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UNB/Year 4/Semester 2/CS3873/2024-01-24.md

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+Lecture Topic: Delay and Internet Layering
+
+# Single Packet over Same Rate Links
+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?
+
+# 4 Packets over 2 Same Rate Links
+$d_{trans} = (L/R) = \tau$
+$d_{e2e} = 5\tau$
+Visual in slides
+
+Two phases:
+- Phase 1 has transmitted P-1 packets out
+- Phase 2 has 1 Packet left
+$(P \times \tau) + 1$ ?
+
+# 4 Packets over 2 Links of different rates
+$$d_{e2e} \approx \frac{\text{Total package size}}{\text{E2E throughput}}$$
+So, estimating
+$d_{e2e} \approx \frac{4 \times L}{R} = 4\tau$
+while the real end to end delay is $5\tau$
+
+# Internet Layering
+Also called TCP/IP model
+## Layers (inverse order due to markdown)
+1. Application
+2. Transport
+3. Network
+4. Link
+5. Physical
+## Applications
+- SMTP 
+- HTTP 
+- DNS
+## Transport
+- UDP
+- TCP
+## Network
+- IP
+- Routing protocols
+## Link
+- Ethernet
+- WiFi
+## Physical
+- Moving individual bits from one node to the next
+-