INTERNET-DRAFT Mohammed Umair
Intended Status: Proposed Standard Kingston Smiler S
Shaji Ravindranathan
IP Infusion
Lucy Yong
Donald Eastlake 3rd
Huawei Technologies
Expires: May 05, 2016 November 02, 2015
Date Center Interconnect using TRILL
<draft-muks-trill-dci-00.txt>
Abstract
This document describes a TRILL based DCI solution using VTSD. VTSD
(Virtual TRILL Service/Switch Domain) is specified in [draft-VTSD].
This draft describes the advantages provided by a TRILL based DCI
solution over an existing MPLS L2VPN solution, advantages such as
bandwidth scaling and providing multiple active pseudowires.
Status of this Memo
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Copyright and License Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Date Center Topology . . . . . . . . . . . . . . . . . . . . . 6
2. Appointed Forwarders . . . . . . . . . . . . . . . . . . . . . 7
3. Multiple Parallel pseudowires. . . . . . . . . . . . . . . . . 8
4. Active-Active Pseudowire . . . . . . . . . . . . . . . . . . . 9
4.1. Port-based AC operations. . . . . . . . . . . . . . . . . . 10
4.2. VLAN-based AC operations. . . . . . . . . . . . . . . . . . 10
5. MPLS encapsulation and Loop free provider PSN/MPLS . . . . . . 10
6. Frame processing . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Frame processing between data center T2 switch and TIR. . . 10
6.2. Frame processing between TIR's . . . . . . . . . . . . . . 11
7. MAC Address learning and withdrawal . . . . . . . . . . . . . . 12
8. Active-Active Access with VTSD . . . . . . . . . . . . . . . . 12
9. ARP/ND proxy . . . . . . . . . . . . . . . . . . . . . . . . . 12
10. MAC mass-withdrawal . . . . . . . . . . . . . . . . . . . . . 12
11. Security Considerations . . . . . . . . . . . . . . . . . . . 13
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
13.1. Normative References . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1 Introduction
Pseudo Wire Emulation Edge-to-Edge (PWE3) is a mechanism that
emulates the essential attributes of a service such as Ethernet over
a Packet Switched Network (PSN). The required functions of PWs
include encapsulating service-specific PDUs arriving at an ingress
port, and carrying them across a path or tunnel, managing their
timing and order, and any other operations required to emulate the
behavior and characteristics of the service as faithfully as
possible.
The IETF Transparent Interconnection of Lots of Links (TRILL)
protocol [RFC6325] [RFC7177] [rfc7180bis] provides transparent
forwarding in multi-hop networks with arbitrary topology and link
technologies using a header with a hop count and link-state routing.
TRILL provides optimal pair-wise forwarding without configuration,
safe forwarding even during periods of temporary loops, and support
for multipathing of both unicast and multicast traffic. Intermediate
Systems (ISs) implementing TRILL are called Routing
Bridges(RBridges)or TRILL Switches.
The [draft-VTSD] introduces a new terminology called VTSD. VTSD is a
logical RBridge resides inside TIR (TRILL Intermediate Router) that
should be capable of performing all the operations that a standard
TRILL switch can do, along with IP and MPLS functions. A TIR is a
Provider Edge (PE) device where VTSD resides and provides TRILL DCI
solution. VTSD is connected to the Layer2 interface towards the DC
and PW interface towards the MPLS core
TRILL as a protocol enables optimal use of the links in a layer2
network and running TRILL inside the TIR or VTSD provides a way for
optimally utilizing the following:
1. The PWE3 mesh connectivity in the MPLS core using parallel
pseudowires.
2. The PWE3 attachment circuit interface, when there are more
than one attachment circuit interfaces using active-active
pseudowires.
3. Providing a RING based DCI solution along with traditional
mesh / hub-spoke topology.
4. Optimally re-route the traffic from one pseudowire to another
pseudowire when there is a failure. This is possible as VTSD doesn't
follow split-horizon for loop free topology.
When there is a requirement to increase the bandwidth of a particular
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DCI link, with TRILL DCI, new pseudowires could be created with the
same endpoints. These pseudowires are termed as parallel pseudowires.
As these pseudowires are attached to VTSD (which is a TRILL RBridge),
the TRILL protocol takes care of optimally load sharing the traffic
across these parallel pseudowires.
Similarly when there is a requirement to increase the bandwidth of
customer facing interface (attachment circuit), this can be achieved
effectively by adding new attachment circuit interfaces and attaching
them to the same VTSD.
The objective of a pseudowire (PW) connected in parallel or mesh or
ring is to maintain connectivity across the packet switched network
(PSN) used by the emulated service. In this model all pseudowires
that are part of a service domain will carry data traffic without
making any of the pseudowire go in to standby mode.
1.1 Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Acronyms used in this document include the following:
AC - Attachment Circuit [RFC4664]
Access Port - A TRILL switch port configured with
the "end station service enable" bit
on, as described in Section 4.9.1
of [RFC6325]. All AC's, VTSD ports
connected to CE's, should configured
as TRILL Access port.
AF - Appointed Forwarder [RFC6325],
[RFC6439] and [RFC6439bis].
Data Label - VLAN or FGL
ECMP - Equal Cost Multi Pathing
FGL - Fine-Grained Labeling [RFC7172]
IS-IS - Intermediate System to Intermediate
System [IS-IS]
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LAN - Local Area Network
Link - The means by which adjacent TRILL
switches or VTSD is connected.
May be a bridged LAN
MLAG - Multi-Chassis Link Aggregation
MPLS - Multi-Protocol Label Switching
PE - Provider Edge Device
PSN - Packet Switched Network
PW - Pseudowire [RFC4664]
RBridge - An alternative name for TRILL Switch
TIR - TRILL Intermediate Router
(Devices where Pseudowire starts and
Terminates)
TRILL - Transparent Interconnection of Lots
of Links OR Tunneled Routing in the
Link Layer
TRILL Site - A part of a TRILL campus that
contains at least one RBridge.
TRILL switch - A device implementing the TRILL
protocol. An alternative name
for an RBridge.
Trunk port - A TRILL switch port configured with
the "end station service disable"
bit on, as described in Section 4.9.1
of [RFC6325]. All pseudowires should
be configured as TRILL Trunk port.
VLAN - Virtual Local Area Network
VPLS - Virtual Private LAN Service
VPTS - Virtual Private TRILL Service
VSI - Virtual Service Instance [RFC4664]
VTSI - Virtual TRILL Service Instance
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VTSD - Virtual TRILL Switch Domain OR
Virtual TRILL Service Domain
A Virtual RBridge that segregates
one tenant's TRILL database as well
as traffic from the other.
VTSD-AP - A VTSD TRILL Access port can be a
AC or a logical port connected with
CE's. it can be a combination of
physical port and Data Label.
OR just Physical port connected to
CE's
2. Date Center Topology
The reference topology that will be used for our discussion is a 3
tier traditional topology. Although other topologies may be utilized
within the data center, most of such L2 based data centers may be
modeled as a 3 tier traditional topology. The reference topology is
illustrated in Figure 1. To keep terminologies simple and uniform, in
this document these layers will be referred to as Tier-1, Tier-2 and
Tier-3 "tiers", and the switches in these layers will be termed as
T1SW, T2SW etc. For simplicity reasons, the entire DC topology will
not be mentioned in the further sections. Only the relevant nodes
will be shown with the above mentioned node nomenclature.
+------+ +------+
| | | |
| T1SW |--| T1SW | Tier-1
| | | |
+------+ +------+
| | | |
+---------+ | | +----------+
| +-------+--+------+--+-------+ |
| | | | | | | |
+----+ +----+ +----+ +----+
| | | | | | | |
|T2SW|-----|T2SW| |T2SW|-----|T2SW| Tier-2
| | | | | | | |
+----+ +----+ +----+ +----+
| | | |
| | | |
| +-----+ | | +-----+ |
+-|T3SW |-+ +-|T3SW |-+ Tier-3
+-----+ +-----+
| | | | | |
<- Servers -> <- Servers ->
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Figure 1: Typical DC network topology
2. Appointed Forwarders
TRILL supports multi-access LAN (Local Area Network) links that can
have multiple end stations and RBridges attached. Where multiple
RBridges are attached to a link, native traffic to and from end
stations on that link is handled by a subset of those RBridges called
"Appointed Forwarders" [rfc6439bis], with the intent that native
traffic in each VLAN be handled by at most one RBridge. An RBridge
can be Appointed Forwarder for many VLANs.
The Appointed Forwarder mechanism is irrelevant to any link on which
end station service is not offered. This includes links configured
as point-to-point IS-IS links and any link with all RBridge ports on
that link configured as trunk ports. (In TRILL, configuration of a
port as a "trunk port" just means that no end station service will be
provided. It does not imply that all VLANs are enabled on that
port). Furthermore, Appointed Forwarder status has no effect on the
forwarding of TRILL Data frames. It only affects the handling of
native frames.
By default, the DRB (Designated RBridge) on a link is in-charge of
native traffic for all VLANs on the link. The DRB may, if it wishes,
act as Appointed Forwarder for any VLAN and it may appoint other
RBridges that have ports on the link as Appointed Forwarder for one
or more VLANs.
The DRB may appoint other RBridges on the link with any one of the
mechanism described in [rfc6439bis].
A RBridge on a multi-access link forms adjacency [RFC7177] with other
RBridge if the VLAN's configured/enabled between them are common. For
example there are four RBridges attached to multi-access link, say
RB1, RB2, RB3 and RB4. RB1 and RB2 are configured with single VLAN
"VLAN 2", whereas RB3 and RB4 are configured with "VLAN 3". Assume
that there are no Native VLAN's present on any of the RBridges
connected to multi-access link. Since TRILL Hellos are sent with VLAN
Tag enabled on the interface, RB3 and RB4 drops the hellos of RB1 and
RB2 (since they are not configured for VLAN 2). Similarly RB1 and RB2
drops the Hellos of RB3 and RB4. This results in RB1 and RB2 not
forming adjacency with RB3 and RB4. RB1 and RB2 after electing DRB
and forming adjacency between them, will decide about VLAN 2 AF.
Similarly RB3 and RB4 decide about the VLAN 3 AF.
As VTSD should be capable of performing all the operations a standard
TRILL Switch should do, it should also be capable of performing
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Appointed Forwarder selection. A group of VTSD that are configured
for same service's (VLAN's in our case) on different TIR's will form
adjacencies, whereas VTSD which are enabled for different VTSI will
never form adjacencies.
3. Multiple Parallel pseudowires.
TRILL supports multiple parallel adjacencies between neighbor
RBridges. Appendix C of [RFC6325] and section 3.5 of [RFC7177]
describes this in detail. Multipathing across such parallel
connections can be done for unicast TRILL Data traffic on a per-flow
basis, but is restricted for multi-destination traffic. VTSD should
also support this functionality.
TRILL DCI Pseudowires which belong to same VTSD instance in a TIR and
connected to same remote TIR are referred to as parallel pseudowires.
These parallel pseudowires corresponds to a single link inside VTSD.
Here all pseudowires should be capable of carrying traffic.
|<-------------- Emulated Service ------------------>|
| |
| |<------- Pseudo Wire ------>| |
| | | |
| | |<-- PSN Tunnels-->| | |
| V V V V |
V AC +-----+ PW1 +-----+ AC V
+------+ | |VTSD1|==================|VTSD1| | +-------+
| |----------| | | |-------| |
|T2SW | | T1SW|==================| T1SW| | T2SW |
| | +-----+ PW2 +-----+ | |
+------+ +-------+
<-----DataCenter1------> <-----DataCenter2------>
Figure 2: Parallel pseudowires with TRILL DCI
In above Figure 2, PW1 and PW2 are parallel pseudowires, as these
pseudowires belongs to same VTSD and provides a connectivity across
same TIRs.
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This mechanism provides a way for actively increasing and optimally
utilizing the bandwidth in the service provider network without
affecting the existing traffic.
4. Active-Active Pseudowire
[RFC6718] describes pseudowire Redundancy mechanism, wherein among
the pair of pseudowires, one pseudowire will be selected as a active
pseudowire and the other will be selected as a standby pseudowire.
The standby pseudowire will not forward any user traffic under normal
circumstances. The introduction of VTSD in TRILL DCI provides a very
simple mechanism for providing multiple active pseudowires.
Pseudowires which belongs to the same VTSD instance inside the same
TIR or between TIR's will be in active-active state. These
pseudowires are able to carry data-traffic without making any one of
pseudowire to go in standby mode.
To distribute traffic between pseudowires, TRILL protocol will be
used.
|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudo Wire ------>| |
| | | |
| | |<-- PSN Tunnels-->| | |
| V V V V |
V AC +----+ +----+ AC V
+-----+ | |TIR1|==================| | | +-----+
| |----------|....|..PW1..(active)...|....| | | |
| | |T1SW|==================| | | | |
| | +----+ |TIR3| | | |
| | | | | |T2SW |
| | | |----------| |
|T2SW | | | | |
| | |T1SW| | |
| | +----+ | | +-----+
| | |TIR2|==================| |
| |----------|....|..PW2..(active)...|....|
+-----+ | |T1SW|==================| |
AC +----+ +----+
<-----DataCenter1------> <-----DataCenter2------>
Figure 3: Dual-Home AC with Active-Active PW's
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In the above Figure 3, pseudowires PW1 and PW2 are in active state
and will be capable of carrying user traffic without making anyone of
the pseudowire go in standby mode. The above Figure illustrates an
application of multiple active pseudowires, where DC1's T2 switch
(T2SW) is dual-homed with the TIR switch. This scenario is designed
to actively load share the emulated service among the two TIRs
attached to the multi-homed switch.
The attachment circuit can be of either Port-based Attachment Circuit
or VLAN-based Attachment Circuit.
4.1. Port-based AC operations.
In this case, the VTSDs in TIR1 and TIR2 will form TRILL adjacency
via AC ports. If the attachment circuit port can carry N number of
end-station service VLANs, then TIR1 and TIR2's VTSDs can equally
distribute them using AF Mechanism of TRILL.
4.2. VLAN-based AC operations.
Likewise in Port-based AC, in this case also the VTSDs in TIR1 and
TIR2 will form TRILL adjacency via AC ports. Since only one VLAN end-
station service is enabled, only one TIR's VTSD can become AF for
that VLAN. Hence native traffic can be processed by any one of the
AC.
5. MPLS encapsulation and Loop free provider PSN/MPLS
TRILL with MPLS encapsulation over pseudowire is specified in
[RFC7173], and requires no changes in the frame format.
TRILL DCI doesn't require to employ Split Horizon mechanism in the
provider PSN network, as TRILL takes care of Loop free topology using
Distribution Trees. Any multi-destination frame will traverse a
distribution tree path. All distribution trees are calculated based
on TRILL base protocol standard [RFC6325] as updated by [RFC7180bis].
6. Frame processing
This section specifies frame processing from data center T2 switch
and TIR's
6.1. Frame processing between data center T2 switch and TIR.
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In a multi-homed CE topology where in a data center switch is
connected to two PEs / TIRs, AF mechanism described in section 2 will
be used to decide which TIR/VTSD will carry the traffic for a
particular VLAN. This is applicable to the case wherein the data
center switch is connected to a PE/TIR device via multiple layer 2
interfaces to increase the bandwidth.
As a frame gets ingressed into a TIR (or any one of the TIR, when the
tier2 switches are connected to multiple TIR's) after having AF
check, the TIR encapsulates the frame with TRILL and MPLS headers and
forwards the frame on a pseudowire. If parallel pseudowires are
present, the TRILL protocol running in VTSD will select any one of
the pseudowire and forward the TRILL Data packet. Multi-destination
packets will be forwarded on Distribution tree's path [rfc7180bis]
The advantage of using TRILL for distribution of frames is, even if
any of the paths or links fails between DC switch and TIR's or
between TIR's, frames can be always be forwarded to any of available
UP links or paths through other links/pseudowires.
If multiple equal paths are available, TRILL will distribute traffic
among all the paths.
Also VTSD doesn't depend on the routing or signaling protocol that is
running between TIRs, provided there is a tunnel available with
proper encapsulation mechanism.
Any multi-destination frames when ingressed to TIR's will traverse
one of the Distribution-Trees, with strong RFC Checks. Hop count
field in TRILL Header will avoid loops or duplication of Traffic.
6.2. Frame processing between TIR's
When a frame gets ingressed into a VTSD inside TIR, the TRILL
protocol will forward the frames to the proper pseudowire. When
multiple paths / pseudowires are available between the TIR's then
shortest path, calculated through TRILL protocol, will be used. If
multiple paths are of equal cost, then TRILL protocol will do ECMP
load spreading. If any multi-destination frame gets received by the
VTSD through a pseudowire, TRILL will do an RPF check and will take
proper action.
Once a frame gets to the VTSD through pseudowire, MPLS header will be
de-capsulated, further action will be taken depending on the egress
nickname field of TRILL header. If egress nickname is the nickname of
this VTSD, MAC address table and AF lookup will be performed and the
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frame will be forwarded by decapsulating the TRILL header. If egress
nickname belongs to some other VTSD, frame will be forwarded on a
pseudowire connected to that VTSD by encapsulating with an MPLS
header.
7. MAC Address learning and withdrawal
MAC address learning and withdrawal mechanism on a RBridge is
specified in section 4.8. of [RFC6325], this document requires no
changes for MAC address learning and its withdrawal.
8. Active-Active Access with VTSD
TBD
9. ARP/ND proxy
TBD
10. MAC mass-withdrawal
TBD
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11. Security Considerations
TBD
12. IANA Considerations
TBD
13. References
13.1. Normative References
[IS-IS] "Intermediate system to Intermediate system routeing
information exchange protocol for use in conjunction with
the Protocol for providing the Connectionless-mode Network
Service (ISO 8473)", ISO/IEC 10589:2002, 2002".
[rfc7180bis] Eastlake, D., et al, "TRILL: Clarifications,
Corrections, and Updates", draft-ietf-trill-rfc7180bis,
work in progress.,.
[draft-VTSD] Umair, M., Smiler, K., Eastlake, D., Yong, L.,
"TRILL Transparent Transport over MPLS"
draft-muks-trill-transport-over-mpls, work in
progress.,.
[rfc6439bis] Eastlake, D., et al., "TRILL: Appointed Forwarders",
draft-eastlake-trill-rfc6439bis, work in progress.,.
10.2. Informative References
Authors' Addresses
Mohammed Umair
IP Infusion
RMZ Centennial
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Mahadevapura Post
Bangalore - 560048 India
EMail: mohammed.umair2@gmail.com
Kingston Smiler S
IP Infusion
RMZ Centennial
Mahadevapura Post
Bangalore - 560048 India
EMail: kingstonsmiler@gmail.com
Shaji Ravindranathan
IP Infusion
3965 Freedom Circle, Suite 200
Santa Clara, CA 95054 USA
EMail: srnathan2014@gmail.com
Lucy Yong
Huawei Technologies
5340 Legacy Drive
Plano, TX 75024
USA
Phone: +1-469-227-5837
EMail: lucy.yong@huawei.com
Donald E. Eastlake 3rd
Huawei Technologies
155 Beaver Street
Milford, MA 01757
USA
Phone: +1-508-333-2270
EMail: d3e3e3@gmail.com
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