How We See ITThe History and Capabilities of Application Delivery Controllers

Which Vendor Ranks Highest in ADC Performance?

Written by: Ahmed Abdalla, Solutions Architect at CentricsIT

Data Center Relocation Services

3140 Northwoods Parkway Norcross, GA 30071 Phone: 1-877 531-7466 Fax: (678) 495-1302 www.CentricsIT.comCentricsIT United States Canada United Arab Emirates United Kingdom Czech Republic

1

3140 Northwoods Parkway Norcross, GA 30071 Phone: 1-877 531-7466 Fax: (678) 495-1302 www.CentricsIT.comCentricsIT United States Canada United Arab Emirates United Kingdom Czech Republic

IntroductionModern consumers of network applications, both customers and internal users, demand increasingly available access to services. To satisfy these demands, companies must focus on high availability and scalability of networks, servers, and software. Managers, architects, and administrators have to consider a number of disparate systems that must successfully work together to meet these requirements. Both the fundamental interdependence of these systems and the architecture required to ensure stable operation need to be considered and accounted for in a modern data center.

Recent and ongoing trends in data center operations show an increasingly consolidated approach to hosting and delivery. Vendors are focusing on merging multiple services onto single platforms; network devices are becoming more application-aware and software advances enable improved support for multi-system operation. Discussing all these topics in detail would require multiple texts. However, this whitepaper, written and distributed by CentricsIT, will focus specifically on the Application Delivery Controller, a bridge between the vertical network and horizontal scalability.

TechnologyAn Application Delivery Controller (ADC) is a network device or software package tasked with handling client requests and passing those requests to one or more private target servers. This may initially seem like load balancing, but ADCs offer additional functionality beyond that of a simple load balancer. A network load balancer works at layer 4 of the network model, responsible for simply spreading connections between servers. More advanced load balancers may be stateful, or have better load balancing algorithms available, but their overall functionality does not expand significantly beyond network address translation.

In comparison to a load balancer, an ADC not only works on layer 4 of the network model, but expands upward to layer 7. An ADC spreads traffic to a target pool of servers and has the ability to understand the underlying application traffic itself. Available ADC functionality will vary slightly by vendor and can range from providing SSL offloading for web applications (decrypting SSL traffic before handing over to HTTP servers), to selecting certain pools of available servers based on options specified in the application. Because of this fundamental application awareness, ADCs are not just network components needed to get your application online; instead they are an integral part of how your application functions.

HistoryMany network administrators or managers may look at an ADC and consider it an additional cost or headache that increases complexity or shifts focus from core business. In some cases that may be true. As with any machine, it is not a silver bullet for all problems. For those managers and administrators who look to the future and anticipate expansion, an ADC is an investment that should be strongly considered. The reason for this lies in historical advances, how networks work, and improvements in overall application design.

Original enterprise servers were physically massive machines, and applications developed for them were often self-contained. Networks were uncommon or limited, as it was easiest to maintain software on a single server. As servers got smaller and networked applications became more prevalent, applications were spread beyond individual machines in multi-tiered software paradigms. Data was moved to servers separate from the applications that used it. This ability on a software level, plus the reduced cost of servers and hardware, allowed for the building of redundant servers and therefore more reliable applications. A single server failure no longer caused an entire application to go down completely—an improvement in service availability.

While the introduction of redundant servers increased application uptime, it did not provide an easy path to respond to the increased user base created by the improved cost and availability of personal computers. In order for standalone and redundant servers to handle the increased workload the user expansion caused, companies had to invest in continual hardware upgrades. Because software itself was not particularly scalable, the only way to improve application performance was to give the application more resources. This limitation of software would potentially require significant funds to constantly upgrade, in addition to outages to perform the improvements.

Distributed computing, the ability of multiple servers to run the same software concurrently without impacting one another, gives developers the ability to write software that is not limited to a single active server. Now, instead of an active-passive pair of servers, a service can be run across a number of systems actively. The question then becomes, “How is network traffic sent to all these active machines?” One solution is DNS round-robin, a method of sending individual requests for name resolutions to each host listed in order. This method does not take into account server outages, updates can take a long time to propagate through the DNS tree, and connections are not persistent to a target server. A local alternative was to use a network load balancer. With MAC address

manipulation, traffic could be distributed to physically attached servers, but this limited servers to a single data center and confined space. Network address translation allowed source and destination ports to be changed while packets were in transit. Response to server outages was faster because a local administrator could manually update the pool of available servers; however, most load balancers did not perform extensive network testing to ensure that a server was actually up (and that the application was running). Some load balancers used state tables to provide some stateful or persistent connections, but generally this functionality was limited.

These limitations in response to incoming network traffic, and the inherent need to transition a single stream of network connections into a horizontally scalable infrastructure prompted further advancement of load balancers into application-aware ADCs. An ADC in a modern data center can monitor servers for availability at the physical and application layers, dynamically scale the number of servers based on incoming network connections, and help mitigate target attacks against applications. Application Delivery Controllers are found in many areas of current networked applications. As applications become more reliant on cloud infrastructure, the use of ADCs will continue to grow. Web applications and managed hosting environments rely on the functionality and automated scalability that ADCs can provide. Distributed computing has become increasingly affordable, especially on commodity hardware. The monolithic hardware and software solutions of the past are transitioning to clusters of servers, and ADCs are needed to make the leap.

State of the IndustryA number of networking vendors provide varying levels of ADC offerings, but only a small few are able to compete strongly in the space. With Cisco announcing the discontinuation of its ACE product, the largest switch manufacturer has ceded the ADC space to the market leaders. Gartner’s magic quadrant lists these leaders as F5 Networks, Citrix, and Radware. There are a number of other vendors, but they are generally smaller companies or companies that provide limited or niche offerings.

Of the three market leaders, Citrix and Radware are relative newcomers, both entering the space through acquisitions. Citrix’s purchase of NetScaler and Radware’s purchase of Nortel’s Alteon are both positioned to augment existing products. Long term plans and viability in the ADC space has not been proven for either of these companies. On the other hand, F5 developed load balancers in the mid-1990s and grew its products into ADCs with associated modules from this base.

The available feature set provided by each vendor must also be taken into account. Citrix has done extensive work to integrate NetScalers into its existing software products, leading some to question future support for competitors’ applications. Radware takes a more general approach to ADCs, similar to that of F5; however, it may be some time before customers see a completely consolidated solution. Radware currently offers security products and some application-specific appliances and software. As these involve different hardware purchases in many cases, the long-term costs may be higher. F5’s offerings have been consolidated to a limited set of hardware devices, allowing the deployment of different software modules on the same device. A single ADC from F5 can load balance connections, terminate remote VPNs, and secure web applications against attacks. Radware and Citrix offer similar solutions, but not to the same degree of integration or with the same footprint as F5 Networks.

ConclusionsOur industry is a constantly evolving ecosystem. New products, customer demands, and ideas are introduced each year. As IT professionals, we must do our best to look forward and make the best decisions for the future with the best information available today. We cannot deny that customers and users demand always-on applications, and one of the tools at our disposal is the Application Delivery Controller. In the last ten years, we’ve embraced virtualization, commodity hardware, and mobile computing. Well-planned application delivery allows us to tie these new technologies together and empower us to meet our business objectives as managers, architects, and administrators.

Of the available ADC solutions, the clear winner at this point is F5 Networks. In situations involving a homogenous Citrix environment, NetScalers may be a worthwhile investment, but F5’s integration with Citrix is on par with NetScaler and offers comparable support for VMware. Radware’s offerings are interesting and should be watched over time, but right now they’re too disjointed to recommend strongly. Likewise, many of the smaller vendors have products of varying functionality and levels of innovation, but in enterprise situations, F5 is the proven winner.

Data Center Relocation Services

IntroductionModern consumers of network applications, both customers and internal users, demand increasingly available access to services. To satisfy these demands, companies must focus on high availability and scalability of networks, servers, and software. Managers, architects, and administrators have to consider a number of disparate systems that must successfully work together to meet these requirements. Both the fundamental interdependence of these systems and the architecture required to ensure stable operation need to be considered and accounted for in a modern data center.

Recent and ongoing trends in data center operations show an increasingly consolidated approach to hosting and delivery. Vendors are focusing on merging multiple services onto single platforms; network devices are becoming more application-aware and software advances enable improved support for multi-system operation. Discussing all these topics in detail would require multiple texts. However, this whitepaper, written and distributed by CentricsIT, will focus specifically on the Application Delivery Controller, a bridge between the vertical network and horizontal scalability.

TechnologyAn Application Delivery Controller (ADC) is a network device or software package tasked with handling client requests and passing those requests to one or more private target servers. This may initially seem like load balancing, but ADCs offer additional functionality beyond that of a simple load balancer. A network load balancer works at layer 4 of the network model, responsible for simply spreading connections between servers. More advanced load balancers may be stateful, or have better load balancing algorithms available, but their overall functionality does not expand significantly beyond network address translation.

In comparison to a load balancer, an ADC not only works on layer 4 of the network model, but expands upward to layer 7. An ADC spreads traffic to a target pool of servers and has the ability to understand the underlying application traffic itself. Available ADC functionality will vary slightly by vendor and can range from providing SSL offloading for web applications (decrypting SSL traffic before handing over to HTTP servers), to selecting certain pools of available servers based on options specified in the application. Because of this fundamental application awareness, ADCs are not just network components needed to get your application online; instead they are an integral part of how your application functions.

HistoryMany network administrators or managers may look at an ADC and consider it an additional cost or headache that increases complexity or shifts focus from core business. In some cases that may be true. As with any machine, it is not a silver bullet for all problems. For those managers and administrators who look to the future and anticipate expansion, an ADC is an investment that should be strongly considered. The reason for this lies in historical advances, how networks work, and improvements in overall application design.

Original enterprise servers were physically massive machines, and applications developed for them were often self-contained. Networks were uncommon or limited, as it was easiest to maintain software on a single server. As servers got smaller and networked applications became more prevalent, applications were spread beyond individual machines in multi-tiered software paradigms. Data was moved to servers separate from the applications that used it. This ability on a software level, plus the reduced cost of servers and hardware, allowed for the building of redundant servers and therefore more reliable applications. A single server failure no longer caused an entire application to go down completely—an improvement in service availability.

While the introduction of redundant servers increased application uptime, it did not provide an easy path to respond to the increased user base created by the improved cost and availability of personal computers. In order for standalone and redundant servers to handle the increased workload the user expansion caused, companies had to invest in continual hardware upgrades. Because software itself was not particularly scalable, the only way to improve application performance was to give the application more resources. This limitation of software would potentially require significant funds to constantly upgrade, in addition to outages to perform the improvements.

Distributed computing, the ability of multiple servers to run the same software concurrently without impacting one another, gives developers the ability to write software that is not limited to a single active server. Now, instead of an active-passive pair of servers, a service can be run across a number of systems actively. The question then becomes, “How is network traffic sent to all these active machines?” One solution is DNS round-robin, a method of sending individual requests for name resolutions to each host listed in order. This method does not take into account server outages, updates can take a long time to propagate through the DNS tree, and connections are not persistent to a target server. A local alternative was to use a network load balancer. With MAC address

manipulation, traffic could be distributed to physically attached servers, but this limited servers to a single data center and confined space. Network address translation allowed source and destination ports to be changed while packets were in transit. Response to server outages was faster because a local administrator could manually update the pool of available servers; however, most load balancers did not perform extensive network testing to ensure that a server was actually up (and that the application was running). Some load balancers used state tables to provide some stateful or persistent connections, but generally this functionality was limited.

These limitations in response to incoming network traffic, and the inherent need to transition a single stream of network connections into a horizontally scalable infrastructure prompted further advancement of load balancers into application-aware ADCs. An ADC in a modern data center can monitor servers for availability at the physical and application layers, dynamically scale the number of servers based on incoming network connections, and help mitigate target attacks against applications. Application Delivery Controllers are found in many areas of current networked applications. As applications become more reliant on cloud infrastructure, the use of ADCs will continue to grow. Web applications and managed hosting environments rely on the functionality and automated scalability that ADCs can provide. Distributed computing has become increasingly affordable, especially on commodity hardware. The monolithic hardware and software solutions of the past are transitioning to clusters of servers, and ADCs are needed to make the leap.

State of the IndustryA number of networking vendors provide varying levels of ADC offerings, but only a small few are able to compete strongly in the space. With Cisco announcing the discontinuation of its ACE product, the largest switch manufacturer has ceded the ADC space to the market leaders. Gartner’s magic quadrant lists these leaders as F5 Networks, Citrix, and Radware. There are a number of other vendors, but they are generally smaller companies or companies that provide limited or niche offerings.

Of the three market leaders, Citrix and Radware are relative newcomers, both entering the space through acquisitions. Citrix’s purchase of NetScaler and Radware’s purchase of Nortel’s Alteon are both positioned to augment existing products. Long term plans and viability in the ADC space has not been proven for either of these companies. On the other hand, F5 developed load balancers in the mid-1990s and grew its products into ADCs with associated modules from this base.

The available feature set provided by each vendor must also be taken into account. Citrix has done extensive work to integrate NetScalers into its existing software products, leading some to question future support for competitors’ applications. Radware takes a more general approach to ADCs, similar to that of F5; however, it may be some time before customers see a completely consolidated solution. Radware currently offers security products and some application-specific appliances and software. As these involve different hardware purchases in many cases, the long-term costs may be higher. F5’s offerings have been consolidated to a limited set of hardware devices, allowing the deployment of different software modules on the same device. A single ADC from F5 can load balance connections, terminate remote VPNs, and secure web applications against attacks. Radware and Citrix offer similar solutions, but not to the same degree of integration or with the same footprint as F5 Networks.

ConclusionsOur industry is a constantly evolving ecosystem. New products, customer demands, and ideas are introduced each year. As IT professionals, we must do our best to look forward and make the best decisions for the future with the best information available today. We cannot deny that customers and users demand always-on applications, and one of the tools at our disposal is the Application Delivery Controller. In the last ten years, we’ve embraced virtualization, commodity hardware, and mobile computing. Well-planned application delivery allows us to tie these new technologies together and empower us to meet our business objectives as managers, architects, and administrators.

Of the available ADC solutions, the clear winner at this point is F5 Networks. In situations involving a homogenous Citrix environment, NetScalers may be a worthwhile investment, but F5’s integration with Citrix is on par with NetScaler and offers comparable support for VMware. Radware’s offerings are interesting and should be watched over time, but right now they’re too disjointed to recommend strongly. Likewise, many of the smaller vendors have products of varying functionality and levels of innovation, but in enterprise situations, F5 is the proven winner.

2

Data Center Relocation Services

3140 Northwoods Parkway Norcross, GA 30071 Phone: 1-877 531-7466 Fax: (678) 495-1302 www.CentricsIT.comCentricsIT United States Canada United Arab Emirates United Kingdom Czech Republic

IntroductionModern consumers of network applications, both customers and internal users, demand increasingly available access to services. To satisfy these demands, companies must focus on high availability and scalability of networks, servers, and software. Managers, architects, and administrators have to consider a number of disparate systems that must successfully work together to meet these requirements. Both the fundamental interdependence of these systems and the architecture required to ensure stable operation need to be considered and accounted for in a modern data center.

Recent and ongoing trends in data center operations show an increasingly consolidated approach to hosting and delivery. Vendors are focusing on merging multiple services onto single platforms; network devices are becoming more application-aware and software advances enable improved support for multi-system operation. Discussing all these topics in detail would require multiple texts. However, this whitepaper, written and distributed by CentricsIT, will focus specifically on the Application Delivery Controller, a bridge between the vertical network and horizontal scalability.

TechnologyAn Application Delivery Controller (ADC) is a network device or software package tasked with handling client requests and passing those requests to one or more private target servers. This may initially seem like load balancing, but ADCs offer additional functionality beyond that of a simple load balancer. A network load balancer works at layer 4 of the network model, responsible for simply spreading connections between servers. More advanced load balancers may be stateful, or have better load balancing algorithms available, but their overall functionality does not expand significantly beyond network address translation.

In comparison to a load balancer, an ADC not only works on layer 4 of the network model, but expands upward to layer 7. An ADC spreads traffic to a target pool of servers and has the ability to understand the underlying application traffic itself. Available ADC functionality will vary slightly by vendor and can range from providing SSL offloading for web applications (decrypting SSL traffic before handing over to HTTP servers), to selecting certain pools of available servers based on options specified in the application. Because of this fundamental application awareness, ADCs are not just network components needed to get your application online; instead they are an integral part of how your application functions.

HistoryMany network administrators or managers may look at an ADC and consider it an additional cost or headache that increases complexity or shifts focus from core business. In some cases that may be true. As with any machine, it is not a silver bullet for all problems. For those managers and administrators who look to the future and anticipate expansion, an ADC is an investment that should be strongly considered. The reason for this lies in historical advances, how networks work, and improvements in overall application design.

Original enterprise servers were physically massive machines, and applications developed for them were often self-contained. Networks were uncommon or limited, as it was easiest to maintain software on a single server. As servers got smaller and networked applications became more prevalent, applications were spread beyond individual machines in multi-tiered software paradigms. Data was moved to servers separate from the applications that used it. This ability on a software level, plus the reduced cost of servers and hardware, allowed for the building of redundant servers and therefore more reliable applications. A single server failure no longer caused an entire application to go down completely—an improvement in service availability.

While the introduction of redundant servers increased application uptime, it did not provide an easy path to respond to the increased user base created by the improved cost and availability of personal computers. In order for standalone and redundant servers to handle the increased workload the user expansion caused, companies had to invest in continual hardware upgrades. Because software itself was not particularly scalable, the only way to improve application performance was to give the application more resources. This limitation of software would potentially require significant funds to constantly upgrade, in addition to outages to perform the improvements.

Distributed computing, the ability of multiple servers to run the same software concurrently without impacting one another, gives developers the ability to write software that is not limited to a single active server. Now, instead of an active-passive pair of servers, a service can be run across a number of systems actively. The question then becomes, “How is network traffic sent to all these active machines?” One solution is DNS round-robin, a method of sending individual requests for name resolutions to each host listed in order. This method does not take into account server outages, updates can take a long time to propagate through the DNS tree, and connections are not persistent to a target server. A local alternative was to use a network load balancer. With MAC address

manipulation, traffic could be distributed to physically attached servers, but this limited servers to a single data center and confined space. Network address translation allowed source and destination ports to be changed while packets were in transit. Response to server outages was faster because a local administrator could manually update the pool of available servers; however, most load balancers did not perform extensive network testing to ensure that a server was actually up (and that the application was running). Some load balancers used state tables to provide some stateful or persistent connections, but generally this functionality was limited.

These limitations in response to incoming network traffic, and the inherent need to transition a single stream of network connections into a horizontally scalable infrastructure prompted further advancement of load balancers into application-aware ADCs. An ADC in a modern data center can monitor servers for availability at the physical and application layers, dynamically scale the number of servers based on incoming network connections, and help mitigate target attacks against applications. Application Delivery Controllers are found in many areas of current networked applications. As applications become more reliant on cloud infrastructure, the use of ADCs will continue to grow. Web applications and managed hosting environments rely on the functionality and automated scalability that ADCs can provide. Distributed computing has become increasingly affordable, especially on commodity hardware. The monolithic hardware and software solutions of the past are transitioning to clusters of servers, and ADCs are needed to make the leap.

State of the IndustryA number of networking vendors provide varying levels of ADC offerings, but only a small few are able to compete strongly in the space. With Cisco announcing the discontinuation of its ACE product, the largest switch manufacturer has ceded the ADC space to the market leaders. Gartner’s magic quadrant lists these leaders as F5 Networks, Citrix, and Radware. There are a number of other vendors, but they are generally smaller companies or companies that provide limited or niche offerings.

Of the three market leaders, Citrix and Radware are relative newcomers, both entering the space through acquisitions. Citrix’s purchase of NetScaler and Radware’s purchase of Nortel’s Alteon are both positioned to augment existing products. Long term plans and viability in the ADC space has not been proven for either of these companies. On the other hand, F5 developed load balancers in the mid-1990s and grew its products into ADCs with associated modules from this base.

The available feature set provided by each vendor must also be taken into account. Citrix has done extensive work to integrate NetScalers into its existing software products, leading some to question future support for competitors’ applications. Radware takes a more general approach to ADCs, similar to that of F5; however, it may be some time before customers see a completely consolidated solution. Radware currently offers security products and some application-specific appliances and software. As these involve different hardware purchases in many cases, the long-term costs may be higher. F5’s offerings have been consolidated to a limited set of hardware devices, allowing the deployment of different software modules on the same device. A single ADC from F5 can load balance connections, terminate remote VPNs, and secure web applications against attacks. Radware and Citrix offer similar solutions, but not to the same degree of integration or with the same footprint as F5 Networks.

ConclusionsOur industry is a constantly evolving ecosystem. New products, customer demands, and ideas are introduced each year. As IT professionals, we must do our best to look forward and make the best decisions for the future with the best information available today. We cannot deny that customers and users demand always-on applications, and one of the tools at our disposal is the Application Delivery Controller. In the last ten years, we’ve embraced virtualization, commodity hardware, and mobile computing. Well-planned application delivery allows us to tie these new technologies together and empower us to meet our business objectives as managers, architects, and administrators.

Of the available ADC solutions, the clear winner at this point is F5 Networks. In situations involving a homogenous Citrix environment, NetScalers may be a worthwhile investment, but F5’s integration with Citrix is on par with NetScaler and offers comparable support for VMware. Radware’s offerings are interesting and should be watched over time, but right now they’re too disjointed to recommend strongly. Likewise, many of the smaller vendors have products of varying functionality and levels of innovation, but in enterprise situations, F5 is the proven winner.

3

Data Center Relocation Services

3140 Northwoods Parkway Norcross, GA 30071 Phone: 1-877 531-7466 Fax: (678) 495-1302 www.CentricsIT.comCentricsIT United States Canada United Arab Emirates United Kingdom Czech Republic

IntroductionModern consumers of network applications, both customers and internal users, demand increasingly available access to services. To satisfy these demands, companies must focus on high availability and scalability of networks, servers, and software. Managers, architects, and administrators have to consider a number of disparate systems that must successfully work together to meet these requirements. Both the fundamental interdependence of these systems and the architecture required to ensure stable operation need to be considered and accounted for in a modern data center.

Recent and ongoing trends in data center operations show an increasingly consolidated approach to hosting and delivery. Vendors are focusing on merging multiple services onto single platforms; network devices are becoming more application-aware and software advances enable improved support for multi-system operation. Discussing all these topics in detail would require multiple texts. However, this whitepaper, written and distributed by CentricsIT, will focus specifically on the Application Delivery Controller, a bridge between the vertical network and horizontal scalability.

TechnologyAn Application Delivery Controller (ADC) is a network device or software package tasked with handling client requests and passing those requests to one or more private target servers. This may initially seem like load balancing, but ADCs offer additional functionality beyond that of a simple load balancer. A network load balancer works at layer 4 of the network model, responsible for simply spreading connections between servers. More advanced load balancers may be stateful, or have better load balancing algorithms available, but their overall functionality does not expand significantly beyond network address translation.

In comparison to a load balancer, an ADC not only works on layer 4 of the network model, but expands upward to layer 7. An ADC spreads traffic to a target pool of servers and has the ability to understand the underlying application traffic itself. Available ADC functionality will vary slightly by vendor and can range from providing SSL offloading for web applications (decrypting SSL traffic before handing over to HTTP servers), to selecting certain pools of available servers based on options specified in the application. Because of this fundamental application awareness, ADCs are not just network components needed to get your application online; instead they are an integral part of how your application functions.

HistoryMany network administrators or managers may look at an ADC and consider it an additional cost or headache that increases complexity or shifts focus from core business. In some cases that may be true. As with any machine, it is not a silver bullet for all problems. For those managers and administrators who look to the future and anticipate expansion, an ADC is an investment that should be strongly considered. The reason for this lies in historical advances, how networks work, and improvements in overall application design.

Original enterprise servers were physically massive machines, and applications developed for them were often self-contained. Networks were uncommon or limited, as it was easiest to maintain software on a single server. As servers got smaller and networked applications became more prevalent, applications were spread beyond individual machines in multi-tiered software paradigms. Data was moved to servers separate from the applications that used it. This ability on a software level, plus the reduced cost of servers and hardware, allowed for the building of redundant servers and therefore more reliable applications. A single server failure no longer caused an entire application to go down completely—an improvement in service availability.

While the introduction of redundant servers increased application uptime, it did not provide an easy path to respond to the increased user base created by the improved cost and availability of personal computers. In order for standalone and redundant servers to handle the increased workload the user expansion caused, companies had to invest in continual hardware upgrades. Because software itself was not particularly scalable, the only way to improve application performance was to give the application more resources. This limitation of software would potentially require significant funds to constantly upgrade, in addition to outages to perform the improvements.

Distributed computing, the ability of multiple servers to run the same software concurrently without impacting one another, gives developers the ability to write software that is not limited to a single active server. Now, instead of an active-passive pair of servers, a service can be run across a number of systems actively. The question then becomes, “How is network traffic sent to all these active machines?” One solution is DNS round-robin, a method of sending individual requests for name resolutions to each host listed in order. This method does not take into account server outages, updates can take a long time to propagate through the DNS tree, and connections are not persistent to a target server. A local alternative was to use a network load balancer. With MAC address

manipulation, traffic could be distributed to physically attached servers, but this limited servers to a single data center and confined space. Network address translation allowed source and destination ports to be changed while packets were in transit. Response to server outages was faster because a local administrator could manually update the pool of available servers; however, most load balancers did not perform extensive network testing to ensure that a server was actually up (and that the application was running). Some load balancers used state tables to provide some stateful or persistent connections, but generally this functionality was limited.

These limitations in response to incoming network traffic, and the inherent need to transition a single stream of network connections into a horizontally scalable infrastructure prompted further advancement of load balancers into application-aware ADCs. An ADC in a modern data center can monitor servers for availability at the physical and application layers, dynamically scale the number of servers based on incoming network connections, and help mitigate target attacks against applications. Application Delivery Controllers are found in many areas of current networked applications. As applications become more reliant on cloud infrastructure, the use of ADCs will continue to grow. Web applications and managed hosting environments rely on the functionality and automated scalability that ADCs can provide. Distributed computing has become increasingly affordable, especially on commodity hardware. The monolithic hardware and software solutions of the past are transitioning to clusters of servers, and ADCs are needed to make the leap.

State of the IndustryA number of networking vendors provide varying levels of ADC offerings, but only a small few are able to compete strongly in the space. With Cisco announcing the discontinuation of its ACE product, the largest switch manufacturer has ceded the ADC space to the market leaders. Gartner’s magic quadrant lists these leaders as F5 Networks, Citrix, and Radware. There are a number of other vendors, but they are generally smaller companies or companies that provide limited or niche offerings.

Of the three market leaders, Citrix and Radware are relative newcomers, both entering the space through acquisitions. Citrix’s purchase of NetScaler and Radware’s purchase of Nortel’s Alteon are both positioned to augment existing products. Long term plans and viability in the ADC space has not been proven for either of these companies. On the other hand, F5 developed load balancers in the mid-1990s and grew its products into ADCs with associated modules from this base.

The available feature set provided by each vendor must also be taken into account. Citrix has done extensive work to integrate NetScalers into its existing software products, leading some to question future support for competitors’ applications. Radware takes a more general approach to ADCs, similar to that of F5; however, it may be some time before customers see a completely consolidated solution. Radware currently offers security products and some application-specific appliances and software. As these involve different hardware purchases in many cases, the long-term costs may be higher. F5’s offerings have been consolidated to a limited set of hardware devices, allowing the deployment of different software modules on the same device. A single ADC from F5 can load balance connections, terminate remote VPNs, and secure web applications against attacks. Radware and Citrix offer similar solutions, but not to the same degree of integration or with the same footprint as F5 Networks.

ConclusionsOur industry is a constantly evolving ecosystem. New products, customer demands, and ideas are introduced each year. As IT professionals, we must do our best to look forward and make the best decisions for the future with the best information available today. We cannot deny that customers and users demand always-on applications, and one of the tools at our disposal is the Application Delivery Controller. In the last ten years, we’ve embraced virtualization, commodity hardware, and mobile computing. Well-planned application delivery allows us to tie these new technologies together and empower us to meet our business objectives as managers, architects, and administrators.

Of the available ADC solutions, the clear winner at this point is F5 Networks. In situations involving a homogenous Citrix environment, NetScalers may be a worthwhile investment, but F5’s integration with Citrix is on par with NetScaler and offers comparable support for VMware. Radware’s offerings are interesting and should be watched over time, but right now they’re too disjointed to recommend strongly. Likewise, many of the smaller vendors have products of varying functionality and levels of innovation, but in enterprise situations, F5 is the proven winner.

Figure 1. Gartner’s Magic Quadrant for Application Delivery Controllers

4

Data Center Relocation Services

3140 Northwoods Parkway Norcross, GA 30071 Phone: 1-877 531-7466 Fax: (678) 495-1302 www.CentricsIT.comCentricsIT United States Canada United Arab Emirates United Kingdom Czech Republic