20.22 Max-Forwards

The Max-Forwards header field must be used with any SIP method to
limit the number of proxies or gateways that can forward the request
to the next downstream server. This can also be useful when the
client is attempting to trace a request chain that appears to be
failing or looping in mid-chain.

The Max-Forwards value is an integer in the range 0-255 indicating
the remaining number of times this request message is allowed to be
forwarded. This count is decremented by each server that forwards
the request. The recommended initial value is 70.

This header field should be inserted by elements that can not
otherwise guarantee loop detection. For example, a B2BUA should
insert a Max-Forwards header field.

Example:

Max-Forwards: 6