Netflix.com uses DynECT, AWS Route53, UltraDNS at the same time

dig NS netflix.com netflixc.com itp.netflix.com

; <<>> DiG 9.8.3-P1 <<>> NS netflix.com netflixc.com itp.netflix.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 8149
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0

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

;; ANSWER SECTION:
netflix.com.		198	IN	NS	pdns154.ultradns.biz.
netflix.com.		198	IN	NS	pdns154.ultradns.net.
netflix.com.		198	IN	NS	pdns154.ultradns.com.
netflix.com.		198	IN	NS	pdns154.ultradns.org.

;; Query time: 20 msec
;; SERVER: 10.255.0.6#53(10.255.0.6)
;; WHEN: Thu Mar 12 16:55:55 2015
;; MSG SIZE  rcvd: 162

;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35036
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0

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

;; ANSWER SECTION:
netflixc.com.		86298	IN	NS	ns1.p19.dynect.net.
netflixc.com.		86298	IN	NS	ns4.p19.dynect.net.
netflixc.com.		86298	IN	NS	ns3.p19.dynect.net.
netflixc.com.		86298	IN	NS	ns2.p19.dynect.net.

;; Query time: 23 msec
;; SERVER: 10.255.0.6#53(10.255.0.6)
;; WHEN: Thu Mar 12 16:55:55 2015
;; MSG SIZE  rcvd: 116

;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29203
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;itp.netflix.com.		IN	NS

;; ANSWER SECTION:
itp.netflix.com.	172174	IN	NS	ns-912.awsdns-50.net.
itp.netflix.com.	172174	IN	NS	ns-1064.awsdns-05.org.
itp.netflix.com.	172174	IN	NS	ns-1784.awsdns-31.co.uk.
itp.netflix.com.	172174	IN	NS	ns-349.awsdns-43.com.

;; Query time: 33 msec
;; SERVER: 10.255.0.6#53(10.255.0.6)
;; WHEN: Thu Mar 12 16:55:55 2015
;; MSG SIZE  rcvd: 170