with an
    IP address.
  • Dynamic addressing
  • Reverse Address Resolution Protocol (RARP)
  • Bootstrap Protocol (BOOTP)
  • Dynamic Host Configuration Protocol (DHCP)
  • DHCP initialization sequence
  • Function of the Address Resolution Protocol
  • ARP operation within a subnet

How does a computer get its IP address?
  • 1) Static given to it by the administrator
  • 2) Dynamic
  • RARP (reverse address resolution protocol) the
    computer sends out a broadcast and the RARP
    server responds with an IP address
  • BOOTP (BOOTstrap Protocol) similar to RARP but
    the bootp server returns other information, BOOTP
    datagrams can include the IP address, the address
    of a router (default gateway), the address of a
    server, and a vendor-specific field.
  • Both RARP and Bootp use a static table of MAC and
    IP addresses.

DHCP Dynamic host connection protocol
  • DHCP Dynamic host connection protocol
  • Host sends request for IP address for DHCP server
  • Server responds with offer and lease time
  • Host replies with acknowledgement
  • Server acknowledges IP assignment

  • A DHCP service can be created on a server, the
    user tells the server the range of IP addresses
    it can give out e.g.
    The user also tells the service how long a host
    can keep this address either indefinitely or for
    days/weeks/sessions. This is often used for
    computers not in use all the time, therefore the
    IP addresses are not permanent.

  • The Bootstrap Protocol (BOOTP) operates in a
    client/server environment and only requires a
    single packet exchange to obtain IP information.
  • BOOTP packets can include the IP address, as well
    as the address of a router, the address of a
    server, and vendor-specific information.

Dynamic Host Configuration Protocol
  • Allows a host to obtain an IP address using a
    defined range of IP addresses on a DHCP server.
  • As hosts come online, contact the DHCP server,
    and request an address.

Problems in Address Resolution
  • In TCP/IP communications, a datagram on a
    local-area network must contain both a
    destination MAC address and a destination IP
  • There needs to be a way to automatically map IP
    to MAC addresses.
  • The TCP/IP suite has a protocol, called Address
    Resolution Protocol (ARP), which can
    automatically obtain MAC addresses for local
  • TCP/IP has a variation on ARP called Proxy ARP
    that will provide the MAC address of an
    intermediate device for transmission outside the
    LAN to another network segment.

Address Resolution Protocol (ARP)
  • Each device on a network maintains its own ARP
  • A device that requires an IP and MAC address pair
    broadcasts an ARP request.
  • If one of the local devices matches the IP
    address of the request, it sends back an ARP
    reply that contains its IP-MAC pair.
  • If the request is for a different IP network, a
    router performs a proxy ARP.
  • The router sends an ARP response with the MAC
    address of the interface on which the request was
    received, to the requesting host.

(No Transcript)
  • The users computer builds the packet and then a
    frame (needs the destination and source MAC
  • Each computer knows its own MAC address (build
    into NIC card)
  • A packet must be enclosed in a frame if it is to
    be transmitted
  • All frame headers for LANs require a destination
    MAC address
  • ARP is used to locate an unknown destination MAC

The following method is used.
  • Destination IP address is checked using the
    subnet mask to see if the destination is on the
    same network/ subnet as the source.
  • The ARP table is checked, this contains a list of
    IP addresses and their corresponding MAC
  • If entry is present in the ARPtable the
    destination MAC address is used in the frame and
    the frame is sent.
  • If entry is not present then an ARP request is

  1. The ARP request contains the destination and
    source IP address and the source IP address and
    the broadcast IP address as destination (48
    binary 1s or 12 F hex)
  2. All hosts on the same segment open the frame
    since it is addressed to all computers. The host
    with a matching address will return an ARP reply
    containing its MAC address.
  3. All other computers update their ARPtables with
    senders MAC address and IP address.
  4. When sender receives the ARP reply it records the
    details in its ARPTable and then send the frame.

  • If the initial check in step 1 indicates that the
    destination computer is on a different network/
    subnet then the frame must be sent to the default
    gateway (the router).
  • The destination IP address will always identify
    the computer we want to talk to (not the router)
    the destination MAC address will point the frame
    to the router which will be the first leg of the
    packets journey. If the routers MAC address is
    not known then an ARP request may be sent.
  • Each host must be told what the IP address of its
    default gateway is. The ARPtable is stored in the
    computers RAM with table entries aged out, a
    timer is set as soon as the request is sent out.
    This keeps the tables upto date.

  • Class A and B addresses were quickly depleted.
    The Internet faced running out of IP addresses.
  • IPv6 uses 128 bits rather than the 32 bits
    currently used in IPv4. IPv6 uses hexadecimal
    numbers to represent the 128 bits. IPv6 provides
    640 sextrillion addresses.

ARP (Address Resolution Protocol)
  • ARP is more important than RARP or Bootp