Download - Lecture 5 - Routing On the Flat Labels
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Lecture 5Lecture 5- Routing On the Flat Labels- Routing On the Flat Labels
M.Sc Ilya Nikolaevskiy
Helsinki Institute for Information Technology (HIIT)
T-110.6120 – Special Course in Future Internet Technologies
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Routing On the Flat Labels Based on and pictures borrowed from:
Matthew Caesar, Tyson Condie, Jayanthkumar Kannan, Karthik Lakshminarayanan, and Ion Stoica. ROFL: routing on flat labels, SIGCOMM Comput. Commun. Rev. 36, 4 (August 2006)
I. Stoica, R. Morris, D. Lieben-Nowell, D. Karger, M. Kaashoek, F. Dabek, H. Balakrishnan. Chord: a scalable peer-to-peer lookup protocol for Internet applications, IEEE Transactions on Networks, 11(1) 17-32, 2003.
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Flat Labels
Identification/location split: Mobility, Multihoming
In this architecture – no location at all (routing on names)
No network semantics in the identities – any identities may be used
=> Flat Labels
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Advantages
All advantages of location-identity split (multihoming, mobility, …)
No new infrastructure – no additional resolving
Fate-sharing: No need to contact resolution center
Simple allocation and management
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Reason
Does the scalable routing require structured location information in the packet header?
Prior to ROFL all FIA rely on structural location information.
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Chord
Scalable P2P lookup protocol Given a key Chord maps it to the node.
Consistent hashing: when hashes space size changes only fraction of keys will have new hash When node leaves or arrives only
fraction of keys will be moved Hashes space is a circle with 2m points
numbered in clockwise order
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Chord: Consistent Hashing
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Chord: Lookup
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Chord: Lookup Optimization
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Chord: Enhanced Lookup
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Chord Conclusions
Each node stores small amount of information (O(log n))
Queries are fast (O(log n)) Easy to add/remove node from the
system Recovering techniques to heal from a
node failure
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ROFL Overview
Unique IDs for all nodes 3 types of nodes: routers, stable
hosts, ephemeral hosts Hosts are assigned to a gateway
router Same idea: all labels are organized in
the circle. Routing is performed to the closest node not overrunning destination label.
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Source Paths
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Intra-domain Routing
In each AS there is a separate ROFL ring Routing performed much like Chord lookup Packets are forwarded in a greedy way: to
the closest to the destination known node along the ring Search similar to longest prefix match
Source paths to successors and predecessors are saved in all intermediate nodes in Pointer Cache to optimize packets paths
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Host Join
Host registers in a gateway router Router searches for predecessor of
the host and update its’ successor Router stores source path to the
successor of host Ephemeral hosts can not be
successors
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Inter-domain Routing
Hierarchical structure of ASes Isolation property:
Failure isolation Policies:
Provider-consumer Peering Multihoming
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Hierarchical Ring Merging
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Ring Merging Rules
Idb in Ring 2 is external successor of ida in Ring 1 iff: Idb is a successor of ida in a joined ring There are no nodes with identifiers in
[ida, idb] in either AS
Merges are performed at all levels of hierarchy Each new host must be registered at all
levels
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Packet Forwarding
Essentially the same: forward packet towards Label closest to the destination and not overrunning it.
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Handling Policies
Peering: Virtual AS as a provider for peering ASes Bloom filters to store all nodes in peering ASes
Multihoming: Perform external join for each member of
up-hierarchy
Bloom filters storing all hosts joined below AS are used before using pointer cache
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Virtual AS
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Evaluation
Intra-domain: Trace based on “Rocketfuel” over 4 large
ISPs with hundreds of routers and millions of hosts in each
Used 128-bit IDs 9 Mbits cache memory in routers
Inter-domain: AS graph was derived from “Routeviews”
traces Simulation of 30,000 hosts extrapolated to
600 millions hosts
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Evaluation: Intra-domain
Hosts typically complete join in less than 40ms with less than 45 control messages
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Evaluation: Intra-domain (contd) Average stretch depends on pointer cache
memory: 1.2 to 2 for 9 Mbits of pointer cache
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Evaluation: Inter-domain
Each AS is emulated by a single node Only 30,000 hosts were emulated Join across all provider requires ~445
messages Average stretch is 2.5
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ROFL Strengths
Redesign of internet architecture location/identity split
Policy aware inter-domain routing Cryptographic identities
Spoofing attacks are impossible (on cost of cryptographic signatures)
Implicit Certificates instead of DNS
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ROFL Weaknesses
Not really scalable Possible hash collision Needs large pointer cache Inter-domain routing requires large
Bloom filters for all hosts in ASes below How to recalculate them? Flooding?
Complicated failure recovery