Multicast - Revision history

WikiSysop: Reverted edits by Yhorebapemy (Talk) to last version by Domenico

2010-11-18T10:17:45Z

Reverted edits by Yhorebapemy (Talk) to last version by Domenico

← Older revision		Revision as of 10:17, 18 November 2010
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	>== '''Multicast''' ==		== '''Multicast''' ==

	=== What is ~~"~~Multicast~~"~~ ? ===		=== What is "Multicast" ? ===
	Multicast is a term for a special addressing on IP Networks, which allows to target a group of devices on a LAN/WAN with one block/stream on the network, without affecting devices which are not interested in the data.		Multicast is a term for a special addressing on IP Networks, which allows to target a group of devices on a LAN/WAN with one block/stream on the network, without affecting devices which are not interested in the data.

	Multicast is somewhat similar to [[Broadcast]]. If a block/sequence of blocks is ~~"~~broadcasted~~"~~ on the network, every station (in the same IP address range as the broadcast address) will receive the broadcast. Of course, if there is no listening port open for the received block, it is discarded, but the block at least arrives at every station and will use some resources for processing.		Multicast is somewhat similar to [[Broadcast]]. If a block/sequence of blocks is "broadcasted" on the network, every station (in the same IP address range as the broadcast address) will receive the broadcast. Of course, if there is no listening port open for the received block, it is discarded, but the block at least arrives at every station and will use some resources for processing.

	In contrast to Broadcast, Multicast uses a specific addressing scheme, so a host (and of course also a Barix device) can decide in the early stages of the processing of incoming blocks, often even in hardware, if the block is ~~"~~subscribed to~~"~~ or not - if not, the block is discarded.		In contrast to Broadcast, Multicast uses a specific addressing scheme, so a host (and of course also a Barix device) can decide in the early stages of the processing of incoming blocks, often even in hardware, if the block is "subscribed to" or not - if not, the block is discarded.
	Nowadays, with ~~"~~smart~~"~~/~~"~~managed~~"~~ switches, multicast blocks which a certain host is not interested in are typically not even forwarded from the switch to the host, effectively keeping them off the connection. Of course, this is only possible if the device/host can tell the switch exactly which multicasts it is interested in. This is achieved by the ~~"~~IGMP~~"~~ prototocol.		Nowadays, with "smart"/"managed" switches, multicast blocks which a certain host is not interested in are typically not even forwarded from the switch to the host, effectively keeping them off the connection. Of course, this is only possible if the device/host can tell the switch exactly which multicasts it is interested in. This is achieved by the "IGMP" prototocol.

	Multicast addresses use a specific IP address pattern. Any address in the range 224.x.x.x to 239.x.x.x is a multicast address, and will be sent on Ethernet with special MAC addresses. Devices/Hosts which do not support multicast will typically NOT receive a multicast block, and, as explained above, if a ~~"~~smart switch~~"~~ or router is used, a multicast block will not even show up on the link to a device unless it has requested delivery of multicast to a specific multicast group (identified by the IP address) by IGMP.		Multicast addresses use a specific IP address pattern. Any address in the range 224.x.x.x to 239.x.x.x is a multicast address, and will be sent on Ethernet with special MAC addresses. Devices/Hosts which do not support multicast will typically NOT receive a multicast block, and, as explained above, if a "smart switch" or router is used, a multicast block will not even show up on the link to a device unless it has requested delivery of multicast to a specific multicast group (identified by the IP address) by IGMP.
	This is in contrast to broadcast - all broadcast blocks are forwarded to all devices on a network and must be received by he connected device.		This is in contrast to broadcast - all broadcast blocks are forwarded to all devices on a network and must be received by he connected device.

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	=== How can I generate Multicast from a Barix device ? ===		=== How can I generate Multicast from a Barix device ? ===
	No special functionality or configuration is needed. ALL Barix applications and devices support the generation of Multicast traffic. The target address (of a UDP based application protocol) just needs to be configured as a Multicast address, and the device will generate the outgoing blocks as Multicasts with correct, configured IP address and corresponding ~~"~~special~~"~~ MAC address.		No special functionality or configuration is needed. ALL Barix applications and devices support the generation of Multicast traffic. The target address (of a UDP based application protocol) just needs to be configured as a Multicast address, and the device will generate the outgoing blocks as Multicasts with correct, configured IP address and corresponding "special" MAC address.

	=== Can a Barix device receive Multicast ? ===		=== Can a Barix device receive Multicast ? ===
	This depends on the software application loaded. The standard ~~"~~Exstreamer~~"~~ firmware can not receive multicast in general but it subscribes to a default Multicast Address 239.255.231.187. Whereas the Streaming Client firmware for the Exstreamer family can do Multicast of configurable address. For example, in the Streaming Client, you can configure a URL as rtp://229.1.1.1:1234 and the Streaming Client firmware will subscribe to group 229.1.1.1 and receive an RTP stream sent to this group address, port 1234.		This depends on the software application loaded. The standard "Exstreamer" firmware can not receive multicast in general but it subscribes to a default Multicast Address 239.255.231.187. Whereas the Streaming Client firmware for the Exstreamer family can do Multicast of configurable address. For example, in the Streaming Client, you can configure a URL as rtp://229.1.1.1:1234 and the Streaming Client firmware will subscribe to group 229.1.1.1 and receive an RTP stream sent to this group address, port 1234.
	Standard Annuncicom firmware does not support Multicast reception, but it can send multicast streams.		Standard Annuncicom firmware does not support Multicast reception, but it can send multicast streams.
	The ABCL applications on the Audio Platforms which use RTP or UDP for distribution typically support Multicast reception.		The ABCL applications on the Audio Platforms which use RTP or UDP for distribution typically support Multicast reception.
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	In (A)BCL programming, a UDP socket can be opened with multicast reception by simply giving the multicast address. All IGMP handling is done automatically.		In (A)BCL programming, a UDP socket can be opened with multicast reception by simply giving the multicast address. All IGMP handling is done automatically.

	=== Are there ~~"~~reserved~~"~~ addresses ===		=== Are there "reserved" addresses ===
	Yes. 224.0.0.1 is reserved as a ~~"~~link local~~"~~ Multicast address, used for local link management (to say things simple), and is typically not routed even by switches. So - don't use that address unless you know what you do.		Yes. 224.0.0.1 is reserved as a "link local" Multicast address, used for local link management (to say things simple), and is typically not routed even by switches. So - don't use that address unless you know what you do.

	=== What is the ~~"~~reach~~"~~ of Multicast over a WAN ? ===		=== What is the "reach" of Multicast over a WAN ? ===
	Every IP Packet has a ~~"~~forwarding counter~~"~~, called ~~"~~Time To Live~~"~~, short TTL. This counter is decreased with every router forwarding by one, and when it reaches 0, the block is discarded. This function is important to limit the life of blocks in case of cyclic misconfigurations.		Every IP Packet has a "forwarding counter", called "Time To Live", short TTL. This counter is decreased with every router forwarding by one, and when it reaches 0, the block is discarded. This function is important to limit the life of blocks in case of cyclic misconfigurations.
	Standard Unicast IP packets typically are sent with a TTL of 64 or 128, so they have ample time to get to the destination. A Broadcast is sent with a TTL of one, it is just sent on the local network and not routed. A Multicast is typically sent by Barix devices with a TTL of four, but ~~"~~link local~~"~~ Multicasts of address 224.0.0.1 are sent with a TTL of one. Those don't go to the next network.		Standard Unicast IP packets typically are sent with a TTL of 64 or 128, so they have ample time to get to the destination. A Broadcast is sent with a TTL of one, it is just sent on the local network and not routed. A Multicast is typically sent by Barix devices with a TTL of four, but "link local" Multicasts of address 224.0.0.1 are sent with a TTL of one. Those don't go to the next network.

	=== Can I send Multicast over the Internet ? ===		=== Can I send Multicast over the Internet ? ===
	Generally, no - ISP's typically block Multicast distribution - at least ~~"~~upstream~~"~~ (into the network). For specific applications (such as IPTV distribution), they may distribute Multicast to the subscribers.		Generally, no - ISP's typically block Multicast distribution - at least "upstream" (into the network). For specific applications (such as IPTV distribution), they may distribute Multicast to the subscribers.

	* I have 200 devices on my local network, and want to send a block to 20 of them. What do i do ?		* I have 200 devices on my local network, and want to send a block to 20 of them. What do i do ?
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	=== How does Barix use Multicast ? ===		=== How does Barix use Multicast ? ===
	Barix has defined and designed a system for general audio distribution over multiple subnets which we call ~~"~~[[BARP]]~~"~~ - the Barix Paging Protocol. BARP makes extensive use of Multicast to address many stations at the same time, yet keeping traffic low by using Multicast.		Barix has defined and designed a system for general audio distribution over multiple subnets which we call "[[BARP]]" - the Barix Paging Protocol. BARP makes extensive use of Multicast to address many stations at the same time, yet keeping traffic low by using Multicast.

	=== Does Multicast work over WLAN ? ===		=== Does Multicast work over WLAN ? ===
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	Back to [[FAQ]]		Back to [[FAQ]]

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Yhorebapemy at 23:52, 17 November 2010

2010-11-17T23:52:04Z

Domenico: /* Can a Barix device receive Multicast ? */

2009-12-10T12:48:43Z

Can a Barix device receive Multicast ?

← Older revision		Revision as of 12:48, 10 December 2009
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	=== Can a Barix device receive Multicast ? ===		=== Can a Barix device receive Multicast ? ===
	This depends on the software application loaded. The standard "Exstreamer" firmware can ~~NOT~~ receive ~~multicasts, whereas~~ the Streaming Client firmware for the Exstreamer family can do so. For example, in the Streaming Client, you can configure a URL as rtp://229.1.1.1:1234 and the Streaming Client firmware will subscribe to group 229.1.1.1 and receive an RTP stream sent to this group address, port 1234.		This depends on the software application loaded. The standard "Exstreamer" firmware can not receive multicast in general but it subscribes to a default Multicast Address 239.255.231.187. Whereas the Streaming Client firmware for the Exstreamer family can do Multicast of configurable address. For example, in the Streaming Client, you can configure a URL as rtp://229.1.1.1:1234 and the Streaming Client firmware will subscribe to group 229.1.1.1 and receive an RTP stream sent to this group address, port 1234.
	Standard Annuncicom firmware does not support Multicast reception, but it can send multicast streams.		Standard Annuncicom firmware does not support Multicast reception, but it can send multicast streams.
	The ABCL applications on the Audio Platforms which use RTP or UDP for distribution typically support Multicast reception.		The ABCL applications on the Audio Platforms which use RTP or UDP for distribution typically support Multicast reception.

Sandra at 12:58, 20 March 2009

2009-03-20T12:58:47Z

← Older revision		Revision as of 12:58, 20 March 2009
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	=== Does Multicast work over WLAN ? ===		=== Does Multicast work over WLAN ? ===
	Generally, yes - but '''IMPORTANT''' please read the following page for the limitations: [[WLAN_Broadcast/Multicast]]		Generally, yes - but '''IMPORTANT''' please read the following page for the limitations: [[WLAN_Broadcast/Multicast]]


			Back to [[FAQ]]

Jrietschel at 22:40, 13 January 2009

2009-01-13T22:40:51Z

← Older revision		Revision as of 22:40, 13 January 2009
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	=== How does Barix use Multicast ? ===		=== How does Barix use Multicast ? ===
	Barix has defined and designed a system for general audio distribution over multiple subnets which we call "[[BARP]]" - the Barix Paging Protocol. BARP makes extensive use of Multicast to address many stations at the same time, yet keeping traffic low by using Multicast.		Barix has defined and designed a system for general audio distribution over multiple subnets which we call "[[BARP]]" - the Barix Paging Protocol. BARP makes extensive use of Multicast to address many stations at the same time, yet keeping traffic low by using Multicast.

			=== Does Multicast work over WLAN ? ===
			Generally, yes - but '''IMPORTANT''' please read the following page for the limitations: [[WLAN_Broadcast/Multicast]]

Sandra: /* How does Barix use Multicast ? */

2008-12-23T15:20:41Z

How does Barix use Multicast ?

← Older revision		Revision as of 15:20, 23 December 2008
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	=== How does Barix use Multicast ? ===		=== How does Barix use Multicast ? ===
	Barix has defined and designed a system for general audio distribution over multiple subnets which we call "[[BARP]]" - the Barix Paging Protocol. BARP makes extensive use of ~~Multiast~~ to address many stations at the same time, yet keeping traffic low by using Multicast.		Barix has defined and designed a system for general audio distribution over multiple subnets which we call "[[BARP]]" - the Barix Paging Protocol. BARP makes extensive use of Multicast to address many stations at the same time, yet keeping traffic low by using Multicast.

Jrietschel: /* Multicast */

2008-12-23T01:02:50Z

Multicast

← Older revision		Revision as of 01:02, 23 December 2008
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	* I have 200 devices on my local network, and want to send a block to 20 of them. What do i do ?		* I have 200 devices on my local network, and want to send a block to 20 of them. What do i do ?
	Multicast is ideal for this scenario. By picking an (unused) Multicast address and sending the data feed to that address, every device on the network can subscribe to that Multicast. Of course, you need to configure the 20 receivers so that their application knows they are supposed to receive the Multicast to the picked group - and they need to manage the Switch with IGMP so that it forwards the blocks.		Multicast is ideal for this scenario. By picking an (unused) Multicast address and sending the data feed to that address, every device on the network can subscribe to that Multicast. Of course, you need to configure the 20 receivers so that their application knows they are supposed to receive the Multicast to the picked group - and they need to manage the Switch with IGMP so that it forwards the blocks.

			=== How does Barix use Multicast ? ===
			Barix has defined and designed a system for general audio distribution over multiple subnets which we call "[[BARP]]" - the Barix Paging Protocol. BARP makes extensive use of Multiast to address many stations at the same time, yet keeping traffic low by using Multicast.

Jrietschel: /* What is "Multicast" ? */

2008-12-23T00:44:56Z

What is "Multicast" ?

← Older revision		Revision as of 00:44, 23 December 2008
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	Multicast is a term for a special addressing on IP Networks, which allows to target a group of devices on a LAN/WAN with one block/stream on the network, without affecting devices which are not interested in the data.		Multicast is a term for a special addressing on IP Networks, which allows to target a group of devices on a LAN/WAN with one block/stream on the network, without affecting devices which are not interested in the data.

	Multicast is somewhat similar to Broadcast. If a block/sequence of blocks is "broadcasted" on the network, every station (in the same IP address range as the broadcast address) will receive the broadcast. Of course, if there is no listening port open for the received block, it is discarded, but the block at least arrives at every station and will use some resources for processing.		Multicast is somewhat similar to [[Broadcast]]. If a block/sequence of blocks is "broadcasted" on the network, every station (in the same IP address range as the broadcast address) will receive the broadcast. Of course, if there is no listening port open for the received block, it is discarded, but the block at least arrives at every station and will use some resources for processing.

	In contrast to Broadcast, Multicast uses a specific addressing scheme, so a host (and of course also a Barix device) can decide in the early stages of the processing of incoming blocks, often even in hardware, if the block is "subscribed to" or not - if not, the block is discarded.		In contrast to Broadcast, Multicast uses a specific addressing scheme, so a host (and of course also a Barix device) can decide in the early stages of the processing of incoming blocks, often even in hardware, if the block is "subscribed to" or not - if not, the block is discarded.

Jrietschel: /* How can i generate Multicast from a Barix device ? */

2008-12-23T00:44:19Z

How can i generate Multicast from a Barix device ?

← Older revision		Revision as of 00:44, 23 December 2008
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	Yes. RTP is based on UDP, and UDP is the datagram (packet) service of the IP protocol stack. If the endpoints (=devices) and switches/routers support Multicast, it can be used on a network infrastructure, and RTP is just one application protocol on top of UDP.		Yes. RTP is based on UDP, and UDP is the datagram (packet) service of the IP protocol stack. If the endpoints (=devices) and switches/routers support Multicast, it can be used on a network infrastructure, and RTP is just one application protocol on top of UDP.

	=== How can i generate Multicast from a Barix device ? ===		=== How can I generate Multicast from a Barix device ? ===
	No special functionality or configuration is needed. ALL Barix applications and devices support the generation of Multicast traffic. The target address (of a UDP based application protocol) just needs to be configured as a Multicast address, and the device will generate the outgoing blocks as Multicasts with correct, configured IP address and corresponding "special" MAC address.		No special functionality or configuration is needed. ALL Barix applications and devices support the generation of Multicast traffic. The target address (of a UDP based application protocol) just needs to be configured as a Multicast address, and the device will generate the outgoing blocks as Multicasts with correct, configured IP address and corresponding "special" MAC address.

Jrietschel: /* Can i send Multicast over the Internet ? */

2008-12-23T00:44:05Z

Can i send Multicast over the Internet ?

← Older revision		Revision as of 00:44, 23 December 2008
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	Standard Unicast IP packets typically are sent with a TTL of 64 or 128, so they have ample time to get to the destination. A Broadcast is sent with a TTL of one, it is just sent on the local network and not routed. A Multicast is typically sent by Barix devices with a TTL of four, but "link local" Multicasts of address 224.0.0.1 are sent with a TTL of one. Those don't go to the next network.		Standard Unicast IP packets typically are sent with a TTL of 64 or 128, so they have ample time to get to the destination. A Broadcast is sent with a TTL of one, it is just sent on the local network and not routed. A Multicast is typically sent by Barix devices with a TTL of four, but "link local" Multicasts of address 224.0.0.1 are sent with a TTL of one. Those don't go to the next network.

	=== Can i send Multicast over the Internet ? ===		=== Can I send Multicast over the Internet ? ===
	Generally, no - ISP's typically block Multicast distribution - at least "upstream" (into the network). For specific applications (such as IPTV distribution), they may distribute Multicast to the subscribers.		Generally, no - ISP's typically block Multicast distribution - at least "upstream" (into the network). For specific applications (such as IPTV distribution), they may distribute Multicast to the subscribers.

	* I have 200 devices on my local network, and want to send a block to 20 of them. What do i do ?		* I have 200 devices on my local network, and want to send a block to 20 of them. What do i do ?
	Multicast is ideal for this scenario. By picking an (unused) Multicast address and sending the data feed to that address, every device on the network can subscribe to that Multicast. Of course, you need to configure the 20 receivers so that their application knows they are supposed to receive the Multicast to the picked group - and they need to manage the Switch with IGMP so that it forwards the blocks.		Multicast is ideal for this scenario. By picking an (unused) Multicast address and sending the data feed to that address, every device on the network can subscribe to that Multicast. Of course, you need to configure the 20 receivers so that their application knows they are supposed to receive the Multicast to the picked group - and they need to manage the Switch with IGMP so that it forwards the blocks.

← Older revision		Revision as of 23:52, 17 November 2010
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	== '''Multicast''' ==		>== '''Multicast''' ==

	=== What is "Multicast" ? ===		=== What is "Multicast" ? ===
	Multicast is a term for a special addressing on IP Networks, which allows to target a group of devices on a LAN/WAN with one block/stream on the network, without affecting devices which are not interested in the data.		Multicast is a term for a special addressing on IP Networks, which allows to target a group of devices on a LAN/WAN with one block/stream on the network, without affecting devices which are not interested in the data.

	Multicast is somewhat similar to [[Broadcast]]. If a block/sequence of blocks is "broadcasted" on the network, every station (in the same IP address range as the broadcast address) will receive the broadcast. Of course, if there is no listening port open for the received block, it is discarded, but the block at least arrives at every station and will use some resources for processing.		Multicast is somewhat similar to [[Broadcast]]. If a block/sequence of blocks is "broadcasted" on the network, every station (in the same IP address range as the broadcast address) will receive the broadcast. Of course, if there is no listening port open for the received block, it is discarded, but the block at least arrives at every station and will use some resources for processing.

	In contrast to Broadcast, Multicast uses a specific addressing scheme, so a host (and of course also a Barix device) can decide in the early stages of the processing of incoming blocks, often even in hardware, if the block is "subscribed to" or not - if not, the block is discarded.		In contrast to Broadcast, Multicast uses a specific addressing scheme, so a host (and of course also a Barix device) can decide in the early stages of the processing of incoming blocks, often even in hardware, if the block is "subscribed to" or not - if not, the block is discarded.
	Nowadays, with "smart"/"managed" switches, multicast blocks which a certain host is not interested in are typically not even forwarded from the switch to the host, effectively keeping them off the connection. Of course, this is only possible if the device/host can tell the switch exactly which multicasts it is interested in. This is achieved by the "IGMP" prototocol.		Nowadays, with "smart"/"managed" switches, multicast blocks which a certain host is not interested in are typically not even forwarded from the switch to the host, effectively keeping them off the connection. Of course, this is only possible if the device/host can tell the switch exactly which multicasts it is interested in. This is achieved by the "IGMP" prototocol.

	Multicast addresses use a specific IP address pattern. Any address in the range 224.x.x.x to 239.x.x.x is a multicast address, and will be sent on Ethernet with special MAC addresses. Devices/Hosts which do not support multicast will typically NOT receive a multicast block, and, as explained above, if a "smart switch" or router is used, a multicast block will not even show up on the link to a device unless it has requested delivery of multicast to a specific multicast group (identified by the IP address) by IGMP.		Multicast addresses use a specific IP address pattern. Any address in the range 224.x.x.x to 239.x.x.x is a multicast address, and will be sent on Ethernet with special MAC addresses. Devices/Hosts which do not support multicast will typically NOT receive a multicast block, and, as explained above, if a "smart switch" or router is used, a multicast block will not even show up on the link to a device unless it has requested delivery of multicast to a specific multicast group (identified by the IP address) by IGMP.
	This is in contrast to broadcast - all broadcast blocks are forwarded to all devices on a network and must be received by he connected device.		This is in contrast to broadcast - all broadcast blocks are forwarded to all devices on a network and must be received by he connected device.

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	=== How can I generate Multicast from a Barix device ? ===		=== How can I generate Multicast from a Barix device ? ===
	No special functionality or configuration is needed. ALL Barix applications and devices support the generation of Multicast traffic. The target address (of a UDP based application protocol) just needs to be configured as a Multicast address, and the device will generate the outgoing blocks as Multicasts with correct, configured IP address and corresponding "special" MAC address.		No special functionality or configuration is needed. ALL Barix applications and devices support the generation of Multicast traffic. The target address (of a UDP based application protocol) just needs to be configured as a Multicast address, and the device will generate the outgoing blocks as Multicasts with correct, configured IP address and corresponding "special" MAC address.

	=== Can a Barix device receive Multicast ? ===		=== Can a Barix device receive Multicast ? ===
	This depends on the software application loaded. The standard "Exstreamer" firmware can not receive multicast in general but it subscribes to a default Multicast Address 239.255.231.187. Whereas the Streaming Client firmware for the Exstreamer family can do Multicast of configurable address. For example, in the Streaming Client, you can configure a URL as rtp://229.1.1.1:1234 and the Streaming Client firmware will subscribe to group 229.1.1.1 and receive an RTP stream sent to this group address, port 1234.		This depends on the software application loaded. The standard "Exstreamer" firmware can not receive multicast in general but it subscribes to a default Multicast Address 239.255.231.187. Whereas the Streaming Client firmware for the Exstreamer family can do Multicast of configurable address. For example, in the Streaming Client, you can configure a URL as rtp://229.1.1.1:1234 and the Streaming Client firmware will subscribe to group 229.1.1.1 and receive an RTP stream sent to this group address, port 1234.
	Standard Annuncicom firmware does not support Multicast reception, but it can send multicast streams.		Standard Annuncicom firmware does not support Multicast reception, but it can send multicast streams.
	The ABCL applications on the Audio Platforms which use RTP or UDP for distribution typically support Multicast reception.		The ABCL applications on the Audio Platforms which use RTP or UDP for distribution typically support Multicast reception.
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	In (A)BCL programming, a UDP socket can be opened with multicast reception by simply giving the multicast address. All IGMP handling is done automatically.		In (A)BCL programming, a UDP socket can be opened with multicast reception by simply giving the multicast address. All IGMP handling is done automatically.

	=== Are there "reserved" addresses ===		=== Are there "reserved" addresses ===
	Yes. 224.0.0.1 is reserved as a "link local" Multicast address, used for local link management (to say things simple), and is typically not routed even by switches. So - don't use that address unless you know what you do.		Yes. 224.0.0.1 is reserved as a "link local" Multicast address, used for local link management (to say things simple), and is typically not routed even by switches. So - don't use that address unless you know what you do.

	=== What is the "reach" of Multicast over a WAN ? ===		=== What is the "reach" of Multicast over a WAN ? ===
	Every IP Packet has a "forwarding counter", called "Time To Live", short TTL. This counter is decreased with every router forwarding by one, and when it reaches 0, the block is discarded. This function is important to limit the life of blocks in case of cyclic misconfigurations.		Every IP Packet has a "forwarding counter", called "Time To Live", short TTL. This counter is decreased with every router forwarding by one, and when it reaches 0, the block is discarded. This function is important to limit the life of blocks in case of cyclic misconfigurations.
	Standard Unicast IP packets typically are sent with a TTL of 64 or 128, so they have ample time to get to the destination. A Broadcast is sent with a TTL of one, it is just sent on the local network and not routed. A Multicast is typically sent by Barix devices with a TTL of four, but "link local" Multicasts of address 224.0.0.1 are sent with a TTL of one. Those don't go to the next network.		Standard Unicast IP packets typically are sent with a TTL of 64 or 128, so they have ample time to get to the destination. A Broadcast is sent with a TTL of one, it is just sent on the local network and not routed. A Multicast is typically sent by Barix devices with a TTL of four, but "link local" Multicasts of address 224.0.0.1 are sent with a TTL of one. Those don't go to the next network.

	=== Can I send Multicast over the Internet ? ===		=== Can I send Multicast over the Internet ? ===
	Generally, no - ISP's typically block Multicast distribution - at least "upstream" (into the network). For specific applications (such as IPTV distribution), they may distribute Multicast to the subscribers.		Generally, no - ISP's typically block Multicast distribution - at least "upstream" (into the network). For specific applications (such as IPTV distribution), they may distribute Multicast to the subscribers.

	* I have 200 devices on my local network, and want to send a block to 20 of them. What do i do ?		* I have 200 devices on my local network, and want to send a block to 20 of them. What do i do ?
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	=== How does Barix use Multicast ? ===		=== How does Barix use Multicast ? ===
	Barix has defined and designed a system for general audio distribution over multiple subnets which we call "[[BARP]]" - the Barix Paging Protocol. BARP makes extensive use of Multicast to address many stations at the same time, yet keeping traffic low by using Multicast.		Barix has defined and designed a system for general audio distribution over multiple subnets which we call "[[BARP]]" - the Barix Paging Protocol. BARP makes extensive use of Multicast to address many stations at the same time, yet keeping traffic low by using Multicast.

	=== Does Multicast work over WLAN ? ===		=== Does Multicast work over WLAN ? ===
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	Back to [[FAQ]]		Back to [[FAQ]]

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