This document discusses multicast in OpenStack. It begins by defining multicast as one-to-many communication driven by receivers using a multicast IP address, without the need for the sender to duplicate packets. It then outlines the components of multicast including addressing, group management using IGMP, and multicast routing. The document notes that while OpenStack does not natively support multicast, it is possible to enable it by configuring IGMP snooping, security groups, and using plugins like Cisco's ASR1k and ACI drivers for Neutron. It recommends using provider networks without Neutron routing or these plugins to implement multicast routing externally. Finally, it discusses some multicast use cases and limitations.

1. Multicast in OpenStack
Vikram Hosakote
vhosakot@cisco.com
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2. What is multicast?
• One-to-many communication
• Driven by receivers
• A multicast “group” is identified by a multicast IP address
• Without multicast, sender must duplicate each packet
• Analogy: TV and radio broadcasting
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3. What is multicast?
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4. Components of multicast
• Multicast addressing
Group addresses range from 224.0.0.0 to 239.255.255.255 (class D
addresses)
Mac addresses range from 01-00-5E-00-00-00 to 01-00-5E-7F-FF-FF
• Multicast group management (IGMP)
• Multicast routing and IGMP querying
• Multicast clients
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5. Multicast use cases
• One-to-many corporate communications such as
Employee training videos
Quarterly company meetings
Company-wide corporate communications
Executive announcements
• Music/media streaming
• Video podcasts
• IPTV services
• One-to-many software updates/patches
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6. Multicast use cases
• Social networking (Facebook, Twitter feeds, Instagram)
• Financial services, banks, stock exchange
• Government/Federal agencies
• RTP (Real Time Protocol) applications
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7. Multicast in OpenStack
• No multicast available out-of-the-box
• Open vSwitch 2.5 supports IGMP snooping
• Linux Bridge 2.4 supports IGMP snopping
• Neutron router (L3-Agent) does not support multicast
routing, PIM and querying
• No CLI or API to configure multicast
• Multicast cannot be configured in Horizon
• Anti-spoofing rules and security groups drop multicast
packets
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8. How to do Multicast in OpenStack?
• Enable IGMP snooping in OVS/Linux bridge
• Add rules to allow multicast UDP port in security groups
• Disable neutron port-security for ports in multicast path
• Use neutron’s --allowed-address-pairs attribute
and allow multicast IP and MAC addresses
• SR-IOV ports may also be used
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9. How to do Multicast in OpenStack?
Three recommendations:
1. Use provider networks without neutron router (L3-agent)
and do multicast routing on upstream L3 devices connected
to TOR outside OpenStack
2. Use Cisco’s ASR1k plugin for neutron instead of L3-agent
3. Use Cisco’s ACI and APIC driver for neutron
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10. Provider networks
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11. ASR1k plugin for neutron
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12. ACI and APIC driver for neutron
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13. UCSM multicast policy
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14. ACI/APIC multicast policy
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15. Multicast for media applications
• Cisco’s video conferencing apps – Telepresence, Webex,
Jabber
• Cisco’s video and collaborations apps – Virtualized Video
Processing (V2P), Videoscape AnyRes, IPTV devices, video
encoders and video surveillance
• VLC player http://www.videolan.org/projects/multicat.html
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16. Multicast limitations
• IGMP snooping degrades performance of layer-2 switch
• High bandwidth multicast traffic degrades unicast routing
• Needs plugin (ASR1k, APIC) integration with neutron
• Best-effort and out-of-sequence delivery (UDP is unreliable)
• Lack of TCP windowing results in network congestion
• Duplicate packets and occasional loops when unicast routing
is broken
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17. Multicast testing tools
• Iperf - https://iperf.fr
• Nuttcp - http://www.nuttcp.net
• OpenStack VMTP - https://github.com/openstack/vmtp
• OpenStack Kloudbuster -
https://github.com/openstack/kloudbuster
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18. Multicast talk in Cisco Live Las Vegas 2016
http://www.slideshare.net/Vikram_Hosakote/multicast-in-openstack
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19. Q & A
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