The failure of links in software defined networks based on Open Flow will result in the need to converge on a new topology which will be the same at layer 2 or 3 since open flow seems to merge to control and data planes resulting in topologies. Since Open Flow utilizes flow tables the concept of feasible successors can be applied to flow tables by inserting alternate paths as less preferred flow entries. The use of successor routes will result in no need to contact a controller on link failures.
Tag Archives: SDN
The primary goal i would be seeking to meet when i decide to implement Open Flow or some other SDN framework is management simplicity.Below i have listed two things that i hope SDN will address when it becomes main stream in enterprises.
Automatic VLAN Grafting
Connectivity issues resulting from the absence of Vlans on trunk links is a common problem that network techs face when provisioning access ports.SDN can be really valuable if it is able to graft vlans to trunk links based on learnt layer two traffic flow.
Advanced Optimized Edge Routing that integrates QOS
Currently OER/PFR is unable to implement QOS policy decisions on flows that are not operating within a certain threshold. An OPEN FLOW controller that implements QOS policies while managing policies below edge devices such as those in the network core would greatly enhance policy based routing design and overall network architecture design.
Multi Tenant data centers being used to provide cloud services has led to a number of network requirements that are difficult to meet using VRF, Q-In-Q or other tunneling techniques.A Cloud data center customer needs to be able to provision network resources such as virtual switches and RFC 1918 IP addresses without needing to consider similar resources being used by other tenants. Software Defined networking seeks to provide an END-to-END virtual network that consists of virtual forwarding tables ,virtual routers,virtual switches and controllers. Software Defined Networking can be used to create logical networks that consist of virtual network gear. SDN tracks the state of the underlying physical data center network along with the overlaying virtual networks.
State changes are recorded and the Physical or Logical components affected by these said state changes are configured to have their settings and operations updated to support the changes made by the data center’s customer. Software defined networking’s ability to provide distributed,rule driven control of large physical network elements presents a new way of virtualizing network resources.
Software Defined Networking is an attempt at providing a programmable network protocol that can be used to virtualize entire network infrastructures. By virtualiziing your network infrastructure Open Flow will someday allow us to overcome network vendor compatibility issues surrounding how routing protocols are implemented and also to manage layer 2 and layer 3 network constructs such as SONET and IP using a single protocol without worrying about a Layer three IP addresses or Layer Two Virtual Circuit numbers. At layer three Open Flow seems like a protocol that is used to implement distributed policy based routing at layer two i see no current equivalent tool or tech.
SDN Advantages as i see it (note my knowledge of SDN is nascent)
1: Easier to Manage End to End Infrastructure Elements at layer two and three (Reduce Opex?)
2: Network equipment prices should fall since SDN/Open Flow relies on a central controller to push policies to devices (Capex reduction).
3: Enhance Traffic Engineering at Layer two without the need for spanning tree.
4: Engineers can now acquire knowledge instead of studying vendor specific equipment commands
5: Being Open Source there will be less RFC interpretation discrepancies between vendors (Yes OSPF is implemented differently by vendors trying to enhance/lock out the competition)
Questions for the Experts:
1: While being an advantage, isn’t the programmability of Software Defined Networking also a way of adding complexity to current networking paradigm,programming is viewed as being complex imagine if we could create macros for all our current tasks it would reduce future work but would be difficult and time consuming upfront.
2: The SDN controller will control traffic flows by adding and removing entries from flow tables embedded in our switches and routers. By using a central controller will this not add latency to policy execution in large infrastructres ?
3: Will Open Flow replace current Layer 2 and layer three protocols such as MPLS, BGP and OSPF ?