1. CSE452:Computer Networks
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CSE452:Computer Networks
The Internet Protocol(IP)
IPv4 & IPv6
CIDR, Subnet

2. The Internet Network layer
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The Internet Network layer
Host, router network layer functions:
Transport layer: TCP, UDP
IP protocol
addressing conventions
datagram format
packet handling conventions
Routing protocols
path selection
RIP, OSPF, BGP
Network
layer
routing
table
ICMP protocol
error reporting
router “signaling”
Link layer
physical layer
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3. IP Addressing: introduction
IP address: 32-bit identifier for host, router interface
interface: connection between host, router and physical link
router’s typically have multiple interfaces
host may have multiple interfaces
IP addresses associated with interface, not host, router =
223 1 1 1
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4. IP Addressing IP address:
network part (high order bits)
host part (low order bits)
What’s a network ? (from IP address perspective)
device interfaces with same network part of IP address
can physically reach each other without intervening router
LAN
network consisting of 3 IP networks
(for IP addresses starting with 223,
first 24 bits are network address)
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5. IP Addressing How to find the networks?
Detach each interface from router, host
create “islands of isolated networks
Interconnected
system consisting
of six networks
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6. IP Addresses given notion of “network”, let’s re-examine IP addresses:
“class-full” addressing:
class A to
network
host B to 10
network
host to C
110
network
host to D
1110
multicast address
32 bits
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7. 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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8. Decimal and Binary Conversion
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9. IPv4 Addressing
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10. Class A, B, C, D, and E IP Addresses
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11. 4/17/2017

12. 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 broadcast address.
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13. Network Address
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14. Broadcast Address
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15. 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.
Procedure was needed to make sure that addresses were in fact unique.
Originally, an organization known as the Internet Network Information Center (InterNIC) handled this procedure. InterNIC no longer exists and has been succeeded by the Internet Assigned Numbers Authority (IANA).
IANA carefully manages the remaining supply of IP addresses to ensure that duplication of publicly used addresses does not occur.
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.
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16. Public and Private IP Addresses
RFC 1918 sets aside three blocks of IP addresses for private, internal use.
Addresses that fall in these ranges are not routed on the Internet backbone. Internet router immediately discard private addresses.
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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17. IP addressing: CIDR Classful addressing:
inefficient use of address space, address space exhaustion
e.g., class B net allocated enough addresses for 65K hosts, even if only 2K hosts in that network
CIDR: Classless InterDomain Routing
network portion of address of arbitrary length
address format: a.b.c.d/x, where x is # bits in network portion of address
network
part
host
/23
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18. Why Subnet? Millions of Addresses Available Over 16,000,000 Efficiency
Non-subnetted networks are wasteful
Division of networks not optimal
Smaller Network
Easier to manage
Smaller broadcast domains
So Make the network as small as possible
Divide the network into subnetworks
Borrow some bits from the host add.
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19. What You Need Understand Address System Understand Classes of Networks
“Two-Tums” Table
Formulas
Magic Numbers
Subnet Mask
“ANDing” Process
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20. Dissecting the Address > Classes <
CLASS RANGES:
A: 0 – N . H . H . H
B: 128 – 191 N . N . H . H
C: 192 – 223 N . N . N . H
Network
HOST
_ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _
(Digital)
(Decimal)
CLASS B
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21. TWO-TUMS
MAGIC NUMBERS:
SUBNET MASK:
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22. Number of Usable Subnets Number of Usable Hosts/Subnet
Magic Formulas
Number of Usable Subnets
2n – 2
= = -1
= = 0
= = 2
= = 6
Number of Usable Hosts/Subnet
2h-n – 2
= = 254 =?
= ? =?
n = # borrowed bits
h = # bits available in host address
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23. Subnet Mask What is a Subnet Mask? Why is it needed? How?
“Extended Network Prefix”
Indicates extent of the Network numbers
_ _ _ _ _ _ _ _
Why is it needed?
Used by router to determine Network Address
How?
Uses “ANDing” to compare Mask to IP Address
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24. ANDing Process
MASK:
IP:
Network Address:
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25. How to Subnet? * Subnet: Borrow
_ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _ ._ _ _ _ _ _ _ _
(Digital)
(Decimal)
Network 19
Host 13
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26. Easy Example
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27. Set Up Subnets 200.200.200.10 5 Subnets What is the Subnet Mask?
What are the Network Addresses?
What is the Broadcast Domain
What IP Addresses are available?
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28. Steps…. C [Range: 192 – 223]] What is the CLASS?
5 Subnets [23-2 = 6]
Use Subnet Mask #
Borrow 3 Bits 32
Wire Range BC
What is the CLASS?
How many BITS do we need to borrow?
Determine Subnet Mask
Determine “Magic Number”
Set up Table for IP Address (“Wire”), Range & Broadcast Domain
Fill in Table
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29. Table
WIRE
RANGE BC
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30. Table 200.200.200.10 WIRE RANGE BC Borrow 5 Bits Class C 200.200.200.0
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31. Table 200.200.200.10 WIRE RANGE BC +.32 +.32 Magic Number
+.32
+.32
Magic Number
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32. Table 200.200.200.10 WIRE RANGE BC Subnet Mask 200.200.200.0
Subnet Mask
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33. Table
WIRE
RANGE BC
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34. Table 200.200.200.10 WIRE RANGE BC Broadcast Domain 200.200.200.0
Broadcast Domain
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35. Table
WIRE
RANGE BC
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36. Table
WIRE
RANGE BC – – – – – – –
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37. Table 200.200.200.10 WIRE RANGE BC Reserved for Network Addresses – – – – – – –
Reserved for
Network
Addresses
Reserved for
Broadcast
Addresses
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38. Table
WIRE
RANGE BC – – – – –
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39. Set Up Subnets
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40. 4/17/2017

41. 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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42. Obtaining an IP Address
A network host needs to obtain a globally unique address in order to function on the Internet.
MAC has only significance only in LAN to identify host.
Router does not use MAC address(?) to forward packets outside LAN.
IP addresses are used for Internet communication.
IP is hierarchical addressing Scheme that allows individual addresses to be associated together and treated together.

43. Obtaining an IP Address
Regardless of the method chosen no two interfaces can have the same IP address.
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44. Static Assignment of an IP Address
Static assignment works best on small, infrequently changing networks.
The system administrator manually assigns and tracks IP addresses for each computer, printer, or server on the intranet.
Servers should be assigned a static IP address so workstations and other devices will always know how to access needed services.
Other devices that should be assigned static IP addresses are network printers, application servers, and routers.
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45. IP addresses: how to get one?
hard-coded by system admin in a file
Wintel: control-panel->network->configuration->tcp/ip->properties
UNIX: /etc/rc.config
DHCP: Dynamic Host Configuration Protocol: dynamically get address: “plug-and-play”
host broadcasts “DHCP discover” msg
DHCP server responds with “DHCP offer” msg
host requests IP address: “DHCP request” msg
DHCP server sends address: “DHCP ack” msg
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46. DHCP client-server scenario
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47. DHCP client-server scenario
DHCP server:
arriving
client
DHCP discover
src : , dest.: ,67
DHCPDISCOVER
yiaddr:
transaction ID: 654
DHCP offer
src: , dest: , 68
DHCPOFFER
yiaddrr:
transaction ID: 654
DHCP server ID:
Lifetime: 3600 secs
DHCP request
src: , dest:: , 67
DHCPREQUEST
yiaddrr:
transaction ID: 655
DHCP server ID:
Lifetime: 3600 secs
time
DHCP ACK
src: , dest: , 68
DHCPACK
yiaddrr:
transaction ID: 655
DHCP server ID:
Lifetime: 3600 secs
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48. DHCP IP Address Management
DHCP allows a host to obtain an IP address dynamically without the network administrator having to set up an individual profile for each device.
All that is required when using DHCP is a defined range of IP addresses on a DHCP server.
As hosts come online, they contact the DHCP server and request an address.
The DHCP server chooses an address and leases it to that host.
With DHCP, the entire network configuration of a computer can be obtained in one message.
The major advantage that DHCP has over BOOTP is that it allows users to be mobile.
This mobility allows the users to freely change network connections from location to location.
The importance to this DHCP advancement is its ability to lease an IP address to a device and then reclaim that IP address for another user after the first user releases it.
This means that DHCP offers a one to many ratio of IP addresses and that an address is available to anyone who connects to the network.
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49. IP addresses: how to get one?
Network (network portion):
get allocated portion of ISP’s address space:
ISP's block /20
Organization /23
Organization /23
Organization /23
… … ….
Organization /23
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50. Hierarchical addressing: route aggregation
Hierarchical addressing allows efficient advertisement of routing
information:
Organization 0
/23
Organization 1
/23
“Send me anything
with addresses
beginning
/20”
Organization 2
/23 .
Fly-By-Night-ISP .
Internet
Organization 7
/23
“Send me anything
with addresses
beginning
/16”
ISPs-R-Us
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51. Hierarchical addressing: more specific routes
ISPs-R-Us has a more specific route to Organization 1
Organization 0
/23
“Send me anything
with addresses
beginning
/20”
Organization 2
/23 .
Fly-By-Night-ISP .
Internet
Organization 7
/23
“Send me anything
with addresses
beginning /16
or /23”
ISPs-R-Us
Organization 1
/23
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52. IP addressing: the last word...
Q: How does an ISP get block of addresses?
A: ICANN: Internet Corporation for Assigned
Names and Numbers
allocates addresses
manages DNS
assigns domain names, resolves disputes
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