Transparent Interconnection of Lots of Q. Wu
Links Working Group W. Hao
Internet-Draft Huawei
Updates: 6325 (if approved) October 22, 2012
Intended status: Standards Track
Expires: April 25, 2013
LSP extension for Tree Distribution Optimization across sites
draft-wu-trill-lsp-ext-tree-distr-opt-01
Abstract
This document specifies an extension to LSP for the Rbridge in one
site to advertise Global VLAN scope and associated link attribute to
all the Rbridges both in the site of that Border Rbridge and the
other adjacent sites in the same campus. With this extension,
RBridges can prune the distribution tree of multi-destination frames
according to the scope of the VLAN and link attribute defined in this
document.
Status of this Memo
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This Internet-Draft will expire on April 25, 2013.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. TLV and Sub-TLV Extensions to IS-IS for Inter-site
Distribution Tree . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Global-VLANs Sub-TLV for the Router Capability TLV . . . . 6
4.1.1. Definition of Fields in Sub-TLV . . . . . . . . . . . 6
4.2. Link-Attributes Sub-TLV extension for extended IS
reachability TLV . . . . . . . . . . . . . . . . . . . . . 7
5. Use of TLV and Sub-TLV for Tree Distribution Optimization
across sites . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Unicast Forwarding Consideration . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 15
Appendix A. Change Logs . . . . . . . . . . . . . . . . . . . . . 16
A.1. draft-wu-trill-lsp-ext-tree-distr-opt-01 . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
Large datacenters are often multi-site in nature and may contain a
large number of Rbridges in each site. A trill Campus network may
also be designed to be multilevel can be divided in to multiple IS-IS
[IS-IS][RFC1195]L1 Areas interconnected by L2 backbone area. Routing
between Rbridges within a IS-IS L1 area/ site is known as "Level 1
routing". Routing between IS-IS L1 areas or sites is known as "Level
2 routing". The IS-IS L1 area supports Level 1 routing and consists
of Rbridges within the site and link between Rbridges within the
site. The L2 backbone area supports Level 2 routing and consists of
Border Rbridges and links between the Border Rbridges. Border
Rbridges may participate in one or more L1 areas as Level-1 Rbridges
inside each site, in addition to their role as Level 2 Rbridge across
sites.
In Trill campus network, RBridges use distribution trees to forward
multi-destination frames. In case of one Trill campus network having
multiple sites, the traffic associated with some distributed trees
may travel between sites while the traffic associated with other
distributed trees may be limited to only one site and not allowed to
go across other sites. The traffic spanning across sites is also
referred to as the traffic with global scope. In order to support
scaling and performance of large TRILL networks in the real
deployments, it is desirable to forward most of Multi-destination
Trill traffic within the site and reduce the traffic that is required
to span across sites within the entire TRILL campus. According to
The TRILL base protocol, each distribution tree SHOULD be pruned per
VLAN. When it is inevitable to construct trees that have a scope
across sites throughout the TRILL campus, it is necessary to treat
traffic tagged with VLAN differently based on VLAN scope and distinct
the link between Rbridges in one site and link between two Border
Rbridge in two sites to support large scale multi-tenants
application.
This document specifies an extension to LSP for the Rbridge in one
site to advertise Global VLAN scope and associated link attribute to
all the Rbridges both in the site of that Border Rbridge and the
other adjacent sites in the same campus. With this extension,
RBridges can prune the distribution tree of multi-destination frames
according to the scope of the VLAN and link attribute defined in this
document.
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2. Conventions used in this document
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 RFC2119 [RFC2119].
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3. Motivations
Distinguishing global vlan from local vlan is to increase the number
of tenants by not breaking the VLAN tag size limits. E.g. one campus
being divided into n sites, without distinction between global vlan
and local vlan, at most support 4K tenants. However, if we
distinguish global vlan from local vlan, suppose each site support
only local vlan. Then each site support 4K tenants, the total number
of tenants supported by one campus can be increased to 4n*K.Suppose
some sites support local vlan, some sites support both local vlan and
global vlan, the total number of tenants supported by one campus
(4K,4n*K).
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4. TLV and Sub-TLV Extensions to IS-IS for Inter-site Distribution Tree
This section describes data formats and code points for the TLVs and
sub-TLVs added to IS-IS defined by this specification to support the
multi-level TRILL or re-used from that already contained in the
standard IS-IS extensions defined in [RFC6326].
4.1. Global-VLANs Sub-TLV for the Router Capability TLV
The optional Global-VLANs sub-TLV specifies the VLANs that have
global scope and enable Construction of global multi-destination
trees among different sites. It has the following format:
+-+-+-+-+-+-+-+-+
| Type | (1 byte)
+-+-+-+-+-+-+-+-+
| Length | (1 byte)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESV | Start VLAN ID | (2 bytes)
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VLAN bit-map....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Report Block Structure
4.1.1. Definition of Fields in Sub-TLV
Type: 8bits
Router Capability sub-TLV type, set to TBD (GLOBAL-VLANs).
Length: 8bits
Variable, minimum 3.
RESV: 4bits
4 reserved bits that MUST be sent as zero and ignored on receipt.
Start VLAN ID:12bits
The 12-bit VLAN ID that is represented by the high order bit of
the first byte of the VLAN bit-map.
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VLAN bit-map:
The highest order bit indicates the VLAN equal to the start VLAN
ID, the next highest bit indicates the VLAN equal to start VLAN ID
+ 1, continuing to the end of the VLAN bit-map field.
4.2. Link-Attributes Sub-TLV extension for extended IS reachability TLV
The link-attribute sub-TLV is carried within the TLV 22 and has a
format identical to the sub-TLV format used by the Traffic
Engineering Extensions for IS-IS ([RFC3784]): 1 octet of sub-type, 1
octet of length of the value field of the sub-TLV followed by the
value field -- in this case, a 16 bit flags field.
The Link-attribute sub-type is 19 and the link-attribute has a length
of 2 octets.
This sub-TLV is OPTIONAL and MUST appear at most once for a single IS
neighbor. If a received Link State Packet (LSP) contains more than
one Link-Attribute Sub-TLV, an implementation SHOULD decide to
consider only the first encountered instance. The following bit is
defined:
Public Link Type For TRILL(0x03) When set, this indicates that the
link is public link for TRILL sites interconnection.
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5. Use of TLV and Sub-TLV for Tree Distribution Optimization across
sites
When the TRILL campus is divided into multiple sites, each site may
have one or more Border Rbridges used to interconnect other remaining
sites and form the Level 2 IS-IS Trill network. Such Level2 IS-IS
Trill network can be used to construct global multi-destination tree
spanning across various sites.
TRILL Site 1 TRILL Site 2
+-------------------+ +---------------+ +-------------------+
| | | | | |
| +---+ +----+ | | WAN | |+----+ +---+ |
| |RB1|------+BRB2| |--|L2 Connectivity|---||BRB3|-------|RB4| |
| +---+ +----+ | | | |+----+ +---+ |
| | | | | |
+-------------------+ +---------------+ +-------------------+
|
|
+-------------------+
| +----+ |
| |BRB5| |
| +----+ |
| +---+ | +---+ |
| |RB6|---+---|RB7| |
| +---+ +---+ |
+-------------------+
TRILL Site 3
Figure 1: Example of multiple sites within one Trill Campus
In order to support scaling and performance of large TRILL networks
in the real deployments, firstly, not all the links between the level
2 Rbridges need to be used to Construct global multi- destination
trees. If the link between the level 2 Rbridges is allowed to
construct global multi-destination trees, we can set this link
attribute into "public interface for global tree construction". In
this document, we reuse Link Attribute sub-TLV for the extended IS
reachability TLV and allocate a new bit value inside link Attribute
Sub-TLV to support indication of "public link for global tree
Construction". The Border Rbridge in one site need to advertise this
link attribute Sub-TLV to all the neighboring Border Rbridges in
other neighboring sites and then this sub-TLV will be further
forwarded to all the Rbridges in the site of each neighboring Border
Rbridge. RBridges in each site can prune the distribution tree of
multi-destination frames according to such link attribute.
Secondly, not all traffic should have global scope and need to span
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across sites. Since each distribution tree SHOULD be pruned per VLAN
according to [RFC6325], we can specify a set of Global VLANs to
identify the traffic that has global scope. In this document, we
define one new sub-TLV for the Router Capability TLV, i.e., Global-
VLANs Sub- TLV. This Sub-TLV can be used by Rbriges in one site to
determine whether Construction of global multi-destination trees
across sites is allowed. In order to achieve this, the tree root or
highest priority RBridge in one site configured to know a number of
appropriate VLANs as Global VLANs and announce such information to
the nearest border Rbridge; Then such Border Rbridge in this site
need to advertise Global VLAN Sub-TLV to all the neighboring Border
Rbridges in other neighboring sites and then this sub-TLV will be
further forwarded to all the Rbridges in the site of each neighboring
Border Rbridge. When Global VLAN and link attribute Sub-TLV
described above has been distributed to all the corresponding
Rbridges in the downstream of the tree root or highest priority
RBridge, RBridges can prune the distribution tree of multi-
destination frames according to the scope of the VLAN and link
attribute defined in this document, eliminating branches that own
link type mismatching with Distribution Tree scope identified by
VLAN. If the distribution tree is local tree and has branches
including a link with link attribute is set to public link for global
tree construction, those branches should be eliminated. If the
distribution tree is global tree and has branches containing a link
with link attribute not set to public link for global tree
construction, those branches also should be eliminated.
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+---+
| a |
+---+
L1 \ \ L2
\ \
\ \
+---+ +---+
| b | | c |
+---+ +---+
L3 \ \ L4
VLAN20 \ \
\ \
+---+ +---+
| d | | e |
+---+ +---+
_ _
_ _ \
public link _L5 _L6 \ L7
_ _ \
+---+ +---+ +---+
| f | | g | | h |
+---+ +---+ +---+
VLAN10 VLAN10 VLAN20
Figure 2: Distribution Tree
Take distribution tree in Figure 2 as an example, Rbridge a is root
node. Rbridge f,g are leaf nodes that have end station on VLAN 10
while Rbridge b,h are another two leaf nodes and that have end
station on VLAN 20. The link between Rbridge d and f is public link
used across sites while the other links in the figure 2 are links
owned by one single site. Assume VLAN 10 are local VLAN and VLAN 20
are Global VLAN, after distribution tree pruning is done, Rbrige c
should eliminate branch that has Rridge d and f since distribution
tree is pruned based on local VLAN 10 and Link 5 in that branch is
public link, which mismatch with each other.
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6. Unicast Forwarding Consideration
In unicast forwarding, the MAC forwarding table for a Trill Border
Rbridge is usually learned through the data plane, i.e.,MAC address
is learnt from received Broadcast,Unknown, Unicast,Multicast packet
through distribution tree. For end stations on the local vlan, the
broadcast scope is limited to one local site, the Border Rbridge only
learns MAC address of locally attached end station and the forwarding
path between end stations within one site can be built for unicast.
For end stations on global VLAN, end stations between two sites are
within the same layer 2 broadcast domain, the Border Rbridge can
learn MAC address of end stations across sites and the forward path
between two sites can be built as well for unicast. Therefore
unicast forwarding between sites can be controlled through LSP
extension we defined in this document.
If the Border Rbridge is statically configured with unicast
forwarding table and the nickname of the destination Rbridge is
specified as one Rbridge's nickname in other sites, the unicast
packet must be forced to forward to the other sites. In this case,
the Border Rbridge in other sites performs security check to the
received packet. If the VLAN associated with the received packet is
local VLAN and the packet is ingressed from public link across site,
the packet should be discarded. If the VLAN associated with the
received packet is Global VLAN, the packet should be allowed to
ingress from public link across sites.
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7. IANA Considerations
IANA is requested to assign a new codepoint for the Global-VLANs Sub-
TLV defined in this document and carried within TLV 242.
IANA has created a registry for bit values inside the link-attributes
sub-TLV called "link-attribute bit values for sub-TLV 19 of TLV 22".
This document instructs IANA to add a new bit value in the link-
attribute bit values for sub-TLV 19 of TLV 22 registry as follows:
Value Name Reference
----- ---- ---------
0x3 Public Link Type between sites [This document]
Further values are to be allocated by the Standards Action process
defined in [RFC2434], with Early Allocation (defined in [RFC4020])
permitted.
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8. Security Considerations
The security considerations documented in [RFC4971][RFC5305] are
applicable for the Sub-TLV extension defined in this document.
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9. References
9.1. Normative References
[IS-IS] "Intermediate System to Intermediate System Intra-Domain
Routing Exchange Protocol for use in Conjunction with the
Protocol for Providing the Connectionless-mode Network
Service (ISO 8473)", ISO/IEC 10589:2002 Second Edition,
2002.
[RFC1195] Ohta, M., "Use of OSI IS-IS for routing in TCP/IP and dual
environments", December 1990.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 2434,
October 1998.
[RFC3784] Smit, H., "Intermediate System to Intermediate System
(IS-IS) Extensions for Traffic Engineering (TE)",
June 2004.
[RFC4020] Kompella, K. and A. Zinin, "Early IANA Allocation of
Standards Track Code Points", RFC 4020, February 2005.
[RFC4971] Vasseur, J., "Intermediate System to Intermediate System
(IS-IS) Extensions for Advertising Router Information",
July 2007.
[RFC5029] Vasseur, J. and S. Previdi, "SDP: Session Description
Protocol", September 2007.
[RFC5305] Li, T. and H. Smit, "S-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
[RFC6325] Perlman, R., Eastlake , D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, July 2011.
[RFC6326] Eastlake , D., Banerjee, A., Dutt, D., Perlman, R., and A.
Ghanwani, "Transparent Interconnection of Lots of Links
(TRILL) Use of IS-IS", RFC 6326, July 2011.
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9.2. Informative References
[TRILL-ML]
Perlman , R., Eastlake, D., Ghanwani, A., and H. Zhai,
"RBridges: Multilevel TRILL",
ID draft-perlman-trill-rbridge-multilevel-03,
October 2011.
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Appendix A. Change Logs
A.1. draft-wu-trill-lsp-ext-tree-distr-opt-01
The following are the major changes to previous version
draft-wu-trill-lsp-ext-tree-distr-opt-00:
o Add one new section to discuss Unicast Forwarding.
o Add one new section to clarify the motivation to write this draft.
o Some other editorial changes.
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Authors' Addresses
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: bill.wu@huawei.com
Weiguo Hao
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: haoweiguo@huawei.com
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