overview

如何理解OSI或TCP/IP协议的层次划分和结构 ? - 向往美的回答 - 知乎

Bandwidth Vs. Latency: Which Is More Important?

overview

what: 分层协议，解决如何在互联网传输数据

history:

1. IETF(前身国防部) 指定ip层以上相关协议
   1. key rfc: rfc 1122, define layer; rfc 2616, define http1.1
2. IEEE管指定 物理层和链路层的协议

layer detail

osi vs tcp/ip:

1. tcp/ip: 实际使用的模型，更简化
2. osi: 概念模型，未被实现

tcp/ip layers:

1. linker layer
2. internet layer
3. transport layer:
4. application layer

链路层(linker layer): 局域网内如何传输 protocol list: mac

internet layer: 网路层如何路由 protocol list: ip

transport layer: 点对点传输 protocol list:tcp,udp

application layer: 应用相关数据 protocol: ethernet

What happens when you type a URL in the browser

how:

1. DNS resolve: GET IP
2. shake: tcp and ssl shake
3. client: send data with http format
4. sever: send response with http format
5. browser: parse data and display

how transport by ip:

2. blow transport
   1. arp protocol get ip->mac address
   2. liner: send by mac address

command

1. ifconfig lo: virtual network interface that your computer use to communicate with itself;

2. tcpdump inspect netwrok

   1 2 3 4

   tcpdump -# -S -n -i lo0 tcp and host 127.0.0.1 and port 8000 tcpdump -nl eth0 tcpdump -eni any ip

   1. -#: print a optinal package number
   2. -S: print the absolute sequence number
   3. -n: don’t convert address to names
   4. -i:interface
   5. -e: Print the link-level header on each dump line
   6. 4. expression: xxx and xxx

3. nc: create or connect tcp/udp connection

   1. nc -l: create a listener
   2. nc localhost 8000: connect the address

Test

1. lantency vs bandwith

   1. lantency: a packet round-trip time，两点之间距离,ms，

      主要是客观距离因素造成，交钱也无法提高

   2. bandwidth: mbps, total data in a second, 类似单位时间人流量，管道的横街面积； mbps;

      运营商限制了，可以交钱提高

2. affect:

   1. lantency important in: live, game, videochat， 需要实时响应
   2. bandwidth in : movies; 持续大量传输数据

3. in browsering

   1. low bandwidth and low lantency: 初始立即有内容，但页面加载慢
   2. high lantency and high bandwidth: 初始白屏时间长，后续流畅；

basic information

1. router

forward data  between different networks

2. gateway

a router provide access for packets  of local network
gatway must be a router;

mtu

MTU: max transfer unit MSS: max segment size: 1460

mss announcementL: