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IXP400 Software
Access-Layer Components: Ethernet Access (IxEthAcc) API
Programmer’s Guide IXP400 Software Version 2.0 April 2005
Document Number: 252539, Revision: 007 143
IPv4 Payload Detection
For every received frame delivered to the Intel XScale core, the NPE microcode reports whether
the payload of the frame is an IPv4 packet by setting the
ixp_ne_flags.ip_prot flag bit in the buffer
header (as described in Table 22 on page 152). The NPE microcode examines the Length/Type
field to determine whether the payload is IP. A value of 0x0800 indicates that the payload is IP.
The IPv4 payload detection service is enabled in all Ethernet-capable NPE microcode images. An
NPE microcode version that is not VLAN-capable will always report VLAN-tagged frames as non-
IP.
9.5.4 Data-Plane Endianness
All data structures provided to the IxEthAcc components, such as IX_OSAL_MBUF headers or
statistic structures, are defined by the target system byte order. No changes to data structures are
required in order to use the access component data path interfaces as IxEthAcc effects any
conversion required to communicate to the NPEs. The data pointed to by the IX_OSAL_MBUF
(the IX_OSAL_MBUF payload) is expected to be in network byte order (big endian). No byte
swapping takes place on the data prior to transmission to the Ethernet MAC.
9.5.5 Maximum Ethernet Frame Size
The maximum supported Ethernet frame size is 16,320 bytes. This value is set on a per-port basis
using the IxEthDB API.
9.6 Control Path
The main control path functions are performed by two external components: IxEthMii and
IxEthDB.
IxEthMii is used primarily to manipulate a minimum number of necessary configuration registers
on Ethernet PHYs supported on the IXDP425 / IXCDP1100 platform and IXDP465 platform
without the support of a third-party operating system. IxEthMii exists as a separate function in
order to make IxEthAcc independent of the specific PHY devices used in a system. However,
IxEthAcc does retain control of configuring the Ethernet MAC devices on the NPEs and drives the
MII and MDIO interfaces, which are used by IxEthMii to communicate physically with the PHYs.
IxEthDB is the learning and filtering database that runs within the context of the Intel XScale core.
The IxEthDB component handles the database structure, maintenance, searching, and aging, and
has an API for the provisioning of dynamic and static addresses. This database populates filtering
entries on the NPEs and also retrieves learning entries from the NPEs. An API is provided to the
access layer.