Intradomain Anycast for Content Centric Networks.
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Transcript of Intradomain Anycast for Content Centric Networks.
Network graph• Nodes obtain a complete network graph
– link state routing algorithm• Nodes know the shortest path for every destination node
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B’s routing table*Dest Next Hop--------------------------A AC CD CE FF FG FF F
*Metric is hop count
Routing• Information objects have a unique ObjectId• ObjectIds and NodeIds share the same id space• NodeIs partition the ID space (DHT like)• Network routes messages for ObjectIds to correspodent
Nodes via the shortest path
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A requests H1
D requests H1
Duplicate Objects• A copy of an object is located at a different node– E.g. Caching
• Requests should be routed to nearest location• Cached object is announced to neighborhood
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CACHE H1
Shortcuts• Upon receiving a CACHE ANNOUNCEMENT, a node compares if it’s
worth creating a shortcut entry• Compares distance between caching node and correspondent node• Distance is subject to link state metric
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CACHE H1
If (distance(C) < distance(H) create shortcut entry for H1
If (distance(C) < distance(H) create shortcut entry for H1
Object NextHopH1 C
B’s shortcut table
Limiting the flood• Nodes relay cache announcements if it’s really
worth it • Otherwise flooding is stopped
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CACHE H1
d(c) == d(h)Not worth it. Drop it
A already forwards H1 to B. Not worth creating a shortcut entry.
Relay cache announcement
Relay cache announcement
d(c) > d(h)Not worth it. Drop it
Anycast• Upon receiving a message
– Inspect shortcut table– If shortcut for this object is found, forward message to
shortcut.nextHop– Else forward message to shortest path
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Request H1
Object NextHopH1 C
B’s shortcut tableCACHE H1
Advantages• Messages are routed through the shortest path,
unless a detour is found along the way• Link state routing ensures topological shortest
paths– Not key based routing.– Logical distance d(ObjectId, NodeId) is not decreased
on every hop.• Cache announcements are flooded in a limited
way– Nodes relay cache announcements as long as it’s
worth willing
Can also be seen as
• Combination of structured and unstructured p2p systems
• DHT like key partitioning creates deterministic paths– If an object is not found at its correspondent
node, then it’s not there at all• Gossip style flooding is good for popular
objects– In network caches
Relation to Architectures
• Suitable for PSIRP– Rendezvous Network : publications and
subscriptions are routed to correspondent node, unless a cache if found near by
– Topology function in intradomain level– Nobody has actually presented a solution for
intradomain yet• Argument against CCN– CCN floods requests to network, we flood only
caches (and that’s limited)
Usage Example: Probabilistic caching
• Assuming that object items can be distinguished based on popularity– Follow a Zipf distribution– Follow the 80-20 rule
• A relatively small portion of the objects are responsible for the majority of traffic
• Let every node in the network cache an object with a probability p (e.g. 0.01%)
• Then, with high probability, popular items are cached in near by nodes
• Anycast scheme provides fast access to these objects