Thank you P.J. Aitken.

The length of IPFIX message is sufficient for BGP standard communities, since 
the length of standard community is 4 octets. But the sizes of extended 
community, large community and wide community are bigger than the size of 
standard community. If the working group agrees to cover the above all kinds of 
communities in this draft, do you think we should open the discussion for IPFIX 
and basicList message splitting?

Sorry for the duplicate mails.

Best Regards
Zhenqiang Li



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在2017-02-16 19:59:59
李振强<13911635...@139.com>写道:


发件人:PJ Aitken<pjait...@brocade.com>
日期:2017-02-16 19:16:00
收件人:lizhenqi...@chinamobile.com<lizhenqi...@chinamobile.com>, 
grow-bounces<grow-boun...@ietf.org>, zhoutianran<zhoutian...@huawei.com>
主题:Re: [IPFIX] [GROW] [OPSAWG] WG adoption poll 
fordraft-li-opsawg-ipfix-bgp-community-02


Ignas Bagdonas wrote:



>The upper limit may be reaching 16000 standard communities per prefix - would 
>that fit into resulting IPFIX IE? If there is a limit, how does it work?



A quick calculation suggests that the maximum would be 16376 x 4-octet ASNs. 
See the figure below.



The constraining factor is the RFC7011 IPFIX Message Header "Length" field, 
since this is only 16 bits.



Splitting a list across multiple IPFIX messagesis a question which the IPFIX 
community hasn't discussed.Unfortunately the basicList "Semantic" field only 
defines the relationship among the different values within a single message; 
the relationship among values in different messages is not defined.



IPFIX Collectors might reasonably assume that information in subsequent 
messages supersedes information in earlier messages, so splitting a list across 
multiple messages would not have the desired effect.






0          1          2          3   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 
1 2 3 4 5 6 7 8 9 0 1   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |    
Version Number     |    Length =65532|   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |           
   Export Time             |   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |           
 Sequence Number             |   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |          
Observation Domain ID           |   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |     Set 
ID = 256     |     Length =65516|   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   255   | 
  List Length =65509| semantic=allOf|   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   bSCL 
FieldId = 459    |   bSCL Field Length=4   |   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |       
bgpSourceCommunityList value 1 = x        |   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |       
bgpSourceCommunityList value 2 = x        |   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               
   ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |  
     bgpSourceCommunityList value16376= x      |   
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





P.



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