(F) Chapter 3 Transpor Layer Flashcards
What is Transport Layer?
- [Transport layer] primary function is to provide reliable and efficient data transfer between devices across a network. In summary, involved transmitting data from application to application across devices, over the underlying network layers.
… like this
sender: breaks application messages into segments, passes to network layer
receiver: reassembles segments into messages, passes to application layer
- [Transport layer] does this by breaking down large messages into smaller parts, adding labels to them, and making sure try arrive in the correct order. The transport layer ensures that data sent between devices is delivered accurately
Key protocols of [Transport layer]
TCP (Transmission Control Protocol)
UDP (User Datagram Protocol)
TCP vs UDP
- [TCP] is a connection-oriented protocol that ensures reliable and ordered delivery of data
#TCP characteristics:- reliable, in-order delivery
- congestion control
- flow control
- connection setup
- while… [UDP] is a simpler, connectionless protocol that does not guarantee delivery or order
#UDP characteristics:- unreliable, unordered delivery
- lack of built-in flow control
Example: TCP is like sending a registered mail with acknowledgement of receipt, whereas UDP is like sending a standard letter without a guarantee it’ll be delivered.
Connection-oriented vs connectionless
- [Connection-oriented] communication involves a prelim
inary setup phase (like a handshake) before data transfer and ensures data is received in order
-while… [Connectionless] does not establish a dedicated connection and sends data without ensuring order or delivery
Example: a phone call is connection-oriented (you establish a connection before talking), while postal mail is connectionless (you send it without ensuring the recipient is ready to achieve)
sidenote: preliminary setup phase for connection-oriented mean two devices on a network establish a connection and agree on communication parameters before the start exchanging data
What is traceroute?
[It is a network layer diagnostic tool. We can measure transit delays of packets across the Internet using traceroute]
How does traceroute work?
[Traceroute sends sets of UDP segments to the destination. It adjusts the Time-To-Live (TTL) of each packet, with TTL = 1 in the first round, TTL = 2 in the second round, etc. When the datagram in the n-th set arrives at the n-th router, datagram is discarded and the router sends an ICMP reply back to the source, possibly including the name and IP address of the router. ]
What is flow control?
- [Flow Control ] is a technique to ensure that the sender does not overwhelm the receiver by sending data faster than it can be processed
example: it’s like a conversation where one person ensures that other has understood the last point before continuing to the next
What is congestion control?
- [Congestion control] is a network mechanism to prevent too much data from being injected into the network, thereby avoiding traffic congestion and data loss
example: similar to traffic lights controlling the flow of cars to prevent traffic jams.
What is connection-setup and why its beneficial?
[Connection setup] in TCP involves a process called the three-way handshake, which is the first step to establish a reliable connection between two devices before they start exchanging data
1. Verifies availability. ensures that sender and receiver are ready to communicate and are both aware of the attempt to establish a connection
2. Synchronizes sequence number: establishes initial sequence numbers to keep track of data packets, which are used to assemble the data in the correct order at the destination
3. Prevents duplication: helps avoid any duplicated or delayed attempts to establish a session
In summary, provides a foundation for a reliable, ordered, and error-checked stream of data between devices. Without this setup hpase, as in connectionless protocols like UDP, there would be no guarantee that the data you send would arrive, be in order, or be free from errors, which is fine for applications like video streaming where speed is more critical than reliability, but not ideal for situations where data integrity is crucial, like file transfers or web transactions.
What is the segment header fields values (example [ Th | app.msg]
the header in data packets refers to the essential information about the packet’s source, destination, type, etc. It is crucial because they contain control information, such as source, error checking, destination addresses, codes, and segmentation information which is necessary for the successful delivery and reassembly of the data by the transport protocol
What is segment? (in case you’re wondering)
- [Segment] in networking is a specific chunk or piece or a larger message or stream of data that is packaged for transmission over a network.
if it says “creates segment” (see next flashcard), it refers to the process where the transport layer takes data from an application (like your web browser) and breaks it down into segments that can be sent across the internet efficiently.
Each segment includes not just a piece of the actual data, but also header information like destination and source addresses that routers use to get the segment where it needs to go.
Think of it like taking a long letter, dividing it into numbered pages, and sending each page with its own address label so they can be resassembled in order when they all arrive.
What is the common process to send application-layer message
recall:
[Application layer]
[Transport layer (UDP or TCP)]
[Network layer (IP)]
[Link layer]
[Physical layer]
Sender:
- passed an application-layer message
- determines segment header fields values
- creates segment
- passes segment to IP (IP is network layer)
Receiver:
-receives segment from IP
- checks header values
- extracts application-layer message
- demultiplexes message up to application via socket
