Prescriptive Topology Daemon Dinesh G Dutt Pradosh Mohapatra

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Prescriptive Topology Daemon Dinesh G Dutt, Pradosh Mohapatra Cumulus Networks 1

Prescriptive Topology Daemon Dinesh G Dutt, Pradosh Mohapatra Cumulus Networks 1

Data Center Network Design Transition Scale-up → Scale-out Layer 2 → Layer 3 Legacy

Data Center Network Design Transition Scale-up → Scale-out Layer 2 → Layer 3 Legacy software → Linux ecosystem 2

Network topologies that cater to the transition 3

Network topologies that cater to the transition 3

Topology properties High cross-sectional bandwidth No single point of failure Predictable performance Recent proposals

Topology properties High cross-sectional bandwidth No single point of failure Predictable performance Recent proposals for irregular topologies, e. g. Jellyfish from UIUC • Randomness has good properties 4

Scale-out and cabling complexity With network growth, #cables grows rapidly An “m x n”

Scale-out and cabling complexity With network growth, #cables grows rapidly An “m x n” 2 -level fat tree cluster requires O(mn) cables • Goes higher as #levels increase • Tens of thousands of cables in a data center Topology design → Network blueprint → Cable install Steady state → Failures → Recabling How do we ensure cabling correctness? 5

Cabling Errors “To err is human” – Alexander Pope Issues caused by improper cabling:

Cabling Errors “To err is human” – Alexander Pope Issues caused by improper cabling: • Reachability issues • Unpredictable (and low) performance 6

Prescriptive Topology Manager Verify connectivity is as per operator specified cabling plan S 1

Prescriptive Topology Manager Verify connectivity is as per operator specified cabling plan S 1 Take defined actions on topology check dynamically For example, routing adjacency is brought up only if physical connectivity check passes Example: T 1, port 1 is connected to M 1, port 1 T 1, port 2 is connected to M 2, port 1 … M 1, port 3 is connected to S 1, port 1 M 1, port 4 is connected to S 2, port 1 S 2 M 1 M 2 M 3 M 4 T 1 T 2 T 3 T 4 … 7

Building Blocks Graphviz: Network topology specified via DOT language Well understood graph modeling language

Building Blocks Graphviz: Network topology specified via DOT language Well understood graph modeling language Wide range of supported tools Open source S 1 Central management tool: Network topology is pushed out to all nodes Each node determines its relevant information LLDP: Use the discovery protocol to verify connectivity digraph G { graph [hostidtype="hostname", version="1: 0", date="06/26/2013"]; S 1: swp 1 -> M 1: swp 3; S 1: swp 2 -> M 2: swp 3; S 1: swp 3 -> M 3: swp 3; S 1: swp 4 -> M 4: swp 3; S 2: swp 1 -> M 1: swp 4; M 1: swp 1 -> T 1: swp 1; M 1: swp 2 -> T 2: swp 1; M 2: swp 1 -> T 1: swp 2; M 2: swp 2 -> T 2: swp 2; } 8

Picture Configuration Management Tool (e. g. Chef, Puppet, Ansible) topology. dot . . .

Picture Configuration Management Tool (e. g. Chef, Puppet, Ansible) topology. dot . . . S 1 1. +++ /etc/ptm. d/topology. dot 2. service ptmd reconfig S 2 M 1 M 2 M 3 M 4 T 1 T 2 T 3 T 4 9

Implementation Developed and tested on Linux (wheezy release of Debian) Written in C and

Implementation Developed and tested on Linux (wheezy release of Debian) Written in C and Python Communicates with LLDPD (based on https: //github. com/vincentbernat/lldpd) PTMD executes scripts on topology pass and topology fail /etc/ptm. d/if-topo-pass, /etc/ptm. d/if-topo-fail Example: add/del routing protocol interface configuration 10

Core implementation details topology. dot port_table port_t + admin_nbr + oper_state LLDPD port_t +

Core implementation details topology. dot port_table port_t + admin_nbr + oper_state LLDPD port_t + admin_nbr + oper_state Clients 11

ptmctl cumulus@S 1: ~# ptmctl ----------------------------------Port Status Expected Nbr Observed Nbr Last Updated ----------------------------------swp

ptmctl cumulus@S 1: ~# ptmctl ----------------------------------Port Status Expected Nbr Observed Nbr Last Updated ----------------------------------swp 1 pass M 1: swp 3 17 h: 39 m: 21 s swp 2 pass M 2: swp 3 17 h: 39 m: 21 s swp 3 pass M 3: swp 3 17 h: 39 m: 21 s swp 4 pass M 4: swp 3 17 h: 39 m: 21 s cumulus@S 1: ~# 12

ptmviz – topology analysis Generate the DOT file corresponding to the observed physical network

ptmviz – topology analysis Generate the DOT file corresponding to the observed physical network topology dot -Tps prescribed. dot -o prescribed. ps dot -Tps physical. dot -o physical. ps 13

ptmviz – topology analysis Generate the DOT file corresponding to the observed physical network

ptmviz – topology analysis Generate the DOT file corresponding to the observed physical network topology dot -Tps prescribed. dot -o prescribed. ps dot -Tps physical. dot -o physical. ps 14

Quagga integration New command to enable PTM oper-state based routing protocol bring-up Quagga acts

Quagga integration New command to enable PTM oper-state based routing protocol bring-up Quagga acts as PTM client. Listens to oper-state notifications cumulus@S 1: ~# sudo vtysh -c 'conf t' -c 'ptm-enable' cumulus@S 1: ~# sudo vtysh -c 'show interface swp 1' Interface swp 1 is up, line protocol is up PTM status: pass index 3 metrix 1 mtu 1500 flags: <UP, BROADCAST, RUNNING, MULTICAST> HWaddr: 00: 02: 00: 00: 11 inet 21. 0. 0. 2/24 broadcast 21. 0. 0. 255 inet 6 fe 80: : 202: ff: fe 00: 11/64 cumulus@S 1: ~# 15

Interoperability Any device running an LLDP daemon Routing adjacencies can be brought by the

Interoperability Any device running an LLDP daemon Routing adjacencies can be brought by the device running PTM. digraph G { graph [hostidtype="hostname", version="1: 0", date="06/26/2013"] S 1: swp 1 -> S 2: swp 1; S 1: swp 2 -> S 2: swp 2; S 1: swp 3 -> "procurve 1. lab": 21; S 1: swp 4 -> "procurve 1. lab": 22; S 1: swp 5 -> "cisco 1. lab": "Gigabit. Ethernet 0/1"; S 1: swp 5 -> "jmx 480": "xe-0/0/0"; S 1: swp 7 -> webserver 1: eth 0; S 1: swp 8 -> webserver 1: eth 1; } cumulus@S 1: ~# ptmctl ----------------------------------Port Status Expected Nbr Observed Nbr Last Updated ----------------------------------swp 1 pass S 2: swp 1 17 m: 2 s swp 2 pass S 2: swp 2 17 m: 2 s swp 3 pass procurve 1. lab: 21 17 m: 10 s swp 4 pass procurve 1. lab: 22 17 m: 10 s swp 5 pass cisco 1. lab: Gigabit. Ethernet 0/1 cisco 1 lab: Gigabit. Ethernet 0/1 swp 6 pass jmx 480. lab: xe-0/0/0 17 m: 1 s swp 7 pass webserver 1: eth 0 17 m: 3 s swp 8 pass webserver 1: eth 1 17 m: 3 s 16 17 m: 8 s

Availability Open source, published under Eclipse Public License (EPL) https: //github. com/Cumulus. Networks/ptm 17

Availability Open source, published under Eclipse Public License (EPL) https: //github. com/Cumulus. Networks/ptm 17

Roadmap Provide abstractions for: • routing configuration • Network troubleshooting 18

Roadmap Provide abstractions for: • routing configuration • Network troubleshooting 18

Thank you Questions? www. cumulusnetworks. com 19

Thank you Questions? www. cumulusnetworks. com 19

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