Strongswan IPSec error..

ipsec stroke up safaricom_vpn
initiating Main Mode IKE_SA safaricom_vpn[1] to xx.xx.xx.xx
generating ID_PROT request 0 [ SA V V V V ]
sending packet: from yy.yy.yy.yy[500] to xx.xx.xx.xx[500] (216 bytes)
received packet: from xx.xx.xx.xx[500] to yy.yy.yy.yy[500] (120 bytes)
parsed ID_PROT response 0 [ SA V V ]
received NAT-T (RFC 3947) vendor ID
received FRAGMENTATION vendor ID
generating ID_PROT request 0 [ KE No NAT-D NAT-D ]
sending packet: from yy.yy.yy.yy[500] to xx.xx.xx.xx[500] (308 bytes)
received packet: from xx.xx.xx.xx[500] to yy.yy.yy.yy[500] (368 bytes)
parsed ID_PROT response 0 [ KE No V V V V NAT-D NAT-D ]
received Cisco Unity vendor ID
received XAuth vendor ID
received unknown vendor ID: c9:b2:a2:af:4a:88:74:f0:92:c2:b1:32:ae:3e:da:a9
received unknown vendor ID: 1f:07:f7:0e:aa:65:14:d3:b0:fa:96:54:2a:50:01:00
generating ID_PROT request 0 [ ID HASH ]
sending packet: from yy.yy.yy.yy[500] to xx.xx.xx.xx[500] (76 bytes)
received packet: from xx.xx.xx.xx[500] to yy.yy.yy.yy[500] (40 bytes)
parsed INFORMATIONAL_V1 request 0 [ N(PLD_MAL) ]
ignoring unprotected INFORMATIONAL from xx.xx.xx.xx
message verification failed
ignore malformed INFORMATIONAL request
INFORMATIONAL_V1 request with message ID 0 processing failed
sending retransmit 1 of request message ID 0, seq 3

KIndly someone help on what cud be the issue