Cloud Architects tasked to lift and shift workloads frequently face some common challenges. Quite frequently they are handed over application dense servers containing applications which were never meant to scale (metal love) and limited budget and time. Not to forget the fact that the communication channel used by the applications was never secured because the applications were previously accessible only over local network (and maybe in house hacking was not a possibility or maybe internet was not invented till then 😄) and the marketing team sold the idea of a mobile workforce to the customer.
The Cloud Architects are expected to make the applications not only scalable, but also secure over the wire (SSL Certificates). I personally had to call ARR (Application Request Routing) into play in a few of such scenarios and apply some workarounds and proxies in some others.
Azure Application Gateway, which is Load Balancer layer 7, is a modern service that reduces the time to market of your application and fixes many of the issues we noted above. Azure Application Gateway currently supports layer 7 application delivery for HTTP load balancing, cookie based session affinity and SSL offload.
What is OSI?
Load Balancer layer 7 sounds like science fiction if you are not a little familiar with computer networking. It’s a good time for a little college knowledge recap now. The OSI (Open Systems Interconnection) model was created by the ISO (International Organization for Standardization) to help standardize communication between computer systems. It divides communications into seven different layers, which each includes multiple hardware standards, protocols, or other types of services. Following is a fun representation of the OSI stack (courtesy 9tut.com)
Layer 1: The Physical Layer
It activates, maintain and deactivate the physical connection. Voltages and data rates needed for transmission are defined in the physical layer. It converts the digital bits into electrical signals.
Layer 2: Data Link Layer
Data link layer synchronizes the information which is to be transmitted. Error controlling is done at this layer. The encoded data is then passed to the physical layer. Error detection bits are used and errors are also corrected. Outgoing messages are assembled into frames and transmitted. The system then waits for the acknowledgements to be received after the transmission. It sends messages reliably.
Layer 3: The Network Layer
It routes the signal through different channels to the other end. It acts as a network controller. It decides the route data should take. It divides the outgoing messages into packets and assembles incoming packets into messages for higher levels.
Layer 4: Transport Layer
It decides whether data transmission should be on parallel paths or single path. Functions such as multiplexing, segmenting or splitting of the data are performed by the transport layer. Transport layer breaks the message (data) into small units so that they are handled more efficiently by the network layer.
Layer 5: The Session Layer
Session layer manages and synchronizes the conversation between two different applications. Transfer of data from one destination to another are marked as sessions and are resynchronized properly so that the ends of the messages are not cut prematurely and data loss is avoided.
Layer 6: The presentation Layer
Presentation layer takes care that the data is sent in such a way that the receiver will understand the information (data) and will be able to use the data. Languages (syntax) of the two communicating systems may be different. Under this condition presentation layer plays the role of a translator.
Layer 7: Application Layer
It is the topmost layer. Manipulation of data (information) in various ways is done in this layer. Transferring of files and distributing the results to the user is also done in this layer. Mail services, directory services, network resource, etc. are services provided by the application layer.
#microsoft azure #application gateway
