Gunter, I am not getting into your other questions because of what I’ve
mentioned above 😊
Thanks,
Ketan
[1] Note that over time we have introduced such mechanisms (RFC8510),
but they have all been optional and not “base/required” behavior.
*From:*Lsr <lsr-boun...@ietf.org> *On Behalf Of *Acee Lindem (acee)
*Sent:* 30 November 2020 23:18
*To:* Van De Velde, Gunter (Nokia - BE/Antwerp)
<gunter.van_de_ve...@nokia.com>; Alexander Okonnikov
<alexander.okonni...@gmail.com>; Peter Psenak (ppsenak)
<ppse...@cisco.com>; Acee Lindem (acee) <a...@cisco.com>
*Cc:* lsr@ietf.org
*Subject:* Re: [Lsr] Link Data value for Multi-area links
You are welcome to propose an alternate solution which could possibly be
accepted as a BIS document. However, this is not something that can be
simply changed in an Errata to reduce the complexity.
Thanks,
Acee
*From: *Lsr <lsr-boun...@ietf.org <mailto:lsr-boun...@ietf.org>> on
behalf of Gunter Van de Velde <gunter.van_de_ve...@nokia.com
<mailto:gunter.van_de_ve...@nokia.com>>
*Date: *Monday, November 30, 2020 at 12:21 PM
*To: *"Acee Lindem (acee)" <acee=40cisco....@dmarc.ietf.org
<mailto:acee=40cisco....@dmarc.ietf.org>>, Alexander Okonnikov
<alexander.okonni...@gmail.com <mailto:alexander.okonni...@gmail.com>>,
"Peter Psenak (ppsenak)" <ppse...@cisco.com <mailto:ppse...@cisco.com>>
*Cc: *"lsr@ietf.org <mailto:lsr@ietf.org>" <lsr@ietf.org
<mailto:lsr@ietf.org>>
*Subject: *Re: [Lsr] Link Data value for Multi-area links
The oddnes is that the architecture decision in RFC5185 to select
remote-ip-address instead of local-ip-address for the ‘Link Data’ is
making things much more complicated.
I am surprised to see that using the remote-ip-address is seen as the
‘better’ choice as selecting local-ip-address. To me it seems as a worse
choice.
A question that was asked: How router will be able to match Link TLV
(RFC 3630) to corresponding Link in Router LSA?
Answer:
For unnumbered links we can match Link TLV with Router TLV using the
IfIndex when there is no stub type 3 link (=easy)
For numbered:
1.we must first look if the there is a stub type 3 link
2.If stub type 3 exists, then the RFC3630 local ip address must be used
to identify the correspond link within the router TLV to the neighbor
3.If the stub type 3 link did not exist in Router TLV link, then the
maybe the link is unnumbered, and we try to match upon IfIndex… This may
give a match or no match
4.If there is no match, then maybe the link is MADJ and we must use the
RFC3630 remote IP address to match upon the Link Data
5.= over-complex. (If we used for RFC5185 ‘Link Data = local ip
address’ then (2) would given answer directly)
In addition, for a router it is much simpler to learn and advertise
local-ip-address in Router LSAs then using a remote-ip-address.
I also believe that if we want to search something in TEDB after
receiving a TE Link TLV. How can we identify from the TE Link TLV if
multi-area or not multi-area? If we can not, then how can we create the
correct key?
Looking at the above, the choice of using remote-ip-address for RFC5185
Link Data seems not the best design that we can do, and is adding OSPF
complexity without benefits.
Should this not be corrected in RFC5185 and simply use local-ip-address
instead of the remote-ip-address for Multi-area Link Data and avoid the
additional unnecessary complexity the current RFC for numbered links?
Brgds,
G/
*From:*Lsr <lsr-boun...@ietf.org <mailto:lsr-boun...@ietf.org>> *On
Behalf Of *Acee Lindem (acee)
*Sent:* Monday, November 30, 2020 18:01
*To:* Alexander Okonnikov <alexander.okonni...@gmail.com
<mailto:alexander.okonni...@gmail.com>>; Peter Psenak (ppsenak)
<ppse...@cisco.com <mailto:ppse...@cisco.com>>
*Cc:* lsr@ietf.org <mailto:lsr@ietf.org>
*Subject:* Re: [Lsr] Link Data value for Multi-area links
Hi Alex,
Multi-Area interface disambiguation is required to support the OSPF MIB
as specified in RFC 4750. The table indexing doesn’t include the area.
For example:
-- OSPF Interface Table
ospfIfTable OBJECT-TYPE
SYNTAX SEQUENCE OF OspfIfEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The OSPF Interface Table describes the interfaces
from the viewpoint of OSPF.
It augments the ipAddrTable with OSPF specific information."
REFERENCE
"OSPF Version 2, Appendix C.3 Router interface
parameters"
::= { ospf 7 }
ospfIfEntry OBJECT-TYPE
SYNTAX OspfIfEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The OSPF interface entry describes one interface
from the viewpoint of OSPF.
Information in this table is persistent and when this object
is written the entity SHOULD save the change to non-volatile
storage."
INDEX { ospfIfIpAddress, ospfAddressLessIf }
::= { ospfIfTable 1 }
Note that if you really want to support this optimally, you could use a
separate subnet pre-area and have adjacencies on secondary addresses. My
Redback/Ericsson implementation allowed for this.
Thanks,
Acee
*From: *Lsr <lsr-boun...@ietf.org <mailto:lsr-boun...@ietf.org>> on
behalf of Alexander Okonnikov <alexander.okonni...@gmail.com
<mailto:alexander.okonni...@gmail.com>>
*Date: *Monday, November 30, 2020 at 5:27 AM
*To: *"Peter Psenak (ppsenak)" <ppse...@cisco.com
<mailto:ppse...@cisco.com>>
*Cc: *"lsr@ietf.org <mailto:lsr@ietf.org>" <lsr@ietf.org
<mailto:lsr@ietf.org>>
*Subject: *Re: [Lsr] Link Data value for Multi-area links
Hi Peter,
30 нояб. 2020 г., в 12:56, Peter Psenak <ppse...@cisco.com
<mailto:ppse...@cisco.com>> написал(а):
Hi Alex,
On 27/11/2020 13:49, Alexander Okonnikov wrote:
Hi Peter,
Which kind of ambiguity is meant? In case of numbered
point-to-point each link has its own unique IP address, so there
is no ambiguity.
Per my understanding this problem has appeared due to follow
reasons:
1) In old versions of the draft (up to -05) it was proposed that
multi-area links are treated as unnumbered. ifIndex to be
encoded in Link Data field, irrespectively whether interface has
its own IP address (numbered) or borrow it (unnumbered);
2) From -06 to -08 multi-area links are still treated as
unnumbered, but if interface is numbered, then IP address of the
neighbor (rather than local one) to be encoded into Link Data,
in order to make the link look like unnumbered;
3) In version -09 of the draft and in RFC 5185 itself there is
no more mentions that multi-area link to be treated as
unnumbered. Rather, another approach is used - if router's
interface is numbered, then link is also numbered; if router's
interface is unnumbered, then link is unnumbered. The rule that
specifies omitting corresponding type 3 link is added. Mention
of 'unnumbered' link is also removed from section 3 in RFC 5185. >
Hence, in version -09 with removing unnumbered nature of
multi-area links Link Data for numbered links had to be changed
from Neighbor's IP address to own IP address, as it is specified
in RFC 2328. From perspective of other routers this link can be
treated as numbered or unnumbered, depending on configuration of
neighbor's corresponding interface.
you are free to advertise the link as unnumbered. RFC5185 is not
mandating to send IP address really.
The same valid for numbered ones. I.e. I'm free to advertise the link as
numbered. This is straightforward when the link is numbered indeed. And
if we would prefer to have deal with unnumbered interfaces, we would not
need RFC 5185 (section 1.2).
One question - how neighboring router will perform next-hop
calculation (in case it needs to do so)? If neighbor is
configured with numbered interface, it will treat Link Data as
IP next hop, which will be its own IP interface address.
Another question - how router will be able to match Link TLV
(RFC 3630) to corresponding Link in Router LSA? For example, we
want to calculate RSVP-TE LSP based on IGP metric (RFC 3785) and
thus router needs to match IGP link to TE link.
I don't believe you are going to do any traffic engineering over a
multi-area adjacency. MADJ is there to address the OSPF route
preference rules that may lead to sub-optimal routing. MADJ link is
not advertised for TE purposes.
Why not? We need multi-area configuration and at the same time we need
ability to build intra-area RSVP-TE LSPs within each of areas. And what
about calculating IP next hop? Which compatibility is meant in section 3?
thanks,
Peter
Thank you.
Thank you.
27 нояб. 2020 г., в 14:50, Peter Psenak <ppse...@cisco.com
<mailto:ppse...@cisco.com>> написал(а):
Alexander,
On 26/11/2020 17:58, Alexander Okonnikov wrote:
Hi WG,
RFC 5185 says that Neighbor's IP address to be encoded
into Link Data field. Per RFC 2328 router's own IP
address to be encoded into Link Data. What is the reason
to advertise neighbor's IP address for multi-area links
and not local IP address? It seems like bug. Could
someone comment on this?
Advertising a neighbor address/ifindex helps to eliminate
ambiguity in case of parallel point-to-point adjacencies.
It's not perfect, but that's how it was specified. So it's
not a bug.
thanks,
Peter
Thanks in advance.
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