A Bit Mask corresponding to the neighbor's op- tions field.

Bit 0, if set, indicates that the system will operate on Type of Service metrics other than TOS 0. If zero, the neighbor will ignore all metrics except the TOS 0 metric.

Bit 1, if set, indicates that the associated area accepts and operates on external informa- tion; if zero, it is a stub area.

Bit 2, if set, indicates that the system is ca- pable of routing IP Multicast datagrams; i.e., that it implements the Multicast Extensions to OSPF.

Bit 3, if set, indicates that the associated area is an NSSA. These areas are capable of carrying type 7 external advertisements, which are translated into type 5 external advertise- ments at NSSA borders.