Hardware IP Multicast Forwarding
If your network uses smart routers, you can configure your network to filter out unwanted data packets at the router-level such that machines further down the network pipe never receive the packets. This is called hardware IP multicast forwarding and is based also on the subscription process:
- If a router that connects two networks does not have a node that subscribes to a multicast, it ignores those multicasts and does not pass the information to the other network segment.
- If the router has nodes that subscribe to a multicast and the router receives this multicast, the router passes it onto the other network.
In the context of TT Trading Systems, native IP multicast and TTM express subscriptions differently:
- IP Multicast: Uses numeric group IDs (i.e., Class D IP addresses, 126.96.36.199 through 188.8.131.52). This manual refers to these IDs as multicast addresses.
- TTM: In addition to using multicast addresses, TTM further refines its network communications by assigning subscription identifiers. This manual refers to subscription identifiers as multicast subjects, or more simply as ‘subjects.’ By default, TTM broadcasts all subjects on the same multicast address.
Considerations on Use
Depending on the type of network interconnect you have, TT recommends that you use the following techniques to send data packets between network segments:
- Low-speed interconnects: Forward TT communications using WAN Routers with TT's middleware. In this manner, you can further refine information that gets passed across networks using TT's middleware subscription identifiers. Network segments separated by WAN Routers become unique multicast domains. Each multicast domain can contain multiple network segments as long as they use high-speed interconnects and IP multicast forwarding.
- High-speed interconnects: Pass along TT communications
using IP multicast forwarding at the hardware router level. Examples
of high-speed interconnects include:
- Multiple (Fast) Ethernet segments connected to the same router
- High-speed WAN links (e.g., (fractional) DS3)
The following network devices might not support IP multicast forwarding:
- Older routers
- Low-quality routers (i.e., non-brand name)
For information on configuring your hardware to support IP multicast forwarding, refer to Multicast and Hardware Setup.