Floodless in SEATTLE : A Scalable Ethernet ArchiTecTure for Large Enterprises. Changhoon Kim, Matthew Caesar and Jenifer Rexford. Princeton University 2009, 3rd MarchPresented by Chervet Benjamin Animation on page 9, 14, 15 and 16 come from Changhoon Kim’s presentation. 1

Motivation  Networks are getting larger  Up to hosts and switchs for large enterprises Networks.  Larger and larger datacenter at Google, Yahoo or Microsoft for the largest ones.  Everyone in a University has access to the Internet. 2

Motivation (2) Networks are getting larger Hard to keep efficient, recquires networks administrators and operators. More money is spent on maintenance than improving the Network with new materials. Need to find out where the problems is and how to solve it. 3

Outline  Find where the problem is : Current Networks  Ethernet Network  Hybrid (Ethernet/IP) Network  Comparison Ethernet/IP  Solve the problem : Seattle architecture  Objectives  Solutions offered  Evaluate the solutions :  Simulation results  Experimental results  Conclusion  Benefits  Lessons Learned 4

Current Networks  Ethernet Network -Heavily rely on broadcast to know where a host is (ARP, DHCP) - large use of bandwidth, - privacy concerns + learn automatically the address, + ensure mobility of a machine -Flat addressing : Switch maintains a table associating all the Mac Address of the Network with its output ports. -can lead to very large table -Build a spanning tree + No loops in the Network - links unused - uneven loads 5

Actual Networks  Ethernet Network 6

Actual Networks  Hybrid IP/Ethernet Networks IP Network LAN Machine sharing the same subnets. The subnet are interconnect by IP Networks. -The broadcast stay in a subnet. + No flood on the entire Network. - Manual configuration needed. - No mobility possible. -Routing done though OSPF + Efficient use of links + No loops 7

Actual Networks  Hybrid IP/Ethernet Network 8

Comparaisons Architectures Features Ethernet Bridging IP Routing Ease of configuration  Optimality in addressing  Host mobility  Path efficiency  Load distribution  Convergence speed  Tolerance to loop  SEATTLE        9

Comparaisons  SEATTLE :  Get the best of Ethernet and IP.  Configuration free (like Ethernet) and Scalable (as IP). 10

Seattle architecture  Objectives  Avoid flooding  Send a message only to the receiver  Never broadcast unicast traffic  Limits broadcasting  Directory service  Keep forwarding tables small  Host location should be kept only where it is needed  Distribution of the data. 11

Seattle architecture  Objectives (2)  Path efficient.  Need a routing protocol  Switch can learn the topology  Backward compatible  Compatible with IP and Ethernet Network  Does not modify end-hosts view 12

Seattle architecture  Solution offered :  Network layer one hop DHT All the Switch implement a hash function F, associating pair. - For every key F returns the same value. - F returns one of the switch from a key. - Each Switch must know about all the other living switch. Cache system is used :the switch cache some frequently used information Smart cache update implemented : retrieves the information by surveying the traffic. 13

How does it works ? Host discovery or registration B D x y Hash ( F ( x ) = B ) Store at B Traffic to x Hash ( F ( x ) = B ) Tunnel to egress node, A Deliver to x Switches End-hosts Control flow Data flow Notifying to D Entire enterprise (A large single IP subnet) LS core E Optimized forwarding directly from D to A C A Tunnel to relay switch, B 14

Response to host mobility Relay (for x ) x y B A Src D when shortest-path forwarding is used G Old Dst New Dst 15

SEATTLE Architecture  Handling ARP requests 1. Host discovery 2. Hashing F ( IP a ) = r a 3. Storing ( IP a, mac a, s a ) 4. Broadcast ARP req for a 5. Hashing F ( IP a ) = r a Switch End-host Control msgs ARP msgs sasa a b rara sbsb 6. Unicast ARP req to r a 7. Unicast ARP reply ( IP a, mac a, s a ) to ingress Owner of ( IP a, mac a ) 16

Evaluation of the solutions  We want to know if the new solutions performs better than current networks ?  Simulation using a packet simulator  4 different topologies  Campus network (517 routers and switches)  AP-small (87 routers)  AP-large (315 routers)  DC (Data center network) 17

Stretch: Path Optimality Stretch = Current path length / Shortest path length 18

Control messages 19

Size of the tables 20

Experimentation on Emulab  Emulab: similar to planetLab: set of PC around the world.  Useful to test real world networks with some practical values for latency and bandwidth  In this experimentation: 10 PC Free BSD Nodes 21

Number of messages exchanged 22

Conclusions:  Benefits :  Reduce the flow of data exchanged by order of magnitude  Fast and efficient reaction to changes  Reliability and capacity grows with the size of Network  Less man-made configuration needed Plug and Playable Networking ensuring efficiency and scalability. 23

Conclusions  Lessons learned  A new protocols has been created by combining different technologies from different background.  DHT Based routing used first in P2P technologies.  Link state routing  Caching 24