D-Link Dsh8 Manual

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Port-based Priority 
Configure the priority level for each port . With the drop-down selection item of 
Priority Type above being selected as Port -based, this control item will then be 
available to set the queuing policy for each port. 
Figure 5-50:  QoS Configurat ion - Port-Based Priority 
 
This page includes the following fields: 
 
Object Description 
Port x: Each port has 4 priority levels—High, Middle, Low, and...

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Figure 5-51:  802.1p Tag Priority 
 
802.1Q Tag and 802.1p priority 
User Priority CFI  VLAN ID (VID) 
3 bits    1 bits    12 bits  
TPID (Tag Protocol  Identifier)  TCI (Tag Control 
Information) 
2 bytes   2 bytes 
 
Preamble  Destination 
Address  Source 
Address 
VLAN TAG Ethernet  Type  Data FCS 
6 bytes    6 bytes  4 bytes    2 bytes  46-1517 bytes   4 bytes 
Set up the COS priority level. With the dro
p-down...

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TOS Configuration 
DiffServ Code Point (DSCP) - is the traffic prio ritization bits within an IP header that are 
encoded by certain applications and/or de vices to indicate the level of service 
required by the packet across a network.  
The Quality of Service page provides fields  for defining output queue to specific DSCP 
fields. When TCP/IPs TOS/DSCP mode is  applied, the Switch recognizes TCP/IP 
Differentiated...

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IGMP Snooping 
Theory 
The Internet Group Management Protocol (IGMP) lets host and routers share 
information about multicast groups membersh ips. IGMP snooping is a switch feature 
that monitors the exchange of IGMP me ssages and copies them to the CPU for 
feature processing. The overall purpose of IG MP Snooping is to limit the forwarding of 
multicast frames to only ports that  are a member of the multicast group....

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Figure 5-55:  Multicast flooding 
 
Figure 5-56:  IGMP Snooping multicast stream control 
 
  

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IGMP Versions 1 and 2 
Multicast groups allow members to join or leave at any time. IGMP provides the 
method for members and multicast routers  to communicate when joining or leaving 
a multicast group. 
IGMP version 1 is defined in RFC 1112. It ha s a fixed packet size and no optional data. 
The format of an IGMP  packet is shown below: 
 
IGMP Message Format 
Octets 
0             8                                 16...

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IGMP version 2 introduces some enhanc ements such as a method to elect a 
multicast queried for each LAN, an explic it leave message, and query messages that 
are specific to a given group. 
The states a computer will go  through to join or to leave a multicast group are shown 
below: 
Figure 5-57:  IGMP State Transitions 
 
•  IGMP Querier  
A router, or multicast-enabled switch, can peri odically ask their hosts if...

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Figure 5-58:  IGMP Configuration interface 
 
This page includes the following fields: 
 
Object Description 
IGMP Protocol:  Enable or disable the IGMP protocol. 
IGMP Query: Enable or disable the IGMP query function. The IGMP query 
information will be displayed in IGMP status section. 
X-Ring 
X-Ring provides a faster redundant recovery than Spanning Tree topology. The action 
is similar to STP or RSTP, but the...

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Figure 5-59:  X-Ring Application 
 
In the network, it may have more than on e X-Ring group. By using the coupling ring 
function, it can connect each X-Ring fo r the redundant backup. It can ensure the 
transmissions between two ring groups not to  fail. The following figure is a sample of 
coupling ring application. 
  

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Figure 5-60:  Coupling Ring Application 
 
Dual Homing Application 
Dual Homing function is to prevent the connection lose from between X-Ring group 
and upper level/core switch. Assign two port s to be the Dual Homing port that is 
backup port in the X-Ring group. The Dual  Homing function only works when the X-
Ring function is active. Each X-Ring  group only has one Dual Homing port. 
Figure 5-61:  Dual Homing Ring...