343 Too many hops

Originator sent Max-Forwards: 0 in the Invite packet.

According to the RFC3261 call should not be forwarded any further and must be dropped.

RFC 3261            SIP: Session Initiation Protocol           June 2002

8.1.1.6 Max-Forwards

  The Max-Forwards header field serves to limit the number of hops a
  request can transit on the way to its destination.  It consists of an
  integer that is decremented by one at each hop.  If the Max-Forwards
  value reaches 0 before the request reaches its destination, it will
  be rejected with a 483(Too Many Hops) error response.

  A UAC MUST insert a Max-Forwards header field into each request it
  originates with a value that SHOULD be 70.  This number was chosen to
  be sufficiently large to guarantee that a request would not be
  dropped in any SIP network when there were no loops, but not so large
  as to consume proxy resources when a loop does occur.  Lower values
  should be used with caution and only in networks where topologies are
  known by the UA.

ITU-T Q.850 Code 25 / SIP Code 483 will be returned to the Originator in this case.

This cause indicates that the destination indicated by the user cannot be reached, because an intermediate exchange 
has released the call due to reaching a limit in executing the hop counter procedure. This cause is generated by an 
intermediate node, which when decrementing the hop counter value, gives the result 0.

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See also:

• M2 Hangupcause Codes