NLB NLB Network Load Balance Network Load Balance Understanding NLB Understanding NLB * * Network Load Balancing works by creating on each Network Load Balancing works by creating on each host a host a virtual network adapter virtual network adapter that represents the that represents the cluster as a single entity cluster as a single entity . . * * The virtual adapter has its own IP and media The virtual adapter has its own IP and media access control (MAC) addresses, independent of access control (MAC) addresses, independent of the addresses assigned to the physical network the addresses assigned to the physical network interface adapters in the computers interface adapters in the computers . . * * On each host in an NLB cluster, a Network Load On each host in an NLB cluster, a Network Load Balancing service functions as a filter between Balancing service functions as a filter between the cluster adapter and the computer’s TCP/IP the cluster adapter and the computer’s TCP/IP stacks stacks . .
Transcript
NLBNLBNetwork Load BalanceNetwork Load Balance
NLBNLBNetwork Load BalanceNetwork Load Balance
Understanding NLBUnderstanding NLB** Network Load Balancing works by creating on each host a Network Load Balancing works by creating on each host a virtual virtual
network adapternetwork adapter that represents the cluster as a single entitythat represents the cluster as a single entity..
** The virtual adapter has its own IP and media access control (MAC) The virtual adapter has its own IP and media access control (MAC) addresses, independent of the addresses assigned to the physical addresses, independent of the addresses assigned to the physical network interface adapters in the computersnetwork interface adapters in the computers..
** On each host in an NLB cluster, a Network Load Balancing service On each host in an NLB cluster, a Network Load Balancing service functions as a filter between the cluster adapter and the computer’s functions as a filter between the cluster adapter and the computer’s TCP/IP stacksTCP/IP stacks..
IP addressingIP addressingIP addressingIP addressing
* *The cluster is assigned a The cluster is assigned a primary IP addressprimary IP address, which , which represents a virtual IP address to which all cluster hosts represents a virtual IP address to which all cluster hosts respondrespond
* *Each cluster host also can be assigned a Each cluster host also can be assigned a dedicated IP dedicated IP addressaddress for network traffic unique to that particular host for network traffic unique to that particular host within the clusterwithin the cluster
* *Network Load Balancing never load-balances traffic for Network Load Balancing never load-balances traffic for the dedicated IP address. Instead, it load-balances the dedicated IP address. Instead, it load-balances incoming traffic from all IP addresses other than the incoming traffic from all IP addresses other than the dedicated IP addressdedicated IP address..
* *NLB has two operational modesNLB has two operational modes::unicastunicast mode mode and and multicastmulticast mode mode
In unicast mode, Network Load Balancing replaces the MAC address In unicast mode, Network Load Balancing replaces the MAC address of the physical network interface adapter in each server with the of the physical network interface adapter in each server with the MAC address of the virtual adapter representing the clusterMAC address of the virtual adapter representing the cluster
so the cluster servers cannot communicate among themselves so the cluster servers cannot communicate among themselves in the normal wayin the normal way
In multicast mode, NLB assigns a cluster MAC address to the In multicast mode, NLB assigns a cluster MAC address to the physical network interface adapter, but also retains the adapter’s physical network interface adapter, but also retains the adapter’s original MAC addressoriginal MAC address
In this case the routers on the network must support the use In this case the routers on the network must support the use of multicast MAC addressesof multicast MAC addresses..
Host PrioritiesHost PrioritiesHost PrioritiesHost Priorities * *Each cluster host is assigned a unique Each cluster host is assigned a unique host priorityhost priority in the in the
range of 1 to 32, where lower numbers denote higher range of 1 to 32, where lower numbers denote higher prioritiespriorities The host with the highest host priority (lowest numeric The host with the highest host priority (lowest numeric value) is called the value) is called the default hostdefault host. .
* *Cluster servers emit a Cluster servers emit a heartbeatheartbeat message message to other hosts in to other hosts in the cluster, and listen for the heartbeat of other hoststhe cluster, and listen for the heartbeat of other hosts
If the heartbeat stops for 5 times the convergence If the heartbeat stops for 5 times the convergence ((recalculating the traffic distribution algorithm)recalculating the traffic distribution algorithm) startsstarts . .
Port RulesPort RulesPort RulesPort Rules * *Network Load Balancing uses Network Load Balancing uses port rulesport rules to customize to customize
load balancing for a consecutive numeric range of load balancing for a consecutive numeric range of server portsserver ports
* *Port rules can be used to block undesired network Port rules can be used to block undesired network access to certain IP portsaccess to certain IP ports . .
* *Port rules can select either Port rules can select either multiple-hostmultiple-host or or single-hostsingle-host load-balancing policiesload-balancing policies
11-- Multiple-host load balancingMultiple-host load balancing, incoming client , incoming client requests are distributed among all cluster hosts, and a requests are distributed among all cluster hosts, and a load percentage can be specified for each hostload percentage can be specified for each host
22-- Single-host load balancing Single-host load balancing directs all client directs all client requests to the host with highest requests to the host with highest handling priorityhandling priority
11-- TheThe single-clientsingle-client affinity mode load-balances affinity mode load-balances allall network traffic from a given client's IP address on a network traffic from a given client's IP address on a single-cluster hostsingle-cluster host
22-- The The class Cclass C affinity mode load-balances affinity mode load-balances allall network network traffic from a given class C subnet on a single-cluster traffic from a given class C subnet on a single-cluster hosthost
33-- The The no affinityno affinity mode load-balances client traffic mode load-balances client traffic from one IP address and different source ports on from one IP address and different source ports on multiple-cluster hostsmultiple-cluster hosts..
* *Many clusters in different location produce the same Many clusters in different location produce the same servicesservices
* *The load is distributed among the clusters via DNS server The load is distributed among the clusters via DNS server using Round Robin Techniqueusing Round Robin Technique
Round robinRound robin is a local balancing mechanism used is a local balancing mechanism used by DNS servers to share and distribute network by DNS servers to share and distribute network resource loads. You can use it to rotate all resource resource loads. You can use it to rotate all resource record (RR) types contained in a query answer if record (RR) types contained in a query answer if multiple RRs are foundmultiple RRs are found
* *The load is distributed among the hosts via the The load is distributed among the hosts via the clustering softwareclustering software..
