Duleep,
So a bit confused here.
How do want the decision making to go if a path has a shorter
AS-PATH and longer latency than the alternative?? If latency is the prime
motivator why do you care about AS-PATH length at all.. Comments In-Line..
Jim Uttaro
From: Duleep Thilakarathne [mailto:[email protected]]
Sent: Friday, August 07, 2015 9:31 AM
To: Robert Raszuk
Cc: UTTARO, JAMES; [email protected]
Subject: RE: [bess] BGP route selection criteria - geographic distance when
AS_PATH are equal
Hi Raszuk,
Question 1: How does the router know about user's high latency ?
Actually I am referring ISP edge router to another ISP edge router delay due to
transmission distance.
[Jim U>] The underlying facility and it’s representative transmission distance
will most likely differ from geographical distance. Which do you want to
address? To Robert’s point you still need to acquire that knowledge and it may
be orthogonal to an attribute that is defined as delay.
Question 2: How do you assure Internet stability where you start churning paths
based on the latency of data plane ?
It is not required to consider stability in this situation since it is
unavoidable. What is refer is, router need to select best outgoing path
considering physical distance whenever possible when AS-PATH length is equal.
If router selects long distance path randomly, it impacts to latency.
Question 3: What you are after has effectively been solved many years ago .. it
is called Optimized Edge Routing (OER) / Performance Routing (PFR) - I suggest
you google for those terms.
Thank for the suggestion. I gone through these proposals. But what I am
suggesting is whether we can address this idea from BGP protocol level. For
example by introducing new attribute related to physical distance/delay similar
to AS-PATH. New attribute need to update across the As path. My ultimate
objective is to prevent router randomly select outgoing path when AS-PATH
lengths are equal. Further I am trying SDN based simulation these days. Hope I
can share output. But this could similar to what you have proposed except geo
distance calculation mechanism.
Refer below standard BGP route selection criteria. I suggest item 5. Wordings
may different from vendor to vendor.
1. Discarding the routes with the unreachable Next_Hop.
2. Preferring the route with the highest Local_Pref.
3. Preferring the aggregated route. The preference of an aggregated route is
higher than the preference of a non-aggregated route.
4. Preferring the route with the shortest AS-Path.
5. If AS-Path finds equal, consider shortest GEO distance. If still distance is
same follow next steps.
6. Comparing the Origin attribute and selecting the routes with the Origin
attribute as IGP, EGP, or Incomplete in order.
Regsrds
Duleept
From: [email protected]<mailto:[email protected]> [mailto:[email protected]] On
Behalf Of Robert Raszuk
Sent: Friday, August 7, 2015 6:29 PM
To: Duleep Thilakarathne
Cc: UTTARO, JAMES; [email protected]<mailto:[email protected]>
Subject: Re: [bess] BGP route selection criteria - geographic distance when
AS_PATH are equal
Duleep,
> Then end user experiences high latency to reach destination. In such
> a case, I suggest router need to consider geographic distance to
> destination and select path via NTT to reach destination by default.
Question 1: How does the router know about user's high latency ?
Question 2: How do you assure Internet stability where you start churning paths
based on the latency of data plane ?
Question 3: What you are after has effectively been solved many years ago .. it
is called Optimized Edge Routing (OER) / Performace Routing (PFR) - I suggest
you google for those terms.
Regards,
R.
On Fri, Aug 7, 2015 at 2:51 PM, Duleep Thilakarathne
<[email protected]<mailto:[email protected]>> wrote:
Hi Jim,
Please refer below example.
Assume destination IP is in Asian region. Particular ISP in a different
location (Say India) has upstream peering to US POP (Say AT&T) and Asia POP
(Say NTT). If we check BGP routing table, assume it shows
XX.XX.XX.XX/24 -------->AS - AT&T,AS-XX,AS-Destination
-------->AS - NTT,AS-YY,AS-Destination
In above case AS-PATH is equal and assume router automatically select path via
AT&T. Then end user experiences high latency to reach destination. In such a
case, I suggest router need to consider geographic distance to destination and
select path via NTT to reach destination by default. Deciding geo distance is a
challenge but there are options. Here geo distance means shortest distance to
reach IP destination from upstream POP. Current practice is to use community
strings, but it depends on upstream ISP capability.
Can you comment my idea.
Regards
Duleept
From: UTTARO, JAMES [mailto:[email protected]<mailto:[email protected]>]
Sent: Friday, August 7, 2015 4:09 PM
To: Duleep Thilakarathne; 'Robert Raszuk'
Cc: '[email protected]<mailto:[email protected]>'
Subject: Re: [bess] BGP route selection criteria - geographic distance when
AS_PATH are equal
Duleep,
Assuming AS-PATH is equal and AS-Content different how can you
know that the internal metrics of each AS are consistent and mirror actual
geographic distances? You have to be assured that each administrative domain
applies the same metric assignment. I do not believe this is possible when
there are multiple administrative domains.
Jim Uttaro
From: BESS [mailto:[email protected]] On Behalf Of Duleep Thilakarathne
Sent: Friday, August 07, 2015 5:19 AM
To: Robert Raszuk
Cc: [email protected]<mailto:[email protected]>
Subject: Re: [bess] BGP route selection criteria - geographic distance when
AS_PATH are equal
Hi Raszuk,
I went through RFC7311 and my concern is different than RFC 7311. I have
analyzed full BGP routing table (541,199 routes) with two tier 1 ISP
multi-homing scenario and found nearly 50% of routes have equal AS-PATH length.
In this analysis It was considered, there was no route policy applied to
influence local preference. According to BGP best path selection algorithm,
when AS-PATH lengths are equal, router breaks tie condition based on route
internal logic. This does not grantee proper outgoing path selection.
Appreciate your concern on above analysis.
Regards
Duleept
From: Robert Raszuk [mailto:[email protected]]
Sent: Monday, July 27, 2015 2:40 AM
To: Duleep Thilakarathne
Cc: [email protected]<mailto:[email protected]>
Subject: Re: [bess] BGP route selection criteria - geographic distance when
AS_PATH are equal
Hi Duleep,
Please consider RFC 7311 and provide feedback why you think it is not
sufficient for your objective.
https://tools.ietf.org/html/rfc7311
Best,
R.
On Sun, Jul 26, 2015 at 9:15 PM, Duleep Thilakarathne
<[email protected]<mailto:[email protected]>> wrote:
Hi,
I would like to suggest to consider geographic distance when AS_PATH are equal
in BGP route selection criteria. (as tie breaking rule). Can anybody comment on
my idea.
Regards
Duleept
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