D ATA C ENTER E THERNET M. Keshtgary

O VERVIEW Residential vs. Data Center Ethernet Review of Ethernet Addresses, devices, speeds, algorithms Enhancements to Spanning Tree Protocol Virtual LANs Data Center Bridging Extensions 2

R ESIDENTIAL VS. D ATA C ENTER E THERNET 3

IEEE 802 A DDRESS F ORMAT 4

E THERNET VS IEEE The source address is always a unicast (single node) address, while the destination address may be unicast, multicast (group), or broadcast (all nodes). In Ethernet frames, the 2-byte field following the source address is a type field. This field specifies the upper- layer protocol to receive the data after Ethernet processing is complete. In IEEE frames, the 2-byte field following the source address is a length field, which indicates the number of bytes of data that follow this field In IEEE 802.3, the upper-layer protocol must be defined within the data portion of the frame, if at all 5

N AMES, ID S, L OCATORS 6

I NTERCONNECTION D EVICES 7

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E THERNET S PEEDS 9

L INK A GGREGATION C ONTROL P ROTOCOL (LACP) 10

S PANNING T REE A LGORITHM 11

P ROBLEMS WITH STP A topology change can result in 1 minute of traffic loss with STP and All TCP connections break Does not support VLAN Solution is Rapid Spanning Tree Protocol (RSTP) 12

R APID S PANNING T REE P ROTOCOL (RSTP) IEEE 802.1w-2001 incorporated in IEEE 802.1D One tree for all VLANs => Common spanning tree Many trees => Multiple spanning tree (MST) protocol IEEE 802.1s-2002 incorporated in IEEE 802.1Q One or more VLANs per tree. 13

RSTP RSTP fixes STP problems by: 1. Being time + event driven instead of just event driven Once converged, STP sends BPDUs only on change RSTP sends Hellos every 2 seconds. Quick failure detection. 2. Differentiating between edge ports (servers) and non-edge ports (switches). No loops ever on edge ports 3. Differentiating between point-to-point links (full duplex) and shared links (half-duplex). RSTP only on full-duplex 14

RSTP (C ONT ) Merging three port states (Disabled, blocking, listening) in to one (discarding). 5. Adding 4 new flags in BPDU, that allow sending a proposal and accepting or not accepting the received proposal RSTP is backward compatible with STP. RSTP- unaware bridge drop RSTP and RSTP is 15

RSTP E XAMPLE 16

MSTP (M ULTIPLE S PANNING T REE ) 17

IS-IS P ROTOCOL Intermediate System to Intermediate System ( IS-IS ) is a routing protocol designed to move information efficiently within a computer network, a group of physically connected computers or similar devices.routing protocolcomputer network It accomplishes this by determining the best route for datagrams through a packet-switched network. routepacket-switched network The protocol was defined in ISO/IEC 10589:2002 as an international standard within the Open Systems Interconnection (OSI) reference designOpen Systems Interconnection IS-IS Protocol is link state 18

IS-IS P ROTOCOL 19

S HORTEST P ATH B RIDGING 20

W HAT IS A LAN? 21

W HAT IS A V IRTUAL LAN 22

V IRTUAL LAN 23

T YPES OF V IRTUAL LAN S 24

IEEE 802.1Q-2011 T AG 25

L INK L AYER D ISCOVERY P ROTOCOL (LLDP) 26

D ATA C ENTER B RIDGING 27

E THERNET F LOW C ONTROL : P AUSE F RAME 28

P RIORITY - BASED F LOW C ONTROL (PFC) Ref: J. L. White, “Technical Overview of Data Center Networks,” SNIA, 2013, te_Technical%20Overview%20of%20Data%20Center%20Networks.pdf 29

E NHANCED T RANSMISSION S ELECTION 30

ETS (C ONT ) 31

Q UANTIZED C ONGESTION N OTIFICATION (QCN) 32 Ref: I. Pepelnjak, “DCB Congestion Notification (802.1Qau),” congestion.html

DCBX Data Center Bridging eXchange, IEEE 802.1Qaz Uses LLDP to negotiate quality metrics and capabilities for Priority-based Flow Control, Enhanced Transmission Selection, and Quantized Congestion Notification New TLV’s Priority group definition Group bandwidth allocation PFC enablement per priority QCN enablement DCB protocol profiles 33

S UMMARY Ethernet’s use of IDs as addresses makes it very easy to move systems in the data center => Keep traffic on the same Ethernet Spanning tree is wasteful of resources and slow. Ethernet now uses shortest path bridging (similar to OSPF) VLANs allow different non-trusting entities to share an Ethernet network Data center bridging extensions reduce the packet loss by enhanced transmission selection and Priority-based flow control 34