DNS 服务商如何解析自己的域名

也许这个问题比较傻

比如说 dnspod.com 的ns是a.dnspod.com

那么a.dnspod.com是如何解析的
不会陷入死循环吗
以下是dig记录

$ dig dnspod.com ns

; <<>> DiG 9.8.3-P1 <<>> dnspod.com ns
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29268
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;dnspod.com. IN NS

;; ANSWER SECTION:
dnspod.com. 21599 IN NS c.dnspod.com.
dnspod.com. 21599 IN NS a.dnspod.com.
dnspod.com. 21599 IN NS b.dnspod.com.

$ dig cloudflare.com ns

; <<>> DiG 9.8.3-P1 <<>> cloudflare.com ns
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34698
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;cloudflare.com. IN NS

;; ANSWER SECTION:
cloudflare.com. 2014 IN NS dns2.cloudflare.com.
cloudflare.com. 2014 IN NS dns3.cloudflare.com.