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Reference -​http://conferences.sigcomm.org/co-next/2009/workshops/rearch/papers/Feldmann.pdf

HAIR Hierarchical Architecture for Internet Routing

• Routing table growth
• Restrict visibility of Routing updates
• Support Traffic Engineering
• Mobility and Multipath

Edge Based Approach

N layer -Hierarchial Structure :

*	Group core networks into level 1 of a hierarchy, edge or intermediate networks into levels 2 to n − 1, and local area networks into level n, obtaining a hierarchy consisting of n levels

EDGE

• This would refer to level -n ( directly interact with the end hosts. (bottom layer of hierarchy) [ Ethernet LAN]

INT

• This is the intermediate level ( 2 to n-1).
• Network of routers only
• It provides routing between attached EDGEs or INTs of the next higher level.

CORE

• Ensures global reachability by routing packets between INTs (level-2)

Attachment Points

• Levels are connected via attachment points: a level -k (LkAP) connects level-k routing domain to level k+1 domain
• Allows peering

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Routing Tables

Within a INT

• Need entries for all routers within the INT,
• Routes to the attached EDGEs/INTs,
• Default routes to the INTs of the next higher level or the CORE

Within a CORE

• All routers within CORE
• Routes to directly connected ISPs

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LOCATION/IDENTIFIER SEPARATION

• Separation of location and identity
• Locators are variable length (variable path from core towards end host)

Note | Use GUID for location and identity separation

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PACKET DELIVERY

A packet sent from Host A to Host B

• Forward to CORE
• Forward within CORE
• Forward from CORE down to the destination host

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Question

• Is cluster or level based approach is what mobility first requires
• How feasible similar approach could be to attain standard routing across varied use cases