Stanford CS144笔记（四）

Unit 1 Review

1. What we learned?

1. How an application uses the internaet.
2. Thestructure of the Internet: The 4 layer model.
3. The Internet protocol(IP): Waht it is.
4. Basic architectural ideas and principles:
   1. Packet switching
   2. Layering
   3. Encapsulation

2. Transport Layer Intro:

In this unit, we'll aks and answer questions such as:

• How exactly does TCP set up a connection?
• What do TCP segments look like?
• How can two computers reliably transfer data with high performance?

3. The TCP Service Model

Connection setup: 3-way handshake

Connection teardown(拆除):

1. A发送关闭连接请求，B拒绝并继续发送数据。
2. A发送关闭连接请求，B同意。

The TCP Service Model:

• Reliable delivery:
  • 接收方在接收数据无误后会发送Acknowledge给发送方。
  • 使用校验和(check sum)检验数据出错。
  • 使用序列号检验数据丢失。
  • 使用流控制(Flow control)来防止淹没接收方。
• Congestion control:
  TCP使用一些方法为所有TCP连接平均分配网络容量。

The TCP Segment Format:

TCP Segment captured by wireshark

TCP: Port Demultiplexing

Summary
TCP privides in-order, reliable delivery of a stream of bytes between application processes.

4. The UDP Service Model

The UDP Datagram Format

UDP datagram captured by wireshark:

The UDP Service model

使用UDP的应用层协议：

• DNS
• DHCP

Summary:
UDP provides a simpler, datagram delivery service between application processes.

5. ICMP(Internet Control Message Protocol) Service Model

ICMP博客
ICMP协议的功能：

• 差错通知
• 信息查询
  

Make the Network Layer Work

1. The Internet Protocol(IP)

• The creation of IP datagrams.
• Hop-by-hop delivery from end to end.

2. Routing Tables

• Algorithms to populate router forwarding tables.

3. Internet Control Message Protocol(ICMP)

• Communicates network layer information between end hosts and routers.
• Reports error conditions.
• Helps us diagnose problems.

ICMP Service