Presentation on theme: "124.09.2012 1 Lecture 5 - Routing On the Flat Labels M.Sc Ilya Nikolaevskiy Helsinki Institute for Information Technology (HIIT)"— Presentation transcript:
Lecture 5 - Routing On the Flat Labels M.Sc Ilya Nikolaevskiy Helsinki Institute for Information Technology (HIIT) T – Special Course in Future Internet Technologies
2 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.
3 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
4 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
5 Reason Does the scalable routing require structured location information in the packet header? Prior to ROFL all FIA rely on structural location information.
6 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 2 m points numbered in clockwise order
7 Chord: Consistent Hashing
8 Chord: Lookup
9 Chord: Lookup Optimization
10 Chord: Enhanced Lookup
11 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
12 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.
13 Source Paths
14 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
15 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
18 Ring Merging Rules Id b in Ring 2 is external successor of id a in Ring 1 iff: Id b is a successor of id a in a joined ring There are no nodes with identifiers in [id a, id b ] in either AS Merges are performed at all levels of hierarchy Each new host must be registered at all levels
19 Packet Forwarding Essentially the same: forward packet towards Label closest to the destination and not overrunning it.
20 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
21 Virtual AS
22 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
23 Evaluation: Intra-domain Hosts typically complete join in less than 40ms with less than 45 control messages
24 Evaluation: Intra-domain (contd) Average stretch depends on pointer cache memory: 1.2 to 2 for 9 Mbits of pointer cache
25 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
26 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
27 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
28 Thank you for your attention! Questions? Comments?