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Lecture 5 Soft Defined Network Overview

Traditional Computer Networks

Closed & Distributed

  • APP
  • Operating System
    • specialized in Server, not just simple OS like Windows and Linux
  • Specialized Packet Forwarding Hardware
    • encapsulation（封装）

The Ossified(僵化的) Network

  • Control Plane
    • Routing / Management / Access Control / VPNs ...
  • Plane between APP and OS
    • Million of lines of source code (6000+ RFCs)
  • Data Plane
    • Packet forwarding
    • Billion of gates (Bloated, 臃肿的)

The fact is that

  • Many complex functions baked into the infrastructure
  • An industry with a "mainframe-mentality", reluctant to change

Review

History:

Vertically Integrated / Closed / proprietary Slow innovation / Small industry

  • Specialized APPs
  • Specialized Operating System
  • Specialized Hardware

Now:

Horizontal / Open Interfaces / Rapid Innovation / Huge Industry

  • APP
    • Open Interface
  • Windows(OS) / Linux / Mac OS
    • Open Interface
  • Microprocessor

Future:

  • APP
    • Open Interface
  • Control Plane-1 / Control Plane-2 / ...
    • Open Interface
  • Merchant Switching Chips

Software Defined Network

origin:

SDN:

Cogitation (设计思想)

  • Open the black box: decouple the control plane and data plane
  • Make the control plane centralized
  • ( Form a centralized Network Operating System )
    • Examples
      • nox / pox
      • floodlight
      • onos
      • open daylight
  • Standardize the Interface (eg: OpenFlow)
    • Switch send its state-message to Network OS
    • Network OS send its controlling message to Switch
    • Examples
      • CISCO
      • HUAWEI
      • Juniper Networks
      • H3C

Benefits

  • Distributed => Centralized
  • eg:

OpenFlow

Overview

  • APP
    • Open Interface (Northbound)
  • Network Operating System
    • Open Interface (Southbound)
  • Specialized Packet Forwarding Hardware

OpenFlow

  • Offer the Protocol between Network OS and Switches
  • Define the actions of Switches

OpenFlow

  • Original Purpose: make it easy for experiments
    • Not practical to experiment with new network protocol
    • Not practical to persuade vendors (卖家) to provide an open, programmable platform on their switches and routers
    • Most modern switches and routers contain flow-tables that run at line-rate to implement firewalls, QoS, etc.
  • Example
    • the administrator Alice applies the "Alice's code" on the Network OS (Controller)
    • A client called Bob sends an message to a switch
    • This switch receives the message and asks the controller what to do next via a TCP connection
    • The request is answered by "Alice's code" in controller and the decision is made here
    • The Network OS gives orders to those switches which are along the way
    • Then the Bob's message sent along those switches above

The Role of OpenFlow in SDN

1) OpenFlow Rule = Match + Action 2) We use a 2-element tuple to present Rule as (Match, Action)

  • Match
    • Match on any header, or new header
    • Allows any flow granularity(粒度)
    • Only match on Header Part, not Data
    • “通配”可以出现在任何位置，没有限制
  • Action
    • Forward to port(s), drop, send to controller
    • Overwrite header with, mask, push or pop
    • Forward at specific bit-rate (velocity controlling)

3) Hence, we offer a new concept "Flow Table"

OpenFlow Controller

the controller is just a software

  • Receive the events from the switches
    • Topology changes
    • Traffic statistics
    • Arriving packets
  • Make decisions and calculations, and etc.
  • Offer commands to switches
    • (Un)install rules
    • Query statistics
    • Send packets

Reactive Control (响应式)

  1. a packet is sent to one switch
  2. if the rule is defined in this switch, use it ( check by hardware, O(1) );
  3. else, the switch send packet_in message to controller
  4. and then the Controller (Network OS) makes decision what's the packet's correct path
  5. the APPs execute packet_in event handler
  6. the Controller sends and installs rule to this switch for this forwarding packet
  7. the rule installed contains Match + Actions + Counters
  8. PS: if "Actions" is empty, it will discard the packet

Proactive Control (主动式)

  1. the program is running on APP/NOS
  2. Compile program install rules
  3. if "Action" is empty, it will discard the packet
  4. else, ......

SDN vs. OpenFlow

  • SDN \(\neq\) OpenFlow
    • SDN is a general network architecture, OpenFlow is a protocol or standard
  • OpenFlow is an interface protocol for SDN
    • spoken by the controllers and switches
  • OpenFlow is more than just a protocol
    • also including switch specification
    • can be seen as the de factor standard implementation of SDN: SDN / OpenFlow

SDN Applications

Dynamic Access Control (动态访问控制)

  • Inspect(检查) first packet of a connection (检查权限...)
  • Consult(参考) the access control policy
  • Install rules to block or route traffic

Seamless Mobility / Migration (无缝迁移)

  • See host send traffic at new location
  • Modify rules to reroute the traffic

Server Load Balancing (负载均衡)

  • Pre-install load-balancing policy
  • Split traffic based on source IP

Others

  • Routing
  • Dynamic access control
  • Seamless mobility/migration
  • Server load balancing
  • Network virtualization
  • Using multiple wireless access points • Energy-efficient networking
  • Adaptive traffic monitoring
  • Denial-of-Service attack detection