1. Lessons Learned TEIN2 and CERNET
Xing Li

2. Outline Introduction TEIN2 routing policy CERNET BGP Experience
Lessons learned

3. 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

4. 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
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

5. 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)

6. For Transit Network TEIN2 Example

7. TEIN2 Topology

8. 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.

9. 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.

10. For NRN CERNET Example

11. CERNET Topology

12. CERNET Peering DRAGONTAP CNGI-BJIX DRAGONLIGHT Internet CERNET
TEIN2
STARLIGHT
HARNET
ASNET
DRAGONLIGHT
CNGI-BJIX
DRAGONTAP
CERNET 2
Internet
Domestic
Peering
CNGI
APAN
KOREN
3 G
12G
155M
100M 1G
2x155M
622M
10G

13. CERNET Routing Policy Outbound Inbound
Use AS number prepending if possible
Heavily use Local-Preference
Enable additive community tagging to mark the prefixes
Inbound
Announce more specifics

14. Case 1 TAIWAN Earthquake

15. Earthquake on 26th DEC 2006

16. Why did not include this policy before the earthquake?

17. Case 2 Routing and End-to-end performance

18. Ping and dvping beacons

19. Here in the APAN venue WLAN

20. 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
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?

21. 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