Multihoming Issues

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Multihoming Issues on IPv6 networks
APRICOT2002 Dongkyun Kim, Ilsun Whang E-mail
mirr_at_kreonet2.net
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Contents

• Introduction to KREONet2 6Bone
• About IPv6
• Interdomain Routing Issues
• IPv6 Multihoming Requirements
• Related Mechanisms
• IPv6 Multihoming issues
• Summary

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Introduction to KREONet2 6Bone

• KREONet2
• stands for Korea Research Environment Open
  Network 2
• National RD network, run by KISTI, supported by
  Korean government.
• Upgraded name of KREONet and next generation
  research network.
• KREONet2 6Bone
• KREONet2 sTLA 2001320/35
• Peering with 6TAP, KOREN, and 6NGIX.
• Web, DNS, and Tunnel Broker service is ongoing.
• Plan to provide end-to-end IPv6 service this
  year.

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Introduction to KREONet2 6Bone
KIX
STAR TAP 6TAP
200Mbps
10Mbps
Chunchon
Seoul
Seoul
45Mbps
Inchon
45Mbps
Suwon
155Mbps
IMNet
KREONet2 6Bone (AS17579)
256Kbps
Chonan
Chungju
10Mbps
45Mbps
1Gbps
Daejon
Daejeon
16Mbps
Internet
45Mbps
45Mbps
4Mbps
Pohang
Daegu
Jeonju
Ulsan
2Mbps
45Mbps
45Mbps
45Mbps
Kwangju
Pusan
Changwon
4 Mbps
Jeju
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About IPv6

• Background
• Rising crisis of IPv4 address depletion
• Non-hierarchical routing system problem
• Growth of the applications
• Temporary solutions
• - Renumbering, CIDR, NAT, DHCP
• Benefits
• Increased IP address size
• Increased addressing hierarchy support
• Simplified host adddressing
• Simpler Autoconfiguration of address
• And so on

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About IPv6

• The need for further development
• The multihoming problem
• Less-rigid structure for global unicast
  addresses
• Anycast details
• And so on

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Interdomain Routing Issues

• Growth of interdomain routing tables

By Geoff Huston (2001.1)
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Interdomain Routing Issues

• More specific prefixes advertisement

KREONet2 NOC, http//measurement.ipv6.re.kr/bgp/
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Interdomain Routing Issues

• Prefix distribution

KREONet2 NOC, http//measurement.ipv6.re.kr/bgp/
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Interdomain Routing Issues

• Number of ASs

By Geoff Huston, http//www.telstra.net/ops/bgp/
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IPv6 Multihoming Requirements

• Scalability
• Redundancy
• Physical / logical link failure
• Routing protocol failure
• Transit provider failure
• Load Sharing
• Inbound traffic load sharing
• outgoing traffic load sharing
• Performance
• e.g. Avoiding long-term congestion between
  providers

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IPv6 Multihoming Requirements

• Policy
• e.g. cost, acceptable use conditions, etc.)
• Provider selection for a certain traffic class
  or application
• Simple operations and management
• Current multihoming solution is quite
  straightforward to deploy and maintain.
• Transport-layer Survivability
• providing re-homing transparency

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IPv6 Multihoming Requirements

• Security Considerations
• Denial Service attack and spoofing attacks are
  possible, so multihomed sites must be protected
  against such attacks at least as well as
  single-homed sites
• More considerations should be taken into
  possible tunnel link
• Encryptions
• Packets may travel an unwanted path, otherwise
  secondary links are configured with care

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Related Mechanisms

• IPv6 multihoming with route aggregation
• draft-ietf-ipngwg-ipv6multihome-with-aggr-01
  (now obsolete)
• a site multi-homed to more than one ISPs
• Provider level multihoming technique
• IPv6 multihoming support at site exit routers
• RFC 3178
• a site multi-homed to more than one ISPs using
  different site border routers
• Site level multihoming technique

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Related Mechanisms

• Multihoming Mechanism with route aggr.

Inbound Traffic 1. Customer-A Addr-1-A,
specific route advertising (ISP-1, ISP-2) 2.
ISP-2 advertises Addr-1-A to ISP-1 only. 3.
ISP-1 advertises Addr-1-A aggregation block to
ISP-3, ISP-4
ISP-4
ISP-3
3
3
ISP-2
ISP-1
2
Outgoing Traffic - Default route advertising
ISP-1 and ISP-2 - Or selective set of specific
prefixes advertising According to the requirement
of customer-A
1
1
Customer-A
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Related Mechanisms

• Multihoming Mechanism with route aggr.

Load Sharing 1. Inbound Traffic - Achieved by
careful controlling route policy of ISP-1 -
Using IGP Metric, BGP route selection 2. Outbound
Traffic - Achieved by controlling
advertisement from ISP-1 and ISP-2
ISP-4
ISP-3
ISP-2
ISP-1
Redundancy 1. Link-1 failure - In ISP-1
-gt ISP-2 -gt Customer-A - Out Customer-A -gt
ISP-2 2. Link-2 failure - In ISP-1 -gt
Customer-A - Out Customer-A -gt ISP-1
Link-1
Link-2
Customer-A
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Related Mechanisms

• Most Suitable Environments for deploying
• In case that ISPs supporting multi-homed site
  have direct connection to each other gt simple
  arrangement and improved aggregation
• In case of needing good redundancy, not absolute
  redundancy
• Sites with limited to resource for onsite
  sophisticated network administrators Primary
  ISP takes the most part.
• Sites that able to choose a robust ISP as
  primary provider

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Related Mechanisms

• IPv6 multihoming support at site exit routers
• Goals
• Scalability
• Redundancy
• Non-goals
• Choose the best exit link as possible
• Load balancing between multiple exit link

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Related Mechanisms

• multihoming mechanism at site exit routers
• Establish secondary link using IP-over-IP tunnel
• Secondary link should be established through
  different medium with primary link.

ISP-B
ISP-A
ISP-BR-A
ISP-BR-B
Secondary link
Multi-homed Site
E-BR-A, Pref-A
E-BR-B, Pref-B
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Related Mechanisms

• multihoming mechanism at site exit routers
• Redundancy and Scalability

Inbound Traffic 1. Strong Pref-A 2. Weak
Pref-B 3. Strong Pref-B 4. Weak Pref-A
Outbound Traffic 1. Strong Default 4. Weak
Default 3. Strong Default 2. Weak Default
1
2
3
4
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IPv6 Multihoming Issues

• Scalability
• Routing table size has been a major issue (IPv4,
  IPv6)
• In IPv6, routing table size issue is more
  serious negative effects on router memory usage,
  routing table lookup performance
• Global routing table could be reduced using
  aggregation hierarchy in IPv6, but the
  alternatives for multihoming are still be on the
  construction.
• Redundancy
• inbound and outgoing link redundancy

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IPv6 Multihoming Issues

• Load Sharing
• inbound traffic load sharing
• Router Renumbering
• Source address selection between different
  prefixes
• Reliable link operation using tunneling
• Managing and operating tunneled link
• In case of long-term primary link down, usage of
  other ISPs primary link is more efficient.
• Marking Pref-A prefix as deprecated no new
  connection allowed
• New connection requests are to be done using
  newly assigned Pref-B
• RRP makes this work automatic, but be very
  cautious of the links flap

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Summary

• Global routing table issues - Scalability
• Entries advertising more specific prefixes of
  aggregates
• Prefix distribution
• Growth of AS numbers
• IPv6 Multihoming Issues
• Need mechanism that can support scalability,
  load sharing, redundancy.
• Need to achieve better reachability without
  impacting worldwide routing table size issues.

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Thank You !

• Contact Info
• Director
• Il-sun Whang
• - his_at_kreonet2.net
• Engineers
• Dongkyun Kim
• - mirr_at_kreonet2.net
• Hyeakro Lee
• - leehr_at_kreonet2.net