ADC – Application Delivery Controller

Application Delivery Controller aka ADC is an advanced version of server load balancing (SLB) which includes traditional load balancing along with some advance features such as health checks, SSL offloading, DDoS protection, Reverse Proxy, WAF etc.

Application Delivery Controller
Network Panel

History of Application Delivery Controller

Load balancing among several servers is not new. An initial version of load balancing was to have 1 to many relations between the domain name and IP addresses in DNS server. This severely lacked health checks as clients wouldn’t know if given IP is working or not. This drawback gave rise to next level of load balancing where a specific IP address was exposed to the world. This IP was catered by clustering software, which routed the traffic from clients to several servers in the backend.

Next generation load balancers introduced health monitors. If any of the servers goes unresponsive, the load balancer would stop sending traffic to that server until it was recovered. This also allowed system administrators to build some custom logic to add or reduce the servers in the farm based on the monitoring data.

ADCs are current generation load balancers which provide a variety of functions bundled together. Some of them are listed in the section below.

Features of ADC

Application Delivery Controller
Application Delivery Controller – ADC. Source:
  • SSL Offloading: ADC can handle the terminating SSL connection keeping the traffic between ADC and backend servers in plain text. And hence it helps in reducing the load on the application servers in the server farm.
  • Multilayer load balancing: These load balancers can balance traffic at Layer 3/4 as well as Layer 7 of OSI model. Thus it gives an ability to route traffic based on IP addresses, subnets as well as based on the URL patterns, domains and HTTP header fields.
  • Load balancing methods: ADCs can use various methods such as round robin, least packets, least bandwidth, latency or hashing of certain parameters.
  • DDoS Protection: ADCs can look into the incoming traffic and detect DDoS before it starts loading the application servers, thereby defeating the attack.
  • WAF: ADCs can have built-in Web Application Firewall which can prevent common security attacks such as Cross-site scripting XSS.

For a much more comprehensive list, you can to the article in related links section.

Related Links

Related Keywords

Load Balancer, Hardware, WAF, DAF


We all have heard of LAN/WLAN (Wireless Local Area Network), MAN (Metropolitan Area Network), and WAN (Wide Area Network). Maybe you have also heard about PAN (Personal Area Network). Today. let’s know more about BAN / WBAN – Wireless Body Area Network.

What is BAN?

This is a network of multiple interconnected devices worn or implanted in a human’s body. These devices include monitoring devices such as pacemakers or BP monitors. Such a network typically includes a smartphone which acts as a mobile hub to collect data from wearables and implants and push it to a central repository to process/ analyze further.

Now you probably can guess one of the biggest beneficiaries of BAN/WBAN – medical field! Patients can be equipped with wearable monitoring devices and a smartphone. Then the medical team can monitor the patient’s health from a single location. This technology comes handy for remote monitoring or could also be extremely useful during a medical emergency where a small group of medics needs to monitor a large number of patients.

BAN – source:

So is this a standard terminology?

Yes, there’s an IEEE standard 802.15.6 defined for WBAN from Healthcare point of view.

It is a standard for short-range, low power, and highly reliable wireless communication in, on and around human body.

[Source: IEEE website –]

BAN network cannot just monitor the human body, but can also initiate action. e.g. Insulin can be injected automatically into a diabetic patients body if the BAN detects lower levels of insulin in the body.

In some other use cases, a sports person can create BAN to gather data about her performance and subsequently make improvements to her game.

Some concerns about BAN/WBAN

  • Since this is a mobile network, which moves along with the human, security of the data becomes an important consideration. WBAN also needs to ensure that the data is collected from correct human even if there are multiple humans in the vicinity.
  • Privacy – this could be treated as an invasion of privacy and it is utmost important to obtain consent from the human to create and use BAN around his/her body.
  • Data management – data collected using such close monitoring is going to be humongous and hence needs to be managed well.

Related Links

Related Keywords


RFID – Radio Frequency Identification

Radio Frequency Identification i.e. RFID is now a widely used technique and many might have even used it. But how many of us understand the technology behind it? Let’s learn a bit more about it today.

Warehouses typically use RFID
Warehouse Operations Using RFID

How does RFID work?

This technology consists of two parts – a tag and a reader. An RFID Tag is a small object which could be attached to objects that need to be tracked. These tags store some information in a non-volatile memory. This information could be permanent (Read Only) or could be changed using writer devices. The second part is the reader. It is a device which reads the data stored on the tag. The reader sends some signal to the tag and in response to that signal, the tag sends back the data stored with it. This process is known as “interrogation”. The signal that reader sends is a Radio Wave having a frequency between 120kHz and 10GHz.

Typical Use Cases

  • Animal identification
  • Warehouse Stock Identification
  • Promotion Tracking
  • Passport
  • Libraries
  • Payments at the toll booths

Use of RFID tags is growing globally and new use cases or needs are getting addressed.

NFL (National Football League) is using RFID tags on various sports accessories such as football and shoulder pad to collect a lot of data about the game. The data includes parameters like speed, acceleration, deceleration, location etc. Also, this data is captured 25 times per second. This would give a lot of insights to the trainers/coaches as well as to the fans of the NFL.

This type of data collection is possibly done using RFID Tag of type Active Reader Active Tag system. In this system, the readers are set to collect data from a specific interrogation zone so that data collection is strongly controlled.

A drone has been developed by researchers which can read RFID tags in a range which is few hundred square feet, instead of usual few feet range. This could be of significance for large warehouses such as Walmart or Amazon. It could potentially save several thousand dollars and person-hours in finding missing items.

In another significant area of Healthcare, RFID tag has been developed which could read vital body parameters such as heart rate and blood pressure. One central reader can receive data from as many as 200 RFID tags. This could improve the response by the medical team during large-scale emergency situations.

RFID is here to stay and become more and more mainstream.

Related Links

Related Keywords

Radio Waves, Barcode, Big Data, Wireless Communication, NFC



Content Distribution Network or Content Delivery Network is known as CDN. As the name signifies it is a network that allows various applications to distribute their contents to the clients. “Content” that is referred in this term is static content, which doesn’t change frequently. A typical example of such static content is any image you see on the web. The image contents don’t change often and hence it is referred as “static”.

Why does one need CDN?

With global customers, a website can expect traffic from anywhere in the world. However, most of the times servers that host your application would be located in a single location (barring some exceptions). How fast a webpage will be served is constrained by the physical distance between server and a client. As a result, a visitor from the US will have higher latency as compared to a visitor from India when the web server is located in India. In this highly competitive edge, where customer drops of if there’s even a 2-second delay in response, websites strive to deliver contents as fast as possible. And this is where CDN comes into picture.

Content Delivery Network caches the static contents at various places in various geographic locations. These locations are called as Edge locations. The edge locations are configured to fetch data from the base web server, called as “Origin Server”. The data remains in the cache until expiry. After expiration, the Edge location queries the “Origin” server and fetches if the data is modified.

Load websites faster using CDN
CDN gives you speed!!

But how does this solve the problem in latency?

CDN has created the cache locations. But the real question is how would a client know which Edge location to request data from? This is solved by the Content Delivery Network. Each CDN endpoint has multiple IP addresses corresponding to all the Edge locations. CDN uses a concept for GeoDNS. GeoDNS allows the DNS (Domain Name Server) to identify the location of requesting client IP and return an IP address of the nearest Edge location. This is why we say CDN returns the data from nearest geo-location.

How does CDN Work
How does CDN Work – Source:

So when you request a webpage, the request goes to the webserver. The HTML specifies that static resources should be loaded from CDN. As a result, the client makes the request to the CDN. CDN delivers contents from nearest geo-location.

Any other advantages?

Yes. Since your static data is cached to external servers i.e. the edge locations, your web/app server is free to do the operations where logic is involved. Using CDN reduces the load on the web/app server, thereby improving the response times to the clients. This results in the better customer experience.

CDN providers

  • Akamai
  • AWS CloudFront
  • MaxCDN
  • Azure CDN

Related Links

Related Keywords

AWS CloudFront, GeoCDN, Anycast