ME60
Hardware Description
1 Hardware Description
Issue 01 (2018-05-07)
29
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.
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.
3.
The uplink traffic management (TM) chip processes the signal flow as follows:
−
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.
−
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).
4.
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.
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:
1.
Switched network cell assembly on the downstream FIC: The downstream FIC
assembles switched network cells into packets after switched network cells flow from the
SFU to the downlink FIC.
2.
Queuing and scheduling on the downlink TM: The downstream TM puts packets of the
signal flow in queues and schedules them based on the traffic shaping, policing,
congestion avoidance parameters. Then it sends the packets to the downstream NP.
The downlink TM also replicates multicast packets before sending them through several outbound
interfaces.
