ZL50130PBGA ZARLINK [Zarlink Semiconductor Inc], ZL50130PBGA Datasheet - Page 20

• Manufacturer Part Number: ZL50130PBGA
• Description: Ethernet Pseudo-Wires across a PSN
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

Once the class has been determined, a template is applied, extracting up to 96 bits from any field in the first 96
bytes. These are used to determine the individual flow. For example, this could be used to check the cookie value
in the L2TPv3 header. The checksum fields can also be verified now, since the protocol stack in use has been
determined.
When the flow has been identified, up to 64 further bits may be compared to a pre-programmed value as a
mis-connection check. For example, the SSRC field in the RTP header could be checked, or the cookie value in
the L2TPv3 header. It could also be used to check Ethernet or IP source addresses, to check the packet came
from the expected source. These 64 bits may again be extracted from any field in the first 96 bytes. The use of the
mis-connection check helps to protect against denial of service attacks, since the cookie or SSRC values are
usually hard to guess.
At any stage, a failure to match results in the packet being directed to the CPU queue. This enables the host to
view the packet and take appropriate action.
3.5
The ZL50130 device contains four separate, IEEE standard 802.3 compliant, 100 Mbit/s Ethernet MACs. Each
MAC is connected to a Physical Layer (PHY) device via a Media Independent Interface (MII).
The MAC is responsible for data encapsulation/decapsulation. This includes frame alignment and synchronization,
and detection of physical medium transmission errors. The MAC is capable of both full and half-duplex operation. In
half-duplex mode it manages the collision avoidance and contention resolution process. In the event of a collision,
the MAC will back off and attempt to re-send the packet up to 16 times.
Packets for transmission are forwarded to the MAC by the Packet Formatter block. The MAC appends the frame
check sequence, and generates the preamble and start of frame delimiter before transmitting out of the MII port.
During packet reception, the MAC receive section verifies that the frame check sequence is correct, and that the
packet is a valid length. Packets with an invalid frame check sequence, and data packets longer than a
pre-programmed threshold and shorter than 64 bytes are dropped.
For Ethernet pseudo-wire operation, the thresholds on the customer-facing MACs are usually set shorter than on
the PSN-facing MAC. This is to avoid creating over-sized packets when the additional tunnel headers are added to
the packet.
The MAC also checks the destination field to determine if the packet is intended for the device. If the packet is
accepted, it is forwarded on for packet classification, and to be entered into the appropriate destination queue.
Illegal packets, or packets intended for a different destination are discarded.
The MAC also collects statistics on the different types of packets transmitted and received on the Ethernet. The
statistics collected are sufficient to enable the CPU to support the Interfaces sections of some common MIBs.
Features include:
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IEEE 802.3 compliant operation at 100 Mbit/s
Industry-standard MII interface to the physical layer devices
Full and half-duplex operation
Generates preamble, start-of-frame delimiter and frame check sequence
Collision avoidance and contention resolution in half-duplex mode
Verifies frame check sequence and frame length, discarding frames that contain errors
Statistics collection for common MIB support:
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Ethernet MAC
RFC 1213 MIB II
RFC 1757 Remote Network Monitoring MIB (for SMIv1)
Zarlink Semiconductor Inc.
ZL50130
20
Data Sheet