Date: 31 May 96 07:46:59 EDT From: Tony Jeffree <100271.522@CompuServe.COM> To: 802-1 , JoAnn Larson Subject: 802.1p/D3 Ballot SUBJECT: P802.1p/D3 - Traffic Class and Dynamic Multicast Filtering Services in Bridged LANs __X___ I disapprove for the following reasons. Tony Jeffree 1. Technical comments --------------------- Comment 1: The last paragraph of 2.6.1 indicates that it is permissible to mix Mode 1 and Mode 2 working in the same Bridge. This is incorrect, and conflicts with the statements about mode configuration that are made in 2.6.6. Re-word the paragraph as follows: "All Bridges shall support Basic Filtering Services. Support of Extended Filtering Services by a Bridge is optional." Comment 2: The current definitions of Filtering Modes 1 and 2 operation do not easily allow for the integration of "legacy" end stations into an 802.1p Bridged LAN. In particular, legacy nodes may become disenfranchised if they make use of Groups that have been registered by GARP-aware nodes on other LAN segments. In order to fix this, and also to make life easier for devices such as Routers that require promiscuous reception, I propose the following changes: - In 2.6.6., add a third sub-mode, and re-label the sub-modes, as follows: a) Sub mode A: Forward All Addresses. This is the "legacy compatibility" mode. In this submode, the Forwarding Process operates as for Filtering Mode 1; b) Sub mode B: Forward All Unregistered Addresses. <> c) Sub mode C: Filter All Unregistered Addresses. <> - In 9.6.2, modify the operation of the Registrar state machine such that if the default sub-mode of a Port is C, any occurence of "rJoin & no FD space available" forces the default sub-mode to B. - In 9.6.3, modify the operation of the Leave All state machine, such that: a) Recieving a Join All Groups PDU forces a switch from sub-modes B or C to sub-mode A; b) Receiving any other Join All PDU forces a switch from sub-mode C to sub-mode B; c) Receipt of a LeaveAll causes a Join All Groups to be sent if any other Port is in 2A, or a Join All Unregistered Groups if any other Port is in 2B; d) Not receiving a Join All Groups PDU (but recieving any other type of Join All) during an entire Leave All Period allows the sub-mode to return to B IF the default sub-mode is B or C; e) Not receiving any Join All during an entire Leave All Period allows the sub-mode to return to C IF the default sub-mode is C. - Modify the description at the front of section 9, and the text in E2 and E3, to reflect the way these three sub-modes should be used. The main points are: a) Legacy end stations should in general not be mixed on the same segment with GARP-aware end stations. Clearly, this cannot be enforced, but the text should make it clear as to the consequences (for the legacy nodes) of mixing old & new; i.e., the legacy nodes potentially lose connectivity. The default submode for any Ports serving legacy segments should be configured by management to be 2A; b) The default submode for Ports serving GARP-aware devices should be set to 2B or 2C according to the requirements of those devices, and other considerations such as the FDB size; c) Devices such as routers that need a degree of promiscuous reception have the choice of using mode 2A (if they do not want any addresses filtered, or if the are GARP-unaware) or 2B (if they want to use some degree of filtering). It is probably a smart move to isolate such devices on their own personal segment. If they are GARP-unaware, the Ports serving the segment are configured as for a). If they are GRAP-aware, their response to Leave Alls (i.e., what type of Join All PDU they send) allows them to control the submode of the Ports that serve them. - It may also be possible for a Bridge to fall back to Mode 1 operation if it sees that all of its Ports are operating in (and defaulted to) Mode 2A. This might be advantageous from the point of view of throughput & FDB usage. The effect of the above is that the sub-mode of a given Port is propagated across the network, allowing a directed graph of Port sub-modes to be constructed, in much the same way as for Group membership information. The submodes form a hierarchy of filtering capabilities, with 2A providing the lowest level of Group filtering, and 2C providing the highest level. The information propagated ensures that the needs of segments that require the lowest submode override the higer submodes. Hence, if any segment needs Mode 2A service, all Ports pointing towards that segment will switch to 2A operation if they were operating in any other submode; similarly for 2B. The mechanism allows automatic transition back to a higher submode if the default submode is higher than the current submode and the downstream segments no longer require the lower submode, thus ensuring that the network maximises its filtering possibilities for a given configuration. Comment 3: The document needs to state what changes/additions to the Conformance section of 802.1D (1.5) are necessary in order to specify conformance to GARP. These conformance requirements will also need to be reflected in extensions to the PICS proforma in Annex A. I will draft proposed additions to these sections for discussion in July. Comment 4: The current text is unclear about the role of unicast Group registration and its interaction with the Learning Process. I propose that it should work as follows: a) In Filtering Submodes 2A and 2B (using the re-labelling of submodes as per Comment 2:), registration of Groups with unicast addresses is used only as a means of setting the User Priority for a given Filtering Entry. The Registrar does not maintain state machines for any unicast groups, and the Learning Process operates as for current 802.1D. b) In Filtering Submode 2C, the Learning Process is disabled for that Port, and unicast addresses get forwarded only if they have been specifically registered. 2. Editorial comments --------------------- Comment 5: Check that the definition of timer values etc. is in accordance with the appropriate usage, as per American National Standard for Metric Practice (std 268-1992).