Internet Protocols

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Internet Protocols
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ARPAnet, 1971
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Clients and Servers
download
upload
Client Computers
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IP Internet Protocol Store and Forward Switch
Router

• Router in network core receives incoming packets
  and stores them in buffer (temporary storage)
• Routes packets on outgoing links
• May throw packets away if buffer is full

Routing Table
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End to EndIntelligence at Edge of Network

• Routers are relatively dumb and rely on
  intelligence at the edge to compensate

BEST EFFORT
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Packets

• Packet size (1.5 KB max) a compromise
• Small enough that they can be handled quickly
  and with relatively low odds of being damaged
• Large enough that packaging does not outweigh the
  contents or payload

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IP Addresses

• IPv4 32 bits written as 4 decimal numerals less
  than 256, e.g. 141.211.125.22 (UMich)
• 4 billion not enough
• IPv6 128 bits written as 8 blocks of 4 hex
  digits each, e.g. AF4323BCCAA10045A5B290ACFF
  EE8080
• At edge, translate URLs --gt IP addresses, e.g.
  umich.edu --gt 141.211.125.22
• Authoritative sites for address translation
  Domain Name Server (DNS)
• In the network core, IP addresses are used to
  route packets using routing tables

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But who controls the names and numbers?

• ICANN Internet Corporation for Assigned Names
  and Numbers
• A US nonprofit but its a long story.

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The Internet is IP

• Routers do not know what the bits in the packets
  represent
• Do not know if they are email, streaming video,
  html web pages
• Do not know if they are encrypted or unencrypted
• You can invent your own new service adhering to
  IP standards
• Gain Internets best-effort service
• and possibility of undelivered packets

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Packets

• Packet size (1.5 KB max) a compromise
• Small enough that they can be handled quickly
  and with relatively low odds of being damaged
• Large enough that packaging does not outweigh the
  contents or payload

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping

• Smallish packets also make better use of the
  network since later packets can leave before
  earlier packets arrive

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Striping Utilizes the Network

• Store and Forward delays would add up if entire
  message had to be buffered at every router

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Striping Utilizes the Network

• Store and Forward delays would add up if entire
  message had to be buffered at every router

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Striping Utilizes the Network

• Store and Forward delays would add up if entire
  message had to be buffered at every router

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Striping Utilizes the Network

• Store and Forward delays would add up if entire
  message had to be buffered at every router

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Striping Utilizes the Network

• Store and Forward delays would add up if entire
  message had to be buffered at every router

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Striping Utilizes the Network

• Store and Forward delays would add up if entire
  message had to be buffered at every router

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TCPTransport Control Protocol

• Creates logical connection between two machines
  on the edge of the network
• Connected machines seem to have a circuit
  connecting them even though they do not tie up
  the network
• Provide reliable, perfect transport of messages,
  even though IP may drop packets
• Regulates the rate at which packets are inserted
  into the network

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TCP, Basic Idea
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TCP, Basic Idea
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea
1 2

3-Way Handshaking
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TCP, Basic Idea
1 2

3-Way Handshaking
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TCP, Basic Idea
1 2

3-Way Handshaking
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TCP, Basic Idea
1 2

3-Way Handshaking
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TCP, Basic Idea
1 2

3-Way Handshaking
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TCP, Basic Idea
1 2

3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea

1 2
3-Way Handshaking
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TCP, Basic Idea
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Virtual Circuit now established between two
hosts though the routers in between are not aware
of it and the same path need not be followed by
all packets
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TCP, Basic Idea
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TCP, Basic Idea
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TCP, Basic Idea
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TCP, Basic Idea
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TCP, Basic Idea
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TCP, Basic Idea
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TCP, Basic Idea
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ACK1
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TCP, Basic Idea
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ACK1
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TCP, Basic Idea
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ACK1
ACK2
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TCP, Basic Idea
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ACK1
ACK2
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TCP, Basic Idea
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ACK1
ACK2
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TCP, Basic Idea
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ACK2
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TCP, Basic Idea
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ACK2
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TCP, Basic Idea
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ACK2
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TCP, Basic Idea
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TCP, Basic Idea
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Dropped Packets and Retransmission
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Dropped Packets and Retransmission
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Dropped Packets and Retransmission
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Dropped Packets and Retransmission
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Dropped Packets and Retransmission
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Dropped Packets and Retransmission
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Dropped Packets and Retransmission
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Dropped Packets and Retransmission
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Dropped Packets and Retransmission
TIMEOUT
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UDP User Datagram Protocol

• Used for real-time applications (e.g. streaming
  audio and video) where timing is essential but
  perfect delivery is not

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UDP Best Effort Delivery
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UDP Best Effort Delivery
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UDP Best Effort Delivery
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UDP Best Effort Delivery
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UDP Best Effort Delivery
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UDP Best Effort Delivery
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UDP Best Effort Delivery
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UDP Best Effort Delivery
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UDP Best Effort Delivery
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Layered Protocols

• Both TCP (guaranteed delivery) and UDP (fast
  delivery, no guarantees) use the lower-level
  Internet Protocol in the link layer
• But TCP and UDP know nothing about links,
  routing, etc. All that knowledge is embedded in IP

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An analogyPostal Mail Protocols
Higher Level Protocols
Lower Level Protocols