Huaimo, This seems like it’s a job for the NMS/configuration management system and that there are no protocol interactions required.
Oh, and yes, we are working on a YANG model for this feature. We hope that this will be ready by Montreal. The only concern that I would have is that removing dynamic flooding in some dense topologies would enable a cascade failure. No process is going to alleviate that because those topologies simply cannot support legacy flooding. Tony > On May 20, 2019, at 12:53 PM, Huaimo Chen <huaimo.c...@huawei.com> wrote: > > Hi Tony, > > For the case that the IGP running in an area has been doing the flooding > reduction, in order to let the IGP on every node in the area roll back to the > normal flooding quickly and easily, a procedure for migrating from the > flooding reduction to normal flooding is needed. After back to normal > flooding, if we want to let the IGP on every node do flooding reduction some > time later, the procedure should be able to migrate from normal flooding to > the flooding reduction quickly and easily. > > Best Regards, > Huaimo > From: Tony Li [mailto:tony1ath...@gmail.com] On Behalf Of tony...@tony.li > Sent: Saturday, May 18, 2019 1:17 PM > To: Huaimo Chen <huaimo.c...@huawei.com> > Cc: lsr@ietf.org > Subject: Re: [Lsr] Migration between normal flooding and flooding reduction > > > Hi Huaimo, > > Before we get into your procedure, I have to ask an important question: why > is any process necessary? > > In our experience, It Just Works. > > You turn on dynamic flooding and the nodes with the feature start complying > with the flooding topology. Those that are not enabled perform legacy > flooding. Obviously you don’t get the flooding reduction yet, but it grows > incrementally as nodes are enabled. > > What problem are you solving? > > Tony > > > > > On May 18, 2019, at 8:15 AM, Huaimo Chen <huaimo.c...@huawei.com > <mailto:huaimo.c...@huawei.com>> wrote: > > Hi Tony, > > Two possible procedures (Procedure A and B) for the migration are listed > below for discussions. > > In the beginning, the IGP running in a network area does the normal flooding. > The migration from the normal flooding to the flooding reduction (either > centralized mode or distributed mode) or in reverse (i.e., roll back from the > flooding reduction to the normal flooding) may follow a procedure of a few > steps. One of the two procedures below may be used. > > Procedure A: > > 1. For each node that is eligible to become a leader for flooding > reduction in centralized mode, a priority for the leader election is > configured on the node. (This step is called “Priority Configuration”). > 2. Every node advertises its priority for the leader election and the > algorithms that it supports for computing flooding topology for distributed > mode. (This step is called “Priority and Algorithms Distribution”). Note that > this step and the step above may be considered as one step. After a priority > is configured on a node, the node will advertises its priority and algorithms. > 3. On the node that will be elected as the leader, “Start Leader > Election” is configured. The node does the leader election after obtaining > “Start Leader Election”. It also advertises this to all the other nodes in > the area. Each of them will do the leader election after receiving this. > (This step is called “Leader Election”). Note that this step may be removed. > Without this step, the leader election may occur multiple times until the > leader with the highest priority and highest node ID is elected if we want > that the leader is the node that has the highest priority and highest node ID > in the area. > 4. On the node that is elected as the leader, centralized mode or > distributed mode is configured. (This step is called “Flooding Reduction Mode > Configuration”). > For centralized mode (i.e., when centralized mode is configured), > 1) the leader advertises “Flooding Reduction” in the centralized mode to > all the other nodes; > 2) the leader computes the flooding topology and advertises the flooding > topology to the other nodes; > 3) each node floods the link states using the flooding topology after it > receives/has the whole flooding topology. > For distributed mode (i.e., when distributed mode is configured), an > algorithm is also configured to be used by every node to compute flooding > topology > 1) the leader advertises “Flooding Reduction” in the distributed mode > including the algorithm to all the other nodes; > 2) each node computes its flooding topology and floods the link states > using the flooding topology. > At this point, the IGP running in the network area has migrated from the > normal flooding to the flooding reduction (either centralized mode or > distributed mode). > > In centralized mode, configuring distributed mode (or changing the > centralized mode to distributed mode through configuration) will transfer > from centralized mode to distributed mode. In addition to step 1) and 2) > above for the distributed mode, each node uses the centralized flooding > reduction (i.e., floods the link states over its local links on the flooding > topology computed by the leader of the area) until the distributed flooding > reduction is fully functional for a given time such as 5 seconds. After this > time, the node stops its centralized flooding reduction. The leader stops > computing the flooding topology, advertising it to all the other routers, and > using this flooding topology to flood the link states. Each of the other > nodes stops receiving and building the flooding topology computed by the > leader. > > In distributed mode, configuring centralized mode (or changing the > distributed mode to centralized mode through configuration) will transfer > from distributed mode to centralized mode. In addition to step 1), 2) and 3) > above for the centralized mode, each node uses the distributed flooding > reduction (i.e., floods the link states over its local links on the flooding > topology computed and built by itself) until the centralized flooding > reduction is fully functional for a given time such as 5 seconds. > > For the migration (or say roll back) from the flooding reduction to the > normal flooding, > a. on the leader node, “Roll Back to Normal Flooding” is configured; > (This step is called “Roll Back to Normal Flooding Configuration”). > b. the leader advertises “Roll Back to Normal Flooding” to all the > other nodes; (This step is called “Roll Back to Normal Flooding > Distribution”). > c. every node rolls back to the normal flooding after obtaining the > instruction for rolling back to the normal flooding. Every node will floods > link states using all its local links instead of the local links on the > flooding topology. (This step is called “Stop Using Flooding Topology”). > For the centralized mode, after rolling back to normal flooding, the leader > of the area stops computing and advertising the flooding topology, each of > the other nodes stops receiving and building the flooding topology. > For the distributed mode, every node in the area stops computing and building > the flooding topology. > > At this point, the IGP running in the network area has rolled back to the > normal flooding from the flooding reduction (either centralized mode or > distributed mode). > > After this point, if there is a need to migrate from the normal flooding to > the flooding reduction, then go to step 4 (i.e., “Flooding Reduction Mode > Configuration”) above. > > One octet needs to be added into IS-IS and OSPF Area Leader Sub-TLV. Three > bits of this octet are used to indicate an operation (OP) such as “Roll Back > to Normal Flooding”. The other five bits are reserved. The values proposed > for OP are as follows: > 1 for “Flooding Reduction” (mode is implied/indicated by the algorithm) > 2 for “Roll Back to Normal Flooding” > 3 for “Start Leader Election” (This is not needed if step 3 above is removed). > > 4 for “Start Priority and Algorithms Distribution” if Procedure B below is > used. > > In Procedure A, after rolling back to normal flooding, the information about > the priority and algorithms in the LSA/LSP originated by each node is still > in the network. If we want to remove this information from the network after > rolling back to normal flooding, Procedure B below achieves this. It is > derived from Procedure A through some changes which are in blue color. > > Procedure B: > 1. For each node that is eligible to become a leader for flooding > reduction in centralized mode, a priority for the leader election is > configured on the node. (This step is called “Priority Configuration”). > 2. “Start Priority and Algorithms Distribution” is configured on the > node that will be elected as the leader after all the nodes that are eligible > for a leader are configured with their priorities. The node advertises “Start > Priority and Algorithms Distribution” to all the other nodes in the area; > every node advertises its priority and algorithms after obtaining “Start > Priority and Algorithms Distribution”. (This step is called “Start Priority > and Algorithms Distribution”). > 3. On the node that will be elected as the leader, “start leader > election” is configured. The node does the leader election after obtaining > “start leader election”. It also advertises this to all the other nodes in > the area. Each of them will do the leader election after receiving this. > (This step is called “Leader Election”). > 4. On the node that is elected as the leader, centralized mode or > distributed mode is configured. (This step is called “Flooding Reduction Mode > Configuration”). > For centralized mode, > 1) the leader advertises the centralized mode to all the other nodes; > 2) the leader computes the flooding topology and advertises the flooding > topology to the other nodes; > 3) each node floods the link states using the flooding topology after it > receives/has the whole flooding topology. > For distributed mode, an algorithm is configured to be used by every node to > compute flooding topology > 1) the leader advertises the distributed mode including the algorithm to > all the other nodes; > 2) each node computes its flooding topology and floods the link states > using the flooding topology. > At this point, the IGP running in the network area has migrated from the > normal flooding to the flooding reduction (either centralized mode or > distributed mode). > > In centralized mode, configuring distributed mode (or changing the > centralized mode to distributed mode through configuration) will transfer > from centralized mode to distributed mode. In addition to step 1) and 2) > above for the distributed mode, each node uses the centralized flooding > reduction (i.e., floods the link states over its local links on the flooding > topology computed by the leader of the area) until the distributed flooding > reduction is fully functional for a given time such as 5 seconds. After this > time, the node stops its centralized flooding reduction. The leader stops > computing the flooding topology, advertising it to all the other routers, and > using this flooding topology to flood the link states. Each of the other > nodes stops receiving and building the flooding topology computed by the > leader. > > In distributed mode, configuring centralized mode (or changing the > distributed mode to centralized mode through configuration) will transfer > from distributed mode to centralized mode. In addition to step 1), 2) and 3) > above for the centralized mode, each node uses the distributed flooding > reduction (i.e., floods the link states over its local links on the flooding > topology computed and built by itself) until the centralized flooding > reduction is fully functional for a given time such as 5 seconds. > > > For migration (or say roll back) from the flooding reduction to the normal > flooding, > a. on the leader node, “Roll Back to Normal Flooding” is configured; > (This step is called “Roll Back to Normal Flooding Configuration”). > b. the leader advertises “Roll Back to Normal Flooding” to all the > other nodes; (This step is called “Roll Back to Normal Flooding > Distribution”). > c. every node rolls back to the normal flooding after obtaining the > instruction for rolling back to the normal flooding. Every node will floods > link states using all its local links instead of the local links on the > flooding topology. (This step is called “Stop Using Flooding Topology”). > d. every node removes the information about its priority and algorithms > in the LSA/LSP that it originated. (This step is called “Remove Priority and > Algorithms”). > For the centralized mode, after rolling back to normal flooding, the leader > of the area stops computing and advertising a flooding topology, the other > nodes stops receiving and building the flooding topology. > For the distributed mode, every node in the area stops computing and building > flooding topology. > > At this point, the IGP running in the network area has rolled back to the > normal flooding from the flooding reduction (either centralized mode or > distributed mode). > > After this point, if there is a need to migrate from the normal flooding to > the flooding reduction, then go to step 2 (i.e., “Start Priority and > Algorithms Distribution”) above. > > > Best Regards, > Huaimo > > > _______________________________________________ > Lsr mailing list > Lsr@ietf.org <mailto:Lsr@ietf.org> > https://www.ietf.org/mailman/listinfo/lsr > <https://www.ietf.org/mailman/listinfo/lsr> >
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