SMT 2-3 Well known Network Services
Summary
TLDRThis 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
🌐 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.
🔍 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.
Mindmap
Keywords
💡ARP protocol
💡MAC address
💡DHCP
💡HTTP
💡DNS
💡IP address
💡HTTPS
💡TCP/IP
💡Application layer
💡Data link layer
💡TLS
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
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