interdomain issues for ip networks henning schulzrinne (with lots of borrowed slides...)
Post on 20-Dec-2015
216 views
TRANSCRIPT
April 18, 2023 2
Overview
Architecture review Interdomain routing Multicast VPNs Interdomain QoS
– signaling– charging and settlements
Interdomain application signaling Carrier selection and multihoming
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 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 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., [email protected]
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
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 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
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
27-N
ov-
99
28-D
ec-9
9
28-J
an-0
0
28-F
eb-0
0
30-M
ar-
00
30-A
pr-
00
31-M
ay-
00
01-J
ul-00
01-A
ug-0
0
01-S
ep-0
0
02-O
ct-
00
02-N
ov-
00
03-D
ec-0
0
03-J
an-0
1
03-F
eb-0
1
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 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 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 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 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 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