Routing protocols

• 路由协议, 是路由器的协议? 肯定不是指路由器, 路由器可能也只是某一个功能, 这一章, 会不支更实用一些?
• 学完这一章, 能干什么呢, 设置路由器, 搭服务器的时候, 会更清晰? 知道了socket 和 port 的概念, 服务器的搭建基本没问题了, 可能更高级一些的分布式服务器, 会用到?
• 路由协议, 应该也是安全高发区, 黑客的必备知识, 每个环节都有安全隐患, 这里能和黑客关联大吗?

considering befor reading

• Autonomous systems
  • 自治系统
• Types of IP routing and IP routing algorithims.
  • ip routing类型及算法
• Routing Information Protocol (RIP)
• Routing Information Protocol version 2 (RIP-2)
  • 路由信息协议, datagram format
  • 2个版本
• RIPng for IPv6
  • 初步了解 IPv6
• Open Shortest Path First (OSPF)
  • 这个是干嘛的
• Enhanced Interior Gateway Routing Protocol (EIGRP)
  • 加强的内网网关路由协议
• Exterior Gateway Protocol ( EGP )
  • 外网网关协议
• Border Gateway Protocol (BGP)
  • 边界网关协议
• Routing protocol selection
  • 路由协议选择
• Additional functions performed by the router
  • 路由的扩展功能
• Routing processes in Unix-based systems
  • 在unix操作系统处理路由
• 还是还有部分是猜不到意思, 猜到意思的, 重复多遍, 将其纳入思维宫殿

reading record

1. overview
2. This type device attaches to two or more physical networks and forwards datagrams between the networks. 还真就是说的 路由器实物
3. The configuration of the device can be extended to contain information detailing remote networks. This information provides a more complete view of the overall environment.
4. Autonomou systems
5. is integral to understanding the function and scope of a routing protocol.

6. The AS must present a consistent view of the internal destinations.

7. Types of IP routing and IP routing algorithms

8. static routing
   • Static routing is manually performed by netword administrator.
   • Normally static routes are used only in simple topologies.
   • To manually define a default route.
   • To provide more secure network environment.
   • When complex routing policies are required.
   • To define a route that not automatically advertised within a network.

• distance vector routing

  • Distance vector algorithms are examples of dynamic routing protocols.
  • local IP routing table, distance vector table.
  • convergence time, routing loop, unstable packet forwarding, reduce capacity environments.
  • RIP is a popular example of distance vector routing protocol.

• link state routing

  • A link state is the description of an interface on a router (for example, IP address, subnet mask, type of network) and its relationship to neighboring routers. The colletion of these link state forms a link state database.
  • Shortest Path First algorithm.
  • 所有的可达路由表都存在在每个路由器里, 那样的话, 计算就简单了, 而不用去试探

• path vector routing

  • The path vector routing algorithm is somewhat similar to the distance vector algorithm in the sense that each border router advertises the destination it can reach to its neighboring router.
  • advantages:
    • flexibility;
    • computational complexity is smaller than that of the link state protocol;
    • have homogeneous policies for route selection;
    • Only the domains whose routes are affected by the changes have to recompute;
    • Suppression of routing loops;
    • Route computation precedes routing information dissemination.
    • Path vector routing has the ability to selectively hide information.
  • disadvantages:
    • the effect of a topology change can propagate farther than in traditional distance vector algorithms.
    • Unless the network topology is fully meshed or is able to appear so, routing loops can become an issue.
  • BGP is a popular example of a path vector routing protocol.

• hybrid routing

  • These protocols attempt to combine the positive attributes of both distance vector and link state protocols.

1. Routing Information Protocol
2. RIP packet types
3. RIP packet format
4. RIP Modes of operation
   • active mode, passive(silent) mode
5. Calculating distance vectors
   > The distance vector table entries:
   • the desination network (vector)
   • the associated cost (distance)
   • the IP address of the next-hop device
6. Convergence and counting to infinity
   • Each device claims to be able to reach the target network through the partner device.
   • counting to infinity.
   • In a RIP environment, any path exceeding 15 hops is considered invalid.
     > There are two enhancements to the basic distance vector algorithm that can minimize the counting to infinity problem:
   • Split horizon with poison revese
     Whit poison reverse, when a routing updaate indicates that a network is unreachable, routes are immediately removed from the routing table.
     This approach differs from the basic split horizon rule where routes are eliminated through timeouts.
     It might significantly increase the size of routing annoucements exchanged between neighbors.
   • Triggered updates
     With triggered updates, whenever a router changes the cost of a route, it immediately sends the modified distance vector table to the neighboring devices.

7. RIP limitations

   • Path cost limits
   • Network-intensive table updates
   • Relatively slow convergence
   • No support for variable length subnet masking

8. Routing Information Protocol version 2

   It was developed to extend RIP-1 functionality in small networks.

9. Support for CIDR and VLSM (variable length subnet masking)
10. Support for multicasting
11. Support for authentication
12. Support for RIP-1
13. RIP-2 packet format

14. RIP-2 limitations

    • However, the path cost limits and slow convergence inherent in RIP-1 networks are also concerns in RIP-2 environment.
    • It is transmitted in clear text. This makes the network vulnerable to attack by anyone with direct physical access to the environment.

15. RIPng for IPv6

16. RIPng was developed to allow routers within an IPv6-based network to exchange information used to computer routes.
17. RIPng is in RIP family, used the same algorithm, timers, and logic used in RIP-2
18. RIPng has many of the same limitations inherent in other distance vector protocols.
19. Differences between RIPng and RIP-2:
    > Support for authentication: RIP-2 has, RIPng not. RIPng uses the security features inherent in IPv6.
    > Support for IPv6 addressing format: RIPng does.

20. RIPng packet format
    RIPng are transmitted using UDP datagrams.

21. Openg Shortest Path First

    OSPF is a link state protocol,interior gateway protocol, provides a number of features not found in distance vector protocols.

    • Equal cost load balancing
    • Logical partioning of the network
    • Support for authentication
    • Faster convergence time
    • Support for CIDR(无类别域间路由, Classless Inter-Domain Routing) and VLSM

22. OSPF teminology
    *
23. Neighbor communication
24. OSPF neighnor state machine
25. OSPF route redistribution
26. OSPF stub areas

27. OSPF route summarization

28. Enhanced Interior Gateway Routing Protocol

29. Exterior Gateway Protocol
30. Border Gateway Protocol
31. Routing protocol selection
32. Addtional functions performed by the router
33. Routing process in UNIX-based systems

considering after reading

• 看不下去, 进度这么慢, 主要还是因为看不懂, 一会就枯燥了, 想不到看到了什么, 想不到想看什么, 想不到可以看什么
• 一点点敖过去, 但是不对语言去总结归纳, 什么时候能有质的进步呢? 到目前质的进步就是能跟英语正面刚
• 可能还有潜在的语感, 肌肉记忆, 所以, 不坚持下去, 什么问题也说明不了
• 有时候, 就得面对这对无知的恐惧和期待, 才有可能顿悟
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