Lucent Technologies CAJUN P120, User Manual

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Chapter 1 Overview
Cajun P120 User’s Guide 7
Traffic is distributed between the ports according to the packets' addresses, which
are learned on the LAG ports using the Round-Robin algorithm. The session’s order
is retained at all times. There is no possibility of Broadcast loops occurring in a LAG.
The LAG is considered a single logical port for the switch and its functionality,
including the Spanning Tree Protocol (STP), where BPDUs are sent only through
one of the LAG ports.
Early Packet Drop (HOLB-P)
This feature prevents incoming frames from being forwarded to ports that are
blocked. Although this leads to a loss of frames, it prevents the entire switched from
becoming blocked.
Priorities
Priorities for queuing may be established to enhance the Quality of Service (QoS).
Each port can be configured for high or low priority. Priority is also supported using
the priority field in tagged packets. The Cajun P120 supports port-based priority
and Standard IEEE 802.1p tagging.
IP Multicast Filtering
IP Multicast allows you to send a single copy of an IP packet to multiple
destinations and can be used for various applications including video streaming and
video conferencing.
The Multicast packet is forwarded from the sender to the recipients, duplicated
when needed by routers along the way and sent to multiple destinations such that
it reaches all the members of the Multicast group. Multicast addresses are a special
kind of IP addresses (class D), each identifying a Multicast group. Stations join and
leave Multicast groups using IGMP. This is a control-plane protocol through which
IP hosts register with their router to receive packets for certain Multicast addresses.
In addition, routers support one or more Multicast routing protocols (e.g. DVMRP,
PIM) that construct Multicast delivery trees on which the Multicast traffic is
forwarded.
On LANs, IP Multicast packets are transmitted in MAC Multicast frames. Traditional
LAN switches flood these Multicast packets like broadcast packets to all stations in
the VLAN. In order to avoid sending Multicast packets where they are not required,
Multicast filtering functions may be added to the Layer 2 switches, as described in
the IEEE standard 802.1D (802.1p). Layer 2 switches capable of Multicast filtering
send the Multicast packets only to ports connecting members of that Multicast
group. This is typically based on IGMP snooping, GMRP or CGMP.