BGP Communities: Even more Worms in the Routing Can ACM IMC 2018, - - PowerPoint PPT Presentation

bgp communities even more worms in the routing can
SMART_READER_LITE
LIVE PREVIEW

BGP Communities: Even more Worms in the Routing Can ACM IMC 2018, - - PowerPoint PPT Presentation

BGP Communities: Even more Worms in the Routing Can ACM IMC 2018, Boston, MA, USA Florian Streibelt 1 <fstreibelt@mpi-inf.mpg.de> , Franziska Lichtblau 1 , Robert Beverly 2 , Cristel Pelsser 3 , Georgios Smaragdakis 4 , Randy Bush 5 , Anja


slide-1
SLIDE 1

BGP Communities: Even more Worms in the Routing Can

ACM IMC 2018, Boston, MA, USA

Florian Streibelt1 <fstreibelt@mpi-inf.mpg.de>, Franziska Lichtblau1, Robert Beverly2, Cristel Pelsser3, Georgios Smaragdakis4, Randy Bush5, Anja Feldmann1 Nov 1, 2018

1 Max Planck Institute for Informatics (MPII), 2 Naval Postgraduate School (NPS), 3 University of Strasbourg, 4 TU Berlin (TUB), 5 Internet Initiative Japan (IIJ)

slide-2
SLIDE 2

Introduction

slide-3
SLIDE 3
  • Contributions. . .
  • We provide an analysis of BGP community propagation on the Internet
  • We show that BGP communities (as used by operators to realize traffic

management) can be used as attack vector

  • We verify this via experiments in the lab as well as in the wild
  • We provide some hints on the secure usage of BGP communities

1

slide-4
SLIDE 4

BGP Community usage is increasing

  • 2010

2012 2014 2016 2018 Year

  • 2k

3k 5k 10k 20k 40k 70k 0.2B 0.3B 0.5B 1B 2B 4B 7B

  • # Unique ASes in Communities

# Unique Communities # Absolute Communities # BGP table entries

2

slide-5
SLIDE 5

BGP Community usage is increasing

  • 2010

2012 2014 2016 2018 Year 2k 3k 5k 10k 20k 40k 70k 0.2B 0.3B 0.5B 1B 2B 4B 7B

  • # Unique ASes in Communities

# Unique Communities # Absolute Communities # BGP table entries

+296%

Increasing usage warrants a closer look.

2

slide-6
SLIDE 6

BGP (Border Gateway Protocol)

3

slide-7
SLIDE 7

BGP (Border Gateway Protocol)

AS4 AS2 AS3 AS5 AS1 AS6

3

slide-8
SLIDE 8

BGP (Border Gateway Protocol)

p p

AS4 AS2 AS3 AS5 AS1 AS6

Origin−AS

  • AS1 announces prefix p

3

slide-9
SLIDE 9

BGP (Border Gateway Protocol)

p p p p

AS3 AS5 AS1 AS6 AS2 AS4

Origin−AS

  • AS1 announces prefix p, upstreams pickup p

3

slide-10
SLIDE 10

BGP (Border Gateway Protocol)

p p p p p p p p

AS4 AS2 AS3 AS5 AS1 AS6

AS−Paths for p in AS6 Origin−AS AS6, AS4, AS2, AS1 AS6, AS5, AS3, AS1

  • AS1 announces prefix p, upstreams pickup p
  • AS6 receives first anouncements for p

3

slide-11
SLIDE 11

BGP (Border Gateway Protocol)

p p p p p p p p p

AS4 AS2 AS3 AS5 AS1 AS6

AS−Paths for p in AS6

For simplicity assuming AS2−AS5 are transit providers

Origin−AS AS6, AS4, AS2, AS1 AS6, AS4, AS5, AS3, AS1 AS6, AS5, AS3, AS1 AS6, AS5, AS4, AS2, AS1

  • AS1 announces prefix p, upstreams pickup p
  • AS6 receives first anouncements for p
  • eventually AS6 sees multiple available paths for p

3

slide-12
SLIDE 12

BGP (Border Gateway Protocol)

p p p p p p p p p

AS4 AS2 AS3 AS5 AS1 AS6

AS−Paths for p in AS6

For simplicity assuming AS2−AS5 are transit providers

Origin−AS AS6, AS4, AS2, AS1 AS6, AS4, AS5, AS3, AS1 AS6, AS5, AS3, AS1 AS6, AS5, AS4, AS2, AS1

BGP

  • BGP communicates reachability information
  • Announcement messages also carry various attributes
  • One of these attributes are BGP-Communities

4

slide-13
SLIDE 13

BGP Communities

123 456 :

16 bit 32 bit 16 bit

community−value 16 bit AS−Number 0x00000000011110110000000111001000 0x1111011 0x111001000

  • RFC 1997: Optional Attribute in

BGP message (32 bit)

  • By convention written ASN:VALUE
  • ASN can be both sender or intended ’recipient’
  • Every network decides the semantics behind the

values

  • New standard: Large Communities (96 bit),

not yet widely deployed

5

slide-14
SLIDE 14

BGP Communities: Usage

Informational Communities (Passive Semantics)

  • Location tagging
  • RTT tagging

Action Communities (Active Semantics)

  • Remote triggered blackholing
  • Path prepending
  • Local pref/MED
  • Selective announcements

Used by operators to realize policies. Without documentation, you can not tell if a community is active or passive!

6

slide-15
SLIDE 15

BGP Communities As Attack Vector?

Given the increasing popularity of BGP communities and the ability to trigger actions as well as relay information,

  • ne question arises:

To which extend can BGP communities be leveraged for attacks?

7

slide-16
SLIDE 16

Propagation behavior

  • RFC 1997: Communities as a transitive optional attribute
  • RFC 7454: Scrub own, forward foreign communities
  • 14% of transit providers propagate received communities (2.2k of 15.5k)
  • Ratio seems small, but AS graph is highly connected

Still many people do not expect communities to propagate that widely.

8

slide-17
SLIDE 17

Potential (for) misuse

  • Propagated communities might trigger actions multiple AS-hops away
  • No way of knowing if intended or not, e.g., for traffic management
  • But are there also unintended consequences?

Our assessment is that there is a high risk for attacks!

9

slide-18
SLIDE 18

Observations

slide-19
SLIDE 19

BGP Dataset

BGP updates and table dumps of April 2018 from publicly available BGP Collector Projects: RIPE RIS, Routeviews, Isolario, PCH. BGP messages 38.98 bn IPv4 prefixes 967,499 IPv6 prefixes 84,953 Collectors 194 AS peers 2,133 Communities 63,797 More than 75% of all BGP announcements have at least

  • ne BGP community set, 5,659 ASes are using communities.

10

slide-20
SLIDE 20

BGP Communities propagation

11

slide-21
SLIDE 21

BGP Communities propagation

AS2 AS3 AS4 AS1

11

slide-22
SLIDE 22

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

  • AS1 announces prefix p

11

slide-23
SLIDE 23

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

AS−Path: AS4, AS3, AS2, AS1 AS4

  • AS1 announces prefix p, AS4 receives announcement

11

slide-24
SLIDE 24

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

AS2 adds community 2:303 2:303 informational community of AS2 AS−Path: AS4, AS3, AS2, AS1 AS4

  • AS1 announces prefix p, AS4 receives announcement
  • Informational community 2:303 is added by AS2

11

slide-25
SLIDE 25

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

AS2 adds communities AS3 forwards communities 2:303 2:303 2:303 informational community of AS2 AS−Path: AS4, AS3, AS2, AS1 Communities: AS4 2:203

  • AS1 announces prefix p, AS4 receives announcement
  • Informational community 2:303 is added by AS2

11

slide-26
SLIDE 26

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

AS2 adds communities AS3 forwards communities 2:303 3:123 informational community of AS2 action community towards AS3 3:123 2:303 2:303 AS−Path: 2:203 AS4, AS3, AS2, AS1 Communities: AS4

  • AS1 announces prefix p, AS4 receives announcement
  • Informational community 2:303 is added by AS2
  • AS2 also adds action community 3:123 for AS3

11

slide-27
SLIDE 27

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

AS2 adds communities AS3 forwards communities 2:303 3:123 informational community of AS2 action community towards AS3 3:123 3:123 2:303 2:303 AS−Path: 2:203, 3:123 AS4, AS3, AS2, AS1 Communities: AS4

  • AS1 announces prefix p, AS4 receives announcement
  • Informational community 2:303 is added by AS2
  • AS2 also adds action community 3:123 for AS3
  • Both communities are forwarded by AS3 to AS4

11

slide-28
SLIDE 28

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

3:123 3:123 2:303 2:303 AS−Path: 2:203, 3:123 AS4, AS3, AS2, AS1 Communities: AS4

12

slide-29
SLIDE 29

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

3:123 3:123 2:303 2:303 AS−Path: 2:203, 3:123 AS4, AS3, AS2, AS1 Communities: AS4

  • We can only infer which AS added a specific community

12

slide-30
SLIDE 30

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

3:123 3:123 2:303 2:303 AS−Path: 2:203, 3:123 AS4, AS3, AS2, AS1 Communities: AS4

  • We can only infer which AS added a specific community
  • We assume that a community n:value was added by AS n

12

slide-31
SLIDE 31

BGP Communities propagation

p p p

AS2 AS3 AS4 AS1

2:303 3:123 traversed at least two AS−links traversed at least one AS−link 3:123 3:123 2:303 2:303 inferred travel−distance is a lower bound! AS−Path: 2:203, 3:123 AS4, AS3, AS2, AS1 Communities: AS4

  • We can only infer which AS added a specific community
  • We assume that a community n:value was added by AS n
  • This gives a lower bound for the ‘travel distance’
  • In above example we calculate AS-hop-count 1 for 3:123

12

slide-32
SLIDE 32

BGP Community Propagation Observations

  • 2

4 6 8 10 0.0 0.2 0.4 0.6 0.8 1.0 AS hop count Fraction of communities (ECDF)

  • 10% of communities have a AS hop count of more than six
  • More than 50% of communities traverse more than four ASes
  • Longest community propagation observed: 11 AS hops

13

slide-33
SLIDE 33

BGP Community Propagation Observations

2 4 6 8 10 0.0 0.2 0.4 0.6 0.8 1.0 AS hop count Fraction of communities (ECDF)

  • 10% of communities have a AS hop count of more than six
  • More than 50% of communities traverse more than four ASes
  • Longest community propagation observed: 11 AS hops

13

slide-34
SLIDE 34

BGP Community Propagation Observations

2 4 6 8 10 0.0 0.2 0.4 0.6 0.8 1.0 AS hop count Fraction of communities (ECDF)

  • 10% of communities have a AS hop count of more than six
  • More than 50% of communities traverse more than four ASes
  • Longest community propagation observed: 11 AS hops

13

slide-35
SLIDE 35

BGP Community Propagation Behavior

AS1 AS4 AS3 AS2

14

slide-36
SLIDE 36

BGP Community Propagation Behavior

p p p

AS1 AS4 AS3 AS2

  • AS1 announces prefix p

14

slide-37
SLIDE 37

BGP Community Propagation Behavior

p p p

AS1 AS4 AS3 AS2

3:123 3:123 3:123

  • AS1 announces prefix p, tagged with 3:123

14

slide-38
SLIDE 38

BGP Community Propagation Behavior

p p p

AS1 AS4 AS3 AS2

3:123 3:123 3:123

  • AS1 announces prefix p, tagged with 3:123
  • Community is intended for signaling towards AS3

14

slide-39
SLIDE 39

BGP Community Propagation Behavior

p p p

AS1 AS4 AS3 AS2

3:123 3:123 3:123

  • AS1 announces prefix p, tagged with 3:123
  • Community is intended for signaling towards AS3
  • AS4 also receives this announcement

14

slide-40
SLIDE 40

BGP Community Propagation Behavior

p p p

AS1 AS4 AS3 AS2

3:123 3:123 3:123

p: 4, 2, 1 3:123 p: 3, 2, 1 3:123

  • AS1 announces prefix p, tagged with 3:123
  • Community is intended for signaling towards AS3
  • AS4 also receives this announcement

14

slide-41
SLIDE 41

BGP Community Propagation Behavior

p p p

AS1 AS4 AS3 AS2

3:123 3:123 3:123

p: 4, 2, 1 3:123

"on−path"

p: 3, 2, 1 3:123

  • AS1 announces prefix p, tagged with 3:123
  • Community is intended for signaling towards AS3
  • AS4 also receives this announcement

14

slide-42
SLIDE 42

BGP Community Propagation Behavior

p p p

AS1 AS4 AS3 AS2

3:123 3:123 3:123

"on−path"

p: 3, 2, 1 3:123 p: 4, 2, 1

"off−path"

3:123

  • AS1 announces prefix p, tagged with 3:123
  • Community is intended for signaling towards AS3
  • AS4 also receives this announcement

Off-path: ASN from community is not on the observed AS-path at AS4.

14

slide-43
SLIDE 43

On-path versus off-path

1 65000 666 100 3000 2 1000 9498 200 1000 100 1 200 2000 10 2 3000 500 % communities observed 0.0 0.2 0.4 0.6 0.8 1.0 1.2

  • ff-path
  • n-path
  • Blackholing communities (e.g., :666)

’leaking’ off path

  • But AS implementing RTBH

SHOULD add NO ADVERTISE or NO EXPORT (RFC7999) Suggests ASes not implementing RTBH do not filter.

15

slide-44
SLIDE 44

Experiments

slide-45
SLIDE 45

Experimental setup

  • Experiments conducted in a lab environment1
  • Validated on the Internet

Scenarios

  • Remote Triggered Blackholing (RTBH)
  • Traffic redirection attack

...more in the paper.

1Configurations available at: https://www.cmand.org/caas/

16

slide-46
SLIDE 46

RTBH: How It Works

AS5 AS1 AS3 AS4 AS2

17

slide-47
SLIDE 47

RTBH: How It Works

AS5 AS1 AS3 AS4 AS2

BGP announcements

p 17

slide-48
SLIDE 48

RTBH: How It Works

AS5 AS1 AS3 AS4 AS2

BGP announcements Traffic flow

p 17

slide-49
SLIDE 49

RTBH: How It Works

AS1 sends p, tagged 2:666

AS5 AS1 AS3 AS4 AS2

BGP announcements Traffic flow

p

2:666

  • AS announces BH-prefix

to upstream

17

slide-50
SLIDE 50

RTBH: How It Works

AS2 continues announcing p AS1 sends p, tagged 2:666

AS5 AS1 AS3 AS4 AS2

BGP announcements Traffic flow

p

2:666

  • AS announces BH-prefix

to upstream

17

slide-51
SLIDE 51

RTBH: How It Works

AS2 continues announcing p AS1 sends p, tagged 2:666

AS5 AS1 AS3 AS4 AS2

BGP announcements Traffic flow

p

2:666

  • AS announces BH-prefix

to upstream

17

slide-52
SLIDE 52

RTBH: How It Works X

AS2 continues announcing p AS1 sends p, tagged 2:666

AS5 AS1 AS3 AS4 AS2

BGP announcements Traffic flow

p

2:666

  • AS announces BH-prefix

to upstream → Provider blackholes prefix

17

slide-53
SLIDE 53

RTBH: How It Works X

AS2 continues announcing p Traffic to p is dropped at AS2 AS1 sends p, tagged 2:666

AS5 AS1 AS3 AS4 AS2

BGP announcements Traffic flow

p

2:666

  • AS announces BH-prefix

to upstream → Provider blackholes prefix

17

slide-54
SLIDE 54

RTBH: How It Works

X

AS2 continues announcing p Traffic to p is dropped at AS2 AS1 sends p, tagged 2:666

AS5 AS1 AS3 AS4 AS2

BGP announcements Traffic flow

p

2:666

  • AS announces BH-prefix

to upstream → Provider blackholes prefix Safeguards

  • Provider should check customer prefix before accepting RTBH
  • Customer may only blackhole own prefixes
  • Different policies for Customers/Peers
  • On receiving RTBH, add NO ADVERTISE or NO EXPORT (RFC7999)

18

slide-55
SLIDE 55

RTBH: How It Should Not Work

BGP announcements

AS2 AS4 AS1 AS3

p p p p p

19

slide-56
SLIDE 56

RTBH: How It Should Not Work

AS1 announces p

BGP announcements Traffic flow

AS2 AS4 AS1 AS3

p p p p p

19

slide-57
SLIDE 57

RTBH: How It Should Not Work

Community Target Attackee Attacker AS1 announces p

BGP announcements Traffic flow

AS2 AS4 AS1 AS3

p p p p p

19

slide-58
SLIDE 58

RTBH: How It Should Not Work

Community Target Attackee Attacker AS2 tags p with AS3:666 AS1 announces p

BGP announcements Traffic flow

AS2 AS4 AS1 AS3

p p p p

AS3:666

p p

19

slide-59
SLIDE 59

RTBH: How It Should Not Work

Community Target

X

Attackee Attacker AS2 tags p with AS3:666 Traffic to p is dropped at AS3 AS1 announces p

BGP announcements Traffic flow

AS2 AS4 AS1 AS3

p p p p

AS3:666

p p

19

slide-60
SLIDE 60

RTBH: How It Should Not Work

Community Target

X

Attackee Attacker AS2 tags p with AS3:666 Traffic to p is dropped at AS3 AS1 announces p

BGP announcements Traffic flow

AS2 AS4 AS1 AS3

p p p p

AS3:666

p p

  • AS on ’backup’ path adds RTBH-community
  • Provider blackholes prefix
  • Not only traffic traversing AS2 is dropped

19

slide-61
SLIDE 61

RTBH: How It Should Not Work (with hijack)

Community Target

X

Attackee Attacker Traffic to p is dropped at AS3 AS1 announces p

BGP announcements Traffic flow

AS2 hijacks p, with AS3:666

AS2 AS4 AS1 AS3

p p

AS3:666

p p

  • Hijacker announces RTBH
  • Prefix filters circumvented due to misconfiguration
  • Provider blackholes prefix

20

slide-62
SLIDE 62

RTBH: Attack Confirmed

Attack confirmed to work on the Internet, works multi hop and is hard to spot Triggering RTBH is possible for attackers because, e.g.,:

  • BH prefix is more specific, accepted via exception
  • Providers check BH community before prefix filters2
  • NO ADVERTISE or NO EXPORT often is ignored / not set
  • Problem: No validation for origin of community

2we found configuration guides with that bug

21

slide-63
SLIDE 63

Traffic Redirection Attack

AS3 AS6 AS4 AS2 AS1 AS5

22

slide-64
SLIDE 64

Traffic Redirection Attack

p

BGP−Announcements

AS3 AS6 AS4 AS2 AS1 AS5

22

slide-65
SLIDE 65

Traffic Redirection Attack

p

Trafficflow BGP−Announcements

AS−Paths at AS6:

AS3 AS6 AS4 AS2 AS1 AS5

p: p: 5, 4, 2, 1 3, 2, 1 22

slide-66
SLIDE 66

Traffic Redirection Attack

p

Attackee Attacker Community Target

Trafficflow BGP−Announcements

AS−Paths at AS6:

AS3 AS6 AS4 AS2 AS1 AS5

p: p: 5, 4, 2, 1 3, 2, 1 22

slide-67
SLIDE 67

Traffic Redirection Attack

AS3:3x

p p

Attackee Attacker Community Target

Trafficflow BGP−Announcements

AS−Paths at AS6:

AS3 AS6 AS4 AS2 AS1 AS5

p: 3, 3, 3, p: 2, 1 5, 4, 2, 1

  • Attacker AS2 uses community to add path-prepending in AS3

22

slide-68
SLIDE 68

Traffic Redirection Attack

AS3:3x

p p

Attackee Attacker Community Target

Trafficflow BGP−Announcements

AS−Paths at AS6:

AS3 AS6 AS4 AS2 AS1 AS5

p: 3, 3, 3, p: 2, 1 5, 4, 2, 1

  • Attacker AS2 uses community to add path-prepending in AS3
  • AS6 routes traffic towards prefix p via AS5, AS4

22

slide-69
SLIDE 69

Traffic Redirection Attack

AS3:3x

p p

Attackee Attacker Community Target

Trafficflow BGP−Announcements

AS−Paths at AS6:

AS3 AS6 AS4 AS2 AS1 AS5

p: 3, 3, 3, p: 2, 1 5, 4, 2, 1

  • Attacker AS2 uses community to add path-prepending in AS3
  • AS6 routes traffic towards prefix p via AS5, AS4

22

slide-70
SLIDE 70

Traffic Redirection Attack

AS3:3x

p p

Attackee Attacker Community Target

Trafficflow BGP−Announcements

AS−Paths at AS6:

AS3 AS6 AS4 AS2 AS1 AS5

p: 3, 3, 3, p: 2, 1 5, 4, 2, 1

</>

  • Attacker AS2 uses community to add path-prepending in AS3
  • AS6 routes traffic towards prefix p via AS5, AS4
  • Network tap?

22

slide-71
SLIDE 71

Traffic Redirection Attack

AS3:3x

p p

Attackee Attacker Community Target

Trafficflow BGP−Announcements

AS−Paths at AS6:

AS3 AS6 AS4 AS2 AS1 AS5

p: 3, 3, 3, p: 2, 1 5, 4, 2, 1

  • Attacker AS2 uses community to add path-prepending in AS3
  • AS6 routes traffic towards prefix p via AS5, AS4
  • Network tap?
  • Slow/Congested link?
  • ...

22

slide-72
SLIDE 72

Communities Confirmed In Attacks

Attack on 10 July 2018 ”For about 30 minutes, these hijack prefixes weren’t propagated very far. Then they were announced again at 23:37:47 UTC for about 15 minutes but to a larger set of peers — 48 peers instead of 3 peers in the previous hour. It appears a change of BGP communities from 24218:1120 to 24218:1 increased the route propagation.”

Source: https://dyn.com/blog/bgp-dns-hijacks-target-payment-systems/

23

slide-73
SLIDE 73

Discussion

slide-74
SLIDE 74

Discussion

Transitivity Authenticity Documentation Monitoring Standards

24

slide-75
SLIDE 75

Discussion: Authenticity

Authenticity

  • Communities can be modified, added, removed by every AS
  • No attribution is possible
  • No cryptographic protection (RPKI does not help)
  • Still operators rely on their ‘correctness’
  • Large communities partially improve the situation

How can we achieve authenticity, or at least attribution?

25

slide-76
SLIDE 76

Discussion: Transitivity

Transitivity

  • Communities can help in debugging
  • Easy, low overhead communication channel
  • Widely in use, but often only 1-2 hops
  • But: High risk of being abused!

Are fully transitive communities still worth the clear risk?

26

slide-77
SLIDE 77

Discussion: Monitoring

Monitoring

  • There is no global state in BGP
  • Route collectors only see the ’end-result’
  • Inferring modifications between origin-AS

and collector: almost impossible

  • The meaning of a particular community can not be known
  • No universal way for attribution of changes

Monitoring communities to detect abuse is extremely difficult.

27

slide-78
SLIDE 78

Discussion: Standards

Standards

  • There are limited standardized communities
  • Many AS do not implement these
  • Is the lack of standardized communities a problem?
  • Are standards doing harm, by helping attackers?
  • Security by obscurity never works

Standardization is necessary.

28

slide-79
SLIDE 79

Discussion: Documentation

Documentation

  • Communities are individually defined by the ASes
  • Documentation, if available, is scattered over

whois, websites, customer-portals, ...

  • Not in machine-readable format, often natural language
  • Automated parsing can work for limited scope/fixed applications
  • Parsing for general purpose applications is not feasible

Documentation is limited and fragmented.

29

slide-80
SLIDE 80

Summary

Communities Shortcomings

  • Semantics loosely defined, no authenticity
  • Secure usage requires good operational knowledge and diligence
  • Attacks are possible and indeed already happening

30

slide-81
SLIDE 81

Summary

Communities Shortcomings

  • Semantics loosely defined, no authenticity
  • Secure usage requires good operational knowledge and diligence
  • Attacks are possible and indeed already happening

Future Work

  • Attack detection
  • Attribution
  • Distributed realtime monitoring?
  • Protocol improvements for BGP?

30

slide-82
SLIDE 82

Appendix

slide-83
SLIDE 83

Recommendations for Operators

  • AS should filter incoming Informational Communities

carrying their ASN

  • Agreements with Downstreams might be needed, e.g.,

to filter Action Communities

  • Publicly documenting Communities used is key to

enable other AS to filter

  • Monitoring/Logging received communities for tracking abuse
  • Providing public looking glasses, showing communties, helps debugging

31