Interdomain Issues for IP networks

Henning Schulzrinne(with lots of borrowed slides...)

April 18, 2023 2

Overview

Architecture review Interdomain routing Multicast VPNs Interdomain QoS

– signaling– charging and settlements

Interdomain application signaling Carrier selection and multihoming

April 18, 2023 3

Architecture review

Classical view of ISP food chain Tier-1, tier-2

Inter-regional Internet backbone

357 Mbit/s

19’716 Mbit/s

Asia-Pacific

LatinAmerica &Caribbean

2’638

Mbit/s

127 Mbit/s

Arab States, Africa

468 Mbit/s

171 Mbit/s

Europe

56’241 Mbit/sUSA &Canada

Source: TeleGeography Inc., Global Backbone Database. Data valid for Sept. 2000.

April 18, 2023 5

Examples of carriers

Tier 1: UUNet, Cable & Wireless (C&W), Sprint, Qwest, Genuity, AT&T

Tier 2: America Online, Broadwing, @home

Tier 3: RCN, Verizon, Log On America

April 18, 2023 6

Definitions

Peering: exchange of data between ISPs on a sender-keeps-all basis

Access provider (IAP): provide dial-up and leased line access, buy Internet access from tier-1/2 providers

Transit: Using ISP A to reach customers of ISP B, C, ...

Hot potato routing: find earliest exit point to destination network asymmetric routes

April 18, 2023 7

NAP or IXPs

Internet eXchange Points "An Internet Exchange (IX) acts as a junction

between multiple points of Internet presence. Here, peers are able to directly connect to each other to exchange local Internet traffic. Typically, the IX owns and operates the switching platforms used to interconnect the various users/subscribers."

Also known as Metropolitan Area Exchanges (MAEs)

see http://www.telegeography.com/ix/ governed by Multi-Lateral Peering

Agreements (MLPA)

April 18, 2023 8

Some European IXPsAustria - The Vienna Internet eXchange (VIX) Belgium - Belnet (BNIX) Cyprus - The Cyprus Internet eXchange (CyIX) Denmark - Danish Internet eXchange (DIX) Lyngby Finland - Finnish Commercial Internet eXchange (FCIX)

Helsinki) France - Paris Internet eXchange (PARIX) France - French Global Internet eXchange (SFINX) Germany - The Deutsche Central Internet eXchange (DE-

CIX) Frankfurt Greece - The Athens Internet eXchange (AIX) Ireland - The Internet Neutral eXchange (INEX) Italy - The Milan Internet eXchange (MIX) Italy - NAP Nautilus (CASPUR) Luxembourg - The Luxembourg Internet eXchange (LIX) Netherlands - The Amsterdam Internat eXchange (AMS-IX) Norway - Norwegian Internet eXchange (NIX) Portugal - The Portuguese Internet eXchange (PIX) Scotland - Scottish Internet Exchange (ScotIX) Spain - El Punto Neutral Espanol (ESPANIX) Sweden - The Netnod Internet eXchange (D-GIX) Switzerland - The Swiss Internet eXchange (SIX) Switzerland - Geneva Cern (CIXP) Switzerland - Zürich Telehouse Internet Exchange (TIX) United Kingdom - The London INternet eXchange (LINX) United Kingdom - Manchester Network Access Point

(MaNAP)

United Kingdom - London Network Access Point (LoNAP)

Bulgaria - The Sofia Internet eXchange (SIX - GoCIS)

Czech Rep. - Neutral Internet eXchange (NIX) Prague

Latvia - The Global Internet eXchange (GIX) LatNet

Romania - The Bucharest Internet eXchange (BUHIX)

Slovakia - The Slovak Internet eXchange (SIX)

Ukraine - The Central Ukrainian Internet eXchange

April 18, 2023 9

The view from elsewhere

Looking glass sites show BGP routes:

April 18, 2023 10

RADB$ whois -h whois.radb.net AS14aut-num: AS14as-name: COLUMBIAdescr: Columbia University in the City of New York Network Operations Academic Information Systems 612 West 115th Street New York, NY 10025admin-c: CU-NOCtech-c: CU239-ORGimport: from AS1785 action med=100; # ApTh commodity accept ANYimport: from AS701 action med=200; # UUnet commodity accept ANYimport: from AS14:AS-ISPPEERS action pref=10; # private ISP peers accept <^PeerAS+$>import: from AS14:AS-NNPEERS action pref=10; # private NN peers accept <^PeerAS+$>import: from AS145 action med=75; # vBNS I2 accept ANY AND NOT {0.0.0.0/0}import: from AS11537 action med=50; # Abilene I2 accept ANY AND NOT {0.0.0.0/0}import: from AS3754 action med=100; # NYSERNet I2 accept <^AS3754+ AS11537+> AND NOT {0.0.0.0/0}

April 18, 2023 11

QoS

Interdomain SLAs are rare (or non-existent)

Large difference between inter- and intradomain performance?

April 18, 2023 12

Interdomain QoS Issues

Request authentication Uniform service levels – my "gold"

is your "bronze"... Payment

– NJ Turnpike?– Gardenstate Parkway?

April 18, 2023 13

Interdomain QoS metric

April 18, 2023 14

Carrier selection

Allow selection of carrier Easy for multi-homed sites but everything else requires loose

source route – but what IP address?

will work in both directions

April 18, 2023 15

Interdomain multicast

Any-source multicast (ASM) has many operational problems:– PIM-SM/DM are only intradomain– PIM-SM complex– RP has scaling and reliability problems– interdomain never got off the ground– no deployed multicast address

allocation mechanism– spam problem – anybody can send to

group

April 18, 2023 16

Interdomain multicast

Single-source multicast (SSM)– source-filtered IGMPv3– {S,G} as group– avoid address allocation– match many applications:

• Internet radio/TV• conferences with single active source

April 18, 2023 17

Distributed Denial of Service (DDOS)

Need packet tracing (in progress) Need push-back to filter DOS

stream– at source– or close to source

Authentication of filter request to prevent malicious blackouts

April 18, 2023 18

Settlements

= payments between providers long history in telephone network e.g., 4.6b US$ in 2000 net

settlements

April 18, 2023 19

Total Accounting Rate (TAR)

Traditional conceptual cost of connecting a call from country A to country B

Each end contribute the building cost of half circuit to the midpoint

Based on “cost” of early tiny capacity submarine cable

Settlement A to B at 1/2 TARS. Cheng/ITU

April 18, 2023 20

Total Accounting Rate (TAR) - cont’d

Same Rate for the opposite direction

Apply to all PSTN services When the accounting rate change

in one direction the other direction must follow

S. Cheng/ITU

April 18, 2023 21

Termination Rate

Usually based on cost of terminating call by destination carrier

Accounting rate may not be the same for the other direction

Accounting rate in each direction can change independent of each other

May deliver traffic at mid-point or FOB on either end of circuit.

S. Cheng/ITU

April 18, 2023 22

Sender keeps all (Peering) Sender keeps all revenue from

calling party No settlement between carriers Applicable if average cost and

traffic volume are virtually identical in each direction

Usually based on half circuit ownership

S. Cheng/ITU

April 18, 2023 23

US domestic telephony settlements

Doesn't quite fit SKA Long-distance company collects Pays fixed charge/minute to

originating and terminating local exchange carrier (LEC)

Where does the money go? Where does the money go? Typical US ISP cash-flowTypical US ISP cash-flow

$19.95 per month subscription

$7.50-$10.50 Wholesale PoP Access

$2.00 - $3.00 Customer Care

$3.00 amortised customer marketing

$3.50-$7.50 margin per customer

Source: Adapted from Paul Stapleton, ISP$ Market Report, Boardwatch Magazine.

Settlements-based trafficSettlements-based traffic

PTO A

Collectsrevenues

Collectstraffic

PTO B

Retainsrevenues

Terminatestraffic

Delivers traffic

Pays settlement fees

User 1 User 2 User 3 User 1 User 2 User 3

For accounting rate traffic, a direct bilateralrelationship is established between the origin and

termination operators. Intermediate transit operatorsare compensated from the accounting rate which is

usually split 50:50. PTO B retains net settlement.……...

PTO = PublicTelecommunicationsOperator

PTOs A & Bsplit the cost ofthe int’l circuit

Internet Peering traffic (Web)

ISP A

Exchangestraffic

ISP B

Collectsrevenues

Requestsand terminatestraffic

One-way (thick pipe)

User 1 User 2 User 3

For Internet Peering traffic, ISP B pays forboth halves of the International circuit(s) which areused for peering with ISP A. ISP B also pays for traffic exchange.ISP B may pay for the circuit directly, or in conjunction with one or more PTOs.

ISP = InternetServicesProvider

PTO B pays the full cost ofthe int’l circuit

Two-way (thin pipe)

Web 1 Web 1 Web 1

April 18, 2023

Settlements and Peering: What’s the difference?

Settlement-payment traffic– Substantial revenue transfers, from core to

periphery of network– Promotes “organic” network growth– So, Operators generating less traffic than they

receive have an incentive to keep prices high Peering traffic

– Some revenue transfers, from periphery to core of network

– Promotes “spontaneous” network growth– So, ISPs generating less traffic than they receive

have an incentive to force prices down

Internet traffic flows are highly Internet traffic flows are highly asymmetric asymmetric

Public switched telephone serviceTraffic flows are bilateral and broadly match value flow in that caller, who initiates the call, also pays for itCall-back reverses the direction of the call, from a statistical viewpoint, but caller still pays & benefitsTraffic flows unbalanced between developed and developing countries

Public Internet serviceTraffic flows are multi-lateral: A single session may poll many countriesWeb-browsing is dominant form of traffic: traffic flow is dominantly towards user who initiates the call. Web traffic highly asymmetricNewer forms of Internet traffic (telephony, push media, streaming video etc) reverses traffic flow to be from user which initiates the call

April 18, 2023 29

Interdomain AAA

Roaming user identified by NAI (RFC 2486), e.g., alice@example.com

Find DIAMETER AAA via NAPTR + SRV Generic problem different:

– User Alice@A from ISP A visits ISP B– ISP B needs to determine whether Alice is a

valid customer of A– Alice needs to authorize B to query A– Needs to get authorization for maximum €

amount very similar to credit card authorization!

April 18, 2023 30

Clearinghouse models

e.g., iPass or GRIC for roaming dial-up and wireless users– member company charges subscribers– gets access to other dial-up ports via

clearinghouse– gets reimbursed for "visitors"

GSM roaming is not a good model– no price transparency– inefficient routing

April 18, 2023 31

SIP interdomain

Designed to find proxies by request URI

Authentication and anonymity are issues:– how can callee ascertain identity of

random caller?– how can caller know that she's talking

to the right person?– trust provider to remove privacy-

compromising information

April 18, 2023 32

BGP problems

Trust Need route filtering:

In April 1997, a small ISP in Florida made a mistake in configuring the router that joined its small network to Sprint. This ISP, known as AS number 7007, allowed all the routes it learned from Sprint using BGP to be exported back to Sprint as its own routes. This is easy to do, because BGP implementations can take routes from IGP and convert them into EGP routes. In this case, the IGP converted CIDR routes into classful routes. The Sprint BGP speaker wasn't filtering properly either and began sending out updates that added AS7007 as the correct route for a portion of every CIDR block (essentially, the first class C, 24-bit-long network prefix). This misinformation first spread through Sprint's network, then to neighboring NSPs, including ANS, MCI, UUNet, and others. Many routers crashed because their routing tables suddenly doubled in size (an additional route was added for each CIDR block), and the routing instability spread throughout the Internet. Remember that, when a router crashes, it drops its BGP connection with its peer, which then sends out an update withdrawing all the routes announced previously by the crashed router. (Network Magazine, March 2002)

April 18, 2023 33

Alternatives to improving routing

"Resilient Overlay Networks" (Andersen/Balakrishnan/Kashoek/Morris2001)– application-layer routing with one hop

Multihoming:– treat networks like cheap PCs– 99.5% reliability² 99.9975%

reliability

April 18, 2023 34

Multihoming problems

Need either an ASN or two IP address ranges

Only for larger networks don't allow advertisements for /24

Network impact: two /22 entries for each subnet

Alternative: NAT– doesn't help reachability of servers

advertised in DNS

BGP Issues

Geoff Huston

April 18, 2023 36

Why measure BGP?

BGP describes the structure of the Internet, and an analysis of the BGP routing table can provide information to help answer the following questions:

– What is changing in the deployment environment?– Are these changes sustainable?– How do address allocation policies, BGP and the

Internet inter-relate?– Are current address allocation policies still relevant?– What are sensible objectives for address allocation

policies?

April 18, 2023 37

Techniques

Passive Measurement– Takes measurements from a default-free router at the

edge of the local network– Easily configured– Single (Filtered) view of the larger Internet

• What you see is a collection of best paths from your immediate neighbours

Local AS

eBGP

Measurement Point

April 18, 2023 38

Techniques

Multiple Passive measurement points– Measure a number of locations simultaneously– Can be used to infer policy

AS3

Measurement Points

AS2

AS1

April 18, 2023 39

Techniques

Single passive measurement point with multiple route feeds– Best example:

• Route-views.oregon-ix.net• Operating since 1995• 42 peers• Uses eBGP multihop to pull in route views

April 18, 2023 40

Techniques

Active Measurement Tests– Convergence

• Announcement and withdrawal

Monitoring Unit

AS2

AS1

Reporting Points

Route Injection Point

Internet

April 18, 2023 41

Interpretation

BGP is not a link state protocol There is no synchronized overview of the

entire connectivity and policy state Every BGP viewing point contains a filtered

view of the network– Just because you can’t see it does not mean that it

does not exist

BGP metrics are sample metrics

BGP Table GrowthBGP Table Growth – 12 year history

BGP Table Growth – 2 year history

55000

65000

75000

85000

95000

105000

115000

125000

Jan-99 Apr-99 Jul-99 Oct-99 Jan-00 Apr-00 Jul-00 Oct-00 Jan-01

BGP Table Growth – 2 year & 6 month trends

50000

60000

70000

80000

90000

100000

110000

120000

Jan-99 Mar-99 May-99 Jul-99 Sep-99 Nov-99 Jan-00 Mar-00 May-00 Jul-00 Sep-00 Nov-00 Jan-01

50000

100000

150000

200000

250000

300000

350000

400000

450000

Sep-00 Dec-00 Mar-01 Jun-01 Sep-01 Dec-01 Mar-02 Jun-02 Sep-02 Dec-02 Mar-03 Jun-03 Sep-03 Dec-03 Mar-04 Jun-04

BGP Table Growth – Projections

Prefix distribution in the BGP table

/24 is the fastest growing prefix length

/25 and smaller are the fastest growing prefixesin relative terms

April 18, 2023 49

Prefixes by AS Distribution of originating address sizes per AS Address advertisements are getting smaller

0

200

400

600

800

1000

1200

1400

1600

0 5 10 15 20 25 30

Prefix Length

Num

ber

of

AS’s

Non-HierarchicalAdvertisements

April 18, 2023 50

Multi-homing on the rise?

Track rate of CIDR “holes” – currently 41% of all route advertisements are routing ‘holes”

This graph tracks the number of address prefix advertisements which are part of an advertised larger address prefix

0.35

0.37

0.39

0.41

0.43

0.45

Jan-00 Apr-00 Jul-00 Oct-00 Jan-01

Proportion of BGP advertisements which aremore specific advertisements of existing aggregates

April 18, 2023 52

OOPS

Program bug! The number is larger than that. More specific advertisement of existing

aggregates account for 54% of the BGP selected route table from the perspective of AS1221– 56,799 entries from a total of 103,561

Older (mid Jan) data from AS286 has the number at 53,644 from a total of 95,036 (56%)

April 18, 2023 53

Routed Address Space

Large fluctuation is due to announcement / withdrawals of /8 prefixes12 months of data does not provide clear longer growth characteristic

April 18, 2023 54980000000

1000000000

1020000000

1040000000

1060000000

1080000000

1100000000

1120000000

1140000000

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Routed Address Space (/8 Corrected)

Annual compound growth rate is 7% p.a.Most address consumption today appears to beocurring behind NATs/8 Corrected Data

April 18, 2023 55

AS Number Growth

April 18, 2023 56

0

10000

20000

30000

40000

50000

60000

70000

Oct-96 Apr-97 Sep-97 Mar-98 Sep-98 Mar-99 Sep-99 Mar-00 Sep-00 Mar-01 Sep-01 Mar-02 Sep-02 Mar-03 Sep-03 Mar-04 Sep-04 Mar-05 Sep-05

AS Number Use - Extrapolation

Continued exponential growth implies AS number exhaustion in 2005

April 18, 2023 57

Average size of a routing table entry

The BGP routing tale is growing at a faster rate than the rate of growth of announced address space

/18.1

/18.5

April 18, 2023 58

Denser Internet Structure

0

100000000

200000000

300000000

400000000

500000000

600000000

1 2 3 4 5 6 7 8 9 10

Dec-2000

Feb-2001

AS Hops

ReachableAddresses

April 18, 2023 59

Denser Internet Structure

AS Hops

Addre

ss S

pan

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10

Feb-2001

Dec-2000

90% point

April 18, 2023 60

Internet ‘Shape’

Distance

Span

Distance

Span

The network is becoming less ‘stringy’ and more densely interconnected– i.e. Transit depth is getting smaller

April 18, 2023 61

Aggregation and Specifics

Is the prevalence of fine-grained advertisements the result of deliberate configuration or inadvertent leakage of advertisements?

April 18, 2023 62

Publicity helps ? Efforts to illustrate the common problem of

unconstrained table growth appear to have had an impact on growth of the table, as seen on the edge of AS1221 since Dec 2000

95000

100000

105000

110000

115000

Nov-00 Dec-00 Jan-01 Feb-01 Mar-01

April 18, 2023 63

But - the view from KPNQwest

Data from James Aldridge, KPNQwest - http://www.mcvax.org/~jhma/routing/

88000

90000

92000

94000

96000

98000

100000

Nov-00 Dec-00 Jan-01 Feb-01 Mar-01

April 18, 2023 64

Different Views

40000

50000

60000

70000

80000

90000

100000

110000

Jul-97 Oct-97 Jan-98 Apr-98 Jul-98 Oct-98 Jan-99 Apr-99 Jul-99 Oct-99 Jan-00 Apr-00 Jul-00 Oct-00 Jan-01

AS1221

AS286

April 18, 2023 65

Different Views

Route views in prefix-length-filtered parts of the net do not show the same recent reduction in the size of the routing table.

It is likely that the reduction in routes seen by AS1221 appears to be in the prefix-length filtered ranges– Either more transit networks are prefix

length filtering or origin AS’s are filtering at the edge, or both

The underlying growth trend in BGP table size remains strong

April 18, 2023 66

Aggregation possibilities

What if all advertisements were maximally aggregated* ?– 27% reduction (103126 -> 74427)

using AS Path aggregation– 33% reduction (103126 -> 68504)

using AS Origin aggregation

• This assumes that the specific advertisements are not matched by other specific advertisements which have been masked out closer to the origin AS – this is not a terribly good assumption, so these numbers are optimistic to some extent

April 18, 2023 67

Aggregation Potential from AS1221

AS Origin

AS Path

April 18, 2023 68

The aggregation potential view from KPNQwest

55000

60000

65000

70000

75000

80000

85000

90000

95000

100000

May-00 Jul-00 Aug-00 Oct-00 Nov-00 Jan-01 Mar-01

Data from James Aldridge, KPNQwest - http://www.mcvax.org/~jhma/routing/

AS Origin

AS Path

April 18, 2023 69

A Longer Term View from AS286

April 18, 2023 70

Different Views Similar AS Origin, but different AS Path aggregation outcomes Prevalence of the use of specifics for local inter-domain traffic

engineering

0

20000

40000

60000

80000

100000

120000

BGP Table AS Path AS Origin

AS286

AS1221

April 18, 2023 71

Aggregatability?

A remote view of aggregation has two potential interpretations:– Propose aggregation to the origin AS– Propose a self-imposed proxy aggregation

ruleset Any aggregation reduces the information

content in the routing table. Any such reduction implies a potential change in inter-domain traffic patterns.

Aggregation with preserved integrity of traffic flows is different from aggregation with potential changes in traffic flow patters

April 18, 2023 72

Aggregatability

Origin AS aggregation is easier to perform at the origin, but harder to determine remotely IF traffic flows are to be preserved

Proxy Aggregation is only possible IF you know what your neighbors know

Yes this is a recursive statement

– If an AS proxy aggregates will it learn new specifics in response?

April 18, 2023 73

BGP as a Routing Protocol

How quickly can the routing system converge to a consistent state following dynamic change?

Is this time interval changing over time?

April 18, 2023 74

Increased convergence time intervals for BGP

Measured time to withdraw route: – Up to 2 minutes

Measured time to advertise new route: – Up to 30 minutes

April 18, 2023 75

What is happening here?

How long until routes return? (From A Study of Internet Failures)

April 18, 2023 76

Withdraw Convergence

AS1

AS2

AS3

AS4

April 18, 2023 77

Withdraw Convergence

Probability distribution Providers exhibit different, but

related convergence behaviors 80% of withdraws from all ISPs

take more than a minute For ISP4, 20% withdraws took

more than three minutes to converge

April 18, 2023 78

Failures, Fail-overs and Repairs

April 18, 2023 79

Failures, Fail-overs and Repairs

Bad news does not travel fast… Repairs (Tup) exhibit similar convergence

properties as long-short ASPath fail-over Failures (Tdown) and short-long fail-overs

(e.g. primary to secondary path) also similar

–Slower than Tup (e.g. a repair)–60% take longer than two minutes–Fail-over times degrade the greater the degree of multi-homing!

April 18, 2023 80

Conjectures….

BGP table size will continue to rise exponentially

Multi-homing at the edge of the Internet is on the increase

The interconnectivity mesh is getting denser– The number of AS paths is increasing faster than

the number of AS’s– Average AS path length remains constant

AS number deployment growth will exhaust 64K AS number space in August 2005 if current growth trends continue

April 18, 2023 81

More conjecturing….

Inter-AS Traffic Engineering is being undertaken through routing discrete prefixes along different paths -- globally (the routing mallet!)– AS Origin aggregation < AS Path aggregation

RIR allocation policy (/19, /20) is driving one area of per-prefix length growth in the aggregated prefix area of the table

BUT - NAT is a very common deployment tool– NAT, multihoming and Traffic Engineering is driving

even larger growth in the /24 prefix area

April 18, 2023 82

And while we are having such a good time conjecturing…

Over 12 months average prefix length in the table has shifted from /18.1 to /18.5

More noise (/25 and greater) in the table, but the absolute level of noise is low (so far)

Most routing table flux is in the /24 to /32 prefix space – as this space gets relatively larger so will total routing table flux levels– “Flux” here is used to describe the cumulative result of the

withdrawals and announcements– This space appears to be susceptible to social pressure – at

present

April 18, 2023 83

This is fun – lets have even more conjectures…

CIDR worked effectively for four years, but its effective leverage to support long term dampened route table growth and improved table stability has now finished

Provider-based service aggregation hierarchies as a model of Internet deployment structure is more theoretic than real these days

i.e. provider based route aggregation is leaking like a sieve!

April 18, 2023 84

Commentary

draft-iab-bgparch-00.txt– Exponential growth of BGP tables has

resumed– AS number space exhaustion– Convergence issues– Traffic Engineering in a denser mesh

– What are the inter-domain routing protocol evolutionary requirements?

April 18, 2023 85

Objectives and Requirements

Supporting a larger and denser interconnection topology

Scale by x100 over current levels in number of discrete policy entities

Fast Convergence Security Integration of Policy and Traffic

Engineering as an overlay on basic connectivity

Control entropy / noise inputs

April 18, 2023 86

Available Options

Social Pressure on aggregation Economic Pressure on route

advertisements Tweak BGP4 behavior Revise BGP4 community attributes BGPng New IDR protocol(s) New IP routing architecture

April 18, 2023 87

Social Pressure

Social pressure can reduce BGP noise Social pressure cannot reduce

pressures caused by– Denser interconnection meshing– Increased use of multi-homing– Traffic engineering of multiple

connections Limited utility and does not address

longer term routing scaling

April 18, 2023 88

Economic Pressure on Routing

Charge for route advertisements– Upstream charges a downstream per route

advertisements– Peers charge each other

This topic is outside an agenda based on technology scope

Raises a whole set of thorny secondary issues:– Commercial– National Regulatory– International

Such measures would attempt to make multi-homing less attractive economically. It does not address why multi-homing is attractive from a perspective of enhanced service resilience.

April 18, 2023 89

Tweaking BGP4

Potential tweak to BGP-4– Auto-Proxy-Aggregation

• Automatically proxy aggregate bitwise aligned route advertisements

• Cleans up noise – but reduces information• Cannot merge multi-homed environments

unless the proxy aggregation process makes sweeping assumptions, or unless there is an overlay aggregation protocol to control proxy aggregation (this is then no longer a tweak)

April 18, 2023 90

Extend BGP4 Communities We already need to extend community attributes to

take on the 2 / 4 octet AS number transition. Can we add further community attribute semantics to

allow proxy aggregation and proxy sublimation under specified conditions?

Extend commonly defined transitive community attributes to allow further information to be attached to a routing advertisement– Limit of ‘locality’ of propagation– Aggregation conditions or constraints

If we could do this, will this be enough? Can this improve– Scaling properties– convergence properties

April 18, 2023 91

BGPng

Preserve: AS concept, prefix + AS advertisements, distance vector operation, AS policy “opaqueness”

Alter: convergence algorithm (DUAL?), advertisement syntax (AS + prefix set + specifics + constraints), BGP processing algorithm

Issues:– Development time– Potential to reach closure on specification– Testing of critical properties– Deployment considerations– Transition mechanisms

April 18, 2023 92

IDR

A different IDR protocol?– Can we separate connectivity maintenance,

application of policy constraints and sender- and/or receiver- managed traffic engineering?

• SPF topology maintenance• Inter-Domain Policy Protocol to communicate policy

preferences between policy “islands”• Multi-domain path maintenance to support traffic

engineering requirements– Eliminate the need to advertise specifics to

undertake traffic engineering– Multi-homing may still be an issue – is multi-homing

a policy issue within an aggregate or a new distinct routing “entity”?

– Can SPF scale? Will SPF routing hierarchies impose policy on the hierarchy elements?

April 18, 2023 93

New IP Routing Architecture

Separate Identity, Location and Path at an architectural level?

Identity– How do you structure an entirely new unique identity

label space? How do you construct the “identity lookup” mechanism?

Location– How can location be specified independent of

network topology? Path:

– Is multi-homing an internal attribute within the network driven by inter-domain policies, or is multi-homing an end-host switching function

April 18, 2023 94

New IP Routing Architecture

Other approaches?– Realms and RSIP– Inter-Domain CRLDP approaches

where policy is the constraint

April 18, 2023 95

Slide credits

Geoff Huston Tim Kelly, ITU http://www.itu.int/ITU-D/ict/papers/