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1、2020/9/18,TMX Technical Training,Server Load Balancing,2020/9/18,2,Objectives,To understand Server Load Balancing concepts. To understand Array Server Load Balancing configuration steps.,2020/9/18,3,Topics,Unit 1: Basic Server Load Balancing Concepts and Configuration Unit 2: Additional Server Load
2、Balancing Concepts and Configuration Appendix: Web Concepts,2020/9/18,4,Unit 1: Basic SLB Concepts,What is Server Load Balancing? SLB Terminology Array SLB Benefits SLB Modes Real Services Simple Group Methods Virtual Services Simple Policy Types,2020/9/18,5,What is Load Balancing? Its in everywhere
3、 actually!,Emergency,Clinic,Expert Clinic,Load Balancing,AFE,Connection Reuse,SLB: Policy,SLB: Method,2020/9/18,6,What is Server Load Balancing (SLB)?,SLB allows web sites to be scaled from a single service to a group of services (service farm) while distributing the load between the services based
4、on their load and health. SLB Benefits Greater scalability in the number of services for a site reduces load on individual services and improves response time to clients Improved resiliency through Health Checking of services, services, and web content Better control of service resource usage throug
5、h implementation of different load balancing algorithms Traffic management based on TCP/UDP port number, URL, HTTP Host Header, Cookie content, or SSL Session ID,2020/9/18,7,SLB Terminology,Real Service (“Real”) Represents a physical service which will handle client requests Real Service Group (“Gro
6、up”) Represents a group of real services which traffic will be distributed to Defines which load balancing algorithm to use Virtual Service (“Virtual”) Represents a virtual service that clients can connect to Policy Associates real service groups with virtual services,service 1,service 5,service 4,s
7、ervice 3,service 2,Real 1,Real 3,Real 4,Real 5,Real 2,Group 1,Group 2,Virtual 1,Virtual 2,Internet,2020/9/18,8,Server Load Balancing Example,Basic Server Load balancing,Internet,Service Group,Real services,Virtual IP 100.10.10.10,4,DNS,2020/9/18,9,SLB Modes,Server Load Balancing can be performed in
8、two modes: Reverse Proxy Mode Array TM proxies all client connections to real services. Transparent Mode Array TM transparently proxies all client connections to real services.,2020/9/18,10,Reverse Proxy Mode,Packet Flow Client connects to VIP on Array TM and sends request to Array TM. Array TM open
9、s a new connection to real service and sends request to service. service responds to Array TM. Array TM responds to Client.,Virtual,Internet,service1,service2,Inside Interface,Outside Interface,1,2,3,4,2020/9/18,11,Reverse Proxy Mode,Translations,Virtual,Internet,service1,service2,Inside Interface,O
10、utside Interface,1,2,3,4,2020/9/18,12,Reverse Proxy Mode,Benefits One-armed topology is possible. Responses automatically return to the Array TM. Enables connection pooling for increased performance. Limitations service logs do not show real clients IP address (connections proxied). Solution: Enabli
11、ng X-Forwarded-For header insertion allows clients original source IP address to be inserted into HTTP requests before sending to backend real service.,2020/9/18,13,Connection Pooling,Provides TCP acceleration for backend connections to real services. Array opens connection(s) to backend service as
12、needed and leaves it (them) open. Array sends multiple requests from different clients through the same backend service connection(s). This significantly reduces the number of client connections a service has to handle (typically by up to 90% with cache off). Improves service performance. service do
13、esnt spend as much time performing TCP setups/teardowns. service doesnt need to keep so many connections open. Only possible with Reverse Proxy Mode.,2020/9/18,14,Transparent Mode,Packet Flow Client sends request to VIP on Array TM. Array TM forwards request to real service, maintaining the clients
14、IP. Real service returns response via client IP (handled by Array TM). Array TM forwards response to Client.,Virtual IP,Internet,service1,service2,2,3,5,4,6,1,2020/9/18,15,Transparent Mode,Translations,Virtual IP,Internet,service1,service2,2,3,5,4,6,1,2020/9/18,16,Transparent Mode,Benefits service l
15、ogs will show actual client IP address. Limitations Real service responses must be routed through the Array TMX. Ensures that the Array TMX can see the responses. One-armed topology is not always possible. Cannot use connection pooling feature. Array TMX cannot reuse the same service connection for
16、multiple clients since each clients IP address is different. Reverse proxy mode is preferred for performance benefits.,2020/9/18,17,SLB Real Services,The following parameters are associated with a real service: Real service protocol (udp, tcp, ftp, http; tcps and https for SSL) Real service name Real service IP address Real service port Health check method Health check up Health check down,2020/9/18,18,SLB Group Method
