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81

6.

Enter the

Domain Name

to be registered with the DDNS server.

7.

Click

Apply

The

Apply

button will temporarily save this connection. To make the change permanent,

click

Tools

(at the top of the page) and select

System Commands

. On the

System

Commands

page, click

Save All

.

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82

IGMP Proxy

Multicasting is a form of limited broadcast. UDP is used to send datagrams to all hosts that

belong to what is called a Host Group. A host group is a set of one or more hosts identified by a

single IP destination address.

Internet Group Management Protocol (IGMP) Proxy allows for forwarding of multicast traffic

between networks. Unlike broadcast which sends traffic to all possible addresses (and because it

requires duplication and transmission broadcasts may require a great deal of computation time

from the sending device), multicast provides a mechanism so data can be sent to a limited

number of devices. Unlike sending multiple normal unicast transmissions, which send

transmissions a single specific device (then many times over), multicast provides an option which

does not require many transmissions to be sent. Multicast has a group membership mechanism

where one data stream can be received by more than one device, so multicast does not require

the network bandwidth of multiple unicast transmissions.

Multicasting is useful when the same data needs to be sent to more than one device. For

instance, if one device is responsible for acquiring data that many other devices need, then

multicasting is a natural fit. Note that using multicasting as opposed to sending the same data to

individual devices uses less network bandwidth. The multicast feature also enables you to receive

multicast video streams from multicast servers.

With multicast, datagrams are sent to all hosts in a Host Group. A host group is a set of one or

more hosts identified by a single IP destination address. Host groups follow these standards:

•

Anyone can join or leave a host group at will.

•

There are no restrictions on a host’s location.

•

There are no restrictions on the number of members that may belong to a host group.

•

A host may belong to multiple host groups.

•

Non-group members may send UDP datagrams to the host group.

Multicast provides a means for devices in host groups to get the datagrams from the host group

IP address. Multicast also enables you to receive multicast video streams from multicast servers.

IP hosts use IGMP to report their multicast group memberships to neighboring routers. Similarly,

multicast routers use IGMP to discover which of their hosts belong to multicast groups. Your 6381

supports IGMP proxy that handles IGMP messages. When enabled, your 6381 acts as a proxy

for a LAN host making requests to join and leave multicast groups, or a multicast router sending

multicast packets to multicast groups on the WAN side.

On a Join, the proxy sets up a multicast route for the interface and PC requesting the video

content. It then forwards the Join to the upstream multicast router. The Multicast IP traffic will then

be forwarded to the requesting device. Multicast traffic does not pass trough the Firewall or NAT.

On a leave, the Proxy removes the route and then forwards the leave to the upstream Multicast

router.

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The IGMP Proxy page allows you to enable multicast on available WAN or LAN interfaces.

Upstream

The interface from which IGMP requests from hosts are sent to the multicast

router.

Downstream

The interface on the router which sends to hosts in the multicast group database.

Ignore

No IGMP requests nor multicast data is forwarded.

Here are a few examples to demonstrate how to configure interfaces

•

WAN Interface as Upstream IGMP Proxy

The multicast server is in the WAN network. Hosts on the LAN side can send IGMP requests

through the WAN interface. The WAN will pass multicast packets from the multicast server to

hosts on the LAN side.

WAN interface on which the multicast router exists: Upstream

Interface(s) of any LAN groups receiving multicast: Downstream

Interface(s) of any WAN groups receiving multicast: Downstream

Interface(s) of any LAN or WAN

groups not receiving or providing multicast: ignore

•

LAN Interfaces as the Upstream IGMP Proxy

The multicast is on the LAN side. Hosts on the Hosts on the WAN network can send IGMP

requests through the LAN interface. The LAN interface, acting as the upstream interface,

forwards data multicast from the LAN-side multicast server to hosts on the network.

LAN group interface on which the router exists: Upstream

Interface(s) of WAN group(s) receiving multicast: Downstream

Interface(s) of any LAN group(s) receiving multicast: Downstream

Interface(s) of any LAN or WAN group(s) not receiving or providing multicast: ignore

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84

Configure a WAN Interface as the Upstream IGMP Proxy

The following procedure applies when the multicast server in on the network. Hosts on your LAN

side can send IGMP requests through the WAN interface. And the WAN will pass multicast

packets from the multicast server to the hosts on the LAN side.

As shown above the WAN interface DHCP1 is enabled as the upstream IGMP interface, which

forwards IGMP requests from LAN group 1 to the multicast router on the network and forwards

multicast frames from the multicast router to hosts on the downstream interface (LAN group 1).

No IGMP request nor data multicast are forwarded to PPPoE1 or LAN Group 2.

To configure a WAN interface as the Upstream IGMP Proxy:

1.

From the navigation bar at the top of the screen click

Advanced

2.

From the left hand navigation pane select

IGMP Proxy

.

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85

3.

Enter a check in the

Enable IGMP Proxy

check box

4.

From the

Interface

Upstream/Downstream/Ignore

dropdowns select the LAN groups to

and whether they should allow IGMP proxies from upstream or downstream.

To match the example above:

•

DHCP1: Upstream

•

PPPoE1: Ignore

•

LAN group 1: Downstream

•

LAN group 2: Ignore

5.

Click

Apply

The

Apply

button will temporarily save this connection. To make the change permanent,

click

Tools

(at the top of the page) and select

System Commands

. On the

System

Commands

page, click

Save All

.

Configure a LAN interface as the Upstream Interface

The following procedure applies when the multicast server in on the LAN side. Hosts on the

network can sent IGMP request from the WAN side through the LAN interface. And the LAN

interface, acting as the upstream interface, forwards data multicast from the LAN-side multicast

server to hosts on the network.

In the example shown above, there is a multicast router on the LAN side and LAN Group 1

interface is enabled as the upstream IGMP proxy. IGMP requests from the network are forwarded

to LAN group 1 and multicast frames from multicast router 1 are forwarded to hosts on the LAN

side (LAN group 3) and on the WAN side (DHCP1 and PPPoE1). No IGMP request nor data

multicast are forwarded to LAN Group 2.

To configure your LAN group 1 as the upstream interface:

1.

From the navigation bar at the top of the screen click

Advanced