Advanced network accounting notes (V)

The network layer （ Control plane ）

The way

Tradition （ Distribution ）

• On every router Distributed Realization
• Control plane and data plane Integrate In a device

SDN（ focus ）

• stay SDN Centralized computing of network applications on the controller , Generate flow table
• SDN Controller to SDN Switch distribution flow table
• SDN The switch matches the packets according to the flow table + action
• SDN The switch reports the status

Tradition

Routing algorithm

The goal is

According to the collected routing information （ Topology , Link cost, etc ） It is calculated that the source to target is better （ The price is lower ） route

• Main engine room = Between subnets = Between routers route

because IP Addresses are hierarchical

• In fact, routing calculation is to calculate the aggregation tree of routing nodes
• principle
  • Complete and correct
  • Simple
  • robust
  • Stability and fairness
  • The optimal / Suboptimal

classification

• static state / dynamic （ The adaptive ）
• overall situation / Local

LS Algorithm

Global algorithm

• Each node collects neighbor information to form LS,LS whole AS flooding
• The node collects each LS Status grouping , Form a network topology
• Calculate the optimal path

DV Algorithm

Distributed algorithms

• Each node maintains the next hop and cost to all other nodes
• Neighbor nodes exchange regularly DV
• according to Bellman-Ford All target costs and corresponding next hops are generated iteratively

There is a loop problem & Infinite convergence problem

Hierarchical routing

One plane solves the routing problem

• Calculation , transmission , Large storage capacity
• Not expandable
• It does not meet the management needs of different network operators

Divide into AS

• AS Internal node routing is solved by internal gateway protocol
  • OSPF
  • RIP
  • IGRP
• AS The routing between is solved by the external gateway protocol
  • BPG
• Route to gateway , Route from gateway to target gateway （ External gateway protocol ）, Target AS Internal by AS Internal routing solution

advantage

• scale ： Every AS The number of subnets is limited , Routing cost
• management ： Different AS Own agreement

classification

Internal gateway protocol IGP

• RIP & OSPF
  Internal support for hierarchical routing , Support multiple costs at the same time
• IGRP

External gateway protocol EGP

BGP

• The gateway router participates AS Internal route calculation , collect AS Intranet reachable information
• The gateway router passes through AS Inter route notifies other gateways of reachability information
• The gateway router also forwards “ Pass ” Subnet reachable information , but AS Add yourself to the path AS Number （ Prevent loops ）
• Gateway router i-BGP towards AS All internal routing nodes announce the collected subnet reachability information
• The internal router passes through AS Inside you and AS The inter route jointly determines AS Next hop of external subnet
  • Internal routing determines how to get to the gateway
  • The external route determines which gateway can reach the target subnet

SDN

• The control function is realized on the controller
• The directors and switches follow openflow The southbound interface protocol issues the flow table , Report equipment status
• The controller interacts with the network application according to the north interface

ICMP

effect

• error
• echo Request response

message

• echo
• Tracert

IGMP

Multicast management