307307
308308## 五 计算机网络体系结构
309309
310- ![ preview] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426192353.jpg )
310+ ![ preview] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426192353.jpg )
311311
312312### 1 计算网络分层体系结构
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317317
318318### 2 ** OSI参考模型**
319319
320- ![ image-20210320165159104] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426192358.png )
320+ ![ image-20210320165159104] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426192358.png )
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323323
@@ -445,7 +445,7 @@ PDU在不同层往往有不同的叫法, 物理层称为**位流或比特流( bi
445445
446446### 3 ** TCP/IP参考模型**
447447
448- ![ tcpAndOSI] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426192411.png )
448+ ![ tcpAndOSI] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426192411.png )
449449
450450TCP/IP参考模型包括4层, 通常每一层封装的数据包采用不同的名称
451451
@@ -1168,7 +1168,7 @@ UDP是 Internet传输层协议, 提供无连接, 不可靠, **数据报尽力**
11681168
11691169### UDP数据结构
11701170
1171- ![ page_1] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426192425.png )
1171+ ![ page_1] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426192425.png )
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11731173长度字段指示了在UDP报文中的字节数(首部和数据的总和),
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@@ -1590,7 +1590,7 @@ virtual private Networks, VPN
15901590
15911591> transmission control protocol
15921592
1593- ![ 1920px-Tcp_state_diagram_fixed_new.svg] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426193224.png )
1593+ ![ 1920px-Tcp_state_diagram_fixed_new.svg] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426193224.png )
15941594
15951595## TCP的三次握手
15961596
@@ -1614,7 +1614,7 @@ virtual private Networks, VPN
16141614- 能听到, 你听得到我吗?
16151615- 能听到
16161616 实际流程:
1617- ![ 三次握手四次挥手] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426193229.jpg )
1617+ ![ 三次握手四次挥手] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426193229.jpg )
16181618
16191619** 三次握手的目的** : 是连接服务器指定端口,建立TCP连接,并同步连接双方的序列号和确认号并交换 TCP 窗口大小信息.
16201620在socket编程中,客户端执行connect()时。将触发三次握手
@@ -1639,7 +1639,7 @@ virtual private Networks, VPN
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16411641
1642- ![ img] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426193236.png )
1642+ ![ img] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426193236.png )
16431643
16441644TCP的连接的拆除需要发送四个包,因此称为四次挥手(four-way handshake)。客户端或服务器均可主动发起挥手动作,在socket编程中,任何一方执行close()操作即可产生挥手操作。(发起方确认对方关闭了自己在关闭)
16451645
@@ -1693,7 +1693,7 @@ TCP在真正的读写操作之前,server与client之间必须建立一个连
16931693### TCP/IP协议(族)
16941694
16951695因为互联网协议包含了上百种协议标准,但是最重要的两个协议是TCP和IP协议,所以,大家把互联网的协议简称TCP/IP协议(族)
1696- ![ TCP-IPbf545.jpg] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426193247.jpg )
1696+ ![ TCP-IPbf545.jpg] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426193247.jpg )
16971697
16981698# IP协议
16991699
@@ -1835,7 +1835,7 @@ HTTP方法的语义说明:
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18361836响应response
18371837
1838- ![ Web应用处理流程] ( https://wwfyde.oss-cn-hangzhou.aliyuncs.com /images/20210426193258.jpg )
1838+ ![ Web应用处理流程] ( https://pub-5cc26807d034413896ac8a50566eec62.r2.dev /images/20210426193258.jpg )
18391839
18401840## 请求
18411841
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