2014/2/91 Contents All-Path Basics Issues Report of All-Path Demos Report of proposal to AVB WG
Problem Statement IEEE802.1D RSTP has following limitations; –Not all the links cannot be used –The shortest path might not be used anytime –No multipath available –Root bridge tends to be high load –Not scalable 2014/2/92
Objectives To overcome RSTP limitation –Loop free –All links to be used –Provide shortest path –Provide multipath –Compatible with 802.1D/Q –No new tag or new frame to be defined –Zero configuration 2014/2/93 TRILL SPB
S 3 D D Port locked to S Port locked to D S S 4 All-Path Basics (One-way) 2 1 4 5 ARP_re q
S 3 D D Port locked to S Port locked to D S S 5 All-Path Basics (One-way) 2 1 4 5 X X S S ARP_r eq The first received port is locked to S. -Register S to a table -Start lock timer -Learn S at the port The later received port discard the frame S. -Check S w/ the table if the lock timer effective
S 3 D D Port locked to S Port locked to D S S 6 All-Path Basics (One-way) 2 1 4 5 S S S S X X X ARP_re q
S 3 D D Port locked to S Port locked to D S S 7 All-Path Basics (Two-way) 2 1 4 5 S S S S ARP_rep ly D D If DA is on the FDB Unicast forwarding same as 802.1d
S 3 D D Port locked to S Port locked to D S S 8 All-Path Basics (Two-way) 2 1 4 5 S S S S ARP_rep ly D D D
Minimum aging time of Lock timer FP The minimum aging time FP SP x x Second port received (discarding) Processing time (forwarding, learning, classification, tagging, queuing etc.) x First port received (learning) Processing time (forwarding, learning, classification, tagging, queuing etc.) x FP: First Port, SP: Second Port The aging timer shall be valid to discard this frame as received from the second port The First-come table aging time shall be longer than 2 x (one-way link delay + processing delay) If it is for Data center, it can be less than 1ms. Second port received (discarding) First port received (learning) 102014/2/9
11 Scope of All-Path Scalability Manageability Enterprise, Campus, Small datacenter Home network etc. ALL-PATH Simple Less operation Natural load balance Large area, provider network Large datacenter etc. Both support, loop free, shortest path LAN SPB, ECMP TRILL SPB, ECMP TRILL MAN/WAN RSTP/MSTP
2 S 35 1 4 D S S S D 13 S S 1. Path Recovery – Original idea ARP_re q Mechanism: When unknown unicast frame arriving at bridge with failed link, path fail message is generated per MAC entry towards source bridge, that generates corresponding ARP to re-establish tree. Question: If 10K MAC entries are existed in FDB, 10K path fail frames should be generated, is it feasible processing for local CPU, especially in high-speed link (ex. 10GE)?
2 S 35 1 4 D D Port locked to S Port locked to D S S S S D D 14 1. Path Recovery – Original idea Path_fail
2014/2/915 1.Path recovery – Selective flush MAC=a MAC=b bbb b aaaa a a flush b SW1SW2 SW3 SW4 SW5 SW6 1 2 3 2222 2 11 1 1 1 3 flush message is terminated because b is not binded to port1 May includes two or more…ex. 100s of MAC addresses to be flushed as a list. Delete entry b from FDB and re-sends the flush message to SW1. When link failure is detected, MAC flush lists are flooded. 54 frames (187 MAC / 1500B frame) for 10K MAC entry. Avoid unnecessary flooding, MAC entries are deleted to shorten. Issues: How to prevent flush frame loss. May require CPU processing power. Experience: 15ms to flush 10K MACs in a node (1GHz MIPS Core) (Fujitsu)
1. Path Recovery - Loop back(UAH) Low processing at failed (link) bridges: loopback is part of the standard forwarding table Processing load is distributed among source edge bridges involved in flows. Only one side (SA>DA) asks for repair. Resiliency: If first packet looped back is lost the other following looped back frames will follow.
2014/2/917 2. Server Edge Vswitch NIC Question: If a server has two or more NICs, how to find which port is first? vswitch: only vswitch to support All-Path VEB: both VEB and vswitch to support All-Path VEPA: only external switch to support All-Path Vswitch NIC VEB NIC VEB VEPA NIC Ext. switch
3. Load Balance (Fujitsu) 2014/2/918 SW1 SW2 SW3 Elapsed time Throughput Load balance is available in natural way because high load link tend not to be selected with queuing delay. Pros: zero-configuration load balance Cons: you cannot control load balance like SPB/ECMP SW1 SW2 SW3 SW4 SW5
Load Distribution (UAH simulations) Objectives: –Explain native load distribution results of Singapore presentation –Visualize how the on-demand path selection avoids the loaded links Topology: –Links subset of a Small Data Center topology to show path selection at core –Core links capacity is lower (100Mbps) to force load distribubtion and congestion only at core –Queues support up to 100.000 frames (so that they affect as delay and not discarding frames) Traffic: stepped in sequence, left to right –Green servers send UDP packets towards red servers –Groups of 25 servers initiate the communication every second. The first one at second 1, the second at second 2, second 3,…. And finally, the last group is a single server that starts the communication at second 4 of the simulation. –UDP packets (1 packet every 1 ms, simultaneous for all servers). The packet size varies between 90 and 900 bytes in the different simulations to simulate increasing traffic loads.
Simulation I – UDP packet size: 90B x 25 x 25 x1 x 25 1s 2s 3s 4s S4 S2S1 S3 s3-s4 s3-s4 and s3-s2-s4 s3-s1-s4 Note the path s3-s4 is reused several times because is still not so loaded (low traffic) # flows 51 1 124 0 Server Group Paths 12341234
Simulation I – UDP packet size: 300B S4 S2S1 S3 s3-s4 s3-s1-s4 and s3-s2-s4 s3-s2-s4 s3-s4 Note the path s3-s4 is not reused when the 2nd group starts, but instead uses s3-s1-s4 and s3-s2-s4, similar with the 3rd group, the 4rd reuses s3-s4 because its again the fastest once s1 and s2 are loaded because of groups 2 and 3 # flows 26 14 36 0 Server Group Paths 12341234
Simulation I – UDP packet size: 900B x 25 x 25 x1 x 25 1s 2s 3s 4s S4 S2S1 S3 s3-s4 s3-s1-s4 s3-s2-s4 s3-s4 900B means some frames are being discarded at queues (too much traffic). Group 1 chooses s3-s4 and fully loads it, 2 chooses s3-s1-s4 and same happens, 3 chooses s3-s2-s4 and same, when 4 starts, every link (except the one from s1-s2) is fully loaded, so s3-s4 is again the fastest path and is chosen. # flows 26 25 0 Server Group Paths 12341234
Load distribution conclusions Notice how the # of flows gets distributed in the links in the core when the traffic increases due to increased latency. –Load distribution starts with low loads –Path diversity increases with load Similar balancing effect observed in redundant links from an access switch to two core switches On demand path selection finds paths adapted to current, instantaneous conditions, not to past or assumed traffic matrix
2014/2/924 Report on Proposal for AVB TG May 12, Thu, morning session @ AVB Dr. Ibanez presented the materials as used in IW session (Singapore and Santa Fe) Questions and comments –Any other metric than latency e.g. bandwidth? –Path recovery time comparing with RSTP? –Any broadcast storm occurred when link failed? –Whats the status in IW session, any PAR created? AVB status –They try to solve by their own way, using SRP. –Not only latency but also bandwidth can be used as metric –Also redundant path can be calculated
Path Selection with SRP 2014/2/925 at-phkl-SRP-Stream-Path-Selection-0311-v01.pdf
REPORT OF ALL PATH DEMOS - TORONTO: SIGCOM AUGUST 2011 - BONN: LCN OCTOBER 2011
Demo at Sigcom 2011 HW NetFPGA implementation Four NetFPGAs (4*1 Gbps) Demo: Zero configuration Video streaming, high throughput. Robustness, no frame loops Fast path recovery Internet connection, std hosts http://conferences.sigcomm.org/sigcomm/2011/papers/sig comm/p444.pdf http://conferences.sigcomm.org/sigcomm/2011/papers/sig comm/p444.pdf
Demo at IEEE LCN 2011 (october, Bonn) Openflow and Linux (OpenWRT) ALL Path switches NOX Openflow controller Ethernet switch
One NEC switch splitted into 4 Openflow switches Four Soekris boards as 4 Openflow switches Two Linksys WRT routers running ARP Path over Linux implementation Video streaming and internet access without host changes – Some video limitations at OpenWRT routers – Smooth operation on Soekris and NEC. Reference: A Small Data Center Network of ARP-Path Bridges Made of Openflow Switches. Guillermo Ibáñez (UAH); Jad Naous (MIT/Stanford Univ.) ; Elisa Rojas (UAH); Bart De Schuymer (Art in Algorithms, Belgium); Thomas Dietz (NEC Europe Ltd., Germany) Demo at IEEE LCN 2011 (october, Bonn) Openflow and Linux (OpenWRT) ALL Path switches
Feedback from All Path-UAH demos At every demo most people an explanation of how ARP Path works (video available was shown) Intrigued about the mechanism, and interest on the reconfiguration of flows and native loop avoidance Amount of state stored per bridge: per host or per bridge. (Encapsulating versions Q-in-Q, M-in-M are possible, but not the target, already covered by SPB) Questions on compatibility and miscibility with standard bridges (automatic core-island mode, no full miscibility) Collateral questions on NetFPGA and on LCN demo topology Next step : Implementation on a commodity Ethernet Switch (FPGA) (Chip/Switch manufacturers are invited to provide a switch platform) and implementation of interoperability with 802.1D bridges in Linux version
Conclusions All Path bridging is a reality – A new class of transparent low latency bridges Do not compute, find the path by direct probing Zero configuration Robust, loop free Native load distribution Paths non predictable, but resilient, paths adapt to traffic and traffic is not predictable Low latency
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