Des tests que j'ai fait, ne répondent pas Twitter et PayPal depuis les DNS Google, Level3, FDN, Oxid.
Répondent sur mes DNS qui utilisent OpenNIC et pour les domaines ICANN ça tourne entre OpenNIC, Level3, DNS.watch et les root.
Pour ceux qui veulent, mes résultats DNS:
;; QUESTION SECTION:
;twitter.com.			IN	A
;; ANSWER SECTION:
twitter.com.		992	IN	A	104.244.42.129
twitter.com.		992	IN	A	104.244.42.1
;; AUTHORITY SECTION:
twitter.com.		327	IN	NS	ns1.p34.dynect.net.
twitter.com.		327	IN	NS	ns2.p34.dynect.net.
twitter.com.		327	IN	NS	ns3.p34.dynect.net.
twitter.com.		327	IN	NS	ns4.p34.dynect.net.
;; ADDITIONAL SECTION:
ns1.p34.dynect.net.	257	IN	A	208.78.70.34
ns2.p34.dynect.net.	5602	IN	A	204.13.250.34
ns3.p34.dynect.net.	257	IN	A	208.78.71.34
ns4.p34.dynect.net.	5602	IN	A	204.13.251.34
;; Query time: 15 msec
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;paypal.com.			IN	A
;; ANSWER SECTION:
paypal.com.		861	IN	A	64.4.250.23
paypal.com.		861	IN	A	64.4.250.24
;; AUTHORITY SECTION:
com.			4188	IN	NS	i.gtld-servers.net.
com.			4188	IN	NS	d.gtld-servers.net.
com.			4188	IN	NS	b.gtld-servers.net.
com.			4188	IN	NS	f.gtld-servers.net.
com.			4188	IN	NS	k.gtld-servers.net.
com.			4188	IN	NS	c.gtld-servers.net.
com.			4188	IN	NS	g.gtld-servers.net.
com.			4188	IN	NS	l.gtld-servers.net.
com.			4188	IN	NS	j.gtld-servers.net.
com.			4188	IN	NS	e.gtld-servers.net.
com.			4188	IN	NS	a.gtld-servers.net.
com.			4188	IN	NS	m.gtld-servers.net.
com.			4188	IN	NS	h.gtld-servers.net.
;; ADDITIONAL SECTION:
a.gtld-servers.net.	2425	IN	A	192.5.6.30
a.gtld-servers.net.	2425	IN	AAAA	2001:503:a83e::2:30
b.gtld-servers.net.	4574	IN	A	192.33.14.30
b.gtld-servers.net.	4574	IN	AAAA	2001:503:231d::2:30
c.gtld-servers.net.	4119	IN	A	192.26.92.30
d.gtld-servers.net.	1343	IN	A	192.31.80.30
e.gtld-servers.net.	1515	IN	A	192.12.94.30
f.gtld-servers.net.	2528	IN	A	192.35.51.30
g.gtld-servers.net.	3906	IN	A	192.42.93.30
h.gtld-servers.net.	4979	IN	A	192.54.112.30
i.gtld-servers.net.	3494	IN	A	192.43.172.30
j.gtld-servers.net.	3884	IN	A	192.48.79.30
k.gtld-servers.net.	739	IN	A	192.52.178.30
l.gtld-servers.net.	739	IN	A	192.41.162.30
m.gtld-servers.net.	828	IN	A	192.55.83.30
;; Query time: 16 msec