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Quantitative Finance · Begrippenlijst

Wat is IGMP snooping?

Definition 1.7 Networks, Hardware and Trading Infrastructure · Hoofdstuk 1 — Networking for Trading

IGMP snooping is a switch’s practice of reading the IGMP membership reports that cross it and forwarding each group’s traffic only to the ports on which a member has reported, instead of flooding every multicast frame to every port.

IGMP snooping. The switch learns from the servers’ membership reports which ports want which group and replicates each group only to them; server 4 receives nothing. Without snooping, all four ports would carry both groups, and servers that joined nothing would still spend their cards’ and kernels’ time discarding them.
Figure 1.2. IGMP snooping. The switch learns from the servers’ membership reports which ports want which group and replicates each group only to them; server 4 receives nothing. Without snooping, all four ports would carry both groups, and servers that joined nothing would still spend their cards’ and kernels’ time discarding them.

Voorbeelden

Example 1.8 (Two groups, one Ethernet address)

Group 239.255.1.2 maps to 01:00:5e:7f:01:02: the low 23 bits of 255.1.2 are 127.1.2 once the top bit of 255 is dropped. Group 224.127.1.2 maps to the same address. A server that joined only the first receives, from any switch or card that filters by Ethernet address alone, the traffic of the second as well. Venues allocate their groups with this in mind, and a firm that runs its own internal multicast (chapter 27’s ticker plant) should too.

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