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Important: This document is part of the Legacy section of the ADC Reference Library. This information should not be used for new development.

Current information on this Reference Library topic can be found here:

TCP/IP Option Sizes

Q: I'm confused by the size of various TCP/IP options. For example, the documentation says that IP_MULTICAST_LOOP is a 4-byte option, but the IPMulticastPitch sample negotiates a size of 1 byte. What's the scoop?

A: In this case, the documentation is wrong. The following table enumerates all the TCP/IP options and their sizes.

XTI Level XTI Name Size
INET_IP IP_ADD_MEMBERSHIP sizeof(struct ip_mreq)
INET_IP IP_BROADCAST 4
INET_IP IP_BROADCAST_IFADDR 4
INET_IP IP_DONTROUTE 4
INET_IP IP_DROP_MEMBERSHIP sizeof(struct ip_mreq)
INET_IP IP_HDRINCL 4
INET_IP IP_MULTICAST_IF 4
INET_IP IP_MULTICAST_LOOP 1 *
INET_IP IP_MULTICAST_TTL 1
INET_IP IP_OPTIONS <= 40
INET_IP IP_RECVDSTADDR 4
INET_IP IP_RECVIFADDR 4
INET_IP IP_RECVOPTS 4
INET_IP IP_REUSEADDR 4
INET_IP IP_REUSEPORT 4
INET_IP IP_TOS 1
INET_IP IP_TTL 1
INET_TCP TCP_ABORT_THRESHOLD 4
INET_TCP TCP_CONN_ABORT_THRESHOLD 4
INET_TCP TCP_CONN_NOTIFY_THRESHOLD 4
INET_TCP TCP_KEEPALIVE sizeof(struct t_kpalive) *
INET_TCP TCP_MAXSEG 4
INET_TCP TCP_NODELAY 4
INET_TCP TCP_NOTIFY_THRESHOLD 4
INET_TCP TCP_OOBINLINE 4
INET_TCP TCP_URGENT_PTR_TYPE 4
INET_UDP UDP_CHECKSUM 4
INET_UDP UDP_RX_ICMP 1 *
XTI_GENERIC XTI_DEBUG 4
XTI_GENERIC XTI_LINGER sizeof(struct t_linger)
XTI_GENERIC XTI_PROTOTYPE 4
XTI_GENERIC XTI_RCVBUF 4
XTI_GENERIC XTI_RCVLOWAT 4
XTI_GENERIC XTI_SNDBUF 4
XTI_GENERIC XTI_SNDLOWAT 4


Warning:
Inside Macintosh: Networking with Open Transport gives either incorrect or ambiguous values for the options tagged with an asterisk (*) in the above table.



Note:
The IP_REUSEPORT and IP_BROADCAST_IFADDR are not currently supported by Open Transport (as of version 2.0.3). They will be available in a future release of Open Transport.


[Apr 26 1999]