Question Concerning RFC 2052

Bharat Kaul bharat at
Tue Mar 7 02:28:16 UTC 2000


  I had a question regarding RFC 2052. Looking at DNS RFC's seems to be like
navigating in an ocean of RFC and I finally had to take the course to
contacting the authors. I would appreciate some help on this.

In RFC 2052, the format of the SRV record has been defined as 
Service.Proto.Name TTL Class SRV Priority Weight Port Target

I have two questions regarding this.

1. Is my assumption correct that the format given above replaces the format
of RR's as specified in RFC 1035, section 4.1.3 i.e. for ONLY for SRV
records we will receive RR in above format ?  If that is true, then from the
response packet received from the network, how does one figure out what is
the RR format received i.e. if a client has sent out "A Query" and "SRV RR
Query", on receiving response how does one figure out whether first field in
RR is "Service" or "Name" ...I am assuming that the client can be a
stateless entity and hence doesn't remember any information about queries
sent out.

2. For TYPES specified in RFC 1035, looking at the RDLENGTH indicates the
format and possibly the number of targets present in RDATA i.e. if A Query
was sent out for a domain name and response indicated RDLENGTH as 20, we
know that there are 5 ip addresses present for the host name queried. 

I am not sure how SRV records stand here. For example, if we do a lookup and this service is has two possible targets ...will
response packet be like TTL Class Priority Weight 80 TTL Class Priority Weight 80

or will response be like TTL Class Priority Weight 80 

In both example responses how does one figure out where "Target" ends and
something new i.e. "http" in case of example respone 1 or "server2" in case
of example response 2 starts...i.e. is there any explicit delimiter.

I presume example response 1 is correct; however I am not sure what
delimiter is ...

Also, please note that in example responses I am including "http" as string
followed by a "." as delimiter. Is that correct ?

Thanx for your time 

- Bharat

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