From 2ea1af6ec09c5d3f0d4c61c7406e79f7329c3c13 Mon Sep 17 00:00:00 2001
From: Ryan <ryan@alien.gov>
Date: Sat, 4 Jan 2025 15:36:07 +0800
Subject: [PATCH] Explained preserved IPs

---
 1-4-scalability.md | 14 ++++++++++----
 2-4-aws-vpc.md     |  1 +
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/1-4-scalability.md b/1-4-scalability.md
index 3314bbd..31969bc 100644
--- a/1-4-scalability.md
+++ b/1-4-scalability.md
@@ -70,6 +70,7 @@
     - $$Efficiency = E = Speedup / n = 1 / ( \alpha \times n + 1 - \alpha )$$
 - Efficiency is low, when load is large, because most nodes are idling (waiting
   for serial computation to complete)
+- Also called **fixed workload efficiency**
 
 ### Gustafson’s Law
 
@@ -96,18 +97,23 @@
 
 ## Types of scaling
 
-- Strong: How performances changes, by increasing **processors** for **fixed** problem
-- Weak: How the performance changes by increasing **processors** for **problem per processor** 
+- Strong: How performances changes, by increasing **processors** for **fixed**
+  problem
+- Weak: How the performance changes by increasing **processors** for **problem
+  per processor**
 
 ## Scalability in cloud computing
 
 - Elasticity: resource can be altered
 - Virtualization scaling: adding existing system to cloud
-    - Performance issues: Performance of virtualized components may be slower than bare metal
+    - Performance issues: Performance of virtualized components may be slower
+      than bare metal
 - Scale by migrating resources: Regions and Availaility Zones
     - Region: physical geographical location, that consists of one or more zones
 - Load balancing: AWS Elastic Load balancing, distributes incoming application
   traffic across multiple targets.
 - Auto scaling: AWS EC2 auto scaling
-- CDN: AWS CloudFront, use edge caching on edge location to serve content to anywhere closer to the vieweer, in order to achieve lower **latency** and higher **transfer speed** 
+- CDN: AWS CloudFront, use edge caching on edge location to serve content to
+  anywhere closer to the vieweer, in order to achieve lower **latency** and
+  higher **transfer speed**
 - TODO: work the questions
diff --git a/2-4-aws-vpc.md b/2-4-aws-vpc.md
index 86ac2c5..06b2eaf 100644
--- a/2-4-aws-vpc.md
+++ b/2-4-aws-vpc.md
@@ -87,6 +87,7 @@
       available
 - Possible EC **Instances**: Number of possible IP addresses minus **5**
     - AWS reserved the first 4 and last IP addresses (4+1=5)
+        - First and last: network address and broadcast address
     - From the last example, there can be atmost $4096 - 5 = 4091$ instances in
       the network