Computer Networks Fundamentals

Chapter 3 TCP/IP Protocol Suite

Introduction to Computer Networks Protocols

1. Most common protocol as it works in LAN + WAN
2. Open for development - not vendor oriented
3. Most widely used over the internet

All layers were combined into some new layers

Application + Presentation + Session => Application Layer

Network => Internet Layer

Data link + Physical => Network Access Layer

Protocol Meaning : It is about group of rules & agreements were set in order to transmit data in right & fast way.

Application Layer Protocols => HTTP - FTP - SMTP - DNS
Transport Layer => TCP - UDP
Internet Layer => IP

Problematic Protocols => NETBEUI protocol - IPX/SPX - Apple Talk

Application Protocols

There are protocols in application layer that provides:

• file transmission services
• web services
• email services

1- HTTP & HTTPS : for web services
are used to transfer web pages that consist of images, texts and, links from the web server to the client browser or VICE VERCA transfer commands from client to server.

2- FTP
is used to transfer files - can be used through browser or cmd can download files from server to the client machine by using some commands and VICE VERCA.

3- Email Protocols: (1) SMTP: Send email from client to server
send emails from client to server.

4- Email Protocols: (2) POP3: Receive email from client
Post Office Protocol version 3 used for (receiving, reading and, downloading email from server to client)

5- DNS
used for mapping/converting domain names to IPs www.test.gov.eg if DNS (.test) server can't know what ip is => then it'll ask (.gov) DNS Server => if not then ask (.eg) DNS

6- DHCP

specified for distributing IP address, subnet mask, Gateway and, DNS from DHCP server to some clients which it's responsible for in addition to supporting them with files helping to browse & emails.

TCP/UDP

Both protocols do segmentation of data

1. TCP adds sequence identifier ID on each segment as it is connection oriented & reliable communication which means:
   we should first ensure that there's a connection loop existing between source and destination. and data are needed to be received without loss correctly
   and in order i.e.(email - file sharing - downloading) any data.

   Header 32-bit sequence number 32-bit acknowledgment number

Included Protocols:/ 1) HTTP - 80
2) HTTPS - 443
3) FTP - 21
4) SMTP - 25
5) POP3 - 110
6) DHCP - 546
7) DNS - 53

1. UDP (connection less oriented & best effort communication): doesn't add sequencing number ID as the most important thing to consider is to send data as fast as possible because latency in these situations is very sensitive more than data loss i.e. voice OR video streaming

   Header: 16-bit source port - 16-bit destination port 16-bit UDP length - 16-bit UDP checksum

Port Number is the mutual part in header in TCP and UDP Meaning is a (16-bit) number added to the data added ranging from 0 - 65,535 tells me what protocol to use in the application

Included Protocols:/ 1) TFTP - 69 2) SNMP - 161

IP

IP protocol divides data into packets and adds logical addresses to it (which is unique and changeable by geo-location of the device)

1. Source IP address
2. Destination IP address

The Router routes these packets by reading its destination IP addresses on each packet passing through it and neglecting it source IP address

routing is done in router based on the routing table which contains all information about all destination IP addresses

We can create this routing table

1. Statically: inside the router configuration by username + password
2. Dynamically

IP address v4 length is 32-bit (4-byte)
[byte] [byte] [byte] [byte]
[0:255] [0:255] [0:255] [0:255]

IP address Classes:

Class A (1 - 126)
public 1.0.0.0 - ============
Private 10.0.0.0 - 10.255.255.255
public ========= - 126.255.255.255

private starts with 10.
To identify network in class A first digit (1.)

---

Class B (128 - 191)
public 128.0.0.0 - ============
Private 172.16.0.0 - 172.131.255.255
public =========== - 191.255.255.255

private starts with 172.16 -to- 172.31
To identify network in class A first two digits (128.0)

---

Class C (192 - 223)
public 192.0.0.0 - ============
Private 192.168.0.0 - 192.168.255.255
public =========== - 223.255.255.255

private starts with 192.168
To identify network in class A first 3 digits (192.0.0)

---

forEx: 163.121.12.15
Network => 163.121 | Host => 12.15 | class B

TCP/IP Commands

1. IPConfig

   shows configuration of TCP/IP protocol Command: ipconfig /all Command: ipconfig /displaydns

   very useful in troubleshooting

2. PING

   for testing connectivity with another device in the same LAN or on the internet Command: ping www.google.com

3. ARP (Address Resolution Protocol)

   shows the resolution between ip + mac addresses

1. FTP

   connect with FTP server by username & password (enables download or upload)

2. NSLooKUP

   IP address of domain name and i need to know the equivalnt ip to it google.com ip = 172.217.19.132

3. ROUTE

   recognizes routing table of my machine - how this device connects to the internet Command: route print

4. NETSTAT

   shows every connection with any device as a form of troubleshooting my machine make with the outside internet with details (foreign address, state and, local address) Command:netstat -a