[sdnog] Dns Queries

[Philip Paeps]

On 2016-08-22 13:18:27 (+0200), wadah khalid <engwada7 at gmail.com> wrote:

> Domain Name System is a multi-transport protocol which means it uses tcp
> port 53 and udp .
> regarding to the previous information .
> when do you think that DNS can be tcp and when it will use udp ? discuss

DNS will run over UDP unless it can't.

Historically, DNS packets over UDP can only be 512 bytes long.  With the
EDNS0 option, they can be as long as 4096 bytes.  Still not enough for
zone transfers (AXFR) but long enough for most DNSKEY replies.

Philip

-- 
Philip Paeps
Senior Reality Engineer
Ministry of Information