SMT 2-3 Well known Network Services

Summary

This script offers an insightful overview of essential network services, including ARP, DHCP, HTTP, and DNS. It explains how ARP resolves IP to MAC addresses, DHCP dynamically assigns IP addresses, and HTTP facilitates document transfer over the web. The script also highlights the importance of HTTPS for secure communication. Finally, it delves into DNS, which translates domain names into IP addresses, enabling users to access websites easily, and underscores the recursive query process involved in DNS resolution.

Takeaways

• 🔍 The ARP protocol is used to map IP addresses to MAC addresses within the same network, operating at the L2 data link layer.
• 📡 ARP broadcasts a request for MAC addresses when an IP address is known but the corresponding MAC address is not, and stores the response in the ARP table.
• ⚠️ ARP is vulnerable to spoofing attacks where a malicious device can respond first with a false MAC address, leading to misdirected network traffic.
• 📲 DHCP, or Dynamic Host Configuration Protocol, dynamically assigns IP addresses to devices, operating at the L7 application layer and using ports 67 and 68.
• 📈 DHCP is particularly useful for mobile devices that frequently connect and disconnect from a network, preventing IP address wastage.
• 🔄 The DHCP process involves four stages: Discovery, Offer, Request, and Acknowledgment, facilitating dynamic IP allocation.
• 🌐 HTTP, or Hypertext Transfer Protocol, is an L7 application layer protocol used for requesting and responding to HTML documents, typically over TCP port 80.
• 🔒 HTTPS is an encrypted version of HTTP, utilizing TLS to secure data transmission, which is increasingly important as web services become more diverse and sensitive.
• 📝 HTTP requests contain detailed information about the type of request, including the HTTP method (e.g., GET, POST) and any additional headers or body data.
• 📊 HTTP responses include status codes indicating the success or error of the request, along with necessary headers and the body containing the request output.
• 🌐 DNS, or Domain Name System protocol, translates domain names (e.g., google.com) into IP addresses, allowing for easier memorization and access to web services.
• 🔎 The DNS query process involves recursive queries from the user's device through various DNS servers until the correct IP address is found and returned.

Q & A

What is the primary function of the ARP protocol?

The ARP (Address Resolution Protocol) is responsible for mapping IP addresses to MAC addresses within a network, allowing devices to communicate with each other using MAC addresses for data transfer within the same network.

How does the ARP protocol work when an IP address is unknown?

When an IP address is unknown, the device broadcasts an ARP request throughout the network. The device with the matching IP address responds with its MAC address, which is then stored in the ARP table for future communications.

What security vulnerability does the ARP protocol have?

The ARP protocol trusts all responses, which makes it susceptible to ARP spoofing. A malicious user can respond with an incorrect MAC address for a known IP, and if their response is the first to arrive, the incorrect MAC address will be stored in the ARP table, redirecting traffic intended for the legitimate IP to the attacker.

What does DHCP stand for and what is its role in network communication?

DHCP stands for Dynamic Host Configuration Protocol. It dynamically allocates IP addresses to devices on a network, which is particularly useful for mobile devices that frequently connect and disconnect from the network, ensuring efficient IP address distribution and usage.

In which network layer does DHCP operate and what ports does it use?

DHCP operates in the L7 layer, also known as the Application Layer, and it uses ports 67 for UDP and 68 for TCP communication.

What are the four stages of DHCP communication?

The four stages of DHCP communication are Discovery, where the client broadcasts a request for an IP; Offer, where the DHCP server offers an available IP; Request, where the client requests the offered IP; and Acknowledgment (ACK), where the server finalizes the IP allocation.

What is HTTP and what is its main purpose?

HTTP stands for Hypertext Transfer Protocol. It is a protocol used for transferring document information between network devices, primarily for requesting and responding to HTML documents over the World Wide Web.

How has the security of HTTP evolved to address modern web needs?

The security of HTTP has evolved with the introduction of HTTPS, which is HTTP over TLS (Transport Layer Security). This encrypts the data being transferred, providing a secure method for communication over the web and protecting against eavesdropping and tampering.

What information is typically included in an HTTP request?

An HTTP request includes the HTTP version, URL information of the web service being requested, HTTP method (such as GET or POST), and additional headers that may specify data to be sent to the server. If using the POST method, the request also includes a body part with the data to be submitted.

What is the purpose of the DNS protocol and how does it work?

The DNS (Domain Name System) protocol translates domain names, which are user-friendly addresses like google.com, into IP addresses that computers use to communicate. It operates at the L7 application layer and uses ports TCP and UDP 53. When a user enters a domain name, a DNS query is sent to a DNS server, which then returns the corresponding IP address.

Can you describe the process of a DNS query when accessing a website?

When a user wants to access a website, such as example.com, a DNS query is initiated. If there is no cached data, the DNS resolver performs a recursive query, starting with the root DNS server, then querying the TLD (Top-Level Domain) server, and finally obtaining the IP address from the DNS server responsible for the domain. The IP address is then delivered to the user, who can use it to send an HTTP request to the server.

Outlines

00:00

🌐 Network Services Overview

This paragraph introduces various well-known network services, including ARP, DHCP, HTTP, and DNS. ARP is explained as a protocol that connects IP and MAC addresses, necessary for data transfer within the same network. The vulnerability of ARP to spoofing attacks is also discussed. DHCP is described as a protocol that dynamically assigns IP addresses to devices, operating at the application layer and utilizing ports 67 and 68. The DHCP process is broken down into four stages: Discovery, Offer, Request, and Acknowledgment. HTTP is introduced as a protocol for transporting document information, primarily used for HTML documents, and operates at the application layer using TCP port 80, with a mention of the security-enhanced HTTPS. The paragraph concludes with an introduction to the DNS protocol, which translates domain names into IP addresses, facilitating easier access to web services.

05:00

🔍 Deep Dive into HTTP and DNS Protocols

This paragraph provides a detailed look at the HTTP and DNS protocols. HTTP methods such as GET and POST are explained, with GET used for simple page requests and POST for submitting data. The structure of an HTTP request and response is outlined, including the HTTP header and body. HTTP status codes are mentioned, indicating the success or failure of a request. The DNS protocol is then explored in depth, explaining how it resolves domain names to IP addresses using a hierarchical system of DNS servers. The process of a DNS query is described, starting from the user's input in the browser to the recursive queries made by the DNS resolver to find the correct IP address. The paragraph concludes with an example of accessing 'example.com', illustrating the steps involved in a DNS query and the eventual delivery of the IP address to the user.

Keywords

💡ARP protocol

The ARP (Address Resolution Protocol) is a protocol used to map an IP address to a MAC address within a local network. It operates on the data link layer (Layer 2) of the OSI model. In the video, ARP is essential for understanding how devices communicate within the same network by resolving IP addresses to MAC addresses, which are required for direct communication. The script mentions ARP in the context of broadcasting an IP address to find the corresponding MAC address and the potential security issue of ARP spoofing.

💡MAC address

A MAC (Media Access Control) address is a unique identifier assigned to network interfaces for communications on the physical network segment. In the script, MAC addresses are highlighted as crucial for local network communication, where ARP is used to translate IP addresses to MAC addresses, enabling devices to communicate directly with each other.

💡DHCP

DHCP (Dynamic Host Configuration Protocol) is a network management protocol used to dynamically assign IP addresses and other network configuration parameters to devices on a network. The script explains that DHCP operates on the application layer (Layer 7) and is vital for dynamically allocating IP addresses to devices, especially mobile ones that frequently connect and disconnect from the network.

💡HTTP

HTTP (Hypertext Transfer Protocol) is the foundational protocol for data communication on the World Wide Web, used for fetching resources from web servers. The script describes HTTP as an application layer protocol that facilitates the transfer of document information, primarily HTML documents, and highlights the evolution to HTTPS for secure communication.

💡DNS

DNS (Domain Name System) is the protocol for resolving human-readable domain names, like 'google.com', into IP addresses that computers use to identify each other on the network. The script explains the DNS protocol as an essential part of accessing web services by translating domain names into IP addresses, which are then used to establish a connection.

💡IP address

An IP (Internet Protocol) address is a numerical label assigned to devices participating in a computer network that uses the Internet Protocol for communication. The script discusses the role of IP addresses in both local and global network communication, and how they are translated to MAC addresses by ARP or resolved by DNS for domain names.

💡HTTPS

HTTPS (Hypertext Transfer Protocol Secure) is an extension of HTTP that adds security through encryption, typically using TLS (Transport Layer Security). The script mentions HTTPS as an important development for secure web communication, where the HTTP protocol is used in conjunction with TLS to protect data integrity and privacy.

💡TCP/IP

TCP/IP (Transmission Control Protocol/Internet Protocol) is the fundamental communication protocol used for transmitting data over the internet. While not explicitly mentioned in the script, the concepts of IP addresses and HTTP imply the use of TCP/IP for network communication.

💡Application layer

The application layer is the topmost layer of the OSI model and is responsible for providing the interface between the user's application programs and the network. The script refers to the application layer in the context of DHCP and HTTP, explaining how these protocols operate at this layer to facilitate user interactions with network services.

💡Data link layer

The data link layer is the second layer of the OSI model, providing node-to-node data transfer and detecting errors that may occur in the physical layer. The script discusses the ARP protocol's operation at this layer, emphasizing its role in handling MAC addresses for direct communication within a network.

💡TLS

TLS (Transport Layer Security) is a cryptographic protocol designed to provide communications security over a computer network. The script explains that HTTPS uses TLS at the transport layer to secure HTTP communications, making it a critical component for web security.

Highlights

Introduction to well-known Network Services including ARP, DHCP, HTTP, and DNS.

Explanation of ARP protocol's role in connecting IP and MAC addresses within the same network.

Description of the process of IP to MAC address conversion using ARP broadcasts and responses.

Risk of ARP spoofing where a malicious user can hijack IP communication by responding first to ARP requests.

Overview of DHCP (Dynamic Host Configuration Protocol) for dynamic IP address allocation.

DHCP operates on the L7 layer and uses ports 67 and 68 for communication.

DHCP's four-stage communication process: Discovery, Offer, Request, and Acknowledgment.

Importance of DHCP in efficiently managing IP addresses for mobile and frequently connected/disconnected devices.

Introduction to HTTP (Hypertext Transfer Protocol) for document information transfer between network devices.

HTTP is an L7 application layer protocol using TCP port 80, with the option to change ports for specific purposes.

Evolution of web services from simple information sharing to diverse features requiring increased security.

Explanation of HTTPS as an encrypted version of HTTP using TLS for secure communication.

Details of the HTTP communication process including request and response structures.

Importance of HTTP methods like GET and POST for different types of web service interactions.

Introduction to DNS (Domain Name System) protocol for translating domain names to IP addresses.

DNS operates on the L7 layer using TCP and UDP ports 53 for domain name resolution.

Process of DNS query and resolution from user request to server IP delivery.

Role of DNS resolver in performing recursive queries to find the IP corresponding to a domain name.

Final discussion on the practical applications of DNS in accessing web servers using domain names.

Transcripts

this is the last part in this part we

will learn about some of the well-known

Network Services out there including a

RP DHCP HTTP and DNS we will go through

each service together finally I will

introduce you to the most well-known

Network

Services the ARP protocol is a protocol

that connects the IP and Mac addresses

an IP address is used to transfer

packets to different networks however

when transferring data within the same

network it must communicate using m

addresses this requires the process of

converting IP addresses to Mac addresses

the RP protocol is a protocol that

operates in the L2 data link layer

because it deals with Mac addresses as

the main the analogy is quite simple if

there is an IP address that does not

know the MAC address the following IP

addresses will be broadcasted throughout

the network and the device with this IP

responds back with a Mac address among

the various devices that have received

the request packet when you receive an

ARP response the IP and the MAC address

both will be stored in the RP table

afterwards the message is delivered

according to the contents written on the

table but what if another device

responds first that it has the IP even

though the MAC address is different

because the lp protocol trusts all

responses it applies the first ARP

response that arrives the MAC address

requested by the malicious user is then

stored in the RP table with 0.10 IP in

this situation any communication that

must be sent to

0.10 IP is is sent to a malicious

user now let's talk about DHCP DHCP

stands for dynamic host configuration

protocol it is a protocol that

dynamically allocates IP addresses

according to the situation it operates

in the L7 layer or application layer and

uses your DP Port 6768 you can use it

one at a time but you might be wondering

why you need to assign it dynamically in

terms of availability low Mobility

devices such as servers will benefit

more from fixed IP rather than Dynamic

IP however mobile devices such as mobile

phones and laptops can be connected or

disconnected at any time if one IP is

fixed to such a highly mobile device

that IP is wasted if the device is not

using the network in order to

effectively distribute IP in these cases

the DHCP protocol is used to provide IP

dynamically the principle is simple when

new equipment emerges in the network IP

will have to be allocated for

communication the device notifies the

network that it wants to be assigned an

IP

and when the packet arrives the DHCP

server chooses one of the available IP

addresses and informs the device which

IP to be

used if you look at the diagram here

you'll notice that the actual DHCP is

carried out in four stages of

communication the client sends a

broadcast packet to port a67 and the

DHCP server responds to Port 68 of the

client for example the client should

tell the DHCP server that it needs an IP

but doesn't know who the DHCP server is

so instead the client broadcasts and

sends a message to the network saying I

need an IP this process is also known as

Discovery the DHCP server responds by

selecting one of the available IP

addresses this process is called an

offer the client now checks the IP and

requests final approval from the DHCP

server to use it this is called a

request finally the server sends a CK

package to finalize the IP allocation

process now let's talk about HTTP HTTP

stands for hypex transfer protocol a

protocol designed to transport document

information between network devices it

is mainly used to request and respond to

HTML documents it is an L7 application

layer protocol that uses tcp8 ports but

the port can be changed depending on the

purpose typically you can communicate

via a browser using an application that

handles HTTP suchar as Chrome or Firefox

in the early days of the internet web

pages were veloped just for sharing

information however nowadays there are

various Services provided to users over

the web as features of the web become

more diverse and essential information

increases security is becoming more

important therefore https with

encryption is being utilized more

because https is encrypted there is no

need to worry about the analysis https

is actually the same structure as HTTP

but when the HTTP protocol is used with

TLS at the transport layer to strengthen

security it becomes

https let's learn more about the HTTP

communication process first of all HTTP

requests contain detailed information

about what kind of request you want to

make to the server in order to request

HTTP packet you need to specify the HTTP

version for communication as well as the

URL information of the web service you

want to visit if you have filled out

basic information about the web service

you can also specify additional data you

want to obtain from the web service

here I need to specify the HTTP method

and write down what action I will do for

example you can use the get method for

simple page requests and pause for

submitting specific data there are also

many other methods available in addition

to the method various additional

requests are also included in the HTTP

header finally when you write a request

to send some data to the server using

the post method the HTTP request packet

is completed by putting the data

corresponding to the body part

in this part we will go through the HTTP

response that the server receives after

processing the HTTP request the HTTP

response contains various information

about the result of processing the HTTP

request an HTTP status code is returned

to indicate if the request was

successfully processed or if an error

occurred in addition several header

Fields required for response are set and

the body contains the output of the

request process here the status code can

have a variety of values usually

consisting of three-digit integers whose

properties are largely divided based on

the 100

digit next let's move on to domain name

system protocol which can be abbreviated

as DNS protocol originally communication

between the two machines was done using

IP and Mac addresses however in the case

of web services you must know IP in

order to reach the system and it is not

easy to memorize the IP address of each

service instead you can access it by the

nickname of a domain like google.com so

does that mean there is an address Cod

domain instead of Ip and Mac addresses

that communicates with IP addresses the

domain name system is what allows you to

communicate with each domain and in

order for you to use the domain name

system you must follow the DNS protocol

DNS protocol is a protocol that

determines the IP address based on the

domain name and helps communicate with

other nodes using only the domain name

it is an L7 application layer protocol

and it uses ports TCP UDP 53 if you look

at the simple diagram structure the

principle is not difficult if the user

searches the domain name in the address

bar it actually sends a DNS query to the

DNS server the DNS server checks the

domain name in the requested query finds

the appropriate IP and delivers a DNS

response which includes the IP to the

client now let's take a look at the

details of the DNS query for example

when a user wants to access example.com

using a web browser as soon as he types

example.com in the address bar and press

enter DNS query occurs to find the

server where example.com is being

serviced if there is already cache data

the corresponding IP will be returned

immediately cache data here means there

is history on the location of the domain

if there is history of the location then

there is no need to search for the

requested domain but for the sake of

explanation of the principle let's

assume that all DNS servers have no

cache data the DN s resolver recursive

queries to find the IP corresponding to

the requested domain in this diagram

steps 2 to seven are recursive query

processes performed by DNS resolver

first the DNS resolver will query

www.example.com domain to root DNS

server root DNS server will notify the

address of the next server that needs to

be query com DNS server Doom DNS server

is called tldd also known as top level

domain it refers to the highest DNS

server with numerous subdomains such as

com by quering the TLD server you can

get the address of the DNS server that

manages example.com

finally by quering this DNS server you

can acquire the example.com address then

the DNS resolver delivers the final IP

address to the user users can optionally

send HTTP request to the actual server

by using the actual IP address of

example.com as shown in the last two

slides hope you enjoyed this class