RFC 2176 MAPOS June 1997 +-------------------------+------------------------+ | Hardware Address Space | Protocol Address Space | | (25:MAPOS) | (2048 in Dec) | | 16 bits | 16 bits | +------------+------------+------------------------+ | Hard Addr | Proto Addr | Operation Code | | Length (4) | Length (4) |(1:Request 2:Response) | | 8 bits | 8 bits | 16 bits | +------------+------------+------------------------+ | Sender HDLC Address 32 bits | +--------------------------------------------------+ | Sender IP Address 32 bits | +--------------------------------------------------+ | Target HDLC Address 32 bits | +--------------------------------------------------+ | Target IP Address 32 bits | +--------------------------------------------------+ Figure 5 ARP packet format Hardware Address Space (16 bits) The hardware address space for MAPOS ARP is 25 in Decimal as assigned by IANA [6]. Protocol Address Space (16 bits) The protocol address space for IP is 2048 in Decimal. Hardware Address Length (8 bits) The hardware address length is 4. Protocol Address Length (8 bits) The protocol address length for IP is 4. Operation Code (16 bits) The operation code is 1 for request and 2 for response. Sender hardware (HDLC) Address (32 bits) Contains the sender's HDLC address in an ARP request, and the target HDLC address in an ARP response. The 8-bit HDLC address is placed in the least significant place of the 32-bit field. The remaining bits should be zero. Murakami & Maruyama Informational