Hi Thilakarathne, Point #1:
What makes you think that 10 ms over 1 GB ethernet peering is any better then 20 ms RTT over 100 GB ? I would really prefer to get routed over 100 GB peerings even if the RTT would be doubled. Point #2: > There is no reqirment to synchronize different administrative > domains since router itself automatically calculate value and > add when routes advertised similar to AS PATH addition > operation. Sorry to ruin your impression about power and intelligence of routers, but they only do what they are programmed to do. So Jim's point about synchronizing metrics is still valid. Of course I assume that for you the only metric you consider here are milliseconds and therefor do not bother. Imagine one operator chooses to use physical distance and other RTT. So in the new attribute you will get time [ms] vs distance [miles]. Yet one more will also use distance buy expressed in kilometers. Please elaborate how useful such comparison will turn out to be ? Point #3: As you are suggesting use of ICMP to measure RTT please keep in mind that ICMP is not high priority protocol. It may wait in the remote or local router for processing much more then the propagation delay of the link it arrived on. Point #4: How often do you plan to remeasure the eBGP propagation ? Note that today many optical long haul transmission is hidden from ASBRs. That means that your provider of long distance connection may at will reroute you via his own web of fiber which does affect RTT. So it is pretty safe to assume what you have measured yesterday today is irrelevant. Point #5: eBGP propagation may be few orders of magnitude less relevant as propagation within each AS path is traversing. And except the case of few ASes under the same administration we do not have a way to express that one today except AIGP attribute. So if you would like to continue your research perhaps looking at that aspect first may be more valuable .... Cheers, R. On Sat, Aug 8, 2015 at 7:10 AM, Duleep Thilakarathne <dule...@mobitel.lk> wrote: > Richard, > > Yes I am referring eBGP scenario. I suggest distance calculations based on > > 1. ICMP delay between eBGP speakers. > 2. Manually configure binding to remote AS. > > > Each eBGP speaking routers need to accumulate distance value when > advertised routes to external peer.There is no reqirment to synchronize > different administrative domains since router itself automatically > calculate value and add when routes advertised similar to AS PATH addition > operation. > > > > > > ----- Reply message ----- > From: "Richard Li" <renwei...@huawei.com> > To: "Duleep Thilakarathne" <dule...@mobitel.lk>, "UTTARO, JAMES" < > ju1...@att.com>, "'Robert Raszuk'" <rob...@raszuk.net> > Cc: "'bess@ietf.org'" <bess@ietf.org> > Subject: [bess] BGP route selection criteria - geographic distance when > AS_PATH are equal > Date: Fri, Aug 7, 2015 10:11 PM > > There might be a good point here. RFC 7311 only takes care of the IGP > metrics. But In Duleep’s example, the metrics between two eBGP speakers are > not taken into consideration. In order to have AIGP attribute to really > represent the accumulated one, the metrics on such links should be > considered as well. However, there might be some challenges or obstacles: > The way to configure one metrics on the link between two eBGP speakers > might not be consistent with the way to configure another metrics on the > another link between two speakers. > > > > Richard > > > > *From:* BESS [mailto:bess-boun...@ietf.org] *On Behalf Of *Duleep > Thilakarathne > *Sent:* Friday, August 07, 2015 8:41 AM > *To:* UTTARO, JAMES; 'Robert Raszuk' > *Cc:* 'bess@ietf.org' > *Subject:* Re: [bess] BGP route selection criteria - geographic distance > when AS_PATH are equal > > > > Jim, > > > > > > What I want to suggest is to insert item 5 (refer below items listed) to > BGP best path selection algorithm. Once AS-PATH length is equal, next we > can think on how to select best outgoing interface. If we don’t select > proper outgoing interface it will affect to latency. I am talking this > based on practical experience I have in ISP environment. There are several > options to select best outgoing interface when AS-PATH are equal. In this > case I suggest geo distance to destination. Following are options to > calculate geo distance. Router selects outgoing interface with lowest GEO > distance to destination. > > > > 1. BGP speaking router can add distance when advertise to route to > upstream similar to AS-PATH attribute. For example > > > > A----B----C-----D > > > > Router B advertise distance AB to router C. router C advertise accumulated > distance AB+BC to router D. > > > > 2. Above distance can be configured as manual interface command or > dynamically using ICMP or similar mechanism. We can assume ICMP delay > propositional to geo distance. > > > > 3. Alternative option is to calculate real geo distance from coordinate > system. In this case we miss intermediate hops. Accuracy is not much > accurate since cable paths do not follow real coordinate based distance. In > this case we should have knowledge on coordinates of upstream router which > relevant IP block advertise. > > > > Option 1 can be achieved through BGP protocol itself ,if agreed to > introduce new attribute. > > Option 3 more suitable to SDN based implementation. Calculation can be > daily or weekly basis as this is not primary criteria. > > > > Further Consider following scenario. > > > > I am in Sri Lanka. Assume I have upstream POPS to Singapore, AMS, New > York. Assume I need to reach destination IP located at Japan. When I check > BGP routing table, AS-PATH length is equal from all three upstream. Then I > have three options. Then router selects any interface randomly if no policy > configured. I hope you agreed up to this point. In such case I suggest to > consider GEO distance to destination. In most cases lowest distance path is > the best path. This may not correct always but better than random outgoing > interface selection. > > > > > > 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. > > > > > > Regards > > Duleept > > > > > > > > *From:* UTTARO, JAMES [mailto:ju1...@att.com <ju1...@att.com>] > *Sent:* Friday, August 7, 2015 7:44 PM > *To:* Duleep Thilakarathne; 'Robert Raszuk' > *Cc:* 'bess@ietf.org' > *Subject:* RE: [bess] BGP route selection criteria - geographic distance > when AS_PATH are equal > > > > 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:dule...@mobitel.lk > <dule...@mobitel.lk>] > *Sent:* Friday, August 07, 2015 9:31 AM > *To:* Robert Raszuk > *Cc:* UTTARO, JAMES; bess@ietf.org > *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:* rras...@gmail.com [mailto:rras...@gmail.com <rras...@gmail.com>] *On > Behalf Of *Robert Raszuk > *Sent:* Friday, August 7, 2015 6:29 PM > *To:* Duleep Thilakarathne > *Cc:* UTTARO, JAMES; bess@ietf.org > *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 <dule...@mobitel.lk> > 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 ------àAS - AT&T,AS-XX,AS-Destination > > ------àAS - 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:ju1...@att.com] > *Sent:* Friday, August 7, 2015 4:09 PM > *To:* Duleep Thilakarathne; 'Robert Raszuk' > > > *Cc:* 'bess@ietf.org' > *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:bess-boun...@ietf.org <bess-boun...@ietf.org>] *On > Behalf Of *Duleep Thilakarathne > *Sent:* Friday, August 07, 2015 5:19 AM > *To:* Robert Raszuk > *Cc:* bess@ietf.org > *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:rob...@raszuk.net <rob...@raszuk.net>] > *Sent:* Monday, July 27, 2015 2:40 AM > *To:* Duleep Thilakarathne > *Cc:* bess@ietf.org > *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 <dule...@mobitel.lk> > 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 > > > > > > > > This e-mail and any attachments may contain confidential and > privileged information. If you are not the intended recipient, > please notify the sender immediately by return e-mail, delete this > e-mail and destroy any copies. Any dissemination or use of this > information by a person other than the intended recipient is > unauthorized and may be illegal. > Mobitel (Pvt) Ltd. > > > _______________________________________________ > BESS mailing list > BESS@ietf.org > https://www.ietf.org/mailman/listinfo/bess > > > > This e-mail and any attachments may contain confidential and privileged > information. If you are not the intended recipient, please notify the > sender immediately by return e-mail, delete this e-mail and destroy any > copies. Any dissemination or use of this information by a person other than > the intended recipient is unauthorized and may be illegal. 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If you are not the intended recipient, please notify the > sender immediately by return e-mail, delete this e-mail and destroy any > copies. Any dissemination or use of this information by a person other than > the intended recipient is unauthorized and may be illegal. Mobitel (Pvt) > Ltd. > > This e-mail and any attachments may contain confidential and > privileged information. If you are not the intended recipient, > please notify the sender immediately by return e-mail, delete this > e-mail and destroy any copies. Any dissemination or use of this > information by a person other than the intended recipient is > unauthorized and may be illegal. > Mobitel (Pvt) Ltd. >
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