Sept 28, 2004CS573: Network Protocols and Standards D – Selective Multicast Network Protocols and Standards Autumn

Sept 28, 2004CS573: Network Protocols and Standards2 Selective Multicast: Reasons Part of IEEE 802.1D standard Problems Broadcasting of multicast traffic over slower links  Link Saturation Even for networks with all high speed links, transmitting something that no one will use is not a good idea  Multicast volume is unlimited Solution Allow users to explicitly indicate their interest in receiving traffic on given multicast addresses

Sept 28, 2004CS573: Network Protocols and Standards3 The Filtering Database Bridge B1 Filtering Database A’s MAC Address10B’s MAC Address01C’s MAC Address10 Port 1Port 2 0: filtering 1: forwarding Outbound Port 1 Outbound Port 2 ACB Frame: A  B Frame: A  C A bridge maintains a forwarding database (FDB) which it uses to decide where to send the incoming packet

Sept 28, 2004CS573: Network Protocols and Standards4 The Filtering Database The filtering database contains filtering entries that can be: Static Entries – explicitly configured by the administrator and management Dynamic Entries – automatically entered into the FDB by the normal operation of the bridge Each entry (static or dynamic) consists of: A MAC address specification A port map which specifies the filtering state for that MAC address on each outbound port

Sept 28, 2004CS573: Network Protocols and Standards5 Basic Filtering Services An 802.1D bridge must support these services Allow the specification of the following FDB entries: For individual MAC addresses Static entries  Management Dynamic entries  Learning Process For a specific group MAC address Static entries  Management No static entry  Broadcast These entries indicate, for each outgoing port, if the frames destined for the individual or group LAN addresses be forwarded or filtered

Sept 28, 2004CS573: Network Protocols and Standards6 Extended Filtering Services Add the following capabilities to the basic filtering services For individual addresses Static entries may contain a value which indicates that the dynamic filtering information should be used for a specific port rather than always forward or always filter For a specific group MAC address Static entries may contain a value which indicates that the dynamic filtering information should be used Group registration entries that are created and maintained through the use of GMRP protocol Entries corresponding to all group addresses which do not have a specific group MAC address entry Entries corresponding to all unregistered group addresses which do not have a specific group MAC address entry

Sept 28, 2004CS573: Network Protocols and Standards7 Default Group Filtering Behavior Each port may be assigned a default behavior for forwarding frames with group MAC addresses Three default behaviors have been defined: Forward all groups: Frame is forwarded unless an explicit static filtering entry exists Forward all unregistered groups: The frame is forwarded unless: An explicit static filtering entry exists An applicable group registration entry exists Filter unregistered groups: The frame is filtered unless: An explicit static forwarding entry exists An applicable group registration entry exists

Sept 28, 2004CS573: Network Protocols and Standards8 GMRP GARP Multicast Registration Protocol A mechanism that allows: End stations to dynamically register (and subsequently de- register) group membership information with the MAC bridges attached to the same LAN segment Bridges to disseminate that information across all bridges in the bridged LAN that support extended filtering services Operation of GMRP depends upon the services provided by GARP (Generic Attribute Registration Protocol)

Sept 28, 2004CS573: Network Protocols and Standards9 Result of Group Membership Information Registration and Propagation Frames sent to a particular group: Can be received on all LAN segments to which registered GMRP participants are attached Bridges filter frames on ports which have not had group registration entries created by GMRP Multicast frames are not transmitted on those LAN segments which: Neither have registered GARP participants Nor are in the path, through active topology, from source to registered members