In GSLB dynamic proximity RTT measurement, which pair defines the round trip time used for load decisions?

• A. IP address of the client; each of the GSLB services
• B. Local DNS of the client; each of the GSLB sites
• C. Local DNS of the client; each of the GSLB services
• D. IP address of the client; each of the GSLB sites

Answer: (B)

Dynamic proximity in GSLB bases its load decisions on how quickly a DNS query travels between the client’s resolver and each GSLB site. The RTT that matters is measured from the Local DNS of the client to every GSLB site, not from the client’s IP to the sites or from some other point. This perspective captures the actual DNS resolution path and the network path the client will experience, giving a realistic sense of which site will respond fastest for that user.

So, the best answer reflects the RTT measured from the client’s Local DNS resolver to each of the GSLB sites. This is why proximity decisions favor the site with the lowest measured RTT at DNS time, improving end-to-end performance for the client.