wdiff rfc7342.alt-original rfc7342.txt

Network working Group
Independent Submission L. Dunbar
Internet Draft
Request for Comments: 7342 Huawei
Intended status:
Category: Informational W. Kumari
Expires: November 2014
ISSN: 2070-1721 Google
Igor
I. Gashinsky
Yahoo
May 7,
August 2014

Practices for scaling Scaling ARP and ND for large data centers

draft-dunbar-armd-arp-nd-scaling-practices-08 Neighbor Discovery (ND)
in Large Data Centers

Abstract

This draft memo documents some operational practices that allow ARP/ND ARP and
Neighbor Discovery (ND) to scale in data center environments.

Status of this This Memo

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Table of Contents

1. Introduction ..................................................3 ....................................................2
2. Terminology ...................................................4 .....................................................4
3. Common DC network Network Designs .....................................5 .......................................4
4. Layer 3 to Access Switches ....................................5 ......................................5
5. Layer 2 practices Practices to scale Scale ARP/ND .............................6 ...............................5
5.1. Practices to alleviate Alleviate APR/ND burden Burden on L2/L3 boundary
routers .......................................................6
Boundary Routers ...........................................5
5.1.1. Communicating with a peer Peer in a different subnet Different Subnet .....6
5.1.2. L2/L3 boundary router processing of inbound traffic .7 Boundary Router Processing of Inbound
Traffic .............................................7
5.1.3. Inter subnets communications ........................8 Inter-Subnet Communications .........................8
5.2. Static ARP/ND entries Entries on switches ........................8 Switches ..........................8
5.3. ARP/ND Proxy approaches ..................................9 Approaches ....................................9
5.4. Multicast Scaling Issues ................................10 ...................................9
6. Practices to scale Scale ARP/ND in Overlay models ..................10 Models ....................10
7. Summary and Recommendations ..................................11 ....................................10
8. Security Considerations ......................................11 ........................................11
9. IANA Considerations ..........................................11
10. Acknowledgements ............................................12
11. ...............................................11
10. References ..................................................12
11.1. ....................................................12
10.1. Normative References ...................................12
11.2. .....................................12
10.2. Informative References .................................13
Authors' Addresses ..............................................13 ...................................13

1. Introduction

This draft memo documents some operational practices that allow ARP/ND to
scale in data center environments.

As described in [RFC6820], the increasing trend of rapid workload
shifting and server virtualization in modern data centers requires
servers to be loaded (or re-loaded) reloaded) with different VMs Virtual Machines
(VMs) or applications at different times. Different VMs residing on
one physical server may have different IP addresses, addresses or may even be in
different IP subnets.

In order to allow a physical server to be loaded with VMs in
different subnets, subnets or allow VMs to be moved to different server racks
without IP address re-configuration, reconfiguration, the networks need to enable
multiple broadcast domains (many VLANs) on the interfaces of L2/L3
boundary routers and ToR Top-of-Rack (ToR) switches and allow some
subnets to span
across multiple router ports.

Note: The L2/L3 boundary routers as discussed in this draft document are
capable of forwarding IEEE802.1 IEEE 802.1 Ethernet frames (layer (Layer 2) without MAC a
Media Access Control (MAC) header change. When subnets span across multiple
ports of those routers, they still fall under the category of single link,
"single-link" subnets, specifically the multi-access link model
recommended by [RFC4903]. They are different from the ''multi-link'' "multi-link"
subnets described in [Multi-Link] and RFC4903, RFC 4903, which refer to
different physical media with the same prefix connected to one
router. Within the ''multi-link'' "multi-link" subnet described in RFC4903, layer RFC 4903, Layer
2 frames from one port cannot be natively forwarded to another port
without a header change.

Unfortunately, when the combined number of VMs (or hosts) in all
those subnets is large, this can lead to address resolution (i.e. (i.e.,
IPv4 ARP and IPv6 ND) scaling issues. There are three major issues
associated with ARP/ND address resolution protocols when subnets span across
multiple L2/L3 boundary router ports:

1) the The ARP/ND messages being flooded to many physical link segments segments,
which can reduce bandwidth utilization for user traffic; traffic.

2) the The ARP/ND processing load impact on the L2/L3 boundary routers; routers.

3) In IPv4, every end station in a subnet receives receiving ARP broadcast
messages from all other end stations in the subnet. IPv6 ND has
eliminated this issue by using multicast.

Since the majority of data center servers are moving towards 1G or
10G ports, the bandwidth taken by ARP/ND messages, even when flooded
to all physical links, becomes negligible compared to the link
bandwidth. In addition, the IGMP/MLD (Internet Group Management Protocol
and Multicast Listener Discovery) snooping [RFC4541] can further
reduce the ND multicast traffic to some physical link segments.

As modern servers' computing power increases, the processing taken by
a large amount of ARP broadcast messages becomes less significant to
servers. For example, lab testing shows that 2000
ARP/s ARP requests
per second only takes 2% of a single core single-core CPU server. Therefore, the
impact of ARP broadcast impact broadcasts to end stations is not significant on
today's servers.

Statistics done provided by Merit Network [ARMD-Statistics] have shown
that the major impact of a large number of mobile VMs in Data Center a data
center is on the L2/L3 boundary routers, i.e. the i.e., issue #2 2 above.

This draft memo documents some simple practices which that can scale ARP/ND in a
data center environment, especially in reducing processing
load loads to
L2/L3 boundary routers.

2. Terminology

This document reuses much of the terminology from [RFC6820]. Many of
the definitions are presented here to aid the reader.

ARP: IPv4 Address Resolution Protocol [RFC826]

Aggregation Switch: A Layer 2 switch interconnecting ToR switches

Bridge: IEEE802.1Q compliant IEEE802.1Q-compliant device. In this draft, Bridge document, the term
"Bridge" is used interchangeably with Layer "Layer 2 switch. switch"

DC: Data Center

DA: Destination Address

End Station: VM or physical server, whose address is either the
destination or the source of a data frame.

EOR: End of Row frame

EoR: End-of-Row switches in a data center. center

NA: IPv6's IPv6 Neighbor Advertisement

ND: IPv6's IPv6 Neighbor Discovery [RFC4861]

NS: IPv6's IPv6 Neighbor Solicitation

SA: Source Address

ToR: Top of Rack Top-of-Rack Switch (also known as access switch). switch)

UNA: IPv6's IPv6 Unsolicited Neighbor Advertisement

VM: Virtual Machines

Subnet Refer Machine

Subnet: Refers to the Multi-access multi-access link subnet referenced by
RFC4903 RFC 4903

3. Common DC network Network Designs

Some common network designs for a data center include:

1) Layer 3 connectivity to the access switch,

2) Large Layer 2, and

3) Overlay models.

There is no single network design that fits all cases. The following
sections document some of the common practices to scale
Address Resolution address
resolution under each network design.

4. Layer 3 to Access Switches

This network design configures Layer 3 to the access switches; switches,
effectively making the access switches the L2/L3 boundary routers for
the attached VMs.

As described in [RFC6820], many data centers are architected so that
ARP/ND broadcast/multicast messages are confined to a few ports
(interfaces) of the access switches (i.e. (i.e., ToR switches).

Another variant of the Layer 3 solution is a Layer 3 infrastructure
configured all the way to servers (or even to the VMs), which
confines the ARP/ND broadcast/multicast messages to the small number
of VMs within the server.

Advantage: Both ARP and ND scale well. There is no address
resolution issue in this design.

Disadvantage: The main disadvantage to of this network design occurs
during VM movement. During VM movement, either VMs need an
address change or switches/routers need a configuration change
when the VMs are moved to different locations.

Summary: This solution is more suitable to data centers which that have a
static workload and/or network operators who can re-configure reconfigure IP
addresses/subnets on switches before any workload change. No
protocol changes are suggested.

5. Layer 2 practices Practices to scale Scale ARP/ND

5.1. Practices to alleviate Alleviate APR/ND burden Burden on L2/L3 boundary routers Boundary Routers

The ARP/ND broadcast/multicast messages in a Layer 2 domain can
negatively affect the L2/L3 boundary routers, especially with a large
number of VMs and subnets. This section describes some commonly used
practices in for reducing the ARP/ND processing required on L2/L3
boundary routers.

5.1.1. Communicating with a peer Peer in a different subnet Different Subnet

Scenario: When the originating end station doesn't have its default
gateway MAC address in its ARP/ND cache and needs to communicate
with a peer in a different subnet, it needs to send ARP/ND
requests to its default gateway router to resolve the router's MAC
address. If there are many subnets on the gateway router and a
large number of end stations in those subnets that don't have the
gateway MAC address in their ARP/ND caches, the gateway router has
to process a very large number of ARP/ND requests. This is often
CPU intensive intensive, as ARP/ND messages are usually processed by the CPU
(and not in hardware).

Note: Any centralized configuration which pre-loads that preloads the default MAC
addresses is not included in this scenario.

Solution: For IPv4 networks, a practice to alleviate this problem is
to have the L2/L3 boundary router send periodic gratuitous ARP
[GratuitousARP] messages, so that all the connected end stations
can refresh their ARP caches. As a result, most (if not all) end
stations will not need to send ARP requests for the gateway
routers when they need to communicate with external peers.

For the above scenario, IPv6 end stations are still required to send
unicast ND messages to their default gateway router (even with those
routers periodically sending Unsolicited Neighbor Advertisements)
because IPv6 requires bi-directional bidirectional path validation.

Advantage: Reduction This practice results in a reduction of ARP requests to be
processed by the L2/L3 boundary router for IPv4.

Disadvantage: this This practice doesn't reduce ND processing on the L2/L3
boundary router for IPv6 traffic.

Recommendation: If the network is an IPv4-only network, then this
approach can be used. For an IPv6 network, need one needs to consider
the work in progress described in [Impatient-NUD]. [RFC7048]. Note: The ND and
SEND Secure Neighbor
Discovery (SEND) [RFC3971] use the bi-directional bidirectional nature of queries
to detect and prevent security attacks.

5.1.2.L2/L3 boundary router processing

5.1.2. L2/L3 Boundary Router Processing of inbound traffic Inbound Traffic

Scenario: When a an L2/L3 boundary router receives a data frame
destined for a local subnet and the destination is not in the
router's ARP/ND cache, some routers hold the packet and trigger an
ARP/ND request to resolve the L2 address. The router may need to
send multiple ARP/ND requests until either a timeout is reached or
an ARP/ND reply is received before forwarding the data packets
towards the target's MAC address. This process is not only CPU
intensive but also buffer intensive.

Solution: To protect a router from being overburdened by resolving
target MAC addresses, one solution is for the router to limit the
rate of resolving target MAC addresses for inbound traffic whose
target is not in the router's ARP/ND cache. When the rate is
exceeded, the incoming traffic whose target is not in the ARP/ND
cache is dropped.

For an IPv4 network, another common practice to alleviate pain caused
by this problem is for the router to snoop ARP messages between other
hosts, so that its ARP cache can be refreshed with active addresses
in the L2 domain. As a result, there is an increased likelihood of
the router's ARP cache having the IP-MAC entry when it receives data
frames from external peers. [RFC6820]
section Section 7.1 provides a full
description of this problem.

For IPv6 end stations, routers are supposed to send RA Router
Advertisements (RAs) unicast even if they have snooped UNA/NS/NA UNAs/NSs/NAs
from those stations. Therefore, this practice allows an L2/L3
boundary to send unicast RA RAs to the target instead of multicast. multicasts.
[RFC6820] section Section 7.2 has a full description of this problem.

Advantage: Reduction This practice results in a reduction of the number of ARP
requests that routers have to send upon receiving IPv4 packets and
the number of IPv4 data frames from external peers that routers
have to hold due to targets not being in the ARP cache.

Disadvantage: For IPv6 traffic, the The amount of ND processing on routers for IPv6 traffic
is not reduced. IPv4 routers still need to hold data packets from
external peers and trigger ARP requests if the targets of the data
packets either don't exist or are not very active. In this case,
IPv4 process processing or IPv4 buffers are not reduced.

Recommendation: If there is a higher chance of routers receiving data
packets that are destined for non-existing nonexistent or inactive targets,
alternative approaches should be considered.

5.1.3.Inter subnets communications

5.1.3. Inter-Subnet Communications

The router could be hit with ARP/ND requests twice when the
originating and destination stations are in different subnets
attached to the same router and those hosts don't communicate with
external peers often enough. The first hit is when the originating
station in subnet-A initiates an ARP/ND request to the L2/L3 boundary
router if the router's MAC is not in the host's cache (5.1.1 above); (Section 5.1.1
above), and the second hit is when the L2/L3 boundary router
initiates ARP/ND requests to the target in subnet-B if the target is
not in the router's ARP/ND cache (5.1.2 (Section 5.1.2 above).

Again, practices described in Sections 5.1.1 and 5.1.2 can alleviate
some problems in some IPv4 networks.

For IPv6 traffic, the practices described above don't reduce the ND
processing on L2/L3 boundary routers.

Recommendation: Consider the recommended approaches described in
Sections 5.1.1 & and 5.1.2. However, any solutions that relax the bi-directional
bidirectional requirement of IPv6 ND disable the security that the
two-way ND communication exchange provides.

5.2. Static ARP/ND entries Entries on switches Switches

In a datacenter environment data center environment, the placement of L2 and L3 addressing
may be orchestrated by Server (or VM) Management System(s).
Therefore
Therefore, it may be possible for static ARP/ND entries to be
configured on routers and / or and/or servers.

Advantage: This methodology has been used to reduce ARP/ND
fluctuations in large scale large-scale data center networks.

Disadvantage: When some VMs are added, deleted, or moved, many
switches' static entries need to be updated. In a Data Center data center
with virtualized servers, those events can happen frequently. For
example, for an event of one VM being added to one server, if the
subnet of this VM spans across 15 access switches, all of them need to be
updated. Network management mechanisms (SNMP, netconf, the Network
Configuration Protocol (NETCONF), or proprietary)
mechanisms proprietary mechanisms) are
available to provide updates or incremental updates. However,
there is no well defined well-defined approach for switches to synchronize
their content with the management system for efficient incremental update.
updates.

Recommendation: Additional work may be needed within IETF (e.g.
netconf, NVo3, IR2S, working
groups (e.g., NETCONF, NVO3, I2RS, etc.) to get prompt incremental
updates of static ARP/ND entries when changes occur.

5.3. ARP/ND Proxy approaches

RFC1027 Approaches

RFC 1027 [RFC1027] specifies one ARP proxy approach. Proxy approach referred to as
"Proxy ARP". However,
RFC1027 is RFC 1027 does not discuss a scaling mechanism.
Since the publication of
RFC1027 RFC 1027 in 1987 1987, many variants of Proxy ARP proxy
have been deployed.
RFC1027's ARP RFC 1027's Proxy is for ARP technique allows a gateway
to return its own MAC address on behalf of the target station.

[ARP_Reduction] describes a type of ''ARP Proxy'' which is for "ARP Proxy" that allows a ToR
switch to snoop ARP requests and return the target station's MAC if
the ToR has the information in its cache. However, [RFC4903] doesn't
recommend the caching approach described in [ARP_Reduction] because
such a cache prevents any type of fast mobility between
layer Layer 2 ports, ports
and breaks Secure neighbor Neighbor Discovery [RFC3971].

IPv6 ND Proxy [RFC4389] specifies a proxy used between an Ethernet
segment and other segments, such as wireless or PPP segments. ND
Proxy [RFC4389] doesn't allow a proxy to send NA messages on behalf
of the target to ensure that the proxy does not interfere with hosts
moving from one segment to another. Therefore, the ND Proxy
[RFC4389] doesn't reduce the number of ND messages to an L2/L3
boundary router.

Bottom line, the term ''ARP/ND Proxy'' "ARP/ND Proxy" has different interpretations interpretations,
depending on vendors and/or environments.

Recommendation: For IPv4, even though those Proxy ARP variants (not
RFC1023)
RFC 1076) have been used to reduce ARP traffic in various
environments, there are many issues with caching.

The IETF should consider making proxy recommendations for Data Center
environment data center
environments as a transition issue to help DC operators transitioning
to IPv6. The ''Guideline for proxy developers'' Section 7 of [RFC4389] ("Guidelines to Proxy Developers")
should be considered when develop developing any new proxy protocols to
scale ARP.

5.4. Multicast Scaling Issues

Multicast snooping (IGMP/MLD) has different implementations and
scaling issues. [RFC4541] notes that multicast IGMPv2/v3 snooping
has trouble with subnets that include IGMPv2 and IGMPv3. [RFC4541]
also notes that MLDv2 snooping requires the use of either DMAC destination
MAC (DMAC) address filtering or deeper inspection of frames/packet frames/packets
to allow for scaling.

MLDv2 snooping needs to be re-examined for scaling within the DC.
Efforts such as IGMP/MLD explicit tracking [IGMP-MLD-tracking] [IGMP-MLD-Tracking] for
downstream host hosts need to provide better scaling than IGMP/MLDv2
snooping.

6. Practices to scale Scale ARP/ND in Overlay models Models

There are several drafts documents on using overlay networks to scale large
layer
Layer 2 networks (or avoid the need for large L2 networks) and enable
mobility (e.g. draft-wkumari-dcops-l3-vmmobility-00, draft-
mahalingam-dutt-dcops-vxlan-00). TRILL (e.g., [L3-VM-Mobility], [VXLAN]). Transparent
Interconnection of Lots of Links (TRILL) and IEEE802.1ah IEEE 802.1ah
(Mac-in-Mac) are other types of overlay network to networks that can scale
Layer 2.

Overlay networks hide the VMs' addresses from the interior switches
and routers, thereby greatly reduces reducing the number of addresses exposed
to the interior switches and router. The Overlay Edge overlay edge nodes that
perform the network address encapsulation/decapsulation still handle
all remote stations stations' addresses that communicate with the locally
attached end stations.

For a large data center with many applications, these applications'
IP addresses need to be reachable by external peers. Therefore, the
overlay network may have a bottleneck at the Gateway gateway node(s) in
processing resolving target stations' physical address addresses (MAC or IP)
and the overlay edge address within the data center.

Here are some two approaches that can be used to minimize the this problem:

1. Use static mapping as described in Section 5.2.

2. Have multiple L2/L3 boundary nodes (i.e. (i.e., routers), with each
handling a subset of stations stations' addresses which that are visible to
external peers (e.g. (e.g., Gateway #1 handles a set of prefixes,
Gateway #2 handles another subset of prefixes, etc.).

7. Summary and Recommendations

This memo describes some common practices which that can alleviate the
impact of address resolution on L2/L3 gateway routers.

In Data Centers, data centers, no single solution fits all deployments. This memo
has summarized some practices in various scenarios and the advantages
and disadvantages about of all of these practices.

In some of these scenarios, the common practices could be improved by
creating and/or extending existing IETF protocols. These protocol
change recommendations are:

o Relax some bi-directional the bidirectional requirement of IPv6 ND in some
environment.
environments. However, other issues will be introduced when the bi-directional
bidirectional requirement of ND is relaxed. Therefore, it is
necessary to have performed a comprehensive study in of possible
issues prior to making those changes.

o Create an incremental ''update'' schemes "update" scheme for efficient static ARP/ND
entries.

o Develop IPv4 ARP/IPv6 ND Proxy standards for use in the data
center. The ''Guideline for proxy developers'' Section 7 of [RFC4389] ("Guidelines to Proxy Developers")
should be considered when develop developing any new proxy protocols to
scale ARP/ND.

o Consider scaling issues with IGMP/MLD snooping to determine
if
whether or not new alternatives can provide better scaling.

8. Security Considerations

This draft memo documents existing solutions and proposes additional work
that could be initiated to extend various IETF protocols to better
scale ARP/ND for the data center environment.

The security

Security is a major issue for data center environment. environments. Therefore,
security should be seriously considered when developing any future
protocol extension. extensions.

9. IANA Considerations

This document does not request any action from IANA.

10. Acknowledgements

We want to acknowledge the ARMD WG and the following people for their
valuable inputs to this draft: document: Joel Jaeggli, Dave Thaler, Susan
Hares, Benson Schliesser, T. Sridhar, Ron Bonica, Kireeti Kompella,
and K.K.Ramakrishnan.

11. K.K. Ramakrishnan.

10. References

11.1.

10.1. Normative References

[GratuitousARP] S.
Cheshire, ''IPv4 S., "IPv4 Address Conflict Detection'', Detection", RFC 5227,
July 2008.

[IGMP-MLD-tracking] H. Aseda, and N. Leymann, ''IGMP/MLD-Based
Explicit Membership Tracking Function for Multicast
Routers'' (http://tools.ietf.org/html/draft-ietf-pim-
explicit-tracking-02), Oct, 2012.

[RFC826] D.C. Plummer, ''An D., "Ethernet Address Resolution Protocol: Or
Converting Network Protocol Addresses to 48.bit Ethernet address resolution protocol.''
RFC826, Nov
Address for Transmission on Ethernet Hardware", STD 37,
RFC 826, November 1982.

[RFC1027] Mitchell, et al, ''Using Carl-Mitchell, S. and J. Quarterman, "Using ARP to Implement Transparent
Subnet Gateways''
(http://datatracker.ietf.org/doc/rfc1027/)
implement transparent subnet gateways", RFC 1027,
October 1987.

[RFC3971] Arkko, et al, ''Secure J., Ed., Kempf, J., Zill, B., and P. Nikander,
"SEcure Neighbor Discovery (SEND)'',
RFC3971, (SEND)", RFC 3971, March 2005 2005.

[RFC4389] Thaler, et al, ''Neighbor D., Talwar, M., and C. Patel, "Neighbor Discovery
Proxies (ND Proxy)'',
RFC4389, Proxy)", RFC 4389, April 2006 2006.

[RFC4541] Christensen, et al, ''Considerations M., Kimball, K., and F. Solensky,
"Considerations for Internet Group Management Protocol
(IGMP) and Multicast Listener Discovery (MLD) Snooping Switches'',
Switches", RFC 4541, May 2006 2006.

[RFC4861] Narten, et al, ''Neighbor T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6
(IPv6)'', RFC4861, Sept 2007 (IPv6)", RFC 4861,
September 2007.

[RFC4903] Thaler, ''Multilink D., "Multi-Link Subnet Issues'', RFC4903, July 2007 Issues", RFC 4903,
June 2007.

[RFC6820] Narten, et al, ''Address T., Karir, M., and I. Foo, "Address Resolution
Problems in Large Data Center Networks'', RFC6820, Jan 2013
11.2. Networks", RFC 6820,
January 2013.

10.2. Informative References

[Impatient-NUD] E. Nordmark, I. Gashinsky, ''draft-ietf-6man-
impatient-nud''

[ARMD-Statistics] M.
Karir, M. and J. Rees, ''Address "Address Resolution
Statistics'', draft-karir-armd-statistics-01.txt
(expired), Statistics",
Work in Progress, July 2011.
https://datatracker.ietf.org/doc/draft-karir-armd-
statistics/

[ARP_Reduction]
Shah, et al, ''ARP H., Ghanwani, A., and N. Bitar, "ARP Broadcast
Reduction for Large Data Centers'', draft-shah-armd-arp-reduction-02.txt
(expired), Oct Centers", Work in Progress,
October 2011.

[IGMP-MLD-Tracking]
Asaeda, H., "IGMP/MLD-Based Explicit Membership Tracking
Function for Multicast Routers", Work in Progress,
December 2013.

[L3-VM-Mobility]
Kumari, W. and J. Halpern, "Virtual Machine mobility in L3
Networks", Work in Progress, August 2011.
https://datatracker.ietf.org/doc/draft-shah-armd-arp-
reduction/

[Multi-Link]
Thaler, et al, ''Multi-link D. and C. Huitema, "Multi-link Subnet Support in IPv6'',
draft-ietf-ipv6-multilink-subnets-00.txt (expired), Dec
IPv6", Work in Progress, June 2002. https://datatracker.ietf.org/doc/draft-ietf-ipv6-
multilink-subnets/

[RFC1076] Trewitt, G. and C. Partridge, "HEMS Monitoring and Control
Language", RFC 1076, November 1988.

[RFC7048] Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
Detection Is Too Impatient", RFC 7048, January 2014.

[VXLAN] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "VXLAN: A
Framework for Overlaying Virtualized Layer 2 Networks over
Layer 3 Networks", Work in Progress, April 2014.

Authors' Addresses

Linda Dunbar
Huawei Technologies
5340 Legacy Drive, Suite 175
Plano, TX 75024, 75024
USA

Phone: (469) 277 5840
Email:
EMail: ldunbar@huawei.com

Warren Kumari
Google
1600 Amphitheatre Parkway
Mountain View, CA 94043
US
Email:
USA

EMail: warren@kumari.net

Igor Gashinsky
Yahoo
45 West 18th Street 6th floor
New York, NY 10011
Email:
USA

EMail: igor@yahoo-inc.com