Stanford CS144笔记（三）

Byte order

1. Endianness

2. Network Byte Order

• Different processors have different endianness
  • Little endian: x86
  • Big endian: ARM
• To interoperate, they need to agree how to represent multi-byte fields.
• Network byte order is big endian.

IPv4

1. Goal of Internet Protocol Addresses

• Stitch many different networks together.
• Need network-independent, unique address.

2. IPv4

3. Address Structure

Historical:

Today:

• CIDR(无分类域间路由选择)
  

4. IPv4 Address Assignment

Longest Prefix Match

1. Inside the Stream

2. Inside Each Hop

• Each router maintains a routing table.
  

ARP(Address Resolutioin Protocol)

ARP is used to transform the IP address to Hardware address.

Problems：如何通过IP地址找到使用该IP地址的设备的硬件地址？

1. IP地址与硬件地址之间并不存在一个简单的映射关系。
2. 在局域网中，经常地会有新主机加入，旧主机撤走。

ARP解决该问题的方法：
在主机的ARP高速缓存中维护一张从IP地址到硬件地址的动态更新的表。