1. 2-Phased Mapping for Internet Core/Edge Split Scheme
Wei Zhang
Tsinghua University

2. Background RRG Tasks Next generation Internet routing architecture
Focuses:
Routing
Concerns:
Scalability problem
Solutions:
Hierarchical routing
Core/Edge split (LISP,eFIT,IVIP,SIX/ONE...)
Proposals:
Common necessity:
Mapping from Edge/EID to Core/RLoc
Where we are going !

3. Motives
Mapping from EID to RLoc in core/edge schemes may not be scalable if the dynamics of (prefix,ETR) binding is high.
In order to make the routing system really scalable and reduce the overhead on updating, we need to design a relatively more stable mapping mechanism than any EID topology or routing policy changes.

4. A 2-phased mapping model
Phase I
Phase II
Prefixes
AS#
ETRs
An M:1:M mapping model
Introduce AS# in the middle can prevent too much detailed topology/policy changing information from getting into the mapping system.

5. Assumptions
all ASes know better their local prefixes (in the IGP) than others.
ASes also know better their ETRs.
So all mapping information can be collected locally.

6. Implements Phase I mapping system (register/resolve prefix to AS#)
Each AS should have at least one agent to register its local prefixes (range of IP addresses).
May be hierarchical like DNS, or centralized like whois.
Phase II mapping (AS# to ETRs)
XTRs advertise their AS# bindings with each other through BGP extension.

7. Deployments Core Phase I mapping servers Updated border routers (XTRs)
Edge
Register agents

8. Phase I Updating Internet Core Phase I mapping server Edge AS1
Prefix register agent
Prefix register agent
/17
/17
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9. Phase II Updating Internet Core BGP advertisement Edge AS1 Edge AS2
XTR3
XTR1
XTR2
AS1 has ETR1
AS2 has ETR2,ETR3
AS1 has ETR1
Edge AS1
Edge AS2
XTR=ITR/ETR

10. Phase I Lookup Internet Core Phase I mapping server Edge AS1 Edge AS2
Where is
in AS 2
AS1:ITR1
AS2:ETR3
AS2:ETR2
Edge AS1
Edge AS2
Host A

11. Phase II Lookup Internet Core Edge AS1 Edge AS2 Tunnel packets to ETR2
ITR1 will Check which ETR is the closest to AS2
AS2:ETR3
AS2:ETR2
Edge AS1
Edge AS2
Host A

12. Gains
Any prefixes reconfiguration (aggregation/ deaggregation) within an AS will not be notified to mapping system.
Possible highly efficient aggregation of the local prefixes (a range of IP space).
Both phase I and phase II mapping can be stable.
A stable mapping system will reduce the update overhead introduced by topology change/routing policy dynamics.

13. Summary
The 2-phased mapping scheme introduces AS# between the mapping prefixes and ETRs.
The decoupling of direct mapping makes highly dynamic updates stable, therefore it can be more scalable than any direct mapping designs.
The 2-phased mapping scheme is adaptable to any core/edge split proposals.