Huawei CX600-8 Hardware Description page 28

HUAWEI CX600-8/16/X3/X8/X16 Metro Service Platform
Hardware Description
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The SFU switches data between LPUs. Upon receipt of the cells, the SFU caches and schedules
them before sending them to the switching unit. The switching unit balances the cells using
multiple switching planes, which improves the fault tolerance capability. The switching unit
sends data packets through outbound interfaces to a downlink board.
The processing of an outgoing signal flow is as follows:
Issue 03 (2013-11-30)
NOTE
A PIC can receive high-speed services, such as packet over synchronous digital hierarchy (SDH)/
synchronous optical network (SONET) (POS) and Ethernet packets and low-sped services, such as
asynchronous transfer mode (ATM), time division multiplexing (TDM), and Point-to-Point Protocol
(PPP) packets. Services before they are encapsulated are not described here.
The uplink NP searches a forwarding table for an outbound interface for the signal flow.
The processing is as follows:
a. Inbound interface processing: Upon receipt of the signal flow, the inbound interface
of the NP parses the data link layer protocol carried in the packets and obtains the
packet types.
b. Traffic classification: The uplink NP prioritized packets, performs traffic
classification, and re-marks them.
c. Packet forwarding based on the forwarding table: The uplink NP searches for
forwarding entries based on destination MAC addresses, destination IP addresses, and
MPLS labels and obtains outbound interface names or next-hop IP addresses
contained in matching entries.
NOTE
Data packets are classified as Layer 2 MAC address-based packets, Layer 2.5 MPLS label-
based packets, and Layer 3 IP address-based packets. The processing module on the inbound
interface identifies packet types and searches forwarding tables based on these types so that
the outbound interface names or next-hop IP addresses for all types of packets can be found.
d. Traffic policing: The uplink NP limits the rate at which incoming packets are sent
based on the committed access rate (CAR) parameters configured on the inbound
interface or those configured in the incoming traffic classification profile. If the
forwarding behavior is to discard packets, the uplink NP discards them before
performing the CAR function.
The uplink traffic management (TM) chip processes the signal flow as follows:
l Congestion management and avoidance: The uplink TM monitors network resource
usage. If traffic congestion worsens, the uplink TM discards packets and adjusts traffic
to relieve network overload.
l Traffic shaping: If traffic congestion occurs, the uplink TM caches packets in queues
and uses a specific scheduling algorithm to prioritize packets before forwarding them.
After the uplink TM processes packets using QoS functions, it sends them to the uplink
flexible interface card (FIC).
The uplink FIC fragments the signal flows. The SFU switches packets based on a fixed cell
length. Before packets are sent to the SFU, the uplink FIC fragments the packets that are
longer than the fixed cell length. The upstream FIC encapsulates the fragments into cells
before sending them to the SFU.
NOTE
Whether or not the SFU processes packets depends on the hardware architecture. The CX600-X8 and
CX600-X16 devices have switched networks installed so that packets are processed by the SFU on these
devices. The CX600-X1, CX600-X2, and CX600-X3 devices do not have switched network so that the
switch module (SM) determines the link on which packets are transmitted.
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2 Product Signal Flow Overview
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