Teleste MPH241 - Switch Network Features; Congestion Control and MAC Learning; IP Multicast and IGMP Snooping

56 MPH200 series video encoders WebUI user manual
The categorizer analyzes all received frames. It assigns each frame to
one of four QoS classes based on:
1. Port-based priority
2. User priority in the VLAN tag header (IEEE Std 802.1p)
3. Differentiated Services Code Point (DSCP/DiffServ ) from the
IP-header (IPv4 and IPv6 supported)
Based on the priority assigned by the categorizer, higher priority frames
take precedence over lower priority frames during forwarding through
the switching engine. In case of congestion, the lowest priority trafc is
dropped before higher priority frames. In addition, the higher priority
frames are able to overtake the lower priority frames in the queue,
thereby minimizing latency for expedited data.
Congestion control
The ingress and egress directions on all ports can be congured to
manage network congestion independently, either by dropping frames or
by ow control pause frame signalling. Flow control is guaranteed no
dropping for frame sizes up to about 4 kilobytes. Asymmetric ow control
is supported for both the ingress and egress direction. Software can set
up individual high and low thresholds for each FIFO. These thresholds
control the starting and stopping of pause signalling. The internal FIFOs
have enough memory to handle ow control on short-haul, full-duplex
lines without using excessive pause signalling. The switch generates ow
control pause frames, when necessary, to ensure that frames are never
dropped. In half-duplex mode, ow control is supported through back
pressure. In drop mode, the switch handles congestion situations by
dropping frames intelligently according to bandwidth allocations, frame
priorities, and available buffer capacity. The MPH premium switch fea-
tures both strict priority-based forwarding and weighted fairness forward-
ing, with guaranteed bandwidth allocation for the different QoS classes.
MAC address learning
When a frame is received, the source MAC address is looked up in the
MAC address table. If the address is not registered, and it is not a
multicast address, a new entry is created. If necessary, an entry is
discarded to make room for the new one based on a “least recently
used” algorithm. MPH200 Ethernet Switch is capable of looking up and
adding all incoming entries to the MAC table at maximum load, which is
known as “wire-speed learning”.
IP multicast
MPH200 Ethernet Switch provides enhanced support for IP Multicast by
allowing up to 8192 programmable multicast groups to co-exist in the
MAC table. This, in combination with IGMP snooping enables applica-
tions such as digital video distribution.
IGMP snooping
The Internet Group Management Protocol (IGMP) lets host and routers
share information about multicast group memberships. IGMP snooping
is a switch feature that monitors the exchange of IGMP messages and
copies them to the CPU for further processing. The overall purpose of
IGMP-snooping is to limit the forwarding of multicast frames to only
ports that are a member of the multicast group.