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DNS Resolution - Full Journey from Browser to IP

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Steps

setup

Browser initiates DNS query

The browser creates a DNS query packet for www.example.com and sends it to the local DNS resolver.

💡 This step starts the DNS resolution journey by generating the initial query packet from the client side.

Line:

query_packet = create_dns_query('www.example.com')
send_packet(browser, local_resolver, query_packet)

💡 The DNS resolution process begins with the client sending a query to its configured DNS resolver.

def dns_resolution(domain):
    # STEP 1: Browser creates and sends query
    query_packet = create_dns_query(domain)  # STEP 1
    send_packet('browser', 'local_resolver', query_packet)  # STEP 1

    # STEP 2: Local resolver receives and checks cache
    packet = receive_packet('local_resolver')  # STEP 2
    if not cache_hit(domain):  # STEP 2
        send_packet('local_resolver', 'root_dns', packet)  # STEP 2

    # STEP 3: Root DNS server processes and replies with referral
    packet = receive_packet('root_dns')  # STEP 3
    referral = get_tld_referral(domain)  # STEP 3
    send_packet('root_dns', 'local_resolver', referral)  # STEP 3

    # STEP 4: Local resolver sends query to TLD DNS server
    referral = receive_packet('local_resolver')  # STEP 4
    send_packet('local_resolver', 'tld_dns', create_dns_query(domain))  # STEP 4

    # STEP 5: TLD DNS server replies with authoritative referral
    packet = receive_packet('tld_dns')  # STEP 5
    referral = get_authoritative_referral(domain)  # STEP 5
    send_packet('tld_dns', 'local_resolver', referral)  # STEP 5

    # STEP 6: Local resolver queries authoritative DNS server
    referral = receive_packet('local_resolver')  # STEP 6
    send_packet('local_resolver', 'auth_dns', create_dns_query(domain))  # STEP 6

    # STEP 7: Authoritative DNS server replies with IP
    packet = receive_packet('auth_dns')  # STEP 7
    answer = get_ip_address(domain)  # STEP 7
    send_packet('auth_dns', 'local_resolver', answer)  # STEP 7

    # STEP 8: Local resolver caches the IP
    response = receive_packet('local_resolver')  # STEP 8
    cache_store(domain, response.data)  # STEP 8

    # STEP 9: Local resolver sends IP to browser
    send_packet('local_resolver', 'browser', create_dns_response(response.data))  # STEP 9

    # STEP 10: Browser receives IP
    response = receive_packet('browser')  # STEP 10
    ip_address = extract_ip(response)  # STEP 10
    return ip_address

📊

DNS Resolution - Full Journey from Browser to IP - Watch the Algorithm Execute, Step by Step

Watching each packet hop and processing step reveals how DNS resolution works in practice, clarifying the roles of different DNS servers and the flow of queries and responses.

Step 1/10

·Active fill★Answer cell

Browser sends DNS query packet to local resolver

Hop: 1

Browser

Local DNS Resolver

Root DNS Server

TLD DNS Server

Authoritative DNS Server

📦Packet

↗ frombrowser

↘ tolocal_resolver

📄 payloadDNS Query: www.example.com

🔌 protocolDNS

🚩 flagsquery

src→192.168.1.2:5353

dst→192.168.1.1:53

data→www.example.com

flags→query

Query: browser→local_resolver (www.example.com)

Practice

(1/5)

1. Which component in a CDN architecture is primarily responsible for serving cached content closest to the user to reduce latency?

easy

A. Edge server located near the user's geographic region

B. Origin server that stores the master copy of content

C. DNS server that resolves domain names to IP addresses

D. Load balancer distributing requests among origin servers

Start learning this pattern below

Browser initiates DNS query

Local resolver receives query and checks cache

Root DNS server receives query and responds with TLD server referral

Local resolver receives referral and queries TLD DNS server

TLD DNS server receives query and replies with authoritative server referral

Local resolver queries authoritative DNS server

Authoritative DNS server receives query and responds with IP address

Local resolver receives IP and caches it

Local resolver sends IP address response back to browser

Browser receives IP address and completes DNS resolution

Key Takeaways

Practice

Solution

Step 1: Identify the role of the origin server

Step 2: Understand the edge server's function

Step 3: Clarify DNS server's role

Step 4: Load balancer's responsibility

Final Answer:

Quick Check:

Solution

Step 1: Identify the role of each component

Step 2: Understand Proxy and Reverse Proxy roles

Step 3: CDN role

Final Answer:

Quick Check:

Solution

Step 1: Understand the safety property of HTTP methods

Step 2: Analyze other methods

Final Answer:

Quick Check:

Solution

Step 1: Define stale-while-revalidate

Step 2: User experience

Step 3: Background refresh

Step 4: Analyze other options

Final Answer:

Quick Check:

Solution

Step 1: Understand RTO adaptation to RTT variance

Step 2: Analyze handling of large RTT variations

Step 3: Evaluate options

Final Answer:

Quick Check: