Networking protocols

总体介绍互联网传输的的protocols
IP 协议与 IP module 有所区别, IP 协议只是 IP module 中协议的一种, tcp/ip 指的是只是module, 代表当前最通用的传输协议实现方案

1. IP
2. ip addressing
   • 五类IP地址, IP编址, 不能满足全世界的人, 采用子网掩码功能(Subnet)
   • 网络地址 主机地址
   • 那么多的主机, 都通过一个端口, 能处理的过来吗?
     对于外网的ip 是给服务器用的, 虽然ip是共用, 但是能力还是服务器的, 所以处理能力跟服务器有关, 但是同一时间同时访问, 确是对应一条网络, 如果有大量的数据请求, 就是dos攻击的形式了, 所以上限还是线缆的传输容量
   • NAT, Network Address Translation, 网络地址转换技术, 子网掩码是理论, NAT是实现
3. ip subnet
   • 知道了子网的掩码的作用, 关键是需要实际操作
   • 子网掩码是为了解决互联网爆炸似的成长, ip不够用的情况
   • To avoid having to request additional IP network address,
   • 其实对于子网掩码还是疑惑着呢?
     > 子网掩码到底能不能解决 ip 不够的问题呢?
     > 看了半天, 子网掩码, 貌似只是将网络本来的ip分得更细了, A, B, C, D 类网络的 ip总地址并没有增加
     > 解决ip枯竭的思想是多台主机共用一个ip, 这个主要也是靠 NAT 程序?
     > 再看了一遍, 更不明白了, subnet 只是与 remote net 保持同样的形式, 可以根据 local net 的规模来确定 net 与 host 的长度, 但是 net 的长度没有用, 主要是用host的长度, 这样再配合NAT程序, 也能达到扩展网络ip的功能, The entire network still appears as one IP network to the outside world.
   • multihomed hosts, network adapter
     A multihomed host has different IP address associated with each network adapter.
     Each adapter connects to a different subnet or network.
4. IP routing
   • gateway: a system that performs the duties of router.
   • direct, indirect: ascribe physical network
   • A router is needed to forward traffic between subnets.
     so, if I want the outnet device to access the subnet device, also work by the router.
   • ip routing table
     • The ditermination of direct routes is derived from the list of local interfaces. eg. hosts
     • Each host keeps the set of mappings between in following:
       > Destination ip network addresses
       > routes to next gateway
     • Three types of mappings are in this table
       > The direct routes discribing locally attached networks
       > The indirect routes describing networks reachable through one or more gateways.
       > The default route that contains (direct or indirect) route used when the destination ip network is not found in the mappings of the previous typs of type 1 or 2
   • ip routing algorithm
     • a unique algorithm
     • to differentiate between subnets
     • not difficult for algorithm, difficult to read English
5. methods of delivery: unicast, broadcast, multicast, anycast
   • refer name to know sense
   • A connectionless protocol can send unicast, broadcast, multicast, or anycast messages.
   • Brocast addcresses are never valid as a source address. They must specify the destination address.
     BOOTP can use broadcast addresses to allow a diskless workstation to contact a boot server.
   • It is not only way to the netbar, the more senarios is talked in the next chapters.
6. the ip address exhaustion problem
   • The number of networks on the internet has been approximately doubling annually for a number of years.
   • I don`t understand how to solve this problem yet.
   • Class A,B,C,D network, only has 255255255*255 ip, these are less than 6 billion people, so there the subnet tecnology share one ip.
     every class network has limit subnets, this also is not the permanant solution.
     这样的话, A类网络会不会将线路爆
     ipv4 and ipv6
7. Intranets: private ip address
   • Another approach to conserve the IP address space.
8. network address translation (NAT)
   • read finished, but has no information, just know some terms, IPSec, NAPT
   • translate the ip and port, also to resolve the ip exhaustive
   • NAT limit
9. Classes Inter-Domain Routing (CIDR)
   • also have no information, just reading once over
   • TRD, transit routing domains

10. IP diagram

    • The unit of transfer in an IP network is called an IP datagram
    • fragmentation
    • the protocol details interpretation

11. ICMP

12. Internet Control Message Protocol
    • Path MTU Discovery is a draft standard protocol with a status of elective.
    • ICMP Router Discovery is a proposed standard protocol with a status of elective.
13. ICMP can be characterized as follows:
    • ICMP uses IP as though ICMP were a high-level protocol. However ICMP is an integral part of IP and must be characterized by every IP modules.
    • ICMP is used to report errors, not to make IP reliable.
    • ICMP cannot be used to report errors with ICMP messages. This avoids infinite repetitions.
14. ICMP Messages
    • ICMP messages are sent in IP datagrams.
    • transmit status message

15. ICMP Applications

    • ping
      > Packet InterNet Groper, 网络包探索者
      > Ping is the simplest of all TCP/IP applications.
      > Generally, the first test of reachability for a host is to attempt to ping it.
    • traceroute
      > Traceroute is based on ICMP and UDP
      > The Traceroute program is used to determine the route IP datagrams follow through the network.

16. IGMP

17. Internet Group Management Protocol
18. IGMP is also an integral part of IP.

19. It allows host to participate in multicast.

20. ARP

21. Address Resolution Protocol
    • is a network-specific standard protocol
    • is responsible for converting the higher-level protocol address(IP address) to physical network address.
    • A model(ARP) is provided that will translate the IP address to the physical address of the destination host.

22. ARP request, is a broadcast

    • use personal computer to do server host. To do work in the place that make personal computer can be accessed by the out network
    • Proxy-ARP, modified ARP on router
    • old IP protocol, subnet IP protocol

23. RARP

24. Reverse Address Resolution Protocol

25. RARP requires one or more server hosts in the network to maintain a database of mappings between physical addresses and protocol addresses so that they will be able to reply to requests form client hosts.

26. BOOTP

27. bootstrap protocol

28. The BOOTP protocol was originally developed as a mechanism to enable diskless host to be remotely booted over a network as workstations, routers, terminal connectors, and so on.
    –

29. DHCP

问题

• 写完上面的几个协议, 就解决了之前的疑问, IP 是属于网络层的
  这几个主要协议, 构成了网络层, 从名字, 也可知 网络层的功能
• 看前面 Network Interface 是有些枯燥, 到了这里, 可能才更有意思一些
  包括后面的 routing protocol, transprot layer protocol 都主要是了解这些协议的功能构成, 以及查看这些协议的工具, 有何用途, 能做何用
• 为何要看TCP/IP
  想弄明白网络中的那些事, 除了架个服务器, 让自己的电脑能被外网访问, 还能干些什么事? 为何会有这些协议, 路由器还有哪些高级的玩法, 如果管理自己的网络, 如何管理分布式网络, 如何配置自己的局域网络, 如何用网络, 将自己的生活圈子组建起来?
  了解一下SMTP, FTP, HTTP等协议,
• tcp/ip 看完, 能否对 lantern 有所改动, 可以少点会员费, 还能使用优质网络?

思维重组

• 想从tcp/ip中了解一什么?
• 数据是如何从一台设备到另一台设备中?
  按协议来, 二进制对应着高低电平, 高低电平的意义用布尔逻辑来解释
• 其中的实现细节, 我需要了解到哪些?
  这些不清楚, 所以只能先通读, 有所也解后, 再按点突破
• 在linux能用到哪些?
  • 服务器编程
    翻墙
    邮件服务分发器
    局域网络
    路由的操作
    游戏服务器
    操作系统中的端口, 是真得有端口, 还所有数据从一个物理入口进入, 程序按端口来分发消息?
  • 整个网络 基本上是就是数据的存储与搬运, 数据如此重要, 必然要考虑安全问题
    怎么去保证数据互通
    怎么拦截数据, 有哪些部分可以获取到数据
    跟数据相关的安全和攻击有哪些
    数据的加密, 有没有必要了解一番
  • 黑客
    攻
    防
• 从哪里入手
  • 书籍, 就是再枯燥, 也得通读一遍, 至少各个环节能自圆其说
  • 读的过程中, 尽量再发散, 以英文作笔记, 抛开中文都写不好文章的恐惧, 重新学习写作, 从语言开始, 是一个好机会
• 效率
  • 最快得效率, 还是要保持一定的套路, 思维套路来分析, 不然很容易就陷入迷茫, 不知在看些什么的窘境中
  • 看一本书, 先从目录分析, 一本书太广, 就按目标计划来分析, 或一章章的分析
  • 每章每小节, 按标题分析, 分析不到的, 就从是什么, 能解决什么, 应用场景来泛读
  • 根据应用场景与兴趣, 再进一步精读是怎么做到的

review

再次设置网络还是有些迷, 子网掩码如何设置? 两台电脑是如何通信的? 路由是如何转发数据的? 这些还是不明白.

设置一个路由, 使两个设备能通信, 还是现实中很重要的一个场影, 一旦可以找到目的电脑, 那么应用就可以用了.

两台主机直连, 点对点通信, 即在同一个IP局域网内或令牌环网内. 这个时候可以直接被本机的路由列表感知到?

现在主要是攻破, 不在同一个局域网内的通信, 路由如何选路, 数据如何到达目的地的.

首先不要网线的转输能力不用置疑, 在一个子网下肯定可以满足.

不管是主机还是路由都有路由表

网络层, 是对通信过程的抽象. 每一个路由理论上是对每一层协议都要感知的. 每一层管每一层的事, 每一层大都不只一个协议实现.
这样想, 一下子就明了了, 关键还是要理解业务.