TCPIP_传输控制协议因特网互联协议介绍.ppt

* * * * * * * 2.4 IP子网划分 将一个大的主网通过借用主机地址位来当作子网地址位，从而将一个大的主网分割为一系列较小的子网叫IP子网划分。 2.4.1 子网划分的优点 节约IP地址 简化网络管理 缩减网络流量 未做过子网划分的网络 划分过子网的网络 2.4.2 子网划分的方法 子网数量=2M（M 是缺省掩码被扩展的位数）。新建的子网中包含子网0 和子网1。 每个子网能容纳的主机数：2N－2（N 是主机地址的可用位数）。 Other subnets 6 2 8 20 subnets 5 hosts per subnet Class C address: 子网划分实例 2.4.3 子网路由 在路由器进行地址分配过程中，要求不同的接口必须使用不同的网络地址。 路由器的路由表中记录网络地址与接口的对应关系。 00 60 00 50 E0 172.16 Network Network Interface E0 E1 New Routing Table 2 160 Host . . E1 未划分过子网的路由 划分过子网的路由 Address Subnet Mask Class Subnet 0 0 2 Subnet Mask Exercise Address Subnet Mask Class Subnet 0 0 2 B A A Subnet Mask Exercise Answers 2.5 CIDR CIDR，Classless Inter-domain Routing 无类域间路由 CIDR是用于缓解IP地址空间短缺和减小路由表大小的机制。 块地址（Block addresses）能够被汇总成单个条目，而不考虑网络号的类的边界。 汇总块能够被放入路由表中。 CIDR实例 2.6 实现可变长度子网掩码（VLSM ，variable-length subnet mask ） Range Of Addresses for VLSM Breakdown Address Space for Largest Subnet Breakdown Address Space for Ethernets at Remote Sites Break Down Remaining Address Space for Serial Subnets Calculating VLSM: Binary ?thanks * Purpose: This figure explains what is contained in a TCP segment. Emphasize: Source Port and Destination Port are the connections to the upper-layer protocol. Sequence and Acknowledgment numbers are the position in the user’s byte stream of this segment. Sequence numbers are used for establishing reliability. HLEN is the header length. It tells us where the data begins. Six bits are reserved for future use. Code Bits distinguish session management messages from data. Window is a term we will come back to in a few slides. For now, consider it the size of the receivers buffers. Checksum is a cyclic redundancy check（CRC). It verifies that the datagram arrived intact. Urgent Pointer is used to signify out-of-band data. Options are used by vendors to enhance their protocol offering. The data portion of the frame contains the upper-layer protocol data. * * IP地址在编程中用16进制表示； * * * * * * Layer 1 of 2: Purpose: This exercise is for the student