Bandwith utilization over a slow WAN link...

I have a question that I am having trouble finding the answer for.
If you have a DNS server(A) that hosts a primary copy of a zone connected to another server(B) over a slow WAN link, which option would have the lowest bandwidth utilization?
1. Setup server B with a conditional forwarder to server A.
2. Setup server B with a secondary copy of the zone.
Both servers will be serving the same doamin (example.com)
The books I have just talk about using a Caching only server in this type of situation, they don't elaborate on which of these options would be sending more packets.
Can anyone help me understand this type of scenario better?

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dgbarr

Conditional forwarding queries are based on the domain name characteristics. All requests are forwarded to the same servers.

Secondary zone would be the answer, I believe, because it would allow for more fault tolerance, handle loads (slightly) better, and reduce name resolution traffic over wan links.[/img]

CompGuru

So what your saying is:
Even though a secondary zone would involve zone transfers, it would possibly use less bandwidth than conditionaly forwarding every request over the WAN Link.

I guess that does make sense, I was just looking at it from the wrong perspective, I was thinking that the chief objective of reducing bandwidth consumption was reducing zone transfers.
Thanks for the help.

Smallguy

believe the answer is actually conditional forwarding

you would set it up to forward based on a criteria which would mean you are only sending data over the WAN link when the criteria is met.

with a secondary zone there will be traffic going over the WAN anytime something changes in the primary not to mention the first initial transfer could potentially saturate the wan link.

the question doesn't mention anything about achieving redundancy or fault tolerence even though you should have redundancy since the question is not specifying it and it is looking for the best way to conserve bandwidth the answer should be conditional forwarding

dgbarr

I would think it would be a bad idea to just have a single primary DNS server and force users to query over a slow wan link (even conditionally forwarding queries).

I could be wrong. I just feel after the initial zone transfer has been completed the total bandwidth used would compensate later on.

Smallguy

dgbarr wrote:

I would think it would be a bad idea to just have a single primary DNS server and force users to query over a slow wan link (even conditionally forwarding queries).

I could be wrong. I just feel after the initial zone transfer has been completed the total bandwidth used would compensate later on.

I'm not saying you are wrong but your thinking too much about what it should be and not what the question asked.

the question asked the best was to conserve bandwidth over a slow wan link not to have fault tolerance... yes you need or alteast u should have fault tolerance but it was not stated as a requirement in the question

your right after the initial transfer the bandwidth requirements should be minimal with a relatively static DNS setup

but the initial transfer will be more bandwidth intensive than if you are only accessing the server on the slow WAN link when it is absolutely required