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--- fintech:multicast [2023/04/01 18:28] – jotasandoku
+++ fintech:multicast [2025/05/18 10:02] (current) – jotasandoku
@@ Line 1: / Line 1: @@
-  * Cisco fintech architecture: MDNA [[https://www.cisco.com/c/dam/en_us/solutions/industries/docs/finance/md-arch-ext.pdf|External_Link]]
+  * Multicast summary [[https://chatgpt.com/s/dr_6829afd200848191914e65c55e127de2|External_Link]]
 TECH NOTES:
@@ Line 29: / Line 29: @@
     * “BLOCK_OLD_SOURCE” Record type 6 indicating it is no longer interested to hear multicast traffic to that group from specific host.
-MEMBERSHIP-QUERY:\\
+MEMBERSHIP-QUERY (igmp query):\\
   * Sent by the last hop router. Normally when a listener has left a group and it wants to know if there are still anybody in there interested on the group.
   * General Query – to learn complete multicast reception state of the neighboring interface. Sent to 224.0.0.1
@@ Line 71: / Line 71: @@
 ----
 **Remember: dynamic RPs are preferred to statically defined**
-\\
+  * __BSR__: IEEE standard  where multicast control rely entirely on the PIM packets. So no special configs required to advertise RP when yo configure network to pim sparse-mode.
-__BSR__: IEEE standard  where multicast control rely entirely on the PIM packets. So no special configs required to advertise RP when yo configure network to pim sparse-mode.
+  * __AUTO-RP__: Having multiple candidates for the role of RP and mapping agent greatly enhances the redundancy of the PIM-SM network. Redundancy reduces the risk of groups (configured in sparse-dense mode) reverting to dense mode operation if an RP cannot be located. To eliminate this risk, we recommend configuring a sink RP on every router in the network. [[https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/White_papers/rps.html#wp1038139|Link]]
-\\
+  * __ANYCAST RP__ : In practice, anycast is preferred over bsr/auto-rp
-__AUTO-RP__: Having multiple candidates for the role of RP and mapping agent greatly enhances the redundancy of the PIM-SM network. Redundancy reduces the risk of groups (configured in sparse-dense mode) reverting to dense mode operation if an RP cannot be located. To eliminate this risk, we recommend configuring a sink RP on every router in the network. [[https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/White_papers/rps.html#wp1038139|Link]]
+    * Classical anycast: lo100 (shared loopback), msdp betweeen lo0 shared 'sa' state about sources.
-\\
+    * PIM-based anycast (RFC 4610): lo100 (shared loopback). State is shared in the PIM messages themselves. Requires this command ''ip pim anycast-ip <lo100-IP> <member-N-IP>''
-__ANYCAST RP__ : In practice, anycast rp with msdp is preferred over bsr/auto-rp
+  * __SSM__: Is becoming very popular. No RP, all SPT, a little less of state. Requires IGMPv3
-\\
+  * __BIDIR__: ONLY SHARED TRESS (*,G) - central bidirectional RP which is ALWAYS in the datapath
-__SSM__
+    * Bidir would not use source trees to better scale its routing table, so a new mechanism is required for Bidir sources to reach the rendezvous point. This new mechanism is called the designated forwarder (DF).
-\\
+    * There’s no SPT switchover.
-__BIDIR__: ONLY SHARED TRESS (*,G) - central bidirectional RP which is ALWAYS in the datapath
+    * No RPF so traffic can go in both directions.
-\\
+    * In absence of the above, loops are prevented by having a, fixed, DF router.
-Bidir would not use source trees to better scale its routing table, so a new mechanism is required for Bidir sources to reach the rendezvous point. This new mechanism is called the designated forwarder (DF).
+    * DF (designated forwarder) we have one per segment (no per group so several in the way from source to the DR). Role of the DR as well as its election (remember higher IP wins for DR, lower for querier) is important. This is because the DR is the ONLY one forwarding data upstream PER SEGMENT (ie per Ethernet segment, therefore there can be several DRs from  Rest do it downstream only.
-There’s no SPT switchover.
-\\
-No RPF so traffic can go in both directions.
-\\
-In absence of the above, loops are prevented by having a, fixed, DF router.
-\\
-DF (designated forwarder) we have one per segment (no per group so several in the way from source to the DR). Role of the DR as well as its election (remember higher IP wins for DR, lower for querier) is important. This is because the DR is the ONLY one forwarding data upstream PER SEGMENT (ie per Ethernet segment, therefore there can be several DRs from  Rest do it downstream only.
@@ Line 101: / Line 94: @@
   * DESIGNATED ROUTER: Routers configured for IP multicast send PIM hello messages to determine which router will be the designated router (DR) for each LAN segment (subnet). The hello messages contain the router's IP address, and the router with the **highest IP address becomes the DR**
     * in each LAN segment where one or more multicast enabled routers are connected to you can see the three roles of PIM DR, IGMP querier, PIM forwarder.
-      * **PIM DR has to represent the LAN segment/broadcast domain in the PIM tree topology so it is responsible to contact the RP in PIM SM or sparse-dense mode.**
+  * PIM FORWARDER: Is different. When data can be sent to a receiver via two different routers, there's an 'ASSERT' election process to choose one of them, this becomes the pim forwarder
   * QUERIER: When a multicast-enabled router first becomes active on a subnet, it assumes that it is the Querier — the router responsible for sending all General and Group-Specific Queries to the subnet. When there are multiple routers, the rule for electing the Querier is simple: The router whose connected interface has the **lowest IP address is the Querie**. [[http://www.bscottrandall.com/5.1.3.html]]
   show ip igmp snooping querier
@@ Line 220: / Line 214: @@
 **__SERVER SIDE TOOLS (generate multicast traffic):__**\\
-If we cannot install anything but we have pyton, we can paste this script
+If we cannot install anything (and we have pyton3 we can paste these scripts:
+GENERATING MULTICAST TRAFFIC
   #!/usr/bin/python3
   import socket
@@ Line 240: / Line 236: @@
   while true; do ./msend.py; sleep 2; done
-If we can install ''IPERF'':
+SUBSCRIBING TO MULTICAST STREAM
+  #!/usr/bin/python3
+  import socket
+  import struct
+  import sys
+  multicast_group = '239.1.1.1'
+  server_address = ('', 5007)
+  # Create the socket
+  sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+  # Bind to the server address
+  sock.bind(server_address)
+  # Tell the operating system to add the socket to the multicast group
+  # on all interfaces.
+  group = socket.inet_aton(multicast_group)
+  mreq = struct.pack('4sL', group, socket.INADDR_ANY)
+  sock.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, mreq)
+  while True:
+      print('\nwaiting to receive message', file=sys.stderr)
+      data, address = sock.recvfrom(1024)
+      print('\nreceived ' + str(len(data)) + ' bytes from ' + ''.join(str(address)), file=sys.stderr)
+      print(data, file=sys.stderr)
+ #    string = "AcK"
+ #    string_utf = string.encode()
+ #    print('\nsending ack to  ' + ''.join(str(address)), file=sys.stderr)
+ #    sock.sendto(string_utf, address)
+If we can, install ''IPERF'':
   iperf -c 224.0.0.1 -u -B 10.1.0.54 -t 3600 -T 255 # traffic for this group from this address (needs to belong to the switch)
@@ Line 253: / Line 278: @@
   * pim cannot be enabled in loopback interfaces. Nonetheless is not required to enable RP.
-This is for static and BSR RP:
+  ! This is for static and BSR RP:
   interface Vlan100
      ip address 10.1.8.3/24
@@ Line 278: / Line 303: @@
     spt-threshold infinity
     ssm disable
+----
+__IPV6 MULTICAST__
+  * PIM > IPv6 PIM
+  * **IGMPv2 > MLDv1**
+  * **IGMPv3 > MLDv2**
+  ipv6 multicast-routing
+  show ipv6 mroute
+  !
+  show ipv6 pim neighbor
+  !
+  show ipv6 mld group
+  show ipv6 mld interface g0/0
+  show ipv6 mld traffic
 ----

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