DATA CENTERETHERNETM. Keshtgary

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OVERVIEW

Residential vs. Data Center Ethernet Review of Ethernet Addresses, devices,

speeds, algorithms Enhancements to Spanning Tree Protocol Virtual LANs Data Center Bridging Extensions

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RESIDENTIAL VS. DATA CENTER ETHERNET

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IEEE 802 ADDRESS FORMAT

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ETHERNET VS IEEE 802.3 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 802.3 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

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NAMES, IDS, LOCATORS

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INTERCONNECTION DEVICES

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INTERCONNECTION DEVICES

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ETHERNET SPEEDS

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LINK AGGREGATION CONTROL PROTOCOL (LACP)

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SPANNING TREE ALGORITHM

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PROBLEMS 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)

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RAPID SPANNING TREE PROTOCOL (RSTP)

IEEE 802.1w-2001 incorporated in IEEE 802.1D-2004

One tree for all VLANs => Common spanning tree

Many trees => Multiple spanning tree (MST) protocol

IEEE 802.1s-2002 incorporated in IEEE 802.1Q-2005

One or more VLANs per tree.

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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

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RSTP (CONT)

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

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RSTP EXAMPLE

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MSTP (MULTIPLE SPANNING TREE)

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IS-IS PROTOCOL

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.

It accomplishes this by determining the best route for datagrams through a packet-switched network.

The protocol was defined in ISO/IEC 10589:2002 as an international standard within the Open Systems Interconnection (OSI) reference design

IS-IS Protocol is link state

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IS-IS PROTOCOL

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SHORTEST PATH BRIDGING

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WHAT IS A LAN?

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WHAT IS A VIRTUAL LAN

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VIRTUAL LAN

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TYPES OF VIRTUAL LANS

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IEEE 802.1Q-2011 TAG

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LINK LAYER DISCOVERY PROTOCOL (LLDP)

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DATA CENTER BRIDGING

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ETHERNET FLOW CONTROL: PAUSE FRAME

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PRIORITY-BASED FLOW CONTROL (PFC)

Ref: J. L. White, “Technical Overview of Data Center Networks,” SNIA, 2013, http://www.snia.org/sites/default/education/tutorials/2012/fall/networking/JosephWhite_Technical%20Overview%20of%20Data%20Center%20Networks.pdf

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ENHANCED TRANSMISSION SELECTION

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ETS (CONT)

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QUANTIZED CONGESTION NOTIFICATION (QCN)

Ref: I. Pepelnjak, “DCB Congestion Notification (802.1Qau),” http://blog.ipspace.net/2010/11/data-center-bridging-dcb-congestion.html

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DCBX

Data Center Bridging eXchange, IEEE 802.1Qaz-2011

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

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SUMMARY

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