Exchange Points, Route Servers and Registries

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Exchange Points, Route Servers and Registries

• Abha Ahuja
• ahuja_at_umich.edu

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Objectives

• To be able to explain what an exchange point is
• To be able to explain why people use XPs
• To understand why they are important
• To review some current exchange point designs
  used today
• To think about how to set up an exchange point in
  your environment
• To understand why Route Servers are useful
• To be able to explain what routing registries do
  and why you should use one

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Introduction to Exchange Points

• a bit of history
• What are they?
• Why use them?

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A Bit of History

• End of NSFnet - one major backbone
• move towards commercial Internet
• private companies selling their bandwidth
• need for coordination of routing exchange between
  providers
• Traffic from ISP A needs to get to ISP B
• Routing Arbiter project created to facilitate this

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What is an Exchange Point?

• Network Access Points (NAPs) established at end
  of NSFnet
• Major providers connect their networks and
  exchange traffic
• High-speed network or switch
• Simple concept - where providers come together to
  exchange traffic

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Exchange points
ISP A
XP 1
XP 2
ISP B
ISPs connect at Exchange Points or Network Access
Points to exchange traffic
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Conceptual Diagram of XP
Exchange Point Medium
Customer Router
Customer Router
Customer Router
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Why use an Exchange Point?

• Routers are attached to exchange traffic
• MLPA, bilateral, customer/transit relationships
• Examples in U.S
• AADS
• Mae-East/Mae-West
• Pacbell
• PAIX

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Why XPs?

• Multiple service providers
• Each with Internet connectivity

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Why XPs?

• Is not cost effective
• Backhaul issue causes cost to both parties

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Why XPs?

• Domestic Interconnection

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Exchange Structures

• layer 2 models (the NAP or IX)
• tailored bilateral policies

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Why use an Exchange Point?

• Peering
• Shared medium vs. point-to-point
• Shared
• can exchange traffic with multiple peers at one
  location via one interface
• Point-to-Point
• for high volumes of traffic

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The Need for Exchanges
AS 1
US
ASIA
AS 2
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The Need for Exchanges
AS 1
US
ASIA
AS 2
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Why use an Exchange Point?

• KEEP LOCAL TRAFFIC LOCAL!!!
• ISPs within a region peer with each other at
  local exchange
• No need to have traffic go overseas only to come
  back

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Exchange Point Design

• Ethernet
• FDDI
• ATM
• Designs range from the simple to the complex
• Fddi gigaswitches to ethernet switches

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When can an XP be a bad thing?

• Too many exchange points in one region
• competing exchanges defeats the purpose
• Becomes expensive for ISPs to connect to all of
  them

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Exchange Point policies/politics

• AUPs
• Nobody is obliged to peer
• dont spoof

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Exchange Point etiquette

• Dont point default
• Third-party next-hop
• Filter! Filter! Filter!
• Or do reverse path check

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Exchange Point examples

• AADS (Ameritech) in Chicago, USA
• ATM switches
• Pacbell in California, USA
• trunked (geographically diverse) ATM switches
• PAIX in Palo Alto, California, USA
• Fddi gigaswitches
• MAE West in California, USA
• trunked Fddi gigaswitches

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Exchange Point examples

• LINX in London, UK
• Ethernet switches
• AMS-IX in Amsterdam
• Ethernet switches
• NSPIXP-2 in Tokyo, Japan
• Ethernet switches

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Features of XPs

• Redundancy
• multiple switches
• support
• NOC to provide 24x7 support for problems at the
  exchange
• DNS, Routing Registries, NTP servers
• servers often colocated at these centralized
  points

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Features of XPs

• location
• neutral colocation facilities
• address space
• AS
• Route servers
• statistics

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More info about IXs

• http//www.ep.net
• http//www.rsng.net

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Things to think about...

• Do you need to be at an Exchange Point?
• Would you want to start an Exchange Point?
• Would keeping local traffic local benefit your
  ISP?
• Would your environment (politically, etc.)
  support an Exchange Point?

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Discussion

• How would you build an exchange point in your
  environment?
• Who would connect?
• What services would you provide?
• What policies would you enforce?
• What does your environment look like?
• Is it feasible to set up an XP?

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Route Server Background

• What is a Route Server?
• Features of a Route Server
• Advantages of using a Route Server
• Exchange Point Design with a Route Server

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What is a Route Server?

• Unix box which runs Route Server software
• Exchanges routing information with service
  provider routers at a NAP based on policy
• Does not forward packets

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Route Server at an XP
R1
NAP
R3
R2
ROUTE SERVER
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Features of a Route Server

• Scalable Routing
• Simplified Routing Processes on ISP Routers
• Insertion of RS Autonomous System Number in the
  Routing Path

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Features of a Route Server (con)

• Handling of Multi-Exit Discriminator
• Route Flap Dampening Mechanism
• Uses Policy registered in IRR

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Diagram of N-squared Mesh
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With the Route Servers
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RS Exchange Point Routing Flow
TRAFFIC FLOW
ROUTING INFORMATION FLOW
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Advantages of Using a Route Server

• Scalable Routing
• Separation of Routing and Forwarding
• Simplify Routing Configuration Management on ISPs
  routers
• Enforce Good Routing Engineering

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Advantages of Using a Route Server (con)

• PREVENTS SPREAD OF BOGUS ROUTING INFORMATION!

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Peering with the Route Servers

• Any ISP attached to a NAP can peer with the Route
  Servers
• ISP must register their policy in the Internet
  Routing Registry
• Must use BGP

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RSd

• Route Server Daemon
• Originally developed by ISI during RA project
• Developed from GateD
• Multi-view
• eBGP only
• Uses import-from only

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Things to think about...

• How would using a route server benefit you?
• Consider setting one up yourself for your
  community, or talk to Merit...

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Route Server References

• http//www.rsng.net
• http//www.merit.edu/ipma
• http//www.isi.edu/ra

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What is the Routing Registry?

• contact names, email addresses and telephone
  numbers for an AS
• routing policy for an AS (what other ASes does it
  connect to, which routes do they exchange)
• information about routes (most important is which
  AS originates the route)
• several other types of information

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What is the Routing Registry?

• Distributed database collectively known as
  Internet Routing Registry (IRR)
• RADB, RIPE, CW, ANS, Canet
• Providers register routing policy
• Used for planning, debugging and generating
  backbone router configs
• http//www.radb.net/

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What is the Routing Registry?

• Can be used by anyone worldwide
• debugging
• configuring
• engineering routing
• addressing

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What happens if I dont use a database?

• Routing Horror Stories
• AS7007
• announcing bogus routes

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So, I need to use the database because..

• Filters generated off the IRR protect against
  inaccurate routing information
• Makes troubleshooting and debugging easier
• Keep track of policy
• Security
• Filter! Filter! Filter!!

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Why Bother with all of this?

• View of global routing policy in a single
  cooperatively maintained database
• to improve integrity of Internets routing
• generate router configs
• protect against inaccurate routing info
  distribution
• verification of Internet routing

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Why Bother using the database (con)

• Many providers require that you register your
  policy (or they wont peer with you)

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Policy Languages

• express policy with aut-num objects, route
  objects, AS-MACROS
• currently RIPE-181
• moving to RPSL
• more policy control

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What is RPSL?

• Routing Policy Specification Language
• Designed to replace current language (RIPE-181)
• Enhanced and more generalized

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How does the language work?

• Object-oriented
• Express policy in objects
• person
• mntner
• role
• aut-num
• route
• Can make sets of objects

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Describing Policy

• Use the language to describe your relationship
  with other Peers
• routes importing
• routes exporting
• specific policies
• interfaces, MEDs, communities

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Querying the Database

• whois -h whois.radb.net AS237
• whois -h whois.radb.net MAINT-AS237
• whois -h whois.radb.net 198.108.60.0

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How to Register your IRR policy

• Register one or more maintainers
• Register AS and policy information
• Register Routes
• Describes your import and export policy
• At the very least, provides contact information

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Register your maintainer
mntner MAINT-AS237 descr Maintainer
for AS 237 admin-c Abha Ahuja upd-to
ahuja_at_merit.edu mnt-nfy ahuja_at_merit.edu mnt-b
y MAINT-AS237 auth MAIL-FROM
ahuja_at_merit.edu changed ahuja_at_merit.edu
941219 source RADB
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Register your Routes
route 35.0.0.0/8 descr Merit
Network, Inc. descr University of
Michigan descr 4251 Plymouth Road, Suite
C descr Ann Arbor descr MI
48105-2785, USA origin AS237 mnt-by
MAINT-AS237 changed ahuja_at_merit.edu
931113 source RADB
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Register your aut-num

• Describe your policy!
• Peering relationships
• import-from
• export-to
• can use AS-sets

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Register your aut-num (con)
aut-num AS237 as-name
MICHNET-ASN descr MichNet Primary
AS descr Merit Network Inc. descr
Ann Arbor, MI USA as-in AS3561
accept ANY as-out AS3561 announce
AS237 admin-c JMD24 tech-c
JMD24 notify MCI-notify_at_merit.edu mnt-by
MERIT-MAINT-MCI changed
sobo_at_merit.edu 980202 source CW
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Register your aut-num (con)
as-set AS237AS-CUSTOMERS descr
ASs for which MichNet provides descr transit
service members AS229,AS237,AS238,AS7016,AS
10330 tech-c MichNet NOC admin-c
MichNet NOC remark transit ASs of
MichNet notify routing-notify_at_merit.edu mn
t-by MAINT-AS237 changed
ahuja_at_merit.edu 990222 source RADB
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Router Configuration

• Currently configs by hand - slow and inaccurate
• Configuring routers using the IRR
• lots of tools available!!!
• RtConfig by ISI
• route and Aspath filters.
• Import and export
• Filtering is a good thing...

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Router Configuration

• Currently configs by hand - slow and inaccurate
• Configuring routers using the IRR
• lots of tools available!!!
• Filtering is a good thing...
• Plans for some routers to support RPSL directly

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Router Configuration
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How do I use the IRR to generate configs?

• Tools available to generate config files
• gated
• rsd
• Cisco
• RAToolSet
• http//www.isi.edu/ra/RAToolSet
• RtConfig
• Aoe, Roe

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What does the RADB support now?

• RIPE181 whois queries, flags, objects
• RPSL whois queries, flags, objects
• Complete support for RAToolSet queries (fast!)
• Cisco configuration and management interface
• Complete automated mirroring support

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How do I participate?

• Set up your own registry
• Private for your ISP?
• Community for the region?
• Download the software (IRRd)
• Use the RADB

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Things to think about...

• How would you register your policy?
• Try to describe it in an aut-num object
• How would registering your policy benefit you?
  The community?

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Resources

• http//www.radb.net
• http//www.irrd.net
• http//www.isi.edu/ra/rps
• http//www.isi.edu/ra/RAToolSet
• http//www.ietf.org/html.charters/rps-charter.html
  
• http//www.rsng.net
• http//www.ripe.net

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Specifics

• Register your policy in the RADB
• Merit can assist (db-admin_at_radb.net)
• Questions? Need help?
• irrd-support_at_merit.edu
• db-admin_at_radb.net