ZyXEL Communications 2002 Series Guide de l'utilisateur télécharger pdf (Page 48)

VES-1000 Series Ethernet Switch

4-10 General, Switch and IP Setup

IGMP (Internet Group Multicast Protocol) is a session-layer protocol used to establish membership in a multicast

group - it is not used to carry user data. Refer to RFC 1112 and RFC 2236 for information on IGMP versions 1

and 2 respectively.

A layer-2 switch 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 the IP multicast group membership. It checks

IGMP packets passing through it, picks out the group registration information, and configures multicasting

accordingly. Without IGMP snooping, multicast traffic is treated in the same manner as broadcast traffic, that is, it

is forwarded to all ports. With IGMP snooping, group multicast traffic is only forwarded to ports that are

members of that group. IGMP Snooping generates no additional network traffic, allowing you to significantly

reduce multicast traffic passing through your switch.

4.2.8 Quality of Service (QoS)

IEEE 802.1p defines up to 8 separate traffic classes by inserting a tag into a MAC-layer frame that contains bits to

define class of service.

Table 4-8 QoS Priority Listing

PRIORITY DESCRIPTION

Priority 7 Typically used for network control traffic such as router configuration messages.

Priority 6 Typically used for voice traffic that is especially sensitive to jitter (jitter is the variations in delay.

Priority 5 Typically used for video that consumes high bandwidth and is sensitive to jitter.

Priority 4 Typically used for controlled load, latency-sensitive traffic such as SNA transactions.

Priority 3 Typically used for better than best effort; would include important business traffic that can tolerate

some delay.

Priority 2 Typically used for best-effort traffic.

Priority 1 This is the default priority if none is specified.

Priority 0 Typically used for non-critical traffic such as backups, non-critical replications, some electronic mail

and so on.

The switch has 4 physical queues to support the 8 priority levels for each port. On the switch, traffic assigned to

higher index queues gets through faster while traffic in lower index queues is dropped if the network is congested.

You use menu 2.3 to map the priority levels to physical queues.

Frames without explicit priority is given the default priority of the ingress port. You can use menu 6.1 and 6.2 to

configure the default priority for each port.

To configure the priority level-to-physical queue mapping, select Yes in the Edit QoS Support field in menu 2 to

go to Menu 2.3 — QoS Setup. The following figure displays the default queues for each priority level.

1 2 ... 43 44 45 46 47 48 49 50 51 52 53 ... 160 161

Pas de commentaire

ZyXEL Communications 2002 Series Guide de l'utilisateur Page 48