IP

NAME

IP (Internet Protocol)

SPECIFICATION

J. Postel. Internet Protocol. Request for Comments 768, USC Information Sciences Institute, Marina del Ray, Calif., Aug. 1980.

SYNOPSIS

IP handles fragmentation and routing required in transmitting messages across heterogeneous interconnected networks. This implementation is complete, with the exception of some of the optional header fields.

REALM

IP is in the ASYNC realm.

PARTICIPANTS

IP removes a pointer to an IPhost from the top of the stack of each participant. If the local participant is missing or if the local IPhost pointer is ANY_HOST, IP will select an appropriate local IPhost.

CONTROL OPERATIONS

IP_MYNET:

Return local host's IP network number. This is an IP address with the host component set to 0. (session only)

Input:

none

Output:

IPhost

IP_REDIRECT:

Modifies routing table to use a specified gateway when delivering packets to a specified IP address. The first address is for the destination and the second is for the gateway. (session or protocol)

Input:

IPhost[2]

Output:

none

IP_GETPSEUDOHDR:

Fills the buffer with a partial IP pseudoheader, containing the source address, destination address, and the upper protocol type. The packet length field and the zero-block are both set to zero. (session only)

Input:

none

Output:

IPpseudoHdr

IP_PSEUDOHDR:

Used by protocols that use the IP pseudoheader (e.g., TCP and UDP) to alert protocols between them and IP that they must not change the length of packets without worrying about the length field in the pseudoheader. IP itself simply absorbs this control operation and returns.

Input:

none

Output:

none

CONFIGURATION

IP must be configured above VNET:

         name=ip protocols=vnet;

If an explicit route for a remote network is not specified, IP will forward packets for that network to a default gateway, if one has been configured. The default gateway can be set with a rom file entry of the form:

         ip    gateway     127.1.22.11

If no default getway has been configured, or the specified default gateway can not be reached directly, IP will operate without a default gateway and ERR_XOBJ will be returned in cases where a default gateway would otherwise have been used.

AUTHORS

Clinton Jeffery, David Kays and Ed Menze