Transport Layer

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Transport Layer by Mind Map: Transport Layer

1. How TCP Conversion Reliable

1.1. Reliable

1.1.1. Acknowledge each segment

1.1.2. Establish a session before transmission of data

1.1.3. if ACK fail retransmit the segment

1.2. Header field

1.2.1. Source port

1.2.2. Destination port

1.2.3. Sequence no

1.2.4. Acknowledgment no

1.2.5. header

1.2.6. reserved

1.2.7. flag

1.2.8. window size

1.2.9. Tcp Segment

1.2.10. urgent pointer

1.2.11. TCP Checksum

1.2.12. Option

1.2.13. data

2. UDP

2.1. Less header

2.1.1. Source and destination (ports)

2.1.2. application header should take care for order delivery

3. Introduction

3.1. Data Requirements Vary

3.2. Identifying the Applications

3.3. Tracking Individual Conversations

3.4. Segmenting Data

3.5. Reassembling Segments

4. Purpose

4.1. error recovery

4.2. retransmission of damaged data

4.3. Separating Multiple Communication

4.4. multiplexed

4.5. Segmentation

4.6. Conversation

4.7. add header on segments

5. Controls the conversation

5.1. Segmentation and Reassembly

5.2. Conversation Multiplexing

5.2.1. Using ports

5.3. additional information in ports

5.3.1. Connection-oriented conversations

5.3.2. Reliable delivery

5.3.3. Ordered data reconstruction

5.3.4. Flow control

5.4. Establishing a Session

5.4.1. ensures the application to receive data

5.5. Reliable Delivery

5.5.1. lost segments are resent

5.6. Same Order Delivery

5.6.1. manages delivery in congestion host

6. Reliablity

6.1. The three basic operations of reliability

6.1.1. tracking transmitted data

6.1.2. acknowledging received data

6.1.3. retransmitting any unacknowledged data

6.2. Processes place additional overhead

6.2.1. Acknowledgement

6.2.2. Tracking,

6.2.3. Retransmission

6.3. To support reliablity

6.3.1. more "control data" on L4 header

6.4. protocols that specify methods

6.4.1. guaranteed delivery reliable

6.4.2. best-effort delivery. unreliable

6.5. application need reliablity

6.5.1. webpages

6.5.2. database

6.5.3. email

7. 2 common Transport layer protocols

7.1. Transmission Control Protocol (TCP)

7.2. User Datagram Protocol (UDP)

7.2.1. datagrams simple connectionless protocol RFC 768 advantage low overhead sent as "best effort" 8 byte header

7.3. Transmission Control Protocol (TCP)

7.3.1. Segments additional overhead to gain functions same order delivery reliable delivery flow control Connection-oriented protocol, RFC 793 20 bytes header Application used TCP Web Browsers Email File Transfer

8. Port Addressing

8.1. Unique Identity for application

8.1.1. Source Port number dynamic more than > 1023 some times it may use default until there is no conflict act as a return address

8.1.2. Destination port number static default port number assigned may change when specifically mentioned Web Service Email chat

8.1.3. Combination of Port and IP address socket eg:

8.2. Internet Assigned Numbers Authority (IANA)

8.2.1. standards body for assigning address

8.2.2. Different types of port numbers: Well Known Ports commonly used Registered Ports Dynamic or Private Ports

8.3. Some applications may use both TCP and UDP

8.3.1. eg DNS

8.4. Important Utility

8.4.1. "Netstat" Command

9. Segmentation & Reassembly

9.1. TCP

9.1.1. More header Flow control and management Acknowledgment of received segment Sequence & same order delivery Source and destination (ports)

10. TCP Server Process

10.1. Port Number may be Assigned default or manually by system administrator

10.2. A server cannot have two services assigned to the same port number

10.3. How to secure server running service

10.3.1. restrict server access to only those ports associated with the services and applications

10.3.2. accessible to authorized requestors.

11. TCP connection, establishment and Termination

11.1. establish the connection

11.1.1. Three way handshake Establishes that the destination device is present on the network The initiating client sends a segment containing an initial sequence value, which serves as a request to the server to begin a communications session. Verifies that the destination device has an active service and is accepting requests on the destination port number that the initiating client intends to use for the session The server responds with a segment containing an acknowledgement value equal to the received sequence value plus 1, plus its own synchronizing sequence value. Informs the destination device that the source client intends to establish a communication session on that port number Initiating client responds with an acknowledgement value equal to the sequence value it received plus one. This completes the process of establishing the connection.

11.2. 4 steps to terminate a TCP connection.

11.2.1. When the client has no more data to send in the stream, it sends a segment with the FIN flag set.

11.2.2. The server sends an ACK to acknowledge the receipt of the FIN to terminate the session from client to server.

11.2.3. The server sends a FIN to the client, to terminate the server to client session.

11.2.4. The client responds with an ACK to acknowledge the FIN from the server.

12. TCP Segments reassembly

12.1. sequent number is assigned when segment is sent to network

12.1.1. these segment must reorder according to seq no Segment sequence numbers enable reliability

13. Acknowledging and windowing

13.1. expectational acknowledgement

13.1.1. acknowledgement number in segments sent back to the source to indicate the next byte