Re: [Doh] [Ext] DNS Camel thoughts: TC and message size

[Robert Edmonds <[e-mail]>]

Dave Lawrence wrote:
> Paul Hoffman writes:
> > Tony is completely correct here. DNS messages have well-defined
> > length limits: 512-or-more-depending if carried over UDP, and 65535
> > if carried over TCP. 
> 
> Right.  And completely undefined over any other transport.  There is
> no intrinsic limit to the limit of a DNS message, compression pointers
> notwithstanding.

No, there is an intrinsic limit to the size of a DNS message. If I'm not
mistaken:

12 octets header

1 question resource record:
    255 octets QNAME
    2 octets QTYPE
    2 octets QCLASS

3 response sections:
    65535 RR's per section:
        255 octets NAME
        2 octets TYPE
        2 octets CLASS
        4 octets TTL
        2 octets RDLENGTH
        65535 octets RDATA

12 + 1*(255+2+2) + 3*65535*(255+2+2+4+2+65535) = 12936609271 octets, or,
about 13 gigs.

-- 
Robert Edmonds