Glsb involves load balancing algorithm

Topology Algorithm
Two kinds of application Topology Location ：
《1》wideIP Corresponding multiple pool
* Need to define Dest by pool perhaps pool Region Of Topology Record
* If not defined ,F5 DNS take Pool RR
《2》pool Corresponding multiple VS
* Need to define Dest by DC,IP,IP Subnet Or above Region Of Topology Record
* If not defined , be Topology Algorithm Miss

Topology The records are divided into three columns
*LDNS,Destination,Score/Weight
*LDNS,Destination As input
*Score/Weight As the output

F5 DNS matching WideIP after , In the choice pool when pool name Respectively with LDNS Combine in pairs ;
* Just give LDNS,POOL name You can go to topolgy Find the corresponding in the table Score/Weight value ;
* Then take this value as a right Pool name Of Score score ;
According to the Score High and low , Decide which one to choose pool

F5 determine pool after , In the selection of which VS Address as DNS Response when , Will pool Internal VS Respectively with LDNS Combine in pairs ：
* Just give it LDNS,VS IP You can go to topology Find the corresponding in the table Score/Weight value ;
* Then take this value as a right VS Of Score score
According to the Score/Weight High and low , Decide which one to choose VS,Weight Value is preferred

About topology The object of ：
《1》Request source： Definition LDNS Of ip Address meets the conditions , Include continent（ mainland ）、country、ISP、IP Subnet、Region（ region ）、State（ state ）

logest match：
F5 DNS On topology Enabled by default logest match, To speed up Topology Record Match speed of . stay longest match Enable the following ,F5 DNS Will automatically Topology Record Sort , Cannot change... Manually Topology Order of entries . And once the records match to the conditions, they will no longer match down

Use the following command to view Topology Sort the information of ：tmsh list /gtm topology all

Sorting principle ：
IP Subnet>DC>POOL>Region>ISP>State>Country>Continent>LDNS Request Source negatior>Wildcard
When logest match When cancelled ,F5 Will match all the records of satisfaction , Instead of just matching to the first satisfaction, it doesn't match down , If all the records are satisfied, there are multiple , According to Weight Value is higher than the value is selected .



Load balancing algorithm --RTT
Realization principle ： When any one F5 DNS received LDNS When asked , because RTT need F5 DNS Initiated to LDNS Dynamic detection of , therefore F5 DNS First use Falback In the algorithm GA The algorithm will have a serial number of 0 The address of is returned to LDNS, At the same time, the detection is initiated from different links , And write the detection results into memory , When the same LDNS When the resolution request is initiated again ,F5 DNS Use RTT The algorithm returns a VS Address to LDNS;

Load balancing algorithm --QOS
Use virtual server After comprehensive calculation of all parameters and indexes, the optimal choice is made by score .
Parameter indicators include ：
*Round trip time
*Hops
*Connection rate
*Packet rate
*topology
*Link capacity
*VS capacity
*Kilobytes/Second
For simple configuration , You can use the default settings , need iquery Inquire about big-ip vs Performance of .