Hi, Susan: It seems better to introduce one new draft to introduce your “virtual topology” solution, especially the control plane and forward plane behavior, how it interact with the deployed level 1/2 solutions.
I think to improve the convergence performance in large network such as 5G/IP RAN network is one attractive topic but we need to select/make the solutions being deployed easily and smoothly. Aijun Wang China Telecom > On Aug 16, 2019, at 22:23, Susan Hares <[email protected]> wrote: > > Ajun: > > I’ll let Tony provide his answer to your question. Let me provide an > alternate topology that your example might fit into > > draft-hares-lsr-grid-ring-convergence-00.txt describes a problem with IGP > convergence for the grid-ring phone topology that may be deployed in some 5G > networks. One way to solve the convergence problem is to provide an > alternate fast convergence topology that uses hierarchy to provide shorter > paths through the Grid portion of the grid-ring topology. > > Suppose in this topology, the regular IGP (ISIS) algorithm keeps the 2 level > hierarchy. > > The alternate fast convergence algorithm uses a multiple level hierarchy in > order to provide faster convergence. The multiple levels provide > “short-cut” paths for the IGP in a virtual topology in the Grid topology. As > discussions on this forum have indicated, the fast convergence topologies run > in parallel with the normal IGP forwarding providing an alternate forwarding > path. If you would like me to explain how the hierarchy can provide faster > convergence for a grid, I can provide that explanation to you (online or > offline). > > Forwarding on the node needs to handle the multiple IGP routes. Since the > fast convergence topologies provide early notification of forwarding problems > in the normal IGP, the forward processing in the nodes might check this > alternate topology for unknown routes. Other ways of merging the two > forwarding RIBs generated by the two IGPs also exist. Since (per your > example) R1 and R7 since the this link would be known to the regular IGP, the > traffic could flow over this path. > > I hope this helps… > > Sue Hares > > PS – I would refresh the draft-hares-lsr-grid-ring-convergence-00.txt, but > the draft submission seems to have a problem this morning. This draft is > still a rough draft. Some feedback I received indicates I should update > sections. > > > From: Lsr [mailto:[email protected]] On Behalf Of Aijun Wang > Sent: Friday, August 16, 2019 2:48 AM > To: [email protected]; 'Robert Raszuk' > Cc: [email protected] > Subject: [Lsr] 答复: LSR Working Group Adoption Call for "Hierarchical IS-IS" - > draft-li-lsr-isis-hierarchical-isis-01 > > Hi, Tony: > > Would you like to elaborate this in more detail to show how you design the > control plane hierarchically but the traffic can be transported horizontally? > Let’s consider the following graph: > > <image001.png> > If, as you stated, we connect R1 and R7 via one link(although we will not do > so, if we design the network hierarchically), how you flood the link > information hierarchically but let the traffic between the two connected L1 > area bypass the L2 area? > > > Best Regards. > > Aijun Wang > China Telecom > > > > 发件人: [email protected] [mailto:[email protected]] 代表 [email protected] > 发送时间: 2019年8月15日 23:37 > 收件人: Robert Raszuk > 抄送: [email protected]; Aijun Wang > 主题: Re: [Lsr] LSR Working Group Adoption Call for "Hierarchical IS-IS" - > draft-li-lsr-isis-hierarchical-isis-01 > > > Hi Robert, > > > > > The hierarchical arrangement of the control plane does NOT imply that the > > data plane is necessarily hierarchical. > > Since Aijun posted his question I was trying to think of such model, but > failed. > > While it is easy to envision this with DV protocols say BGP - do you have any > pointer to a link state protocol architecture where data plane is non > hierarchical (links do not belong to upper levels) while control plane used > traverses multiple levels ? > > > Consider any topology where two peer areas intersect. At the intersection, > traffic can transition between the areas without entering the parent level.. > > While I’m at it, I should also point out that the existence of hierarchy for > the control plane does not mandate its use. This is another tool in the > toolbox. Use the right tool for the job at hand. > > Tony > > _______________________________________________ > Lsr mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/lsr
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