comms

_data/navigation.yml

@@ -18,6 +18,11 @@
   link: /cpp_workshop/
   sorted: true
 
+
+- name: Intro to Communcations
+  link: /comms/
+  sorted: true
+
 - name: Data Security
   link: /intro_sec
   sorted: true

comms/README.md

@@ -0,0 +1,135 @@
+---
+layout: page
+title: Intro to Computer Communications
+permalink: /comms/
+description: My notes for the intro to computer communications course
+sitemap:
+  priority: 0.7
+  changefreq: "monthly"
+date: '2024-05-04'
+categories: cpp
+tags:
+- Communications
+- UDP
+- TCP
+- ComputerCommunications
+---
+
+TCP/IP Model
+
+5. Application
+
+    - Message
+
+4. Transport
+
+    - Segment
+
+3. Network
+
+    - Datagram
+
+2. Link
+
+    - Frame 
+
+1. Physical
+
+OSI Model takes the Application layer and splits it to 3 different "layers":
+
+* Application
+
+* Presentation
+
+* Session
+
+
+8 Bits = 1 Byte
+
+IPv4: 
+
+    * 32 bit address = 4 bytes 
+
+    * 8 bits.8 bits.8 bits.8 bits In binary
+
+    * Each section can get values from 0-255 = 256 total values
+
+    * Network Address = set all host bits to 0 
+
+    * Broadcast address = set all host bits to 1 
+
+    * number of available host addresses - need to subtract 2 from # of available addresses (cause of net address and broadcast address) 
+
+
+Packet transmission delay: L (bits) / R (bits/sec)
+
+Propagation delay:
+
+    *  d(length of physical link)/s (prop speed)
+
+    *  Often times use speed of light 3*10^8 for fiber 
+
+    *  For copper use 2 * 10^8 
+
+    *  Still quite fast but will never get to speed of light 
+
+ARP: 
+
+   *  Send a request via MAC to broadcast and ask for someone’s IP
+
+   *  MAC broadcast is all bits set to 1, which in HEX will result in an address with lot of F’s
+
+   *  It is a layer 2-ish protocol 
+
+TTL: 
+   *  time to live - 1 byte - so can be from 0 to 255 
+
+   *  Measured in hops not seconds or any other time unit
+
+   *  Start with X for TTL, Every router we pass, TTL = TTL-1
+
+   *  Once we get to 0, packet gets dropped and often we get an ICMP response telling us that happened 
+
+TCP: 
+   *  NO BROADCAST EXISTS HERE  
+
+        - As we need a destination port and 3 way handshake with someone
+
+TCP Socket: 
+
+   *  Needs all 4 of these:  SRC IP, SRC PORT, DEST IP, DEST PORT
+
+   *  Socket is two-way like a pipe with opening on both sides (src - dest)      
+
+Broadcast packet never gets past the router (gets dropped), otherwise many more computers than anticipated will get these packets
+
+Switch - Internal to a network 
+
+Forwarding table - Where to send packet to
+
+Router: 
+
+   *  Sits between your network and the internet (more or less)
+
+   *  Converts your internal IP to a public one via Network Address Translation
+
+ICMP: 
+
+   *  Wrapped in an IP packet
+
+   *   If it is an error report, you will get IP header - ICMP header - IP header 
+
+         -  2nd ip header is a minimum of first 8 bytes of the packet that caused the error
+         -  Can and may be more bytes of previous packet
+
+   *  Layer 3ish protocol 
+
+
+
+### Helpful Links
+
+
+https://gaia.cs.umass.edu/kurose_ross/interactive/ (practice quizzes) 
+
+
+https://www2.ic.uff.br/~michael/kr1999/1-introduction/1_06-delay.htm