Connected: An Internet Encyclopedia
4.2.2. TCP usage
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4.2.2. TCP usage
4.2.2. TCP usage
Messages sent over TCP connections use server port 53 (decimal). The
message is prefixed with a two byte length field which gives the message
length, excluding the two byte length field. This length field allows
the low-level processing to assemble a complete message before beginning
to parse it.
Several connection management policies are recommended:
- The server should not block other activities waiting for TCP
data.
- The server should support multiple connections.
- The server should assume that the client will initiate
connection closing, and should delay closing its end of the
connection until all outstanding client requests have been
satisfied.
- If the server needs to close a dormant connection to reclaim
resources, it should wait until the connection has been idle
for a period on the order of two minutes. In particular, the
server should allow the SOA and AXFR request sequence (which
begins a refresh operation) to be made on a single connection.
Since the server would be unable to answer queries anyway, a
unilateral close or reset may be used instead of a graceful
close.
Next: 5. MASTER FILES
Connected: An Internet Encyclopedia
4.2.2. TCP usage