DLPI Programmer's Guide

24 Chapter 1

Introduction to DLPI

The Data Link Layer

• SNAP SAP format

HP’s DLSAP Address Format for Fibre Channel

The four possible formats for Fibre Channel are:

• 802.2 SAP format

• 802.2 SAP without Process Associator format

| N_Port_Id | FC_Type | DSAP/SSAP |

• SNAP/SAP format

• SNAP/SAP without Process Associator format

Certain DLS providers require the capability of binding on multiple

DLSAP addresses. This can be achieved through subsequent binding of

DLSAP addresses. DLPI supports peer and hierarchical binding of

DLSAPs. When the user requests peer addressing, the DLSAP speciﬁed

in a subsequent bind may be used in lieu of the DLSAP bound in the

DL_BIND_REQ. This will allow for a choice to be made between a

number of DLSAPs on a stream when determining trafﬁc based on

DLSAP values. An example of this would be to specify various ether_type

values as DLSAPs. The DL_BIND_REQ, for example, could be issued

with an ether_type value of IP, and a subsequent bind could be issued

with an ether_type value of ARP. The provider may now multiplex off the

ether_type ﬁeld and allow for either IP or ARP trafﬁc to be sent up this

stream.

When the DLS user requests hierarchical binding, the subsequent bind

will specify a DLSAP that will be used in addition to the DLSAP bound

using a DL_BIND_REQ. This will allow additional information to be

speciﬁed, that will be used in a header or used for demultiplexing. An

example of this would be to use hierarchical bind to specify the

Organizational Unique Identiﬁer (OUI) to be used by SNAP.

If a DLS provider supports peer subsequent bind operations, the ﬁrst

SAP that is bound is used as the source SAP when there is ambiguity.