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Questions and Answers
Non-persistent HTTP response time consists of 2RTT plus file transmission time.
True
Persistent HTTP requires 3 RTTs per object.
False
The POST method uploads data in the request line URL field.
False
The HTTP/1.1 protocol includes the PUT method for uploading files.
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In the HTTP request message format, a carriage return and line feed indicate the end of header lines.
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SMTP uses port 80 to transfer email messages reliably from client to server.
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The message queue on a mail server stores incoming messages for users.
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The SMTP protocol relies on command/response interactions similar to how HTTP operates.
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Messages sent through SMTP must be in 8-bit ASCII format.
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IMAP allows users to organize messages in folders.
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The Domain Name System (DNS) is a centralized database for domain name resolution.
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DNS services include the resolution of IP addresses to domain names.
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The IP address used for datagram addressing is 64 bits long.
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The core function of DNS is to translate addresses and names.
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Study Notes
Non-Persistent HTTP
- Response time is calculated as 2RTT + file transmission time.
- RTT (Round Trip Time) is the time it takes for a small packet to travel from the client to the server and back.
- Requires 2 RTTs per object
- There is OS overhead for every TCP connection created.
Persistent HTTP
- The server leaves the connection open after sending the response.
- Subsequent messages are sent over the open connection.
- Uses as little as 1 round trip time to fetch all referenced objects.
HTTP request message
- There are two types of HTTP messages: request and response.
- ASCII format is used for the HTTP request message.
- The request line includes method (GET, POST, HEAD), URL, and version.
- Header lines include information about the client and the request.
- The entity body contains data uploaded by the user.
HTTP response message
- The status line includes the protocol, status code, and status phrase.
- Header lines include information about the server and the response.
- The data section contains the requested information or error message.
Method types
- The GET method is used for retrieving information from the server, including data from a URL field.
- The POST method is used for uploading data to the server, including data from the entity body.
- The HEAD method requests the server to send only the header lines of the response.
- The PUT method is used for uploading a file to a specific file path on the server.
- The DELETE method is used for deleting a file specified in the URL field.
Electronic mail
- Mail servers handle incoming and outgoing messages for users.
- User Agents (UAs) are used for composing, editing, and reading mail messages
- SMTP protocol is used for sending email messages between mail servers.
Electronic Mail: SMTP [RFC 2821]
- Uses TCP to transfer messages reliably.
- Transfer is performed in 3 phases: handshaking, message transfer, and closure.
- Commands are sent in ASCII text, and responses are received with a status code and phrase.
POP3
- Allows for messages to be downloaded and deleted from the server.
- Download-and-keep mode allows users to retain copies of messages on different clients.
- Stateless across sessions.
IMAP
- Keeps all messages on the server with multiple folders.
- Allows for organization.
- Keeps user state across sessions.
DNS (Domain Name System)
- A distributed database maintained by a hierarchy of name servers.
- A protocol mapping IP addresses to names.
- Allows for efficient name resolution.
DNS: Services, Structure
- Performs name to IP address resolution and vice versa.
- Allows for domain name registration and management.
- Implemented on every DNS server across the internet.
Socket Programming
- An interface between application processes and transport protocols (TCP/UDP).
- Creates a logical connection between two processes.
- Two socket types, one for UDP and one for TCP.
Chapter 2 Summary
- Most importantly, learned about protocols!
- Control vs. data messages exist.
- Key themes include: centralized vs. decentralized implementations, stateless vs. stateful operations, and reliable vs. unreliable message transfer.
- Complexity at network's edge is an important consideration.
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Description
Dive into the details of Non-Persistent and Persistent HTTP protocols. This quiz explores response times, message types, and the structure of HTTP request and response messages. Test your understanding of key concepts that underlie web communication.
