 A swIPe packet starts with a header, which contains identifying data and authentication information; the header is followed by the original IP datagram, which in turn is followed by any padding required by the security processing.Depending on the negotiated policy, the sensitive part of the swIPe packet (the authentication information and the original IP datagram) may be encrypted.Cisco routers and switches running IOS have been found vulnerable to denial of service (DoS) attacks which may result from processing packets with IP Protocol 53.