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

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

• Introduction to TCP/IP
• Internet addresses
• Obtaining an IP address

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Introduction to TCP/IP
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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.

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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.

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Application Layer Examples
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Transport Layer

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

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Definition

• 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.

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Transport Layer Protocols
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TCP and UDP

• 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
  acknowledgments

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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
taken.
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IP

• 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

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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.

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Comparing the OSI Model and TCP/IP Model
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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
  layers.
• Packet-switched, not circuit-switched, technology
  is assumed.
• Networking professionals need to know both
  models.

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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
  layers.
• TCP/IP transport layer using UDP does not always
  guarantee reliable delivery of packets as the
  transport layer in the OSI model does.

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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.

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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.

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• 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.

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Internet Addresses
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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.

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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

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IPv4 Addressing
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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
  hosts.
• 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.

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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.

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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
  unique.
• 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).

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Introduction to Subnetting

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

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IPv4 versus IPv6

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

IPv4
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Obtaining an IP Address
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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

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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.

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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

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DHCP

• 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. 200.20.50.4 200.20.50.55.
  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.

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BOOTP IP

• 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.

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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.

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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
  address.
• 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
  transmission.
• 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.

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Address Resolution Protocol (ARP)

• Each device on a network maintains its own ARP
  table.
• 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.

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• The users computer builds the packet and then a
  frame (needs the destination and source MAC
  address)
• 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
  address.

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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
  addresses.
• 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
  broadcast.

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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.

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Note

• 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.

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IPv6

• 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.

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ARP (Address Resolution Protocol)

• ARP is more important than RARP or Bootp