Multicast architecture in Linux

1
Multicast architecture in Linux
Laurentiu Barza
Feb. 22, 2001
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Conformance levels

• Level 0 no support for multicast
• Level 1 sending, but not receiving
• Level 2 full support for IP multicasting

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Linux multicast routing forwarding
(4)
Linux kernel
Forwarding
(3)
(1)
(2)
Multicast routing algorithm
Multicast routing table
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Linux multicast programming
int setsockopt (int s, int level, int optname,
const void optval, int optlen) int getsockopt
(int s, int level, int optname, void optval,
int optlen) s the socket the system call
applies to level layer which handle the
option optname identifies the option we are
setting/getting optval the value taken by the
option optlen the size of data structure
optval
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Linux multicast programming

• The optname values involved in multicast
  programming
• IP_MULTICAST_IF set/get IP multicast
  interface.
• IP_MULTICAST_TTL set/get IP multicast ttl
• IP_MULTICAST_LOOP set/get IP multicast
  loopback
• IP_ADD_MEMBERSHIP add an IP group membership
• IP_DROP_MEMBERSHIP drop an IP group membership

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Linux multicast programming- IGMPv3 specific
options -

• For some applications all the sources are
  accepted, for others only souces in a given list
  are allowed.
• IP_BLOCK_SOURCE mute a specific source
• IP_UNBLOCK_SOURCE un-mute the source
• IP_ADD_SOURCE_MEMBERSHIP add a specific
  source
• IP_DROP_SOURCE_MEMBERSHIP drop a specific
  souce
• IP_DROP_MEMBERSHIP drop all sources
• IP_MULTICAST_FILTER set multicast filter

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MGEN test tool

• IP network performance measurements using UDP/IP
  unicast and multicast traffic
• generate real traffic patterns periodic, poisson
• possibility to control packet size and
  transmission rate, RSVP, TOS settings
• fixed-parameter mode, script mode
• distributed with utility programs parses log
  files and outputs statistics

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MGEN test scenarios

• Unicast source -gt receiver
• Multicast one-to-one
• Multicast one-to-many all the receivers in the
  same network
• Multicast one to many the receivers are in
  different networks

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SSM current developments

• IGMPv3 by Sprint
• IGMPv3 lite by Cisco
• solution for application developers to
  immediately start programming SSM applications
• URD host signaling
• allows existing IP multicast receiver
  applications to be used with SSM without the need
  to modify the application

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Future work

• Context the Internet is changing
• Content Distribution Networks (CDN) an overlay
  for the Internet
• performance lower latency
• bandwidth arbitrage push the content where the
  bandwidth is cheaper
• flash crowd control load balancing
• bandwidth multiplication

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Future work

• Utilize multicast (SSM) in CDN networks

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