Ethane: Taking Control of the Enterprise

sdn

Casado M, Freedman M J, Pettit J, et al. Ethane: Taking control of the enterprise[C]//ACM SIGCOMM Computer Communication Review. ACM, 2007, 37(4): 1-12.

该论文提出一种新型网络Ethane，该网络可以说是SDN的前身。
创新点：提出一种新型网络架构
不足：无法与现有的网络相结合，因为替代现有的网络不可能实现
基本内容如下。

1 introduction

3 Ethane principles:

• The network should be governed by policies declared over high-
  level names
• policy should determine the path that packets follow
• The network should enforce a strong binding between a packet
  and its origin

2 design overview

• Controller:decides whether the flow represented by that packet should be allowed
• Switch: packet in the flow,foward them according to the controller's direction,else foward them to the Controller.

2.1 names,bindings,policy language

• packet must come from a machine that is registed
• user are required authenticate themselves

2.2 Ethane in use

registration

all switches,users,hosts are registered at the Controller

Bootstraping

switches bootstrap connectivity by creating spanning tree rooted at the Controller

authentication

• user use host_A
• Controller allocate ip,and bind id with hosta's MAC
• user authenticate through web-form

Ethane in more detail

switches

• fowarding packets,flow table is smaller
• two types flow entries in flow table:drop or foward
• entris is managed by Controller,will delete timeout entry
• switch talk to Controller:use minimum spaning tree protocol(in the same broadcast domain) or create an IP Tunnel(else)
• use neighbor discovering messages to maintain a list of neighbors

Controller

• registration
• authentication
• tracking bindings
• namespace interface
• permission checks and access granting
• enforcing resource limits

handling broadcast and multicast

replicating Controller for scalability and fault-tolerance

cold-standby

backups need only contain the registration state and the network policy

warm-standby

a separate MST is created for every Controller.

link failure

switch use neighbor-discver messages to find,then removes all flow tables entries tied to failed port and sends new link-information to Controller

bootstrapping

the network creates a minimum spanning tree with the Controller advertising itself as the root.all work is to initialize the topo and establish secure channes between Controller and switches

4 Policy language:Pol-Eth

5 Prototype and deployment

6 performance and scalability

perfect

7 shortcomings

• broadcast and sevice discovery
• application-layer routing
• knowing what user is doing
• spoofing Ethernet addresses