Hi Hannes,

Thanks for the correction. My previous description is not accurate.

What I try to say is that, the operator can run either IGP or BGP on the SF 
nodes based on the network deployment consideration.

If a network is deployed as shown in the figure below, we can choose to use IGP 
to advertise the SF information intra AS and BGP-LS to collect these 
information per AS.

 ^      ^                        
 BGP |  | BGP                    
 +------------+ +----------+
 | |
 node1 nodeN
 ^ ^
 | IGP | IGP
+-------------+ +-------------+
|SF11 SF12 | |SFN1 SFN2 |
|..... | ... |..... |
| (IGP AS 1) | | (IGP AS N) |
+-------------+ +-------------+Regards,



发件人:HannesGredler <han...@gredler.at>
抄送人:Acee Lindem <a...@cisco.com>;zzhang_i...@hotmail.com 
<zzhang_i...@hotmail.com>;lsr@ietf.org <lsr@ietf.org>;
日 期 :2020年07月29日 15:14
主 题 :Re: [Lsr] "IGP Extensions for Segment Routing Service 

BGP-LS was designed to solve also the distribution of link-state information 
between BGP speakers (see Figure 1 from RFC 7752 below).

Just ask yourself: why would one want to use a point to multipoint state 
replication protocol as complex as BGP for *just* client server alike 
replication ?

We wanted from day-1 to leverage the graph independent replication abilities of 
BGP - so doing inter BGP-LS graphs is a legit use-case.




 The collection of link-state and TE information and its distribution
 to consumers is shown in the following figure.

 | Consumer |
 | BGP | +-----------+
 | Speaker | | Consumer |
 +-----------+ +-----------+
 ^ ^ ^ ^
 | | | |
 +---------------+ | +-------------------+ |
 | | | |
 +-----------+ +-----------+ +-----------+
 | BGP | | BGP | | BGP |
 | Speaker | | Speaker | . . . | Speaker |
 +-----------+ +-----------+ +-----------+
 ^ ^ ^
 | | |

 Figure 1: Collection of Link-State and TE Information

On 29.07.2020, at 03:57, liu.ya...@zte.com.cn wrote:

Hi Acee,

Thanks for reading the draft.

Yes, the main purpose of this draft is to carry the segment segment information 
via IGP so only one node per AS need to be connected with the controller 
through BGP-LS.

With the existing BGP-LS extension draft, it is certainly one solution to 
configure BGP sessions between all the service function nodes and controller, 
and each node sends the SF information to the controller individually.

And if I get you right, we can also select one node to have a BGP session with 
the controller and configure BGP sessions between the selected node and SF 

But how the selected node get the SF information from SF nodes via BGP needs to 
be solved, since BGP-LS is typically used for exchanging information between 
the south and north rather than nodes of the same level, and there's no other 
existing BGP extension for distribute SIDs information between nodes .

This draft aims to provide an alternate way if the operators prefer running IGP 
on SF nodes.

So we would like to collect comments on the WG session to see how others think 
about it.



_______________________________________________Lsr mailing 

发件人:AceeLindem(acee) <a...@cisco.com>

收件人:刘尧00165286;zzhang_i...@hotmail.com <zzhang_i...@hotmail.com>;

抄送人:lsr@ietf.org <lsr@ietf.org>;

日 期 :2020年07月29日 01:53

主 题 :"IGP Extensions for Segment Routing Service Segment" 

Speaking as WG member:


It seems the sole purpose of this draft is to get service segment information 
from nodes in the IGP domain to the IGP node that has a BGP session with the 
controller. You don’t need to put this information
 into the IGP in order to do this. Simply configure BGP sessions for the BGP-LS 
AF between the nodes with service functions and the node selected to have a BGP 
session with the controller.


Speaking as WG Chair – please let me know if we can omit this draft from the 



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