1. Module 8: Concepts of a Network Load Balancing Cluster

2. Overview Network Load Balancing Concepts
Application and Service Environment
Network Load Balancing Functionality
Network Load Balancing Architecture

3. Network Load Balancing Concepts
Comparing Network Load Balancing Solutions
Network Load Balancing

4. Comparing Network Load Balancing Solutions
Round robin DNS
Easy to Install
Yes
Hardware Requirements
____
Single Point of Failure
Easily Scalable
High Performance
Hardware
Dispatch
Limited
NLB
Fault Tolerance No

5. Network Load Balancing
Cluster with up to
32 hosts
Round Robin DNS
Static group
MyRRDNSWeb   IN  A   MyRRDNSWeb   IN  A  
MyRRDNSWeb   IN  A  
MyNLBWeb IN A 1 2 3 5
DNS Server 6 4
IP:
IP:
IP:
IP:

6. Application and Service Environment
IIS Web site image
Virtual IP:
Web server TCP(80)
HTTPS TCP(443)
Port Rules define which ports the cluster will service
Affinity sets all client connections to a single host
Client TCP Session (Get)
Next client TCP Session (HTTPS)

7. Applications and Services
Compatible Network Load Balancing Applications and Services
Use TCP connections or UDP data streams
Support client updateable data stores
Support maintenance of client session state
Incompatible Network Load Balancing Applications and Services
Bind to or reference computer names
Hold files exclusively and continuously open

8. Network Load Balancing Functionality
Balancing Client Connections
Supporting Multiple Client Connections
Cluster Convergence
Network Load Balancing for High Availability
Network Load Balancing for Scalability
Scaling Network Load Balancing Clusters

9. Balancing Client Connections
Even Balance
Load to virtual IP distributed evenly across hosts
1/3
Priority Based 1 2 3
All load to virtual IP distributed to highest priority host
Manual Balance
30%
60%
10%
Load to virtual IP distributed based on manual configuration

10. Supporting Multiple Client Connections
Virtual IP:
Initial Client TCP session
Initial client request distributed according to Network Load Balancing configuration
Subsequent client requests distributed according to Network Load Balancing configuration
Even balance
without affinity
with affinity
Subsequent client requests accepted by the same server for that client IP address

11. Cluster Convergence Load balance 1/3 each Server B Fails Convergence
Server B Joins
Load Balance 1/3 each
Virtual IP: A B C
Even balance

12. Network Load Balancing for High Availability
Load All on Host 1
Server 1 Fails
Convergence
Load All on Server 2
Virtual IP:
Priority 1 2 3
N-1 Failover
Load balance 1/3 each
Server B Fails
Load Balance ½ each A B C
Even balance

13. Network Load Balancing for Scalability
Virtual IP:
CPUs
Memory
Disk
NIC
Network Load Balancing Cluster
Scale up
Add more resources to a server
Scale out
Add more servers to the cluster

14. Scaling Network Load Balancing Clusters
Cluster 2 with up to 32 hosts 1 2 3 6
DNS Server 5 4
Virtual IP:
Cluster 1 with up to 32 hosts
Query DNS for MybigWeb
DNS resolves to list of IPs
Client selects first in list
Creates session with server
DNS rotates list for each query which statically load balances incoming requests
DNS resolves to list of IP’s
MybigWeb   IN  A   MybigWeb   IN  A  

15. Network Load Balancing Architecture
Network Load Balancing Driver Architecture
Network Load Balancing Topology
Selecting an IP Transmission Mode
Network Load Balancing Addressing
Port Rules
Affinity

16. Network Load Balancing Driver Architecture
Cluster Host
Server Application
Wlbs.exe
Windows 2000 Kernel
TCP/IP
Network Load Balancing Driver
Network Adapter Driver
Cluster
Network Adapter
LAN

17. Network Load Balancing Topology
Cluster with 3 hosts
Hub or switch
Router
Virtual IP:
Single Subnet
Multicast or Unicast
Common MAC address
Driver configuration
Inbound traffic
Outbound traffic and Inbound to dedicated IP

18. Selecting an IP Transmission Mode
Adapters
Single
Multiple
Mode
Unicast
Multicast
MAC
Advantage
Simple
Medium Performance
Best Balance
Disadvantage
Low peer performance
Complex
None
Complex Network Configuration

19. Network Load Balancing Addressing
Cluster with 3 hosts
Virtual IP:
Single Subnet
Multicast or Unicast
Common MAC address
Example
Clients access DNS to resolve IP address
Clients ARP to resolve IP to MAC
All cluster hosts reply to ARP
Client Syn to start TCP connection
Server Asyn for selected cluster host
Client ASyn
Note:
All client traffic arrives at all hosts for virtual IP
Algorithm selected host replies
Traffic to dedicated IP can be the same MAC address
Hub or switch

20. Port Rules
Port Rules
Filtering Modes
Load Weighting
Priority

21. Load balancing granularity
Affinity
Affinity
Load balancing granularity
Algorithm
hashes on
Used for
None
Individual TCP connections
Single
All connections originating from the same source
Class C
All connections originating from the same Class C address space
Source IP address and port
Source IP address
Source IP address with Class C mask applied to it
Most applications
Session support, SSL and multi-connection protocols (ex: FTP, PPTP, etc.)
Property handling sessions for users residing behind scaling proxy arrays

22. Lab A: Planning an Installation

23. Review Network Load Balancing Concepts
Application and Service Environment
Network Load Balancing Functionality
Network Load Balancing Architecture

24. Network Load Balancing Driver Architecture
TCP/IP
Holds Port rules for all inbound traffic
NLB Driver
Network Adapter Driver
Assigns Common Virtual IP and MAC address
Virtual IP:
MAC: 02-BF
Cluster
Network Adapter
Adapter can be Ethernet, Gigabit Ethernet or FDDI
All Virtual IP traffic will be filtered by NLB rules