Internet DRAFT - draft-zhang-trill-aa-multi-attach
draft-zhang-trill-aa-multi-attach
INTERNET-DRAFT Mingui Zhang
Intended Status: Proposed Standard Huawei
Updates: 7176 Radia Perlman
Intel
Hongjun Zhai
ZTE
Muhammad Durrani
Mukhtiar Shaikh
Brocade
Sujay Gupta
IP Infusion
Expires: December 19, 2014 June 17, 2014
TRILL Active-Active Edge Using Multiple MAC Attachments
draft-zhang-trill-aa-multi-attach-04.txt
Abstract
TRILL active-active service provides end stations with flow level
load balance and resilience against link failures at the edge of
TRILL campuses.
This draft specifies a method in which member RBridges in an active-
active edge RBridge group use their own nicknames as ingress RBridge
nicknames to encapsulate frames from attached end systems. Thus,
remote edge RBridges are required to keep multiple locations of one
MAC address in one Data Label. Design goals of this specification are
discussed in the document.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at
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http://www.ietf.org/shadow.html
Copyright and License Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Acronyms and Terminology . . . . . . . . . . . . . . . . . . . 4
2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Incremental Deployable Options . . . . . . . . . . . . . . . . 5
4.1. Detail of Option C . . . . . . . . . . . . . . . . . . . . 6
4.2. Capability Flags TLV . . . . . . . . . . . . . . . . . . . 8
5. Design Goals . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. No MAC Flip-Floping (Normal Unicast Egress) . . . . . . . . 9
5.2. Regular Unicast/Multicast Ingress . . . . . . . . . . . . . 9
5.3. Right Multicast Egress . . . . . . . . . . . . . . . . . . 9
5.3.1. No Duplication (Single Exit Point) . . . . . . . . . . 9
5.3.2. No Echo (Split Horizon) . . . . . . . . . . . . . . . . 10
5.4. No Black-hole or Triangular Forwarding . . . . . . . . . . 11
5.5. Load Balance Towards the AAE . . . . . . . . . . . . . . . 11
5.6. Scalability . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 12
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 12
7.1. TRILL APPsub-TLVs . . . . . . . . . . . . . . . . . . . . . 12
7.2. Active Active Flags . . . . . . . . . . . . . . . . . . . . 12
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Scenarios on Split Horizon . . . . . . . . . . . . . . 14
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
In the TRILL Active-Active Edge (AAE) topology, a Multi-Chassis Link
Aggregation Group (MC-LAG) is used to connect multiple RBridges to a
switch, vSwitch or multi-port end station. An endnode clump is
attached to this switch or vSwitch. It's required that data traffic
within a specific VLAN from this endnode clump (including the multi-
port end station) can be ingressed and egressed by any of these
RBridges simultaneously. End systems in the clump can spread their
traffic among these edge RBridges at the flow level. When a link
fails, end systems keep using the rest of links in the MC-LAG without
waiting for the convergence of TRILL, which provides resilience to
link failures.
Since a packet from each endnode can be ingressed by any RBridge in
the AAE group, a remote edge RBridge may observe multiple attachment
points (i.e., egress RBridges) for this endnode identified by its MAC
address and Data Label (VLAN or Fine Grained Label (FGL)). This issue
is known as the "MAC flip-flopping". Three potential solutions arise
to address this issue:
1) AAE member RBridges use a pseudonode nickname, instead of their
own, as the ingress nickname for end systems attached to the MC-
LAG. [CMT] falls within this category.
2) AAE member RBridges split work among themselves for which one
will be responsible for which MAC addresses. A member RBridge will
encapsulate the packet using its own nickname if it is responsible
for the source MAC address. Otherwise, if the frame is known
unicast, it encapsulates the packet using the nickname of the
responsible RBridge; if the frame is multicast, it needs to
redirect the packet to its responsible RBridge for encapsulation.
3) AAE member RBridges keep using their own nicknames. Remote edge
RBridges are required to keep multiple points of attachment per
MAC address and Data Label attached to the AAE.
The purpose of this document is to develop an approach based on
solution 3. Although it focuses on exploring solution 3, the major
design goals discussed here are common for all three AAE solutions.
Through mirroring the scenarios studied in this draft, other
potential solutions may benefit as well.
The main body of the document is organized as follows. Section 2
lists the acronyms and terminologies. Section 3 gives the overview
model. Section 4 provides three options for incremental deployment.
Section 5 describes how this approach meets the design goals.
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2. Acronyms and Terminology
2.1. Acronyms
AAE: Active-Active Edge
Data Label: VLAN or FGL
ESADI: End Station Address Distribution Information [ESADI]
FGL: Fine Grained Label [RFC7172]
IS-IS: Intermediate System to Intermediate System [ISIS]
MC-LAG: Multi-Chassis Link Aggregation Group
TRILL: TRansparent Interconnection of Lots of Links [RFC6325]
vSwitch: A virtual switch such as a hypervisor that also simulates a
bridge.
2.2. 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].
Familiarity with [RFC6325], [RFC6439] and [RFC7177] is assumed in
this document.
3. Overview
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+-----+
| RB4 |
+----------+-----+----------+
| |
| |
| Rest of campus |
| |
| |
+-+-----+--+-----+--+-----+-+
| RB1 | | RB2 | | RB3 |
+-----\ +-----+ /-----+
\ | /
\ | /
|||MC-LAG1
|||
+---+
| B |
+---+
H1 H2 H3 H4: VLAN 10
Figure 3.1: An example topology for TRILL Active-Active Edge
Figure 3.1 shows an example network for TRILL Active-Active Edge. In
this figure, endnodes (H1, H2, H3 and H4) are attached to a bridge
(B) which communicates with multiple RBridges (RB1, RB2 and RB3) via
the MC-LAG. Suppose RB4 is a 'remote' RBridge out of the AAE group in
the TRILL campus. This connection model is also applicable to the
virtualized environment where the physical bridge can be replaced
with a vSwitch while those bare metal hosts are replaced with virtual
machines (VM).
For a packet received from their attached endnode clumps, a member
RBridge of the AAE group always encapsulates it using its own
nickname as the ingress nickname no matter whether it's unicast or
multicast.
The remote RBridge RB4 will see multiple attachments of one MAC from
each of the end nodes.
4. Incremental Deployable Options
Three options are listed below to cope with incremental deployment
scenarios. Among them, Option C can be hardware independent.
-- Option A
A new capability announcement would appear in LSPs. "I can cope
with multiple attachments for an endnode". Only if all edge
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RBridges announce this capability can the AAE group use this
approach. For those legacy RBridges who are not capable of coping
with multiple endnode attachments, new type TRILL switches will
not establish connectivity with them so that they are isolated
from these new type TRILL switches. Note only edge RBridges (those
that are Appointed Forwarders [RFC6439]) need to be able to
support this. It does not affect totally transit RBridges.
-- Option B
Each edge RBridge in the AAE group ingress data frames from any
MC-LAG into a specific TRILL topology [TRILL-MT]. In this way, the
topology ID is used as the discriminator of different locations of
a specific MAC address at the remote RBridge. TRILL MAY reserve a
list of topology IDs to be dedicated to AAE. RBridges that do not
support this reserved list MUST NOT establish connectivity with
edge RBridges in the AAE group.
-- Option C
As pointed out in Section 4.2.6 of [RFC6325] and Section 5.3 of
[ESADI], one MAC address may be persistently claimed to be
attached to multiple RBridges within the same Data Label in the
TRILL ESADI LSPs. For this option, AAE member RBridges make use of
TRILL ESADI protocol to distribute multiple attachments of a MAC
address. Remote RBridges disable the data plane learning for such
multi-attached MAC addresses.
4.1. Detail of Option C
An RBridge in an AAE MUST advertise all Data Labels enabled for all
its attached MC-LAGs. This causes remote RBridges to disable the MAC
learning via the TRILL Data packet decapsulation within these Data
Labels for this RBridge. The advertisement of such Data Labels can be
realized by allocating one reserved flag from the Interested VLANs
and Spanning Tree Roots Sub-TLV (Section 2.3.6 of [RFC7176]) and one
reserved flag from the Interested Labels and Spanning Tree Roots Sub-
TLV (Section 2.3.8 of [RFC7176]). When this flag is set to 1, the
originating IS is advertising Data Labels for MC-LAGs rather than
plain LAN links. (See Section 7.2)
Whenever a MAC from the MC-LAG of this AAE is learned, it needs to be
advertised via the ESADI protocol. In its TRILL ESADI LSPs, the
originating IS needs to include the identifier of this AAE. Remote
RBridges need to know all nicknames of RBridges in this AAE. This is
achieved by listening to the "MC-LAG Group RBridges" TRILL APPsub-TLV
defined in Section 5.3.2. MAC Reachability TLVs [RFC6165] are
composed in a way that each TLV only contains MAC addresses of end
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nodes attached to a single MC-LAG. Each such TLV is enclosed in a
TRILL APPsub-TLV defined as follows.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = MC-LAG-GROUP-MAC | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
| MC-LAG System ID (8 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
| MAC-Reachability TLV (7 + 6*n bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
o Type: MC-LAG Group MAC (TRILL APPsub-TLV type #TBD)
o Length: The MAC-Reachability TLV [RFC6165] is contained in the
value field as a sub-TLV. The total number of bytes contained in
the value field is given by 15+6*n.
o MC-LAG System ID: The System ID of the MC-LAG as specified in
Section 5.3.2 of [802.1AX]. Here, it also serves as the identifier
of the AAE.
o MAC-Reachability sub-TLV: The MC-LAG-GROUP-MAC APPsub-TLV value
contains the MAC-Reachability TLV as a sub-TLV.
This MC-LAG-GROUP-MAC APPsub-TLV SHOULD be included in a GENINFO TLV
[RFC6823] in the ESADI-LSP. There may be more than one occurrence of
such TRILL APPsub-TLV in one ESADI-LSP fragment.
For those MAC addresses contained in an MC-LAG-GROUP-MAC APPsub-TLV,
this document applies. Otherwise, [ESADI] applies. For example, an
AAE member RBridge continues to enclose MAC addresses learned from
TRILL Data packet decapsulation in MAC-Reachability TLV as per
[RFC6165] and advertise them using the ESADI protocol.
When the remote RBridge learns MAC addresses contained in the MC-LAG-
GROUP-MAC APPsub-TLV via the ESADI protocol, it always sends the
packets destined to these MAC addresses to the closest one (the one
to which the remote RBridge has the least cost forwarding path) of
those RBridges in the AAE identified by the MC-LAG System ID in the
MC-LAG-GROUP-MAC APPsub-TLV. If there are multiple such member
RBridges, the ingress RBridge is required to select a unique one in a
pseudo-random way as specified in Section 5.3 of [ESADI].
When another RBridge in the same AAE group receives an ESADI-LSP with
the MC-LAG-GROUP-MAC APPsub-TLV, it also learns MAC addresses of
those end nodes served by the corresponding MC-LAG. These MAC
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addresses SHOULD be learned as if those end nodes are locally
attached to this RBridge itself.
An AAE member RBridge MUST use the MC-LAG-GROUP-MAC APPsub-TLV to
advertise the MAC addresses learned from a plain local link (a non
MC-LAG link) with Data Labels that happen to be covered by the Data
Labels of any attached MC-LAG. The reason is that data plane learning
within these Data Labels at the remote RBridge has been disabled for
this RBridge.
4.2. Capability Flags TLV
The following Capability Flags TLV will be included in LSP as a TRILL
APPsub-TLV of GENINFO-TLV.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = MULTI-MAC-ATTACH-CAP | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E|H| Reserved | (1 byte)
+-+-+-+-+-+-+-+-+
o Type: Multi-MAC-Attach Capability (TRILL APPsub-TLV type #TBD)
o Length: Set to 1.
o E: When this bit is set, it indicates the originating IS acts as
specified in Option C.
o H: When this bit is set, it indicates that the originating IS
keeps multiple MAC attachments with fast path hardware at the data
plane.
o Reserved: Reserved flags for future use. These MUST be sent as
zero and ignored on receipt.
The Capability Flags TRILL APPsub-TLV is used to notify other
RBridges whether the originating IS supports the capability indicated
by the E and H bits. For example, if E bit is set, it indicates the
originating IS will act as defined in Option C. That is, it will
disable the data plane MAC learning for AAE RBridges within Data
Labels advertised by them while waiting for the TRILL ESADI LSPs to
distribute the {MAC, Nickname, Data Label} association. Meanwhile,
this RBridge is able to act as an AAE RBridge. It's required to
advertise MAC addresses learned from MC-LAGs in TRILL ESADI LSPs
using the MC-LAG-GROUP-MAC APPsub-TLV defined in Section 4.1. AAE
RBridges supporting Options C won't establish connectivity with
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remote edge RBridges unless this RBridge has advertised this
Capability Flags TLV with E bit set.
Capability specification for Option B is out the scope of this
document. It may be specified in documents for TRILL multi-topology
[TRILL-MT].
5. Design Goals
How this specification meets the major design goals of AAE is
explored in this section.
5.1. No MAC Flip-Floping (Normal Unicast Egress)
Since all RBridges talking with the AAE RBridges in the campus are
able to keep multiple locations for one MAC address, a MAC address
learned from one AAE member will not be overwritten by the same MAC
address learned from another AAE member. Although multiple entries
for this MAC address will be created, the remote RBridge is required
to adhere to a unique one of the locations (see Section 4.1) for each
MAC address rather than keep flip-flopping among them.
5.2. Regular Unicast/Multicast Ingress
MC-LAG guarantees that each frame will be sent upward to the AAE via
exactly one uplink. RBridges in the AAE can simply follow the process
per [RFC6325] to ingress the frame. For example, each RBridge uses
its own nickname as the ingress nickname to encapsulate the packet.
In such scenario, each RBridge takes for granted that it is the
Appointed Forwarder for the VLANs enabled on the uplink of the MC-
LAG.
5.3. Right Multicast Egress
A fundamental design goal of AAE is that there is no duplication or
forwarding loop.
5.3.1. No Duplication (Single Exit Point)
When multi-destination packets for a specific Data Label are received
from the campus, it's important that exactly one RBridge out of the
AAE group let through each multicast packet, therefore no duplication
happens. Since AAE member RBridges support MC-LAG, they are able to
utilize the hashing function of MC-LAG to determine the single exit
point. If the output of the hashing function points to the port
attached to the receiver RBridge itself (i.e., the packet should be
egressed out of this node), it egresses this packet. Otherwise, the
packet MUST be dropped.
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5.3.2. No Echo (Split Horizon)
When a multicast frame originated from an MC-LAG is ingressed by an
RBridge of an AAE group, forwarded across the TRILL network and then
received by another RBridge in the same AAE group, it is important
that this RBridge does not egress this frame back to this MC-LAG.
Otherwise, it will cause a forwarding loop (echo). The well known
'split horizon' technique can be used to eliminate the echo issue.
RBridges in the AAE group need to split horizon based on the ingress
RBridge nickname plus the VLAN of the TRILL Data packet. They need to
set up per port filtering lists consists of the tuple of <ingress
nickname, VLAN>. Packets with information matching with any entry of
the filtering list MUST NOT be egressed out of that port. The
information of such filters is obtained by listening to the following
"MC-LAG Group RBridges" TRILL APPsub-TLV included in the GENINFO TLV
in LSPs.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = MC-LAG-GROUP-RBRIDGES | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Nickname | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
| MC-LAG System ID (8 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
o Type: MC-LAG Group RBridges (TRILL APPsub-TLV type #TBD)
o Length: 10
o Sender Nickname: The nickname of the originating IS.
o MC-LAG System ID: The System ID of the MC-LAG as specified in
Section 5.3.2 of [802.1AX].
All enabled VLANs MUST be consistent on all ports connected to an MC-
LAG. So that the enabled VLANs need not to be included in the MC-LAG
Group RBridges TRILL APPsub-TLV. They can be locally obtained from
the port attached to that MC-LAG.
Through parsing an MC-LAG Group RBridges TRILL APPsub-TLV, the
receiver RBridge discovers all other RBridges connected to the same
MC-LAG. The Sender Nickname of the originating IS will be added into
the filtering list of the port attached to the MC-LAG. For example,
RB3 in Figure 3.1 will set up a filtering list looks like {<RB1,
VLAN10>, <RB2, VLAN10>} on its port attached to MC-LAG1. According to
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split horizon, TRILL Data packets within VLAN10 ingressed by RB1 or
RB2 will not be egressed out of this port.
When there are multiple MC-LAGs connected to the same RBridge, these
MC-LAGs may have overlap VLANs. Customer may need hosts within these
overlap VLANs to communicate with each other. In Appendix A, several
scenarios are given to explain how hosts communicate within the
overlap VLANs and how split horizon happens.
5.4. No Black-hole or Triangular Forwarding
If a sub-link of the MC-LAG fails while remote RBridges continue to
send packets towards the failed port, a black-hole happens. If the
AAE member RBridge with that failed port starts to redirect the
packets to other member RBridges for delivery, triangular forwarding
forms.
The member RBridge attached to the failed sub-link can make use of
the ESADI protocol to flush those failure affected MAC addresses as
defined in Section 5.2 of [ESADI]. After doing that, no packets will
be sent towards the failed port, hence no black-hole will happen. Nor
will the member RBridge need to redirect packets to other member
RBridges, which may otherwise lead to the triangular forwarding.
5.5. Load Balance Towards the AAE
Since a remote RBridge can record multiple attachments of one MAC
address, this remote RBridge can choose to spread the traffic towards
the AAE members. Each of them is able to act as the egress point. By
doing this, the forwarding paths may be not limited to the least cost
Equal Cost Multiple Paths from the ingress RBridge to the AAE
RBridges. The traffic load from the remote RBridge towards the AAE
RBridges can be balanced based on a pseudo-random selection method
(see Section 4.1).
Note that the load balance method adopted at the ingress RBridge is
not to replace the load balance mechanism of MC-LAG. These two load
spreading mechanisms should take effect separately.
5.6. Scalability
With option A, multiple attachments need to be recorded for a MAC
address learned from AAE RBridges. More entries may be consumed in
the MAC table. However, MAC addresses attached to an MC-LAG are only
a small part of all MAC addresses in the whole TRILL campus. As a
result, the extra space required by the multi-attached MAC addresses
can be accommodated by RBridges' unused MAC table space.
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With option C, remote RBridges will keep the multiple attachments of
a MAC address in the ESADI link state databases. While in the MAC
table, an RBridge still establishes only one entry for each MAC
address.
6. Security Considerations
Authenticity for contents transported in IS-IS PDUs is enforced using
regular IS-IS security mechanism [ISIS][RFC5310].
For security considerations pertain to extensions hosted by TRILL
ESADI, see the Security Considerations section in [ESADI].
For general TRILL security considerations, see [RFC6325].
7. IANA Considerations
7.1. TRILL APPsub-TLVs
IANA is requested to allocate three new types under the Generic
Information TLV (#251) [RFC6823] for the TRILL APPsub-TLVs defined in
Section 4.1, 4.2 and 5.3.2 of this document.
Reference: [ESADI] and [This document]
Type Name Reference
---------- -------- -----------
0 Reserved
1 ESADI-PARAM [ESADI]
2-254 Unassigned
255 Reserved
256 MC-LAG-GROUP-MAC This document
257 MULTI-MAC-ATTACH-CAP This document
258 MC-LAG-GROUP-RBRIDGES This document
260-65534 Unassigned
65535 Reserved
7.2. Active Active Flags
IANA is requested to allocate two flag bits, as follows:
One flag bit appears in the "Interested VLANs and Spanning Tree Roots
Sub-TLV".
References: [RFC7176], [ESADI] and [This document]
Bit Mnemonic Description Reference
--- -------- ----------- ---------
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0 M4 IPv4 Multicast Router Attached [RFC7176]
1 M6 IPv6 Multicast Router Attached [RFC7176]
2 - Unassigned
3 ES ESADI Participation [ESADI]
4-15 - (used for a VLAN ID) [RFC7176]
16 AA Enabled VLANs for Active-Active This document
17-19 - Unassigned
20-31 - (used for a VLAN ID) [RFC7176]
One flag bit appears in the "Interested Labels and Spanning Tree
Roots Sub-TLV".
References: [RFC7176], [ESADI] and [This document]
Bit Mnemonic Description Reference
--- -------- ----------- ---------
0 M4 IPv4 Multicast Router Attached [RFC7176]
1 M6 IPv6 Multicast Router Attached [RFC7176]
2 BM Bit Map [RFC7176]
3 ES ESADI Participation [ESADI]
4 AA FGLs for Active-Active This document
5-7 - Unassigned
Acknowledgements
Authors would like to thank the comments and suggestions from Erik
Nordmark, Fangwei Hu and Liang Xia.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6165] Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2
Systems", RFC 6165, April 2011.
[RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, July 2011.
[RFC6439] Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F. Hu,
"Routing Bridges (RBridges): Appointed Forwarders", RFC
6439, November 2011.
[RFC6823] Ginsberg, L., Previdi, S., and M. Shand, "Advertising
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Generic Information in IS-IS", RFC 6823, December 20165
[RFC7172] D. Eastlake 3rd and M. Zhang and P. Agarwal and R. Perlman
and D. Dutt, "Transparent Interconnection of Lots of Links
(TRILL): Fine-Grained Labeling", RFC 7172, May 2014.
[RFC7176] D. Eastlake 3rd and T. Senevirathne and A. Ghanwani and D.
Dutt and A. Banerjee, "Transparent Interconnection of Lots
of Links (TRILL) Use of IS-IS", RFC7176, May 2014.
[RFC7177] D. Eastlake 3rd and R. Perlman and A. Ghanwani and H. Yang
and V. Manral, "Transparent Interconnection of Lots of
Links (TRILL): Adjacency", RFC 7177, May 2014.
[ESADI] H. Zhai, F. Hu, et al, "TRILL (Transparent Interconnection
of Lots of Links): ESADI (End Station Address Distribution
Information) Protocol", draft-ietf-trill-esadi-07.txt,
April 2014, Submitted to IESG for Publication.
[802.1AX] IEEE, "IEEE Standard for Local and metropolitan area
networks / Link Aggregation", 802.1AX-2008, 1 January 2008.
8.2. Informative References
[CMT] T. Senevirathne, J. Pathangi, et al, "Coordinated Multicast
Trees (CMT)for TRILL", draft-ietf-trill-cmt-03.txt, April
2014, working in progress.
[TRILL-MT] D. Eastlake, M. Zhang, A. Banerjee, V. Manral, "TRILL:
Multi-Topology", draft-eastlake-trill-multi-topology, work
in progress.
[ISIS] ISO, "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.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic Authentication",
RFC 5310, February 2009.
Appendix A. Scenarios on Split Horizon
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+------------------+ +------------------+ +------------------+
| RB1 | | RB2 | | RB3 |
+------------------+ +------------------+ +------------------+
L1 L2 L3 L1 L2 L3 L1 L2 L3
VL10~20 VL15~25 VL15 VL10~20 VL15~25 VL15 VL10~20 VL15~25 VL15
MC-LAG1 MC-LAG2 LAN MC-LAG1 MC-LAG2 LAN MC-LAG1 MC-LAG2 LAN
B1 B2 B10 B1 B2 B20 B1 B2 B30
Figure A.1: An example topology to explain split horizon
Suppose RB1, RB2 and RB3 are the Active-Active group connecting MC-
LAG1 and MC-LAG2. MC-LAG1 and MC-LAG2 are connected to B1 and B2 at
their other ends. Suppose all these RBridges use port L1 to connect
MC-LAG1 while they use port L2 to connect MC-LAG2. Assume all three
L1 enable VLAN 10~20 while all three L2 enable VLAN 15~25. So that
there is an overlap of VLAN 15~20. Customer needs hosts in these
overlap VLANs to communicate with each other. That is, hosts attached
to B1 in VLAN 15~20 need to communicate with hosts attached to B2 in
VLAN 15~20. Assume the remote plain RBridge RB4 also has hosts
attached in VLAN 15~20 which need to communicate with those hosts in
these VLANs attached to B1 and B2.
Two major requirements:
1. Frames ingressed from RB1-L1-VLAN 15~20 MUST NOT be egressed out
of ports RB2-L1 and RB3-L1. At the same time,
2. frames coming from B1-VLAN 15~20 should reach B2-VLAN 15~20.
RB3 stores the information for split horizon on its ports L1&L2. On
L1: {<ingress_nickname_RB1, VLAN 10~20>, <ingress_nickname_RB2, VLAN
10~20>} and on L2: {<ingress_nickname_RB1, VLAN 15~25>,
<ingress_nickname_RB2, VLAN 15~25>}.
Five clarification scenarios:
a. Suppose RB2/RB3 receives a TRILL multicast data packet with VLAN
15 and ingress nickname RB1. RB3 is the single exit point
(selected out according to the hashing function of MC-LAG) for
this packet. On ports L1&L2, RB3 has covered
<ingress_nickname_RB1, VLAN 15>, so that RB3 will not egress this
packet out of either L1 or L2. Here, _split horizon_ happens.
Beforehand, RB1 obtains a native frame on port L1 from B1 in VLAN
15. RB1 judges it should be forwarded as a multicast frame across
the TRILL campus. Also, RB1 replicates this frame without TRILL
encapsulation and sends it out of port L2, so that B2 will get
this frame.
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b. Suppose RB2/RB3 receives a TRILL multicast data packet with VLAN
15 and ingress nickname RB4. RB3 is the single exit point. On
ports L1&L2, since RB3 has not stored any tuple with ingress_
nickname_RB4, RB3 will decapsulate the packet and egress it out of
both ports L1 and L2. So both B1 and B2 will receive the frame.
c. Suppose there is a plain LAN link port L3 on RB1, RB2 and RB3,
connecting to B10, B20 and B30 respectively. These L3 ports happen
to be configured with VLAN 15. On port L3, RB1 and RB3 stores no
information of split horizon for AAE (since this port has not been
configured to be in any MC-LAG). They will egress the packet
ingressed out of RB1-L1 in VLAN 15.
d. If a packet is ingressed from RB1-L1 or RB1-L2 with VLAN 15, port
RB1-L3 will not egress packets with ingress-nickname-RB1. RB1
needs to replicate this frame without encapsulation and sends it
out of port L3.
e. If a packet is ingressed from RB1-L3, since RB1-L1 and RB1-L2
cannot egress packets with VLAN 15 and ingress-nickname-RB1, RB1
needs to replicate this frame without encapsulation and sends it
out of port L1 and L2.
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Author's Addresses
Mingui Zhang
Huawei Technologies
No.156 Beiqing Rd. Haidian District,
Beijing 100095 P.R. China
EMail: zhangmingui@huawei.com
Radia Perlman
Intel Labs
2200 Mission College Blvd.
Santa Clara, CA 95054-1549 USA
Phone: +1-408-765-8080
EMail: radia@alum.mit.edu
Hongjun Zhai
ZTE Corporation
68 Zijinghua Road
Nanjing 200012 China
Phone: +86-25-52877345
EMail: zhai.hongjun@zte.com.cn
Muhammad Durrani
Brocade
EMail: mdurrani@brocade.com
Mukhtiar Shaikh
Brocade
EMail: mshaikh@brocade.com
Sujay Gupta
IP Infusion
Bangalore, India
EMail: sujayg@ipinfusion.com
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