Network Working Group David Melman
Internet Draft Tal Mizrahi
Intended status: Informational Marvell
Expires: March 2012 Donald Eastlake
Huawei
September 11, 2011
FCoE over TRILL
draft-mme-trill-fcoe-01.txt
Abstract
Fibre Channel over Ethernet (FCoE) and TRILL are two emerging
standards in the data center environment. While these two protocols
are seemingly unrelated, they have a very similar behavior in the
forwarding plane, as both perform hop-by-hop forwarding over
Ethernet, modifying the packet's MAC addresses at each hop. This
document describes an architecture for the integrated deployment of
these two protocols.
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Table of Contents
1. Introduction ................................................ 2
2. Abbreviations ............................................... 3
3. FCoE over TRILL ............................................. 4
3.1. FCoE over a TRILL Cloud................................. 4
3.2. FCoE over RBridge....................................... 5
3.2.1. FCRB .............................................. 5
3.2.2. Topology .......................................... 7
3.2.3. The FCRB Flow...................................... 8
4. Security Considerations..................................... 10
5. IANA Considerations ........................................ 10
6. Acknowledgments ............................................ 11
7. References ................................................. 11
7.1. Normative References................................... 11
7.2. Informative References................................. 11
1. Introduction
Data center networks are rapidly evolving towards a consolidated
approach, where Ethernet is used as the common infrastructure for all
types of traffic. Storage traffic, which was traditionally dominated
by the Fibre Channel (FC) protocol suite, is evolving towards Fibre
Channel over Ethernet (FCoE), where native FC packets are
encapsulated with an FCoE encapsulation over an Ethernet header.
Traffic between two FCoE end nodes (ENodes) is forwarded through one
or more FCoE Forwarders (FCF). An FCF takes a forwarding decision
based on the Fibre Channel destination ID (D_ID), and enforces
security policies between ENodes, also known as zoning. Once an FCF
takes a forwarding decision, it modifies the source and destination
MAC addresses of the packet, to reflect the path to the next hop FCF
or ENode. FCFs use a routing protocol called Fabric Shortest Path
First (FSPF) to find the optimal path to each destination. An FCF
typically has one or more native Fibre Channel interfaces, allowing
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it to communicate with native Fibre Channel devices, e.g., storage
arrays.
TRILL [RFCTRILL] is a protocol for transparent least cost routing,
where RBridges forward traffic to their detination based on a least
cost route, using a TRILL encapsulation header. RBridges forward
TRILL-encapsulated packets based on the Egress RBridge Nickname in
the TRILL header. An RBridge forwards a TRILL-encapsulated packet
after modifying its MAC addresses to reflect the path to the next-hop
RBridge, and decrementing a Hop Count field.
TRILL and FCoE bear a strong resemblance in their forwarding planes.
Both protocols take a forwarding decision based on protocol addresses
above Layer 2, and modify the Ethernet MAC addresses on a per-hop
basis. Each of the protocols uses its own routing protocol rather
than using any type of bridging protocol such as spanning tree
protocol [802.1Q] or the Shortest Path Bridging protocol [802.1aq].
FCoE and TRILL are both targeted at the data center environment, and
their concurrent deployment is self-evident. This document describes
an architecture for the integrated deployment of these two protocols.
2. Abbreviations
ENode FCoE Node such as server or storage array
EoR End of Row
FC Fibre Channel
FCF Fibre Channel Forwarder
FCoE Fibre Channel over Ethernet
FCRB Fibre Channel forwarder over RBridge
FSPF Fabric Shortest Path First
LAN Local Area Network
RBridge Routing Bridge
SAN Storage Area Network
ToR Top of Rack
TRILL Transparent Interconnection of Lots of Links
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WAN Wide Area Network
3. FCoE over TRILL
3.1. FCoE over a TRILL Cloud
The simplest approach for running FCoE traffic over a TRILL network
is presented in Figure 1. The figure illustrates a TRILL-enabled
network, where FCoE traffic is transparently forwarded over the TRILL
cloud. The figure illustrates two ENodes, a Server and an FCoE
Storage Array, an FCF, and a native Fibre Channel SAN connected to
the FCF.
FCoE traffic between the two ENodes is sent from the first ENode over
the TRILL cloud to the FCF, and then back through the TRILL cloud to
the second ENode.
+---+
| |_________
| | \ ___ _
+---+ \/ \_/ \__ _ __
FCoE Storage _/ \ / \_/ \_
Array / TRILL / +---+ \_ \
(ENode A) \_ Cloud /________| |____/ SAN _/
/ \ | | \__ _/
\__/\_ ___/ +---+ \_/
+---+ / \_/ FCF
| |________/
| |
+---+
Server
(ENode B)
Figure 1 The "Separate Cloud" Approach
The configuration in Figure 1 separates the TRILL cloud(s) and the
FCoE cloud(s). The TRILL cloud forwards FCoE traffic as standard
Ethernet traffic, and appears to the ENodes and FCF as an Ethernet
LAN.
The main drawback of the Separate Cloud approach is that RBridges and
FCFs are separate nodes in the network, resulting in more cabeling
and boxes, and communication between Enodes usually requires two
TRILL cloud traversals with twice as many hops. As mentioned above,
data center networking is converging towards a consolidated and cost
effective approach, where the same infrastructure and equipment is
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used for both data and storage traffic, and where high efficiency and
minimal number of hops are important factors when designing the
network topology.
3.2. FCoE over RBridge
3.2.1. FCRB
Rather than the Separate Cloud approach discussed in the previous
subsection, an alternate approach is presented, where each switch
incorporates both an FCF entity and an RBridge entity. This
consolidated entity is referred to as FCoE-forwarder-over-RBridge
(FCRB).
Figure 2 illustrates an FCRB, and its main building blocks. An FCRB
can be functionally viewed as two independent entities:
o An FCoE Forwarder (FCF) entity.
o An RBridge entity.
The FCF entity is connected to one of the ports of the RBridge, and
appears to the RBridge as a native Ethernet host. A detailed
description of the interaction between the layers is presented in
Section 3.2.3.
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+--------------------+
|FCRB |
| +-----------+ |
| | FCF |-+ |
| +-----+-----+ | |
| | | |
| +-----+-----+ | |
| | RBridge | | |
| +-+-+-+-+-+-+ | |
| | | | | | | | |
+---|-|-|-|-|-|---|--+ _ __
FCoE/ / | | | | | \ Native / \_/ \_
+---+ Ethernet / / | | | | \ FC \_ \
| |_________________/ / | | | | \______________/ SAN _/
| | / | | | | \__ _/
+---+ / | | | | \_/
FCoE Storage / | | | | FCoE / Ethernet
Array / |_| | | over TRILL
(ENode A) / / \_/ \__
/ _/ \
+---+ / / TRILL /
| |____________/ \_ Cloud /
| | / \
+---+ \__/\_ ___/
Server \_/
(ENode B)
Figure 2 FCRB Entity in the Network
The FCRB entity maintains layer independence between the TRILL and
FCoE protocols, while enabling both protocols on the same network.
It is noted that FCoE traffic is always forwarded through an FCF, and
cannot be forwarded directly between two ENodes. Thus, FCoE traffic
between ENodes A and B in the topology in Figure 1 is forwarded
through the path
ENode A-->TRILL cloud-->FCF-->TRILL cloud-->ENode B
Traffic between A and B in the topology in Figure 2 is forwarded
through the path
ENode A-->FCRB-->ENode B
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Hence, the usage of FCRB entities allows TRILL and FCoE to use common
infrastructure and equipment, as opposed to the Separate Cloud
topology presented in Figure 1.
3.2.2. Topology
The network configuration illustrated in Figure 3 shows a typical
topology of a data center network. Servers are hierarchically
connected through Top-of-Rack (ToR) switches, and End-of-Row (EoR)
racks. The EoR switches to other clouds, such as an external WAN, or
a native FC SAN.
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_ __ _ __
/ \_/ \_ / \_/ \_
\_ \ \_ \ .....
/ SAN _/ _/ WAN _/
\__ _/ \ / \__ _/
\_/ \ / \_/
| \ / |
| \ / |
| \/ |
EoR +----+_______/\_______+----+
FCoE over | | | |
RBridge | | | |
(FCRB) +----+ +----+
/ \ / \
/ \ / \
ToR +---+ +---+ +---+ +---+
FCoE over | | | | | | | |
RBridge | | | | | | | |
(FCRB) +---+ +---+ +---+ +---+
/ \ / \ / \ / \
/ \ / \ / \ / \
+-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
Servers/ | | | | | | | | | | | | | | | |
ENodes +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
A B C D E F G H
Figure 3 FCoE over RBridge Topology
Note that in the example in Figure 3 all the ToR and EoR switches are
FCRB entities, but it is also possible for some of the network nodes
to be pure RBridges, creating a topology where FCRBs are
interconnected through TRILL clouds.
3.2.3. The FCRB Flow
FCoE traffic sent between two ENodes, A and B, is transmitted through
the ToR FCRB, since A and B are connected to the same ToR. Traffic
between A and C must be forwarded through the EoR FCRB.
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+--------+ +--------+ +--------+ +--------+ +--------+
| FCoE |.....| FCF |.....| FCF |.....| FCF |.....| FCoE |
| ENode | +--------+ +--------+ +--------+ | ENode |
| | |RBridge |.....|RBridge |.....|RBridge | | |
+--------+ +--------+ +--------+ +--------+ +--------+
|Ethernet|<===>|Ethernet|<===>|Ethernet|<===>|Ethernet|<===>|Ethernet|
+--------+ +--------+ +--------+ +--------+ +--------+
Server ToR EoR ToR FCoE Storage
ENode A FCRB FCRB FCRB Array
ENode C
Figure 4 Traffic between two ENodes - Example
Figure 4 illustrates the traffic between ENodes A and C that are not
connected to the same ToR.
o FCoE traffic from A is sent to the ToR over the Ethernet
interface.
o The RBridge entity at the ToR forwards the packet to the FCF,
analogous to forwarding between two Ethernet hosts.
The FCF entity at the ToR takes a forwarding decision, and updates
the destination MAC address of the packet to the address of the
EoR FCF. The packet is then forwarded to the RBridge entity, where
it is encapsulated in a TRILL header, and sent to the EoR FCRB.
o The RBridge entity in the EoR FCRB, acting as the egress RBridge,
decapsulates the TRILL header and forwards the FCoE packet to the
FCF entity. The FCF takes a forwarding decision and updates the
MAC address of the packet according to the next hop ToR. The
packet is then forwarded to the RBridge and encapsulated with a
new TRILL header.
o At the ToR FCRB, the packet reaches the final egress RBridge, and
the TRILL encapsulation is removed. The FCF then forwards the
packet to the RBridge entity after updating its MAC addresses. The
RBridge entity forwards the packet to the target ENode.
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+--------+ +--------+ +---------+ +--------+
| FCoE |.....| FCF |.....| FCF |.....| FC |
| ENode | +--------+ +----+----+ |protocol|
| | |RBridge |.....| RB | | | stack |
+--------+ +--------+ +----+ FC | | |
|Ethernet|<===>|Ethernet|<===>|Eth | |<===>| |
+--------+ +--------+ +----+----+ +--------+
Server ToR EoR Native FC
ENode FCRB FCRB Storage Array
Figure 5 Example Traffic between ENode & Native FC Storage Array
Figure 5 illustrates traffic sent between an ENode and an FC Storage
Array, following the network topology in Figure 3.
o FCoE traffic from the ENode is sent to the ToR over the Ethernet
interface.
o The RBridge entity at the ToR forwards the packet to the FCF. The
FCF entity at the ToR takes a forwarding decision and updates the
destination MAC address of the packet to the address of the EoR
FCF. The packet is then forwarded to the RBridge entity, where it
is encapsulated in a TRILL header, and sent to the EoR FCRB.
o The egress RBridge entity at the EoR FCRB decapsulates the TRILL
header, and forwards the FCoE packet to the FCF entity. The packet
is then forwarded as a native FC packet through the FC interface
to the native FC node.
4. Security Considerations
For general TRILL Security Considerations see [RFCTRILL].
For general FCoE Security Consideration see Annex D of [FC-BB-5].
There are no additional security implications imposed by this
document.
5. IANA Considerations
There are no IANA actions required by this document.
RFC Editor: please delete this section before publication.
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6. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
7. References
7.1. Normative References
[RFCTRILL] Perlman, R., Eastlake, D., Dutt, D., Gai, S.,
Ghanwani, A., "Routing Bridges (RBridges): Base
Protocol Specification", RFC6325, July 2011.
7.2. Informative References
[FC-BB-5] ANSI INCITS 462: Information Technology - Fibre
Channel - Backbone - 5 (FC-BB-5).
[802.1Q] "IEEE Standard for Local and metropolitan area networks
- Virtual Bridged Local Area Networks", IEEE Std
802.1Q-2011, May 2011.
[802.1aq] "IEEE Standard for Local and metropolitan area
networks - Shortest Path Bridging", work in progress,
June 2011.
Authors' Addresses
David Melman
Marvell
6 Hamada St.
Yokneam, 20692 Israel
Email: davidme@marvell.com
Tal Mizrahi
Marvell
6 Hamada St.
Yokneam, 20692 Israel
Email: talmi@marvell.com
Donald Eastlake 3rd
Huawei Technologies
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155 Beaver Street
Milford, MA 01757 USA
Phone: +1-508-333-2270
EMail: d3e3e3@gmail.com
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