Wednesday, December 21, 2005

AON Devices - Server Appliances or Network Appliances

Ever since Cisco announced its AON and now SONA strategy, every SOA appliance vendor has embraced the TLA "AON". The definition of AON however is still as ambiguous as its server side counterpart ESB. IMHO, the answer lies in answering the question "Are AON devices server appliances or network appliances? "

A server appliances is a network attached closed server that performs one function i.e. offload the server. All the devices from SOA appliance vendors available today do exactly this. They offload security processing from the server. Some of the ambitious ones will offload business process orchestration from the server. All of this is to optimize the performance of an application that adhers to SOA principles. A server appliance is sold to a server system administrator.

A network appliance is a "in-line" network device. It does not offload processing from a server. It simply redirects, routes application flows to servers which are attached to the network. This routing is based on metadata that is part of the payload. This single function differentiates it from a standard router which only looks at packet level information to route a flow. Using a network appliance, one can create a VLAN which is SOAP 1.1 only. One could create a load balancer which distributes load based on transaction identity and not just sessions. A network appliance is sold to a network manager.

I have heard folks say network managers are not knowlegeable about SOA and its protocols of communication. Well, they were not aware of HTTP and web protocols in 1995. But they are well versed in it now. The reason these folks are not interested in talking to vendors, is vendors keep taking a server appliance to them and try to sell that as if it were a network appliance.

Friday, December 16, 2005

Cisco's SONA

Cisco announced its SONA (Service Oriented Network Architecture) guest/netsol/ns477/c643/cdccont_0900aecd8039b324.pdf.

When implemented correctly, a SONA like architecture will allow an administrator to login into a network services router and run "show http peers" which will list all the web services that are exposed using http binding in the network. Replace "http" with your favorite protocol and you should be able to see web services exposed on your favorite binding. If you type "show some_peer_webservice", you should be able to see its various bindings, its "EPR", its grouping and almost everything you get from WSDL of the service (without the annoying angle brackets).

Moving web services network management away from developers into the hands of operations personnel is the true promise of SOA and SONA delivers on that promise better than any application server centric (open or otherwise) service bus.