def get_protocol_name(protocol_identifier):
    """
    Returns protocol name for the given identifier.

    :param protocol_identifier: Number representing the protocol.
    :return: string "tcp" if protocol_identifier is 6, "udp" if protocol_identifier is 17, and "other" otherwise
    """

    # Check identifier and return corresponfing string
    if protocol_identifier == 6:
        return "tcp"
    elif protocol_identifier == 17:
        return "udp"
    else:
        return "other"