[Sdnp] SDN Architecture (from Scott Shenker's talk)

[Ping Pan]

Hi,

In the past several days, many have asked about the SDN architecture.
Several of us have had much conversation trying to put it in a concrete
form.

David had forwarded a talk by Prof. Shenker yesterday, (
https://www.youtube.com/watch?v=WVs7Pc99S7w&feature=player_embedded), and I
nearly fall off the chair when watching it. I have watched it a couple of
times already. Highly recommend to the audience here.

Here are some of the things that I agree strongly:


1. SDN Principle vs.Implementation (Time 24:00)

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Here is my takeaway: SDN creates an abstraction of the network, so that the
applications may make the use of the network easily. The SDN implementation
does NOT imply that the packet forwarding decision has to be altered or
re-defined (26:00).



2. Abstraction layer creation (Time: 32:00)


A similar picture has been shown last week in IETF. Nypervisor is where SDN
Controller sits. There are obviously multiple ways in realizing
the abstraction layer.


One example is to create a L2 network over hypervisors (or openvswitch), and
then develop a controller to interface the applications with this "virtual"
L2 network. This enables the ease of operation and service migration,
without touching the underlying networking gears.


Our approach is more of a bottom-up approach, where we create the
network abstraction through the use of SDN plug-in's, and feed the network
information to the SDN controller, which in turns feeds to the
applications.


Either way, IMHO, the name of the game is not in creating the new forwarding
method, rather, it's in creating a more adaptive and
flexible abstraction plug-in's

** **


****


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3. What's network abstraction? (Time: 37 min)


 ** **

This is my favorite part of the talk.


The network abstraction describes the attributes of the underlying
connections, such as bandwidth, delay etc. It does NOT have to reveal the
actual technology that the connections use (MPLS, IP etc.). In other words,
one can create multiple connections using MPLS, IP or WDM between two sites.
So long as the information is made available to the upper applications, the
applications can request the creation, modification of the connections. And
through the abstraction layer, the network gears can make the changes
accordingly (via. routing, TE etc.).


Hope it makes sense.


Regards,



Ping
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