BGP Add-Paths. Hundreds of proposals hiding behind one...

Transcription

1 BGP Add-Paths Hundreds of roosals hiding behind one...

2 ToC draft-ietf-idr-add-aths Why doing Add-aths draft-ietf-idr-add-aths-guidelines (draft-uttaro-idr-add-aths-guidelines) Why only a small subset of roosals will be suorted

3 Motivation for Add-aths Initial motivation was MED oscillation avoidance Emergence of new IDR requirements a few years ago Fast recovery uon eering link / ASBR failure Load balancing among multile rimary BGP NHs Hitless lanned maintenance Otimal hot-otato routing (Churn reduction / convergence concealment)

4 ibgp Path hiding Lack of ath diversity in ibgp deloyments Policies Route Reflection

5 Policies let aths be hidden : localref = 100 ASBR1 ASBR2 : localref = 90

6 Route Reflection hides aths : localref = 100 ASBR1 ASBR2 : localref = 100 RR1 PE

7 Can t we just turn adv-best-external on? : localref = 100 ASBR1 ASBR2 : localref = {100,90} RR1 RR2 Doesn t solve the route reflection roblem PE

8 BGP Add aths ASBR1 ASBR2 Advertise multile BGP aths RR1 towards the same NLRI over a single ibgp session PE draft-ietf-idr-add-aths

9 BGP Add aths ASBR1 ASBR2 PE can RR1 Install PIC state Load balance PE Hitless reroute to alternate

10 Otimal Hot Potato RRs may erform different IGP tie-breaking Deending on which aths it advertises Clients don t get the ath that they would ick Add-aths enabled RRs let the IGP tie-break to clients

11 Churn reduction??? Churn reduction for rimary aths......with internal churn increase for non-rimary ones

12 Churn Reduction : localref = 100 ASBR1 ASBR3 : LP = 80 ASBR2 : localref = 90 PE Withdraw, Udate Withdraw, Udate, Udate Udate (or silence)

13 Churn Reduction : localref = 100 ASBR1 ASBR3 : LP = 80 ASBR2 : localref = 90 Churny internal PE for Quiet external Udate...or silence...

14 draft-ietf-idr-add-aths Adds an identifier to aths Identifier only has session meaning

15 draft-ietf-idr-add-aths-guidelines draft-ietf-idr-add-aths doesn t tell which aths to select Multile motivations lead to different selection modes Evaluate them (what they give, at which cost) analytical numbers

16 Modes All aths N aths AS-Wide best aths (and variants) Best Loc Pref / Second best Loc Pref aths Decisive ste -1 aths Neighbor-AS grou best aths

17 All Paths ASBR1 ASBR3 ASBR2 Known aths almost RR1 like if ibgp full-mesh PE and adv-ext-best on

18 Add-All Easiest Decision Process algorithm Nice mode to turn on towards a BGP monitor Memory/internal udate churn monster Deending on how many aths for each

19 N aths (N is configured) ASBR1 ASBR3 Usually ASBR2 consider NH disjoint aths RR1 (1) (2) PE

20 Add-N-Paths Most ractical use cases Set N to 2 for basic PIC suort Set N to desired number of NHs for LB Memory hit ket under control through configuration of N Doesn t solve MED oscillations Develoers tend to imlement it as N*DP

21 AS-Wide Best aths LP 100 AS Path length : 3 ASBR1 ASBR3 LP 100 AS Path length : 3 ASBR2 Not hiding aths that another node would have referred LP 90 AS Path length : 3 (LP) RR1 (AS Path) PE (MED)

22 AS-Wide Best aths The router doesn t make local decisions DP comlexity < not running add-aths Provides MED oscillation avoidance Provides routing otimality and max LB otential!!! Doesn t feed PIC!!!

23 AS-Wide Best aths LP 100 AS Path length : 3 ASBR1 ASBR3 LP 90 AS Path length : 3 ASBR2 LP 90 AS Path length : 3 (LP) RR1 PE One winner roblem still alies

24 AS-Wide Best aths LP 100 AS Path length : 3 ASBR1 ASBR3 LP 100 AS Path length : 2 ASBR2 LP 90 AS Path length : 3 (LP) RR1 (AS Path) PE One winner roblem still alies

25 Best LP/Second Best LP If #(aths with highest LP) > 1 advertise aths with highest LP else advertise the ath with highest LP advertise the aths with second highest LP

26 Best LP/Second Best LP LP 100 AS Path length : 3 ASBR1 ASBR3 LP 100 AS Path length : 3 ASBR2 LP 90 AS Path length : 3 (LP) RR1 PE

27 Best LP/Second Best LP LP 100 AS Path length : 3 ASBR1 ASBR3 LP 90 AS Path length : 3 ASBR2 LP 80 AS Path length : 3 (LP) RR1 (LP2) PE There are always multile winners

28 Best LP / Second Best LP Adj-Rib-In otimized for this mode contains two or three sets of aths er NLRI Best bin Others Second best bin if required Decision Process : Select what s in first and second bin

29 Decisive ste - 1 Aly normal BGP selection rocess, but If IGP tie-break rule is reached, advertise what remains If best ath is found at a receding rule i, advertise what remained when alying rule i-1 Tries to obtain diversity while advertising as few aths as ossible

30 Decisive ste - 1 LP 100 AS Path length : 3 ASBR1 ASBR3 LP 90 AS Path length : 3 ASBR2 LP 90 AS Path length : 3 (LP) RR1 PE One LP winner --> All aths!

31 Decisive ste - 1 LP 100 AS Path length : 3 ASBR1 ASBR3 LP 100 AS Path length : 2 ASBR2 LP 90 AS Path length : 3 RR1 (LP) (AS Path) One AS Path winner : PE Best Loc Pref aths

32 Neighbor-AS grou best Avoids MED oscillations draft-walton-bg-route-oscillation-sto Advertise the best ath from each neighboring AS No ASBR icks as best a non-lowest MED ath

33 Neighbor-AS grou best Provides aths from different neighboring ASes, but their existence is not guaranteed nothing to deal with ost-convergence aths

34 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

35 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

36 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

37 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

38 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

39 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

40 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

41 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

42 Summary Path otimality Backu availability / otimality Control lane load and stress DP Comlexity MED osc. avoidance All OK OK Max EASIEST OK N? OK /? Bounded Deends on N can be otimized? AS-Wide OK KO / ~OK ~MAX EASY OK LP1/LP2 OK OK ~MAX EASIER OK Decisive-1 OK OK ~MAX Easy but saghetti OK Grou best KO... KO ~MAX? OK

43 Current Recommendations MUST: Add-N Default MUST be 2 N MUST be configurable Otion to not limit N (Add-All) OPTIONAL: AS-Wide best variants OPTIONAL-: All others

44 Tool inut: BGP config, IGP config, as many show i bg all as ossible, riority on RRs, lease adv-ext-best outut: for each mode number of aths in Rib-in otimality of aths ibgp churn uon nextho failure / single udate generated ebgp churn uon nextho failure

45 Deloyment Session wide ugrade required As for all solutions Add-ath easily converted to diverse-aths Forget about deloyments w/o Ingress-Egress enca Transient forwarding loos if naïve PIC imlementation

46 Next Stes Add-ath for ebgp Route Server imlementation draft-jasinska-ix-bg-route-server +Add-All +Filtering +Pick one for clients not suorting add-aths

47 Thanks!