Re: [Lsr] LSR Working Group Adoption Call for "Hierarchical IS-IS" - draft-li-lsr-isis-hierarchical-isis-01

Hi Huaimo,

Ad 1 - Let me observe that constructing hierarchy is not always driven by
number of nodes in a given level can safely support. One could indeed build
a global flat link state network in single level/area if only looking at
number of nodes. But in number of cases benefits from hierarchy could be
seen in reduced flooding radius and enforced summarization. Hint:  me why
my routers in Sydney have to be aware about link flap in POP in Toronto ?

Ad 6 - Interesting .. I asked the same question to authors offline :)

Thx,
R.

On Mon, Aug 19, 2019 at 4:27 PM Huaimo Chen <huaimo.chen@futurewei.com>
wrote:

> Support and have the following comments:
>
>
>
>    1. It seems not necessary to have 8 levels of hierarchies. 3 or at
>    most 4 levels of hierarchies should be enough. IS-IS with 3 levels of
>    hierarchies may support a network with 1k*1k*1k nodes, which is about 10^9
>    = 1 billion nodes. IS-IS with 4 levels of hierarchies may support a network
>    with 1k*1k*1k*1k nodes, which is about 10^12 = 1 trillion nodes.
>    2. For PDU type, section 2.2 of the draft proposes to use 8 bits (all
>    three reserved bits plus the 5 bits for the existing PDU type). It seems
>    better to use 6 bits (one reserved bit plus the 5 bits for the existing PDU
>    type). Adding one reserved bit into the PDU Type allows people to define 32
>    new PDU types, which is enough for the new PDU types needed for new
>    hierarchies.
>    3. Section 3 “Additional PDUs” of the draft, defines 6 new PDU Types
>    for ’Level n LAN IS to IS hello PDU’ (Ln-LAN-HELLO-PDU), where n is 3, 4,
>    5, 6, 7, and 8. In addition, the following new PDU Types should be defined
>    (considering at most 4 levels of hierarchies):
>       1. 2 new PDU Types for ‘’Level n LSP”, where n is 3, and 4
>       2. 2 new PDU Types for ‘’Level n CSNP”, where n is 3, and 4
>       3. 2 new PDU Types for ‘’Level n PSNP”, where n is 3, and 4
>    4. On a broadcast interface, Level 1 LSPs are multicast through MAC
>    0x0180.c200.0014 (which is called AllL1ISs), and Level 2 LSPs are multicast
>    through MAC 0x0180.c200.0015 (which is called AllL2ISs). It seems that
>    Level n LSPs should be multicast through AllLnISs, where n is 3, and 4
>    (considering at most 4 levels of hierarchies), thus
>       1. 2 new MAC should be assigned to AllLnISs, where n is 3, and 4.
>    5. The existing DIS for a broadcast interface periodically multicast
>    through AllL1ISs and AllL2ISs a Complete SNP (CSNP). It seems that the DIS
>    should be extended to periodically multicast a CSNP through AllLnISs, where
>    n is 1, 2, 3, and 4 (considering at most 4 levels of hierarchies).
>    6. When there may be 3 or more levels of hierarchies, is it allowed to
>    have 3 or more levels (consecutive) configured on an interface? It seems
>    that there is no description about this in the draft.
>
>
>
> Best Regards,
>
> Huaimo
>
>
>
> *From:* Lsr <lsr-bounces@ietf.org> *On Behalf Of *Acee Lindem (acee)
> *Sent:* Monday, August 12, 2019 10:33 AM
> *To:* lsr@ietf.org
> *Subject:* [Lsr] LSR Working Group Adoption Call for "Hierarchical IS-IS"
> - draft-li-lsr-isis-hierarchical-isis-01
>
>
>
> This begins a two week LSR Working Group Adoption Poll for the
> "Hierarchical IS-IS" - draft-li-lsr-isis-hierarchical-isis-01. The poll
> will end at 12:00 AM UTC on August 27th, 2019. Please indicate your
> support of objection on this list prior to the end of the adoption poll.
>
>
>
> Thanks,
>
> Acee
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