Mechanisms for Directory Assisting RBridge
draft-dunbar-trill-scheme-for-directory-assist-00
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| Authors | Linda Dunbar , Radia Perlman , Igor Gashinsky , Donald E. Eastlake 3rd | ||
| Last updated | 2012-03-06 | ||
| Replaced by | draft-ietf-trill-directory-assist-mechanisms, RFC 8171 | ||
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draft-dunbar-trill-scheme-for-directory-assist-00
TRILL working group L. Dunbar
Internet Draft D. Eastlake
Intended status: Standard Track Huawei
Expires: Sept 2012 Radia Perlman
Intel
I. Gashinsky
Yahoo
March 5, 2012
Mechanisms for Directory Assisting RBridge
draft-dunbar-trill-scheme-for-directory-assist-00.txt
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Abstract
This draft describes the mechanisms of using directory server(s) to
assist RBridge edge in data center environment.
Conventions used in this document
The term ''Subnet'' and ''VLAN'' are used interchangeably in this
document because it is common to map one subnet to one VLAN. The
term ''TRILL'' and ''RBridge'' are used interchangeably 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 RFC-2119 0.
Table of Contents
1. Introduction ................................................ 2
2. Terminology ................................................. 3
3. Push Model of Directory Assisted RBridge Edge in DC Environment3
3.1. Minimize the mapping entries maintained by RBridge Edge .. 4
3.2. Aggregated entries to push down ......................... 4
3.3. Messages to trigger pushing from directory .............. 5
4. Pull model of Directory Assisted RBridge Edge in DC Environment5
5. Push-Pull Hybrid Model ....................................... 7
6. To be continued ............................................. 7
7. Manageability Considerations................................. 7
8. Security Considerations...................................... 7
9. IANA Considerations ......................................... 8
10. Acknowledgments ............................................ 8
11. References ................................................. 8
Authors' Addresses ............................................. 9
Intellectual Property Statemen ................................. 9
Disclaimer of Validity ........................................ 10
1. Introduction
[Directory-Assisted-RBridge] describes the framework of using
directory to assist TRILL edge nodes to improve TRILL network
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scalability in data center environment. This draft describes
mechanisms of using directory to assist RBridge edge nodes in data
center environment.
2. Terminology
AF Appointed Forwarder RBridge port
Bridge: IEEE 802.1Q compliant device. In this draft, Bridge is used
interchangeably with Layer 2 switch.
DA: Destination Address
DC: Data Center
EoR: End of Row switches in data center. Also known as
Aggregation switches in some data centers
FDB: Filtering Database for Bridge or Layer 2 switch
Host: Application running on a physical server or a virtual
machine. A host usually has at least one IP address and at
least one MAC address.
SA: Source Address
STP: Spanning Tree Protocol
RSTP: Rapid Spanning Tree Protocol
ToR: Top of Rack Switch in data center. It is also known as
access switches in some data centers.
VM: Virtual Machines
3. Push Model of Directory Assisted RBridge Edge in DC Environment
Under this model, Directory Server(s) push down the MAC&VLAN <->
RBridgeEdge mapping for all the hosts which might communicate with
hosts attached to an RBridge edge node. With this environment, it is
recommended that RBridge edge simply drop a data packet (instead of
flooding to RBridge domain) if the packet's destination address
can't be found in the MAC&VLAN<->RBridgeEdge mapping table.
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The mapping entry to be pushed down could leverage the gratuitous
ARP reply with extended fields showing the edge RBridge's name, as
shown in Table 2.
3.1. Minimize the mapping entries maintained by RBridge Edge
One major drawback of the ''Push Model'' is that RBridge edge's
MAC&VLAN<->RBridgeEdge mapping table will have more entries than
it really needs.
One simple step for an RBridge to reduce the number of mapping
entries pushed down from directory is to prune out entries
belonging to VIDs which are not enabled on its bridged LANs ports.
For example, if only {vid#1, vid#2, vid#3} are enabled on bridged
LANs connected to an RBridge edge ports, only MAC&VLAN<-
>RBridgeEdge entries for those three VIDs need to be pushed down
to the RBridge edge.
However, under the situations when hosts/VMs attached to one
RBridge edge rarely communicate with hosts under the same VLAN
attached to different RBridge, the normal process of RBridge
edge's cache aging would have removed those MAC&VLAN entries from
the RBridge's cache. But it can be difficult for Directory Servers
to predict the communication patterns among hosts within one VLAN.
Therefore, even with VLAN pruning, it is likely that the Directory
Servers will push down more the MAC&VLAN entries to RBridge Edges
than the normal cache aging approach.
3.2. Aggregated entries to push down
Using Table 2 requires one entry per host/VM. When directory
pushes down the entire mapping to an edge RBridge for the very
first time, there usually are many entries. To minimize the amount
of data pushed down, summarization should be considered, e.g. with
one edge RBridge Nickname being associated with all attached
hosts' MAC addresses and VLANs as shown below:
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+------------+-------+--------------------------------+
| Nickname1 |VID-1 | MAC1, MAC2, MACn |
| |------ +--------------------------------+
| |VID-2 | MAC1, MAC2, MACn |
| |------ +--------------------------------+
| |.... | MAC1, MAC2, MACn |
+------------+------ +--------------------------------+
| Nickname2 |VID-1 | MAC1, MAC2, MACn |
| |------ +--------------------------------+
| |VID-2 | MAC1, MAC2, MACn |
| |------ +--------------------------------+
| |... | MAC1, MAC2, MACn |
+------------+------ +--------------------------------+
| ------- |------ +--------------------------------+
| |.... | MAC1, MAC2, MACn |
+------------+------ +--------------------------------+
Table 1: Summarized table pushed down from directory
Whenever there is any change in MAC&VLAN <-> RBridgeEdge
mapping, which can be triggered by hosts being added, moved, or
de-commissioned, an incremental update can be sent to the
RBridge edges which are impacted by the change.
3.3. Messages to trigger pushing from directory
In push down model, it is necessary to have a message for RBridge
node to request directory server(s) to start pushing down the
mapping entries. This message should at least include the number
of VLANs enabled on the RBridge edge ports, so that directory
server doesn't need to push down the entire mapping entries for
all the hosts in the data center.
RBridge node can use this message to get mapping entries when it
is initialized or restarted.
4. Pull model of Directory Assisted RBridge Edge in DC Environment
Under this model, ''RBridge'' pulls the MAC&VLAN<->RBridgeEdge mapping
entry from the directory server when needed.
RBridge edge node can send data frames with unknown DA to Directory
Servers, or intercept all ARP/ND requests and forward them to the
Directory Server(s).
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The reply from the Directory Server can be the standard ARP/ND reply
with an extra field showing the RBridge egress node's Nickname, as
depicted in Table 2. RBridge ingress node can cache the mapping.
If there is no response from the directory server, the RBridge edge
node can drop the packet.
RBridge edge can age out MAC&VLAN entries if they haven't been used
for a certain period of time. Therefore, each RBridge edge will only
keep the entries which are frequently used, i.e. mapping table size
can be smaller.
The following table shows how target RBridge nickname can be
attached to a standard ARP Reply when replying to an ARP request
forwarded by ingress RBridge edge.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hardware Type | protocol Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HLEN | PLEN | Operation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Hardware Address (MAC) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sender Hardware Address' cont | Sender Protocol Address (IP) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Sender Protocol Address' cont | Target Hardware Address (MAC)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target Hardware Address' cont (MAC) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Target Protocol Address (IP) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
->| Ingress RBridge's Nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
->|Ingress RBridge's Nickname ext | Egress RBridge's Nickname |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
->| Egress RBridge's Nickname extension |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Table 2: Extended fields added to standard ARP reply
The original ARP reply format consists of the first 28 octets shown
in this table. The last 12 octets in this table marked by ''->'' are
extended fields to indicate the Ingress RBridge to which originating
host is attached and the Egress RBridge to which the target host is
attached. More bits are reserved for RBridge nicknames in case
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multiple levels of nicknames are needed in the future for large data
centers.
There are 16 bits for Operation type field in ARP message. IANA has
assigned 0~25 for various purposes and leave 26~65534 unassigned
[http://www.iana.org/assignments/arp-parameters/arp-parameters.xml].
If this approach is taken, a new ARP Operation code has to be
assigned by IANA.
5. Push-Pull Hybrid Model
For some edge nodes which have great number of VIDs enabled,
managing the MAC&VLAN <-> RBridgeEdge mapping for hosts under all
those VIDs can be challenge. This is especially true for Data Center
gateway nodes, which need to maintain majority of VIDs if not all.
For those RBridge Edge nodes, hybrid model should be considered.
I.e. Push model are used for some VIDs, and pull model are used for
other VIDs. It can be operator's decision (i.e. by configuration) on
which VIDs' mapping entries are pushed down from directory and which
VIDs' mapping entries are pulled.
For example, in a data center when hosts in specific VIDs (vid#1,
vid#2, ? vid#100)communicate regularly with external peers, the
mapping entries for those 100 VIDs should be pushed down to the data
center gateway routers. For hosts in other VIDs which only
communicate with external peers once a day (or once a few days) for
management interface, the mapping entries for those VIDs should be
pulled down from directory whenever the needs come up.
6. To be continued
This draft only describes the high level view of the mechanism on
how to use directory to assist RBridge edge. More details will be
added.
7. Manageability Considerations
TBD.
8. Security Considerations
TBD.
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9. IANA Considerations
There are 16 bits for Operation type field. IANA has assigned 0~25
for various purposes and leave 26~65534 unassigned
[http://www.iana.org/assignments/arp-parameters/arp-parameters.xml].
If this approach is taken, a new ARP Operation code has to be
assigned by IANA.
10. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
11. References
[Directory-assisted-RBridge] Dunbar, et, al ''Directory Assisted
RBridge Edge'', <draft-dunbar-trill-directory-assisted-edge>, March
2012,
[RBridges] Perlman, et, al ''RBridge: Base Protocol Specification'',
<draft-ietf-trill-rbridge-protocol-16.txt>, March, 2010
[RBridges-AF] Perlman, et, al ''RBridges: Appointed Forwarders'',
<draft-ietf-trill-rbridge-af-02.txt>, April 2011
[ARMD-Problem] Dunbar, et,al, ''Address Resolution for Large Data
Center Problem Statement'', Oct 2010.
[ARP reduction] Shah, et. al., "ARP Broadcast Reduction for Large Data
Centers", Oct 2010
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Authors' Addresses
Linda Dunbar
Huawei Technologies
5430 Legacy Drive, Suite #175
Plano, TX 75024, USA
Phone: (469) 277 5840
Email: ldunbar@huawei.com
Donald Eastlake
Huawei Technologies
155 Beaver Street
Milford, MA 01757 USA
Phone: 1-508-333-2270
Email: d3e3e3@gmail.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
Igor Gashinsky
Yahoo
45 West 18th Street 6th floor
New York, NY 10011
Email: igor@yahoo-inc.com
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