Windows Network Load Balancing Dedicated Servers
Network Load Balancer or Clusters that were included in Windows Server OS enabled TCP/IP-based services such as follows:
– Web Services
– Terminal Services
– Virtual Private Networking
– Streaming Media
It basically didn’t require any Hardware Support and distributed IP traffic across cluster hosts which ensures detecting host failures and re-distributes traffic to hosts. It provides control and upgrade from Windows NT 4.0 OS. It delivered high performance and fail-over protection in comparison with other load-balancers.
Financial Transactions, Database access, corporate connections and other functions required more reliability which was offered in Windows NLB. Cluster enabled different servers to manage and operate as a single server increasing availability and management.
Windows 2000 Advanced Server and Data Center Server OS includes cluster technology which also provides fail-over for applications and databases. In terms with NLB, traffic distributed among multi-node clusters.
Advantages of Network Load balancing servers:
> Network Load Balancer Servers are Scalable based upon the activity it hosts. It always adds more no. of servers when we speak of traffic increase.
> Network Load Balancer Server improves reliability of servers. It detects failure of servers and distributes traffic among servers without interrupting any service.
> It distributes traffic based upon the client’s / Users request.
> In comparison, it’s much better than Round Robin Solutions
> 100% Network Uptime
> Centralized access to all cluster servers
> Cost effective when compared to hardware load-balancing techniques
Installation and Management of Network Load-balancing Dedicated Web Servers:
Network Load Balancer is automatically installed and enabled on the Windows Server 2003 and 2008 Operating System. It’s compatible with Ethernet and network adapters, it doesn’t require any hardware. In a NLB, customer is assigned a IP address which is seen as Virtual IP address which all cluster host respond to. Network Load Balancer load-balances only incoming traffic from all IPs. While configuration of NLB, it’s important that there should be a dedicated IP address, primary IPs and Virtual IP’s in order to enable host TCP/IP to respond to IP addresses. Dedicated IP address is entered first and then virtual IP addresses. Services such as PPTP Server does not allow outgoing connections from a different IP address and cannot be used by dedicated IP.
In a cluster, each host is assigned in range of 1 to 32 where lower no. refers to priority. The default host handles all client traffic for virtual IP addresses. Normally, in this case, if the default host fails, the next priority takes place. Network Load Balancer also customized port rules for range of server ports. It can select either Multiple-host or second hosting load balancing policies.
With Multiple-host load balancing, incoming request are distributed among all cluster hosts and load percentage can be specified. In this case, it directs all traffic to most priority server. Rules specified at Ports can block different network access. When we speak of port rule multiple-host NLB, one of them is selected in affinity mode and Network Load Balancer client’s traffic from on IP addresses on multiple-cluster hosts. It reduces the load on the servers and increases the response time.
In order to manage client sessions, single-client affinity mode balances network traffic from client’s IP on a single cluster host. Network Load Balancer is configured with single port rule covers all port with multiple-host balancing and single client affinity. It is used for applications.
Network Load Balancer also has remote control program which allows administrators to check status of clusters from cluster host. Network Load Balancer for port rules can be enabled or disabled. New traffic can be blocked on host while TCP connections to complete removing host from cluster. Cluster host can disable remote control.
Applications do not need to be modified for load balancing. It does not directly monitor applications. Network Load Balancer provides application mechanism to monitor cluster. Servers can be removed from the clusters for maintenance without interference with other cluster servers. It also allows custom hardware of software upgrades.
Network Load Balancer scales the performance of server based program. It distributes request among different servers in a cluster. With NLB, each IP packet is received by each host. Cluster host responds to different client requests even multiple request from a single client. Load percentage can be handled with each cluster server and can be set as required depending upon the activity. In case one cluster host fails, the traffic and is re-distributed among other cluster host.
Network Load Balancer uses are fully distributed software architecture. A copy of Network Load Balancer driver runs on each cluster host. Drivers check for all incoming network traffic for cluster IP address. On each cluster host, they act as filter between network adapter drive and TCP/IP stack allowing portion of incoming network traffic. Incoming client request are partitioned and load-balanced among cluster host. Network Load Balancer runs as network driver which is below higher-level application protocol such as HTTP and FTP.
Network Load Balancer can also run as drive between TCP/IP protocol and network adapter drivers within Windows protocol. It maximizes throughput by broadcasting subnet to deliver incoming network traffic to cluster host and removers requirement to route incoming packers to individual cluster host.
Filtering packets that are not required can be easily be removed than routed packages, it delivers higher Network Load Balancer throughput than any other solution. As network and speed improve, it improves accordingly and reduces dependencies on hardware. It’s availability in fail-over is another advantage.
Network Load Balancer takes advantage of subnet / switch hub to deliver network traffic to cluster host. It increases the load on switches by accessing additional port bandwidth.
However, this is not the concern in many applications. Client-side network switch connections are faster than server-side connection. During packet receiving, Network Load Balancer implements delivery of incoming packages to TCP/IP and receiving other packets by Network adapter driver.
It means it will speed up all the processes and reduces latency. In many cases, it removes packet data in memory. Network Load Balancer uses layer-two broadcast or multi-cast to distribute incoming traffic to cluster host. Network Load Balancer re-assigns MAC address of network adapter for which it is enabled.
And cluster host assigned the same MAC address. Incoming traffic received by cluster host and Network Load Balancer driver for filtering. MAC address is taken from cluster IP address in the Network Load Balancer properties.
Cluster host that is attached to switch, it might create MAC address conflict due to layer-two switches to see unique MAC address on all switch ports. In order to avoid these problems, Network Load Balancer modifies MAC address for outgoing packages.
This prevents switch from learning the cluster’s MAC address and incoming packets for cluster are delivered to all switch ports. Cluster host connected to hub, Network Load Balancer masking for MAC address in Unicast disables to avoid flooding upstream switches. This is done by setting Network Load Balancer registry parameters MaskSourceMAC to 0.
Network Load Balancer unicast mode has a disadvantage of communication disabling between cluster hosts through cluster adapters. Outgoing packets for cluster host are sent to sender’s MAC address, packages are looped within sender by network stack and they do not reach the wire.
Communication between cluster hosts and host outside the cluster is never affected by NLB’s unicast mode. Traffic for all static IP address are received by cluster host due to the same MAC address. Network Load Balancer doesn’t load balance traffic for the IP address, Network Load Balancer deliver the traffic to TCP/IP on host.
With other cluster host, Load balancing Servers checks it’s traffic as load balanced traffic and deliver to TCP/IP. Network Load Balancing also has another mode by distributing incoming traffic to cluster hosts which is called multi-cast mode. Network Load Balancer – Unicast also increases switch flooding by delivering incoming network traffic to cluster hosts, however this is not the case with multi-cast mode.
Network Load balancing have Address Resolution Protocol which is required for the cluster’s main IP and virtual IP address resolving to cluster multi-cast MAC address. Network Load Balancing does not include management of incoming IP traffic other than TCP traffic, UDP traffic, Generic routing encapsulation traffic for each port.