Data forwarding support in dual connectivity

A method, comprising:

• preparing, with a second network node, an indication, the indication indicating that for at least one split bearer, unacknowledged downlink data received prior to the indication is to be forwarded with a first network node to the second network node, and that the at least one split bearer should be kept or maintained at the first network node;
• sending the indication to the first network node responsive to determining that a ciphering key is to be changed for the at least one split bearer;
• receiving, for the at least one split bearer, downlink data forwarded with the first network node;
• deciphering, with the second network node, the forwarded data using an old ciphering key;
• and
• ciphering, with the second network node, the forwarded and deciphered data using a new ciphering key.

An apparatus, comprising:

• at least one processor;
• and
• at least one non-transitory memory including computer program code,
• wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to
• receive an indication indicating that for at least one split bearer, unacknowledged downlink data received prior to the indication is to be forwarded to a second network node, and that the at least one split bearer should be kept or maintained at the apparatus, wherein a reason for the indication comprises a change of ciphering key for the at least one split bearer;
• and
• in response to the received indication, forward the data for the at least one split bearer received prior to the indication to the second network node, wherein forwarding the data comprises forwarding data ciphered with an old ciphering key.

An apparatus, comprising:

• at least one processor;
• and
• at least one non-transitory memory including computer program code,
• wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to
• prepare an indication, the indication indicating that for at least one split bearer, unacknowledged downlink data received prior to the indication is to be forwarded with a first network node to the apparatus, and that the at least one split bearer should be kept or maintained at the first network node;
• send the indication to the first network node responsive to determining that a ciphering key is to be changed for the at least one split bearer;
• receive, for the at least one split bearer, downlink data forwarded with the first network node;
• decipher the forwarded data using an old ciphering key;
• and
• cipher the forwarded and deciphered data using a new ciphering key.