Protocols in multi-service networks
3.5.4 Primitives
T
he two abstract primitives described in the specification of IPv4 are given in Table 9 but, as with TCP, different systems may implement the interface in different ways. In some computer systems the TCP and IP software may be written as a single software module, and in these cases there is not a clear interface between the two layers.
Table 9: IPv4 primitives
| Primitive name | Primitive parameters |
|---|---|
| Recv | Buffer pointer, protocol, source address, destination address, type of service, length of buffer, optional user data |
| Returns a report on the outcome of the primitive | |
| Send | Source address, destination address, protocol, type of service, time to live, buffer pointer, length of buffer, identifier, don’t fragment flag, optional user data |
| Returns a report on the outcome of the primitive |
You should be able to match most of the parameters to fields in IPv4 datagrams.
SAQ 13
Identify the protocol data units and primitives required to send an HTTP command between a client and server in the transport and internetwork layers.