2024-01-24 12:12:09 -04:00
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Lecture Topic: Delay and Internet Layering
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# Single Packet over Same Rate Links
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If each node has the same rate, and you consider only transmission delay, what is the end to end delay to send one packet of length L?
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# 4 Packets over 2 Same Rate Links
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$d_{trans} = (L/R) = \tau$
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$d_{e2e} = 5\tau$
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Visual in slides
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Two phases:
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- Phase 1 has transmitted P-1 packets out
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- Phase 2 has 1 Packet left
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2024-01-29 20:42:41 -04:00
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$$(P + N) \times \tau = d_{e2e}$$
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2024-01-24 12:12:09 -04:00
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# 4 Packets over 2 Links of different rates
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$$d_{e2e} \approx \frac{\text{Total package size}}{\text{E2E throughput}}$$
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So, estimating
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$d_{e2e} \approx \frac{4 \times L}{R} = 4\tau$
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while the real end to end delay is $5\tau$
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# Internet Layering
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Also called TCP/IP model
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## Layers (inverse order due to markdown)
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1. Application
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2. Transport
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3. Network
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4. Link
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5. Physical
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## Applications
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- SMTP
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- HTTP
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- DNS
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## Transport
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- UDP
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- TCP
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## Network
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- IP
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- Routing protocols
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## Link
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- Ethernet
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- WiFi
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## Physical
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- Moving individual bits from one node to the next
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2024-01-24 12:22:37 -04:00
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Terms:
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- Router (Operates on network layer)
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- Switch (Operates on link layer)
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- Modem (Modulation, converting mediums and modes)
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- Access Point (WiFi access)
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## Protocols
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Define how peers communicate and exchange information over the network including rules, procedures, and message formats
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Application layer protocols:
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- Web server to web client (HTTP)
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(More examples for each layer in slides)
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### Encapsulation
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Messages get passed down between each layer, and information gets appended to the header that gets delivered as the payload
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