ZyXEL Communications OMC-2301, User Manual

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Chapter 6 Basic Setting
OMC-2301 User’s Guide
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6.6 IGMP Snooping
The OLT can passively snoop on IGMP Query, Report and Leave (IGMP version 2) packets
transferred between IP multicast routers/switches and IP multicast hosts to learn IP multicast
group membership information. It checks IGMP packets passing through it, picks out the
group registration information, and configures multicasting accordingly. IGMP snooping
allows the OLT to learn multicast groups without you having to manually configure them.
The OLT forwards multicast traffic destined for multicast groups (that it has learned from
IGMP snooping or that you have manually configured) to ports that are members of that
group. The OLT discards multicast traffic destined for multicast groups that it does not know.
IGMP snooping generates no additional network traffic, allowing you to significantly reduce
multicast traffic passing through your OLT.
6.6.1 IGMP Proxy
To allow better network performance, you can use IGMP proxy instead of a multicast routing
protocol in a simple tree network topology.
In IGMP proxy, an upstream interface is the port that is closer to the source (or the root of the
multicast tree) and is able to receive multicast traffic. There should only be one upstream
interface (also known as the query port) on the system to limit bandwidth use. A downstream
interface is a port that connects to a host (such as a computer). A query VLAN determines
which ports are downstream interfaces.
The following figure shows a network example where
A is the multicast source while
computers 1, 2 and 3 are the receivers. In the figure A is connected to the upstream interface
and 1, 2 and 3 are connected to the downstream interface.
Flow Control A concentration of traffic on a port decreases port bandwidth and overflows buffer
memory causing packet discards and frame losses. Flow control is used to regulate
transmission of signals to match the bandwidth of the receiving port.
The OMC uses IEEE802.3x flow control in full duplex mode and back pressure flow
control in half duplex mode.
IEEE802.3x flow control is used in full duplex mode to send a pause signal to the
sending port, causing it to temporarily stop sending signals when the receiving port
memory buffers fill.
Apply Click Apply to save the settings.
Cancel Click Cancel to reset the fields to your previous configuration.
Table 14 Port Setup (continued)
LABEL DESCRIPTION