Operation Manual

SFX SERIES USER’S GUIDE
Rev 2.2 49
In addition to the edit fields there are four table row manipulation keys:
Key Description
Add Add the entered information above the table to the table as the last row.
Remove Delete the selected (highlighted) row.
Up If there is more than one row in the table, move the selected row up one row.
Down If there is more than one row in the table, move the selected row down one row.
Multicast Routing
The Multicast Routing submenu maintains the multicasting routing table associated with the receiver. Each receiver
can support up to 200 multicast routes. The multicast routing function is responsible for managing multicast packets
that are traveling through the receiver (host), from external interface to external interface. It is not responsible for
managing multicast packets that are delivered to an application running on the receiver, but the two functions are inter-
related.
Multicast packets are routed through the host according to a multicast routing table that is maintained by the Linux
kernel. Initially, this table is empty and incoming multicast packets are routed according to a default route.
Multicast Routing follows a number of rules, as described in the list below. Many rules are best described by
examples. Many of these rules are more important where a number of local applications may be consuming multicast
packets (e.g. a streaming media decoder
).
1. IP packets can originate from any of the available network interfaces and are processed by the receiver in
accordance with the data flow in Figure 2- 12.
2. Up to 200 routes may be entered in the Multicast Routing Table, and order doesn’t matter, assuming that
routes don’t overlap.
3. For assigned routes, IGMP is supported.
4. If a multicast packet is received, whose source IP Address matches the IP Address of one of the receiver’s
network interfaces, that packet is discarded regardless of the current multicast routing rules. This happens
because the receiver assumes it is involved in a multicast loop. For a normal device, this behavior does not
pose a problem, but in a satellite environment, care must be taken to ensure that the source IP address of a
multicast source at the head end does not match the source IP address of any receiver .
The following rules and examples are specialized and are applicable only for Users who are developing their
own applications for the SFX series receivers.
5. Local Application Rule 1
: A multicast route is not required in order for a local application program running on
the receiver to receive multicast packets. However, a static route may be needed so that the program can
properly set up a receiving socket. For example, if a program needs to receive multicast data on 224.1.1.1
from the sat0 interface, the following static route must be entered (see Static Routing section of this manual):
Interface: sat0
Gateway: 0.0.0.0
Destination: 224.1.1.1
Netmask: 255.255.255.255
or the more general route could be entered: