Transcript CERNET 40G Experience

Lessons Learned
TEIN2 and CERNET
Xing Li
2007-01-22
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Outline
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Introduction
TEIN2 routing policy
CERNET BGP Experience
Lessons learned
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Simple Case
(where BGP can handle things easily)
• Global transit
– To tier 1 or tier 2 commodity networks
• Care the aggregation
• Care the load balancing
• Don’t care the symmetry
• Peering (no transit, except for the down streams)
– To domestic ISPs (bi-literal or via IX)
• Care the business model
– To academic partners
• Care the performance
• Care the symmetry
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Complicated Case
(where BGP cannot handle things easily)
• Global transit
– To tier 1 or tier 2 commodity networks
• Care the aggregation
• Care the load balancing
• Don’t care the symmetry
• Academic transit
– To multiple transit backbones within academic scope
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Care the aggregation
Care the load balancing
Care the performance
Care the symmetry
Etc.
• Peering (no transit, except for the down streams)
– To domestic ISPs (bi-literal or via IX)
• Care the business model
– To academic partners
• Care the performance
• Care the symmetry
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Two Steps to Implement the Policy
• Identification
– IP prefix
– AS path regular expression
– Community tag
• Path selection
– AS path (inbound and outbound)
– Local-preference (outbound)
– More specific (inbound)
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For Transit Network
TEIN2 Example
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TEIN2 Topology
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The Principle of Routing Design
for the TEIN2 network
• To provide interconnection among TEIN2 partners and
between TEIN2 partners and EU NRENs.
• To provide back-up paths within the TEIN2 network
and/or via partner networks for service resilience when
possible.
• To provide a flexible and transparent routing policy to
TEIN2 NRENs.
• To avoid being selected by GÉANT, Abilene and other
R&E networks outside TEIN2 as the preferred transit
network.
• To minimize the adjustment of the external peers’ routing
policy outside TEIN2 networks, e.g. GÉANT and APAN.
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TEIN2 Routing Policy
• Enable additive community tagging to mark
the prefix announcements.
• Adopt AS number prepending as the preferred
BGP policy for TEIN2 traffic adjustment within
TEIN2 backbone.
– Use ingress AS number prepending for outbound
traffic adjustment, including traffic from TEIN2 POP to
NRENs, GÉANT and APAN.
– Use egress AS number prepending for inbound traffic
adjustment, including traffic from NRENs, GÉANT and
APAN to TEIN2 POP.
• May use Local-Preference amendment as the
last resort of mechanism for fine tuning on
TEIN2 traffic over the backbone.
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For NRN
CERNET Example
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CERNET Topology
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CERNET Peering
3G
Internet
CERNET 2
CERNET
Domestic
Peering
12G
10G
CNGI
Peering
DRAGONTAP
CNGI-BJIX
DRAGONLIGHT
155M
100M
1G
155M
2x155M
622M
HARNET
TEIN2
ASNET
APAN
KOREN
STARLIGHT
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CERNET Routing Policy
• Outbound
– Use AS number prepending if possible
– Heavily use Local-Preference
– Enable additive community tagging to mark
the prefixes
• Inbound
– Use AS number prepending if possible
– Announce more specifics
– Enable additive community tagging to mark
the prefixes
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Case 1
TAIWAN Earthquake
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Earthquake on 26th DEC 2006
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Why did not include this policy
before the earthquake?
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Case 2
Routing and End-to-end
performance
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Ping and dvping beacons
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Here in the APAN venue WLAN
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Lessons Learned (1)
• The nature of BGP is reachability
– Stupid routing happen
– Policy based routing makes thing very complicated
– The routing and topology are very dynamic environment
• The key words are: simple, open and controllability
– For transit network
• Simple
• Open
– For NRN
• Simple
• Controllability
• Why did not include this policy before the earthquake?
– Because it is a NP problem and there are many contradict
requirements
– Mission impossible
– What should be the solution?
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Lessons Learned (2)
• It seems that we still need to do a lot
manual BGP policy adjustment, case by
case with the help of
– Multi-site collaborations
– Routeviews
• We have to compare the routing table with
the end-to-end performance matrix
– dvping tool
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