Transcript Chapter 3 - More on IP & Addresses

Figure 3-13: Internet Protocol (IP)

Basic Characteristics

There were already single networks, and many
more would come in the future

Developers needed to make a few assumptions
about underlying networks

So they kept IP simple
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Figure 3-13: Internet Protocol (IP)

Connection-Oriented Service and
Connectionless Service

Connection-oriented services have distinct starts
and closes (telephone calls)

Connectionless services merely send messages
(postal letters)

IP is connectionless
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IP Packet
PC
Internet Process
First Router
Internet Process
IP Packet
Connectionless
Packets Sent in Isolation
Like Postal Letters
Unreliable
No Error Correction
Discarded by Receiver if Error is Detected
Leaves Error Correction to Transport Layer
Reduces the Cost of Routers
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Figure 3-13: Internet Protocol (IP)
(Study Figure)

IP is Unreliable (Checks for Errors but does
not Correct Errors) (Figure 3-14)

Not doing error correction at each hop between
switches reduces switch work and so switch cost

Does not even guarantee packets will arrive in
order
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Figure 3-13: Internet Protocol (IP)
(Study Figure)

Hierarchical IP Addresses

Postal addresses are hierarchical (state, city,
postal zone, specific address)

Most post offices have to look only at state
and city

Only the final post offices have to be
concerned with specific addresses
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Figure 3-15: Hierarchical IP Address
Network Part (not always 16 bits)
Subnet Part (not always 8 bits)
Host Part (not always 8 bits)
Total always is 32 bits.
128.171.17.13
The Internet
UH Network (128.171)
CBA Subnet (17)
Host 13
126.171.17.13
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Figure 3-13: Internet Protocol (IP)
(Study Figure)

Hierarchical IP Addresses

32-bit IP addresses are hierarchical (Figure 315)

Network part tells what network host is on

Subnet part tells what subnet host is on
within the network

Host part specifies the host on its subnet

Routers have to look only at network or
subnet parts, except for the router that
delivers the packet to the destination host
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Figure 3-13: Internet Protocol (IP)
(Study Figure)

Hierarchical IP Addresses

32-bit IP addresses are hierarchical

Total is 32 bits; part sizes vary

Network mask tells you the size of the
network part (Figure 3-16)

Subnet mask tells you the length of the
network plus subnet parts combined
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Figure 3-16: IP Address Masking with
Network and Subnet Masks
Network Masking
Subnet Masking
Mask Represents
Tells the size of the network
part
Tells the size of the network
and the subnet parts
combined
Eight ones give the decimal
value
255
255
Eight zeros give the decimal
value
0
0
Masking gives
IP address bit where the
mask value is 1; 0 where the
mask bit is 0
IP address bit where the
mask value is 1; 0 where
mask bit is 0
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Figure 3-16: IP Address Masking with
Network and Subnet Masks
Example 1
Network Masking
Subnet Masking
IP Address
128.171.17.13
128.171.17.13
Mask
255.255.0. 0
255.255.255.0
Result
128.171.0. 0
128.171.17.0
Meaning
16-bit network part is 128.171
Combined 24-bit network plus subnet part
are 128.171.17
IP Address
60.47.123.7
60.47.123.7
Mask
255.0.0.0
255.255.0.0
Result
60.0.0.0
60.47.0.0
Meaning
8-bit network part is 60
Combined 16-bit network plus subnet
parts are 60.47
Example 2
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