Tokyo Institute of Technology Multihomed ISPs and Policy Control <draft-ohta-multihomed-isps-00> Masataka Ohta Tokyo Institute of Technology mohta@necom830.hpcl.titech.ac.jp

All the Hosts Should have Full (Default Free) Routing Table Best locator of a peer from multiple ones absence of a TLA in the table means routing system has detected the TLA is unreachable metric entry of the table gives preference Metric can be set according to the policy of a site Source address selection for ingress filtering no forwarding or source address based routing! use source address entry (new!) of the table selection is hard, unless routing system is involved

IP Version 6 Addressing Architecture (RFC237[34]) IPv6 addresses has STRONG hierarchy 13 bits of TLA (Top Level Aggregator) 24 bits of NLA (Next Level Aggregator) Hierarchy of ISPs is assumed TLIs (Top Level ISPs) get globally unique TLAs NLIs (Next Level ISPs) get NLAs unique within TLA

IP Version 6 Addressing Architecture | 3| 13 | 8 | 24 | 16 | 64 bits | +--+-----+---+--------+--------+--------------------------------+ |FP| TLA |RES| NLA | SLA | Interface ID | | | ID | | ID | ID | | <--Public Topology---> Site <--------> Topology <------Interface Identifier-----> IP Version 6 Addressing Architecture

Multihomed ISPs Why multihoming is necessary? Robustness! May NLIs be not so robust? No! NLIs MUST be multihomed to TLIs

TLI NLI Subscribers Typical Scenario of IPv6 ISPs with Multihoming

The Question Can the number of TLAs limited? How much is the limit? Can NLIs be happy enough that not all ISPs require TLAs Can NLIs control policy? How much is the limit? No question: how the limit is imposed to be determined by global/regional/country NICs

Can NLIs Control Policy? ISPs are identified by AS#s An NLI must peer with its TLI the NLI may peer with any other ISP Full egress control by NLIs possible Ingress control? Already limited today locally possible if compatible with egress control

determined as egress ones (local arrangement negotiable) ISP B ISP C ISP D ISP E ISP A ISP F ISP G ISP H ISP I policy essentially determined as egress ones (local arrangement negotiable) Propagation of Prefix of ISP A

Ingress Control Possible as long as NLA is propagated An NLI can ask neighbor ISPs for the propagation The NLA will be filtered by other ISPs the NLI can still receive packets to NLA from corresponding TLA not really a limitation

arrangements with D, H, E and I necessary for ingress control ISP B (TLI of A) ISP C ISP D ISP E ISP A (NLI) ISP F ISP G ISP H ISP I arrangements with D, H, E and I necessary for ingress control Propagation of Prefix of ISP A

arrangement with H fail ISP B (TLI of A) ISP C ISP D ISP E ISP A (NLI) ISP F ISP G ISP H (filter NLA) ISP I arrangement with H fail Propagation of Prefix of ISP A

Propagation of Prefix of ISP A ISP B (TLI of A) ISP C ISP D ISP E ISP A (NLI) ISP F ISP G ISP H (pass NLA) ISP I Propagation of Prefix of ISP A

Propagation of Prefix of ISP A ISP B (TLI of A) ISP C ISP D ISP E ISP A (NLI) ISP F ISP G ISP H (filter NLA) ISP I Propagation of Prefix of ISP A

How Much is the Limit? A lot larger than the number of those ISPs which claims to be global (tier1) Much larger than the number of NICs Better to be compatible with RFC237[34] 1024~8192?

Conclusion NLIs must be multihomed to TLIs NLIs policy can still be controlled The number of TLAs should be limited below 1024~8192