RFC2131 4.4.5 says:
The server SHOULD return T1 and T2.
Other DHCP clients don't request them by default and we can save two
bytes in the message size by not sending them.
define 55 array byte dhcp_parameter_request_list
define 56 string dhcp_message
define 57 uint16 dhcp_max_message_size
-define 58 request uint32 dhcp_renewal_time
-define 59 request uint32 dhcp_rebinding_time
+define 58 uint32 dhcp_renewal_time
+define 59 uint32 dhcp_rebinding_time
define 60 string vendor_class_identifier
define 61 binhex dhcp_client_identifier
define 55 array byte dhcp_parameter_request_list
define 56 string dhcp_message
define 57 uint16 dhcp_max_message_size
-define 58 request uint32 dhcp_renewal_time
-define 59 request uint32 dhcp_rebinding_time
+define 58 uint32 dhcp_renewal_time
+define 59 uint32 dhcp_rebinding_time
define 60 string vendor_class_identifier
define 61 binhex dhcp_client_identifier
define 64 string nisplus_domain