AutoWAN Port for Bridged Multicast

Date: April 2008

Version: v1.0

Abstract: This Application Note provides technical information on multicast video and how this relates to the various devices in the Thomson Gateway family. First, we provide some background information on multicast video. Next, a tested and proven scenario shows how to integrate the Thomson Gateway in a multicast network. In the described scenario, the Thomson Gateway supports a routed Internet connection and bridged multicast traffic. The AutoWAN feature allows the Thomson Gateway to dynamically detect the WAN port (Ethernet or PVC) and the LAN ports used by the STBs. We present the mechanisms that are used to set up the scenario, the configuration of the Thomson Gateway using CLI commands and an illustration of the resulting configuration.

Applicability: This Application Note is relevant to all Thomson Gateway devices that support Flexiport with a single PVC:

Flexiport with a single PVC is supported since R5.3.2.

The scenario presented has been tested on:

The THOMSON ST780 (Wireless) R6.2.16.3.

Updates: THOMSON continuously develops new solutions, but is also committed to improving its existing products.

For more information on THOMSON's latest technological innovations, documents and software releases, visit us at http://www.thomson-broadband.com

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Chapter 1

1 Introduction to Multicast Video

Multicast videoFrom an end user’s point of view, multicast video over IP is similar to broadcast TV:

The video server sends a number of continuous digitized and packetized video streams into the network. Each video stream has its own multicast group address. The various multicast group addresses can be compared to the channel frequencies for broadcast TV. A video display application can become a member of a multicast group, and thus receives a particular video stream. This is just like tuning to the frequency of the channel you would like to watch for broadcast TV.

Differences between multicast video over IP and broadcast TV exist in network and traffic features:

While broadcast TV channels are broadcast at all times to all subscribers, a multicast video stream is only forwarded on the links that lead to the multicast group members.

While broadcast TV sets tune in locally to a particular channel, a multicast client announces its membership to a particular multicast group by means of IGMP signalling.

Differences between multicast video and unicast video are:

While a unicast video stream is dedicated to a single client, a multicast video stream is shared by many clients. A multicast stream is only put once on a logical link that leads to the multicast group members. As a result, a multicast video stream only uses a fraction of the bandwidth used by a large number of duplicated unicast video streams.

While unicast video streams can use both TCP and UDP as transport protocol, multicast streams can only use UDP.

While a unicast video stream starts on request of the video client, multicast video streams are always on. The multicast video clients join the group at a certain moment in time.

Multicast groupA multicast group consists of a number of devices that share a multicast group address for communication. The information is sent no more than once on each link.

The devices are:

Server(s): a multicast server sends multicast streams, each with a “pre-defined” multicast group address.

Routers: a multicast router receives the multicast streams. The router forwards each multicast stream to its multicast peers that are member of the corresponding multicast group. This requires that the multicast peers have announced to which multicast groups they belong by means of IGMP.

Clients: multicast clients receive multicast streams to which they subscribed themselves and decode the data to display them to the end users.

Chapter 2

2 Mechanisms to Support Multicast Video

IntroductionSeveral mechanisms can be used by Thomson Gateway devices to support multicast video:

Port-to-PVC mapping.

Flexiport mechanism.

Internet Group Management Protocol (IGMP) snooping and IGMP proxying.

The mechanism that is used to set up the scenario described in this document is the Flexiport mechanism. This mechanism is shortly described in following subsections.

2.1 Flexiport Mechanism

2.1.1 Why Do We Need Flexiport?

What was missing?Before the introduction of Flexiport, port-to-PVC mapping was the solution for triple play configurations. Using port-to-PVC mapping, the Thomson Gateway classifies Ethernet frames based on the receiving local interface. Per local interface, it is configured to which Permanent Virtual Circuit (PVC) the frames must be forwarded. This implies that:

The configuration can not be altered without having to restart the device.

It is important that the correct devices are connected to the correct local interfaces. The chance of errors is big, resulting in help desk calls and so on.

Once a port-to-PVC map is created, forwarding is limited to bridging in all groups except the default group. Routing and bridging in the default group is not feasible since routing with NAPT requires multiple physical interfaces.

Advantages of FlexiportThe Flexiport mechanism has following advantages:

Pre-defined LAN devices can be recognized on-the-fly and be mapped to the PVC offering the services that are needed. For example, a certain type of STB can be recognized and automatically linked with the PVC towards the video network - no matter which Ethernet port they are plugged in to. This is done by placing the MAC address of the device in a VLAN which has the proper PVC mapped to it. Other devices that are not recognized are still routed over the same default PVC.

Multicast traffic is sent to the STB port only, which is similar to IGMP snooping. When connecting another device to the STB port, it will be routed again.

Wireless ports and WDS ports can also be configured as Flexiport. This can be used to overcome larger distances without the hassle of cables. When running voice or video services over wireless it is recommended to use WMM (WiFi MultiMedia). This feature ensures some kind of Quality of Service.

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2.1.2 Flexiport Concept

IntroductionFollowing illustration shows the concept of the Flexiport mechanism:

ConceptThe STB is recognized as soon as it is plugged into the Thomson Gateway. This is done in seven steps:

1 The Thomson Gateway is up and running, PCs are surfing the Internet through one PVC.

2 The STB is added to one of the ports of the Thomson Gateway and sends out a DHCP discover message.

3 The DHCP relay identifies the STB by its Vendor Class Identifier or MAC address and moves the STB’s MAC address into a second VLAN.

4 The STB re-sends the DHCP discover message, but now as member of the second VLAN.

5 The STB now receives an IP address from the video DHCP server and can start receiving video.

6 The STB’s MAC address is saved, and the next time the Thomson Gateway reboots, it remembers to which VLAN the STB belongs.

7 When the STB reboots, it re-sends a DHCP discover message and restarts the procedure from step 4.

Ethernet port1

Ethernet port 2

Ethernet port 3

Ethernet port 4

Internet

BRAS

DHCP Server

Video Server

Video Network

NATed data traffic

Bridged video traffic

The Flexiport mechanism can also be used for wired and wireless IP phones. This way, the data from the IP phone is bridged to the Voice PVC while other wireless devices can still surf the web over the default PVC.

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Chapter 2

2.1.3 Configuration of Flexiport

IntroductionThe Flexiport mechanism combines several features of the Thomson Gateway, such as VLANs, DHCP, dynamic VLANs and scripts. In this section, we shortly describe the configuration of some Flexiport-related features. For the complete configuration of the Flexiport mechanism, we refer to the description of the scenario.

DHCP rulesA device can be identified based on its MAC address or Vendor Class Identifier (VCI), which are sent out with the DHCP request of the device. The DHCP relay handles received DHCP requests and recognizes devices by the use of DHCP rules.

Configure DHCP rules as follows:

MAC address:

VCI code:

Partial string matchSince Release 6.1, it is possible to use a partial string match in the DHCP rules. This can be done for both MAC address and VCI code. Each of them uses a specific notation.

Configure DHCP rules with partial string match as follows:

MAC address: here, we use an asterisk (“*”) as wild card. Following rule recognizes any device with a MAC address starting with 00:0f:1f as a STB:

VCI code: here, we only put part of the VCI code in the rule and add the option match=as_substring. Following rule recognizes any device with ST20 in its VCI as a VoIP device, e.g. devices with VCI ST2030 or ST2020:

=>:dhcp rule add name=STB type=mac mac=00:0d:56:01:32:fa=>:dhcp rule add name=notSTB type=mac mac=!00:0d:56:01:32:fa

=>:dhcp rule add name=VOIP type=vci vci=ST2030=>:dhcp rule add name=notVOIP type=vci vci=!ST2030

An exclamation mark (“!”) is used to indicate that the device’s MAC address or VCI must differ from the specified value.

=>:dhcp rule add name=STB type=mac mac=00:0f:1f:*:*:*

=>:dhcp rule add name=VOIP type=vci vci=ST20 match=as_substring

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Chapter 2

Assigning DHCP rulesThe DHCP relay checks a DHCP rule, if it is assigned to a DHCP relay forwarding entry as follows:

To assign more than one DHCP rule to a single forwarding entry, keys are used:

AND key: the AND key indicates that a rule applies if all conditions are fulfilled.

OR key: the OR key indicates that a rule applies as soon as one of the conditions if fulfilled.

Flexiport scriptA Flexiport script makes use of dynamic VLANs, moving the MAC address of the recognized device to a specified VLAN.

Create a Flexiport script as follows:

The DHCP relay can trigger a Flexiport script, if it is assigned to a DHCP relay forwarding entry as follows:

If a DHCP relay forwarding entry applies, the corresponding Flexiport script is triggered. The script stores the MAC address of the recognized device in the dynVLAN membership table.

Dynamic MAC addressesMaximum four MAC addresses can be stored in the dynVLAN membership table. As a result, a maximum of four devices can simultaneously make use of dynamic VLANs (and thus of Flexiport). If a fifth device needs to be connected, the dynVLAN membership table should not store the MAC addresses. Since release R6.1, there is a parameter dynamic in the Flexiport script to enable dynamic MAC addresses.

If the parameter is disabled, the MAC address is stored in the dynVLAN membership table. By default, the parameter is disabled.

=>:dhcp relay ruleadd name=video_to_DHCP rulename=STB

=>:dhcp relay ruleadd name=LocalNetwork_to_127.0.0.1 rulename=notSTB=>:dhcp relay ruleadd name=LocalNetwork_to_127.0.0.1 rulename=notVOIP key=and

=>:dhcp relay ruleadd name=video_to_DHCP rulename=STB=>:dhcp relay ruleadd name=video_to_DHCP rulename=VOIP key=or

=>:script add name=dhcr_video index=0 command=“eth bridge dynvlan add hwaddr $1 vlan video”

The script must start with dhcr_ in order to work.

=>:dhcp relay modify name=video_to_DHCP script=video

Here, the name of the script must be entered without the dhcr_ prefix.

=>:eth bridge dynvlan listID MAC Address VLAN RemVLAN (* = dynamic)-- ----------- ---------- ----------0 00:0f:1f:00:00:11 video (none)

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If the parameter is enabled, the MAC address is not stored in the dynVLAN membership table. This allows that more than four devices make use of the Flexiport mechanism. In addition, if the Thomson Gateway reboots, the entries are removed from the dynVLAN membership table.

For example, following Flexiport script enables the use of dynamic MAC addresses:

If this script is triggered, an entry is added to the dynVLAN membership table. The asterisk indicates that a dynamic MAC address is used:

Parameter remVLANIn most scenarios, the Flexiport script moves the MAC address of a STB to a separate VLAN. However, it is also possible that the MAC address of a data PC (e.g. connected to LAN port ethport3) is moved to a separate VLAN and the STB (e.g. connected to LAN port ethport1) remains in the default VLAN. In this case, the dynVLAN membership table and the resulting VLAN membership information look as follows:

Following behaviour can be expected: when the STB requests a multicast video stream, these video packets are also sent out on ethport3 and thus are received by the data PC. This is unwanted behaviour. To obtain the desired behaviour, there is a parameter remvlan in the Flexiport script to explicitly remove the MAC address from a specific VLAN. If the data PC is removed from the default VLAN, it does not receive any multicast packets. For example, following Flexiport script uses the remvlan parameter:

In this case, the dynVLAN membership table and the resulting VLAN membership information look as follows:

=>:script add name=dhcr_video index=0 command=“eth bridge dynvlan add hwaddr $1 vlan video dynamic enabled”

=>:eth bridge dynvlan listID MAC Address VLAN RemVLAN (* = dynamic)

-- ----------- ---------- ----------0 00:0f:1f:00:00:55 video (none) *

=>:eth bridge dynvlan listID MAC Address VLAN RemVLAN (* = dynamic)-- ----------- ---------- ----------50 00:19:b9:2d:0f:c1 data (none)

=>:eth bridge vlan iflistVid Name Bridge interfaces (* = untagged)--- ---- --------------------------------1 default OBC*, ethport1*, ethport2*, ethport3*, ethport4*, WLAN*, wan_video2 data ethport3*

=>:script add name=dhcr_video index=0 command=“eth bridge dynvlan add hwaddr $1 vlan data remvlan default”

=>:eth bridge dynvlan listID MAC Address VLAN RemVLAN (* = dynamic)-- ----------- ---------- ----------50 00:19:b9:2d:0f:c1 data default

=>:eth bridge vlan iflistVid Name Bridge interfaces (* = untagged)--- ---- --------------------------------1 default OBC*, ethport1*, ethport2*, ethport4*, WLAN*, wan_video2 data ethport3*

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Chapter 3

3 AutoWAN Port for Bridged Multicast

3.1 Scenario Overview

IntroductionIn this scenario, we configure the Thomson Gateway with a single PVC and an Ethernet WAN port. The PVC or Ethernet WAN port can be used for:

Data traffic via a routed Internet connection.

Bridged multicast traffic.

Following illustration shows the scenario “AutoWAN port for bridged multicast”:

MechanismsTo set up this scenario, we use following mechanisms:

VLANs: the use of VLANs results in a Layer 2 isolation of the STB and the other LAN devices. We use two VLANs:

Video: this VLAN contains all WAN interfaces and all STBs. By default, all devices are a member of this VLAN.

Routed: this VLAN contains all non-STB devices. By default, only OBC is a member of this VLAN. All non-STB devices are switched from the video VLAN to the routed VLAN.

Flexiport: this mechanism is used to automatically map the MAC addresses of non-STB devices to the routed VLAN.

Video Network IP

Internet

BRAS

DHCP Server

Video Server

Video Network

DSLAM

RoutedConnection

BridgedEthernet

Connection

NATed IP

Private IPfrom DHCP Pool

Thomson Gateway

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Chapter 3

3.2 Practical Realization

Configuration overviewFollowing configuration steps have to be performed to configure the Thomson Gateway for this scenario:

1 Configure the interfaces for the routed PPPoE Internet connection.

2 Create the necessary VLANs.

3 Configure the Flexiport mechanism.

4 Configure VLAN membership of the bridge ports.

5 Disable IGMP snooping.

6 Save the configuration.

Before you startBefore you start to configure the Thomson Gateway, make following preparations:

Reset the Thomson Gateway to the factory defaults and reboot the device.

Make sure the telnet session with the Thomson Gateway never times out.

Remove the factory default interfaces and settings that you do not need for the configuration.

Make these changes permanent. Now, you can start from a clean situation.

PVC and ATM interfaceProceed as follows:

Create a phonebook entry for the PVC (the VPI/VCI value is indicative):

Create the ATM interface on top of the phonebook entry:

=>:system reset factory=yes proceed=yes

=>:env set var=SESSIONTIMEOUT value=0

=>:ppp relay flush=>:ppp flush=>:eth flush=>:atm flush=>:atm phonebook flush=>:ip ipdelete addr=10.0.0.138

=>:saveall

=>:atm phonebook add name=pvc038 addr=0.38

=>:atm ifadd intf=atm038=>:atm ifconfig intf=atm038 dest=pvc038 encaps=llc ulp=mac=>:atm ifattach intf=atm038

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Ethernet bridge portProceed as follows:

Create an Ethernet bridge port and connect it to the ATM interface:

VLANsProceed as follows:

Make the Ethernet bridge VLAN aware:

Create the video VLAN and the routed VLAN:

Place the OBC bridge port in both the video VLAN and the routed VLAN:

Place all the Ethernet bridge ports in the video VLAN:

Remove all Ethernet bridge ports except the Ethernet WAN port from the default VLAN:

Logical Ethernet interfacesProceed as follows:

Create the routed Ethernet interface and assign it to the routed VLAN on the bridge:

=>:eth bridge ifadd intf=br038=>:eth bridge ifconfig intf=br038 dest=atm038=>:eth bridge ifattach intf=br038

=>:eth bridge config vlan=enabled filter=none

=>:eth vlan add name=routed vid=2=>:eth vlan add name=video vid=9

=>:eth bridge vlan ifadd intf=OBC name=routed=>:eth bridge vlan ifadd intf=OBC name=video

=>:eth bridge vlan ifadd intf=ethport1 name=video=>:eth bridge vlan ifadd intf=ethport2 name=video=>:eth bridge vlan ifadd intf=ethport3 name=video=>:eth bridge vlan ifadd intf=ethport4 name=video=>:eth bridge vlan ifadd intf=br038 name=video

=>:eth bridge vlan ifdelete intf=ethport1 name=default=>:eth bridge vlan ifdelete intf=ethport2 name=default=>:eth bridge vlan ifdelete intf=ethport3 name=default=>:eth bridge vlan ifdelete intf=br038 name=default

=>:eth ifadd intf=eth_routed=>:eth ifconfig intf=eth_routed dest=bridge vlan=routed=>:eth ifattach intf=eth_routed

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Chapter 3

Create the video Ethernet interface and assign it to the video VLAN on the bridge:

IP LAN interfaceProceed as follows:

Create the routed IP interface as an IP LAN interface connected to the routed Ethernet interface:

Assign an IP address to the IP interface:

Attach the IP interface:

IP WAN interfaceCreate the video IP interface as an IP WAN interface connected to the video Ethernet interface:

Assign an IP address to the IP interface:

Enable NAT on the video PPPoE interface:

Attach the PPPoE interface:

DHCP clientProceed as follows:

Configure the DHCP client for the IP WAN interface:

=>:eth ifadd intf=eth_video=>:eth ifconfig intf=eth_video dest=bridge vlan=video=>:eth ifattach intf=eth_video

=>:ip ifadd intf=ip_routed dest=eth_routed=>:ip ifconfig intf=ip_routed group=lan linksensing=enabled

=>:ip ipdelete addr 192.168.1.254=>:ip ipadd intf=ip_routed addr=192.168.1.254/24 addroute=enabled

=>:ip ifattach intf=ip_routed

=>:ip ifadd intf=ip_video dest=eth_video=>:ip ifconfig intf=ip_video group=wan linksensing=enabled

=>:ip ipadd intf=ip_video addr=10.0.0.138/24 addroute=enabled

=>:nat ifconfig intf=ip_video translation=enabled

=>:ip ifattach intf=ip_video

=>:dhcp client ifadd intf=ip_video=>:dhcp client ifconfig intf=ip_video metric=10 dnsmetric=10=>:dhcp client ifattach intf=ip_video

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DHCP poolsProceed as follows:

Create a DHCP server pool for the routed network:

Dynamic VLAN membership checkingProceed as follows:

Enable dynVLAN membership checking on the three Ethernet bridge ports:

DHCP relay forwarding entriesProceed as follows:

Enable configuration of the DHCP relay interfaces:

Create a first DHCP relay forwarding entry that will check the MAC address of the device in the DHCP request. If the MAC address of the device matches the MAC address in the rule, the Flexiport script is triggered:

Create a second DHCP relay forwarding entry that will forward a new DHCP request towards the internal DHCP server:

DHCP rulesProceed as follows:

Create a DHCP rule for the STB:

Assign this DHCP rule to the correct DHCP relay forwarding entry:

=>:dhcp server pool flush=>:dhcp server pool add name=LAN_private index=0=>:dhcp server pool config name=LAN_private intf=ip_routed poolstart=192.168.1.64 poolend=192.168.1.253 netmask=24 gateway=192.168.1.254 server=192.168.1.254 primdns=192.168.1.254 leasetime=7200

=>:eth bridge ifconfig intf=ethport1 dynvlan=enabled=>:eth bridge ifconfig intf=ethport2 dynvlan=enabled=>:eth bridge ifconfig intf=ethport3 dynvlan=enabled

=>:dhcp relay ifconfig intf=ip_routed relay=enabled=>:dhcp relay ifconfig intf=ip_video relay=enabled=>:dhcp relay ifconfig intf=LocalNetwork relay=disabled

=>:dhcp relay add name=switch_routed=>:dhcp relay modify name=switch_routed addr=127.0.0.1 intf=ip_video

=>:dhcp relay add name=routed=>:dhcp relay modify name=routed addr=127.0.0.1 intf=ip_routed giaddr=192.168.1.254

=>:dhcp rule add name ROUTED type mac mac=!00:0f:1f:83:d7:5b

=>:dhcp relay ruleadd name=switch_routed rulename=ROUTED=>:dhcp relay ruleadd name=routed rulename=ROUTED

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Flexiport scriptProceed as follows:

Create a flexiport script to move the MAC address of every device that is not a STB to the routed VLAN and remove it from the video VLAN:

Assign the script to a DHCP relay forwarding entry:

Disable IGMP snoopingProceed as follows:

Disable IGMP snooping:

Save the configurationProceed as follows:

To make your changes permanent, save the configuration:

=>:script add name=dhcr_routed index=0 command="eth bridge dynvlan add hwaddr $1 vlan routed remvlan video"

=>:dhcp relay modify name=switch_routed script=routed

=>:eth bridge igmpsnooping config state=disabled

=>:saveall

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3.3 Result

Following illustration shows the resulting configuration of the Thomson Gateway:

If the PVC is used as WAN connection, the DHCP client and the STB receive an IP address via the WAN PVC bridge port (this case is shown in previous illustration).

If the Ethernet interface is used as WAN connection, the DHCP client and the STB receive an IP address via the WAN Ethernet bridge port.

br038...

DHCP ServerLAN_private

192.168.1.[64-253]

DHCP Relay

IP ip_video

ATM atm038

PVC pvc0380.38

OBC

video (vid=9)

3 42

Router

IP ip_routed

ethport

PC STB

ETH eth_video

Bridge

1

192.168.1.254

Flexiport

public IP address

routed (vid=2)

ETH eth_routed

10.0.0.138

DHCP Client

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Copyright

©2008 THOMSON. All rights reserved. The content of this document is furnished for informational use only, may be subject to change without notice, and should not be construed as a commitment by THOMSON. THOMSON assumes no responsibility or liability for any errors or inaccuracies that may appear in this document. The information contained in this document represents the current view of THOMSON on the issues discussed as of the date of publication. Because THOMSON must respond to changing market conditions, it should not be interpreted to be a commitment on the part of THOMSON, and THOMSON cannot guarantee the accuracy of any information presented after the date of publication. This document is for informational purposes only. THOMSON MAKES NO WARRANTIES, EXPRESS OR IMPLIED, AS TO THE INFORMATION IN THIS DOCUMENT. The names of actual companies and products mentioned herein may be the trademarks of their respective owners.