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2-Phased Mapping for Internet Core/Edge Split Scheme. Wei Zhang Tsinghua University. Background. RRG Tasks. Next generation Internet routing architecture. Routing. Focuses:. Concerns:. Scalability problem. Hierarchical routing. Solutions:. Core/Edge split (LISP,eFIT,IVIP,SIX/ONE...).
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2-Phased Mapping for Internet Core/Edge Split Scheme Wei Zhang Tsinghua University
Background RRG Tasks Next generation Internet routing architecture Routing Focuses: Concerns: Scalability problem Hierarchical routing Solutions: Core/Edge split (LISP,eFIT,IVIP,SIX/ONE...) Proposals: Common necessity: Mapping from Edge/EID to Core/RLoc Where we are going !
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.
A 2-phased mapping model Phase I Phase II ETRs Prefixes AS# 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.
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.
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.
Deployments • Core Phase I mapping servers Updated border routers (XTRs) • Edge Register agents
Phase I Updating Internet Core Phase I mapping server AS1:1.1.0.0/16 AS2:2.2.0.0/16 Edge AS1 Edge AS2 Prefix register agent Prefix register agent 1.1.0.0/17 1.1.128.0/17 2.2.0.0/16
Phase II Updating Internet Core BGP advertisement XTR3 XTR1 XTR2 AS1 has ETR1 AS2 has ETR2,ETR3 AS1 has ETR1 Edge AS1 Edge AS2 XTR=ITR/ETR
Phase I Lookup Internet Core Phase I mapping server 2.2.2.2 in AS 2 Where is 2.2.2.2 AS1:ITR1 AS2:ETR3 AS2:ETR2 Edge AS1 Edge AS2 Host A 2.2.2.2
Phase II Lookup Internet Core Tunnel packets to ETR2 ITR1 will Check which ETR is the closest to AS2 AS2:ETR3 AS2:ETR2 Edge AS1 Edge AS2 Host A 2.2.2.2
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.
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.