old_contents: # Copyright (C) 2013 Nippon Telegraph and Telephone Corporation.
  # Copyright (C) 2013 YAMAMOTO Takashi <yamamoto at valinux co jp>
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
  # implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """
  Subsequent Address Family Idenitifier (SAFI)
  http://www.iana.org/assignments/safi-namespace/safi-namespace.xhtml
  """
  
  UNICAST = 1
  MULTICAST = 2
  MPLS_VPN = 128  # RFC 4364
  
new_contents: # Copyright (C) 2013,2014 Nippon Telegraph and Telephone Corporation.
  # Copyright (C) 2013,2014 YAMAMOTO Takashi <yamamoto at valinux co jp>
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #    http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
  # implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """
  Subsequent Address Family Idenitifier (SAFI)
  http://www.iana.org/assignments/safi-namespace/safi-namespace.xhtml
  """
  
  UNICAST = 1
  MULTICAST = 2
  MPLS_VPN = 128  # RFC 4364
  ROUTE_TARGET_CONSTRTAINS = 132  # RFC 4684
  
subject: add a constant for route target constrain