Delay, Loss & Throughput

Delay

The time it takes for processing and transmitting a packet from source to destination.

• 1. Transmission Delay (d_trans)

  Time to push the packet bits into the link.

  LAW: d_trans = L / R

  (L = Packet Length, R = Link Bandwidth)

  ده الوقت اللي بناخده عشان نطلّع فيه الـ Data من الـ Computer للسلك الواصل بيه، أو عشان نطلع بيه الـ Data للهوا مثلاً (WiFi).

• 2. Propagation Delay (d_prop)

  Time for bits to travel through the medium at propagation speed.

  LAW: d_prop = d / s

  (d = Distance, s = Propagation Speed (~2x10⁸ m/s))

  ده الوقت اللي الـ Data بتاخده عشان تتنقل من Host A لـ Host B، وبيتحسب بقسمة المسافة على سرعة الضوء.

• 3. Processing Delay

  Time required by routers to decide where to forward the packet.

  ده الزمن اللي بياخده الراوتر عشان يعمل شوية حسابات على الـ Data ويشوف هيروح فين بالظبط.

• 4. Queuing Delay (d_queue)

  Time the packet waits in the buffer for transmission.

  LAW (Traffic Intensity): I = (L * a) / R

  If I ≈ 0 → Small Delay
  If I → 1 → Large Delay
  If I > 1 → Packet Loss!

  الوقت اللي الباكت بتقضيه وهي مستنية في الطابور عشان تخرج للسلك.

Packet Loss

Occurs when the arrival rate exceeds the buffer capacity (queue is full).

Throughput & Bottleneck

Throughput: Rate (bits/time) at which bits are sent from sender to receiver.

Bottleneck Link: The link that limits the end-to-end throughput (the slowest link).