Hanoi University Of Technology

8/2009

Hanoi University of Technology

8/2009

Hanoi University of Technology

TCP/IP

Faculty of Electronics and Telecommunications

TCP/IP

Faculty of Electronics and Telecommunications

1

8/2009

Hanoi University of Technology

8/2009

Hanoi University of Technology

TCP/IP

Faculty of Electronics and Telecommunications

TCP/IP

Faculty of Electronics and Telecommunications

2

8/2009

TCP/IP

Reset function - Chuyển về trạng thái Listen nếu đang ở trạng thái SYN-RECEIVED - Chuyển về trạng thái CLOSE với các trường hợp khác Hanoi University of Technology

8/2009

Faculty of Electronics and Telecommunications

TCP/IP

Transmission Control Block

Hanoi University of Technology

Faculty of Electronics and Telecommunications

3

8/2009

TCP/IP

- Khởi tạo giá trị SYN (ISN – Initial Sequence Number): tăng 1 đơn vị sau 4 microsecond - MSS (Maximum Segment Size): gửi khi khởi tạo kết nối; mặc định = 536 Hanoi University of Technology

8/2009

Faculty of Electronics and Telecommunications

TCP/IP

MSL=120s Hanoi University of Technology

Faculty of Electronics and Telecommunications

4

8/2009

Hanoi University of Technology

8/2009

TCP/IP

Faculty of Electronics and Telecommunications

TCP/IP

Quản lý thông tin tại Sender/Receiver -Cửa sổ gửi: 4 nhóm - Cửa sổ nhận: 3 nhóm - Con trỏ gửi (sender pointer)

Hanoi University of Technology

Faculty of Electronics and Telecommunications

5

8/2009

TCP/IP

-Con trỏ nhận (receiver pointer)

- SND.UNA= SQ - RCV.NXT=ACK - SND.WND=REV.WND=Window Hanoi University of Technology

8/2009

Faculty of Electronics and Telecommunications

TCP/IP

-Client: -SQ=0; - Receive Windows size = 200 - Server: -SQ=240 -Receive Windows size = 360 - MSS: 536

Hanoi University of Technology

Faculty of Electronics and Telecommunications

6

8/2009

TCP/IP

-Client gửi yêu cầu tới server (140 byte)

-Phía client chưa có data để gửi thêm. Server nhận được yêu cầu và gửi 80 byte tới client

- Client nhận được 80 byte chính xác và ACK cho server. Server có nhu cầu gửi 280 byte tới client. Tuy nhiên nó chỉ được phép gửi 120 byte

Hanoi University of Technology

8/2009

Faculty of Electronics and Telecommunications

TCP/IP

-Client nhận dữ liệu từ server và ACK. Server được lập trình không gửi dữ liệu nhỏ hơn 100 byte.

- Server nhận được ACK.

- Server gửi 160 byte còn lại.

Hanoi University of Technology

Faculty of Electronics and Telecommunications

7

8/2009

TCP/IP

-Client nhận dữ liệu từ server và ACK

- Server nhận ACK và kết thúc truyền

Hanoi University of Technology

8/2009

Hanoi University of Technology

Faculty of Electronics and Telecommunications

TCP/IP

Faculty of Electronics and Telecommunications

8

8/2009

TCP/IP

- Retransmission Queue - Resend segment - Retransmit only time out segment - Retransmit all outstanding segment -SACK -Timer? Æ Adaptive retransmission -New RTT=(α *old RTT+ ((1- α) Newest RTT Measurement) -Karn’ Algorithm

Hanoi University of Technology

8/2009

Hanoi University of Technology

Faculty of Electronics and Telecommunications

TCP/IP

Faculty of Electronics and Telecommunications

9

8/2009

TCP/IP

Hanoi University of Technology

Faculty of Electronics and Telecommunications

8/2009

TCP/IP

- Window size và Flow Control - Giảm cửa sổ để giảm tốc độ truyền - Giảm cửa sổ để dừng truyền dữ liệu mới - Đóng cửa sổ gửi

Hanoi University of Technology

Faculty of Electronics and Telecommunications

10

8/2009

TCP/IP

Hanoi University of Technology

Faculty of Electronics and Telecommunications

8/2009

TCP/IP

- TCP window management -“Shrinking” TCP Window - Gửi bản tin thăm dò (probe segment) khi cửa sổ đóng

Hanoi University of Technology

Faculty of Electronics and Telecommunications

11

8/2009

TCP/IP

Hanoi University of Technology

Faculty of Electronics and Telecommunications

8/2009

TCP/IP

- TCP “Silly window syndrome” - SWS -Khắc phục: -Receiver SWS avoidance -Sender SWS avoidance (Nagle’s Algorithm) -Không có bản tin chưa được ACK hoặc ứng dụng yêu cầu-> truyền ngay - Còn bản tin chưa được ACK -> chỉ truyền khi đã nhận được ACK hoặc bộ đệm phát =MSS

Hanoi University of Technology

Faculty of Electronics and Telecommunications

12

8/2009

TCP/IP

Hanoi University of Technology

8/2009

Faculty of Electronics and Telecommunications

TCP/IP

- TCP Congestion - Slow Start - Congestion Avoidance - Fast Retransmit - Fast Recovery

Hanoi University of Technology

Faculty of Electronics and Telecommunications

13