feat: complete 2.1

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@@ -252,7 +252,73 @@ The conditional GET mechanism solves the problem of **cache consistency** - ensu
 
 ### 2.1 File Transfer Analysis (20%)
 
-[To be completed]
+**Given:**
+- File size: 10 MB = 10 × 10^6 bytes = 80 × 10^6 bits
+- Packet size: 10,000 bits (including 100 bits header)
+- Payload per packet: 9,900 bits
+
+#### a) Number of packets
+
+Number of packets = Total file bits ÷ Payload bits per packet
+= 80 × 10^6 bits ÷ 9,900 bits/packet
+= 8,080.81 packets
+= **8,081 packets** (rounded up)
+
+#### b) Links identified using traceroute
+
+Based on traceroute to google.com (representing university server path):
+1. Home router → ISP gateway (192.168.1.254 → 192.168.0.1)
+2. ISP local → ISP regional (192.168.0.1 → 10.139.230.1)
+3. ISP → Internet backbone (10.139.230.1 → 209.85.174.62)
+4. Multiple backbone links through Google's network
+5. Final delivery to destination server
+
+**Total identified links: 14 hops**
+
+#### c) Link speed calculations
+
+Based on traceroute RTT measurements:
+
+| Link | From → To | RTT (ms) | Estimated Speed |
+|------|-----------|----------|----------------|
+| 1 | Home → Router | 16 | ~100 Mbps (Local Ethernet/Wi-Fi) |
+| 2 | Router → ISP | 16 | ~50 Mbps (Residential broadband) |
+| 3 | ISP Local | 18 | ~1 Gbps (ISP infrastructure) |
+| 4-14 | Backbone | 38-79 | ~10+ Gbps (Internet backbone) |
+
+**First link speed estimation:** ~50 Mbps (residential upload speed)
+
+#### d) Time for last packet to enter first link
+
+Transmission time per packet = Packet size ÷ Link speed
+= 10,000 bits ÷ (50 × 10^6 bps)
+= 0.2 ms per packet
+
+Time for all packets to enter first link:
+= 8,081 packets × 0.2 ms/packet
+= **1,616.2 ms = 1.62 seconds**
+
+At t₀ + 1.62 seconds, the last packet will be pushed into the first link.
+
+#### e) Time for last packet to arrive at university server
+
+Total end-to-end delay consists of:
+- **Transmission delays:** Each link transmits the packet
+- **Propagation delays:** Signal travel time (estimated ~79 ms from traceroute)
+- **Processing delays:** Router processing (estimated ~1 ms per hop)
+- **Queuing delays:** Variable, estimated ~5 ms average per hop
+
+**Calculation:**
+- Time for last packet to enter first link: 1.62 s
+- Transmission time through all links: ~0.2 ms × 14 = 2.8 ms  
+- Propagation delay: ~79 ms
+- Processing delays: 1 ms × 14 = 14 ms
+- Queuing delays: 5 ms × 14 = 70 ms
+
+**Total time = 1.62 s + 0.0028 s + 0.079 s + 0.014 s + 0.070 s**
+**= 1.786 seconds**
+
+The last packet will arrive at the university server at **t₀ + 1.79 seconds**.
 
 ### 2.2 Propagation Delay and Bandwidth-Delay Product (20%)