RFC 6807
Population Count Extensions to Protocol Independent Multicast (PIM)
Pages: 15
Experimental
Experimental
Internet Engineering Task Force (IETF) D. Farinacci Request for Comments: 6807 G. Shepherd Category: Experimental S. Venaas ISSN: 2070-1721 Cisco Systems Y. Cai Microsoft December 2012 Population Count Extensions to Protocol Independent Multicast (PIM)Abstract
This specification defines a method for providing multicast distribution-tree accounting data. Simple extensions to the Protocol Independent Multicast (PIM) protocol allow a rough approximation of tree-based data in a scalable fashion. Status of This Memo This document is not an Internet Standards Track specification; it is published for examination, experimental implementation, and evaluation. This document defines an Experimental Protocol for the Internet community. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6807.
Copyright Notice Copyright (c) 2012 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 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. Pop-Count-Supported Hello Option . . . . . . . . . . . . . . . 4 3. New Pop-Count Join Attribute Format . . . . . . . . . . . . . 5 3.1. Options . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.1. Link Speed Encoding . . . . . . . . . . . . . . . . . 10 3.2. Example Message Layouts . . . . . . . . . . . . . . . . . 10 4. How to Use Pop-Count Encoding . . . . . . . . . . . . . . . . 11 5. Implementation Approaches . . . . . . . . . . . . . . . . . . 12 6. Caveats . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 10.1. Normative References . . . . . . . . . . . . . . . . . . . 14 10.2. Informative References . . . . . . . . . . . . . . . . . . 14
1. Introduction
This document specifies a mechanism to convey accounting information using the Protocol Independent Multicast (PIM) protocol [RFC4601] [RFC5015]. Putting the mechanism in PIM allows efficient distribution and maintenance of such accounting information. Previous mechanisms require data to be correlated from multiple router sources. This mechanism allows a single router to be queried to obtain accounting and statistic information for a multicast distribution tree as a whole or any distribution sub-tree downstream from a queried router. The amount of information is fixed and does not increase as multicast membership, tree diameter, or branching increases. The sort of accounting data this specification provides, on a per- multicast-route basis, are: 1. The number of branches in a distribution tree. 2. The membership type of the distribution tree, that is, Source- Specific Multicast (SSM) or Any-Source Multicast (ASM). 3. Routing domain and time zone boundary information. 4. On-tree node and tree diameter counters. 5. Effective MTU and bandwidth. This document defines a new PIM Join Attribute type [RFC5384] for the Join/Prune message as well as a new Hello option. The mechanism is applicable to IPv4 and IPv6 multicast. This is a new extension to PIM, and it is not completely understood what impact collecting information using PIM would have on the operation of PIM. This is an entirely new concept. Many PIM features (including the core protocols) were first introduced in Experimental RFCs, and it seems appropriate to advance this work as Experimental. Reports of implementation and deployment across whole distribution trees or within sub-trees (see Section 6) will enable an assessment of the desirability and stability of this specification. The PIM Working Group will then consider whether to move this work to the Standards Track. This document does not specify how an administrator or user can access this information. It is expected that an implementation may have a command-line interface or other ways of requesting and
displaying this information. As this is currently an Experimental document, defining a MIB module has not been considered. If the PIM Working Group finds that this should move on to Standards Track, a MIB module should be considered.1.1. Requirements Notation
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].1.2. Terminology
This section defines the terms used in this document. Multicast Route: An (S,G) or (*,G) entry regardless of whether the route is in ASM, SSM, or BIDIR mode of operation. Stub Link: A link with members joined to the group via IGMP or Multicast Listener Discovery (MLD). Transit Link: A link put in the oif-list (outgoing interface list) for a multicast route because it was joined by PIM routers. Note that a link can be both a Stub Link and a Transit Link at the same time.2. Pop-Count-Supported Hello Option
A PIM router indicates that it supports the mechanism specified in this document by including the Pop-Count-Supported Hello option in its PIM Hello message. Note that it also needs to include the Join- Attribute Hello option as specified in [RFC5384]. The format of the Pop-Count-Supported Hello option is defined to be: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OptionType | OptionLength | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ OptionType = 29, OptionLength = 0. Note that there is no option value included. In order to allow future updates of this specification that may include an option value, implementations of this document MUST accept and process this option even if the length is non-zero. Implementations of this specification MUST accept and process the option ignoring any option value that may be included.
3. New Pop-Count Join Attribute Format
When a PIM router supports this mechanism and has determined from a received Hello that the neighbor supports this mechanism, and also that all the neighbors on the interface support the use of join attributes, it will send Join/Prune messages that MAY include a Pop- Count Join Attribute. The mechanism to process a PIM Join Attribute is described in [RFC5384]. The format of the new attribute is specified in the following. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |F|E| Attr_Type | Length | Effective MTU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Options Bitmap | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options | . . . . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The above format is used only for entries in the join-list section of the Join/Prune message. F bit: 0 (Non-Transitive Attribute). E bit: As specified by [RFC5384]. Attr_Type: 3. Length: The minimum length is 6. Effective MTU: This contains the minimum MTU for any link in the oif-list. The sender of a Join/Prune message takes the minimum value for the MTU (in bytes) from each link in the oif-list. If this value is less than the value stored for the multicast route (the one received from downstream joiners), then the value should be reset and sent in a Join/Prune message. Otherwise, the value should remain unchanged. This provides the MTU supported by multicast distribution tree when examined at the first-hop router(s) or for sub-tree for any router on the distribution tree.
Flags: The flags field has the following format:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unalloc/Reserved |P|a|t|A|S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Unallocated/Reserved Flags: The flags that are currently not
defined. If a new flag is defined and used by a new
implementation, an old implementation should preserve the bit
settings. This means that a router MUST preserve the settings
of all Unallocated/Reserved Flags in PIM Join messages received
from downstream routers in any PIM Join sent upstream.
S flag: This flag is set if an IGMPv3 or MLDv2 report with an
INCLUDE mode group record was received on any oif-list entry or
the bit was set from any PIM Join message. This bit should
only be cleared when the above becomes untrue.
A flag: This flag is set if an IGMPv3 or MLDv2 report with an
EXCLUDE mode group record, or an IGMPv1, IGMPv2, or MLDv1
report, was received on any oif-list entry or the bit was set
from any PIM Join message. This bit should only be cleared
when the above becomes untrue.
A combination of settings for these bits indicate:
A flag S flag Description
------ ------ --------------------------------------
0 0 There are no members for the group.
('Stub Oif-List Count' is 0)
0 1 All group members are using SSM.
1 0 All group members are using ASM.
1 1 A mixture of SSM and ASM group members.
t flag: This flag is set if there are any manually configured
tunnels on the distribution tree. This means any tunnel that
is not an auto-tunnel. If a manually configured tunnel is in
the oif-list, a router sets this bit in its Join/Prune
messages. Otherwise, it propagates the bit setting from
downstream joiners.
a flag: This flag is set if there are any auto-tunnels on the
distribution tree. If an auto-tunnel is in the oif-list, a
router sets this bit in its Join/Prune messages. Otherwise, it
propagates the bit setting from downstream joiners. An example
of an auto-tunnel is a tunnel set up by the Automatic Multicast
Tunneling [AMT] protocol.
P flag: This flag is set by a router if all downstream routers
support this specification. That is, they are all PIM Pop-
Count capable. If a downstream router does not support this
specification, it MUST be cleared. This allows one to tell if
the entire sub-tree is completely accounting capable.
Options Bitmap: This is a bitmap that shows which options are
present. The format of the bitmap is as follows:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|T|s|m|M|d|n|D|z| Unalloc/Rsrvd |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Each one of the bits T, s, m, M, d, n, D and z is associated with
one option, where the option is included if and only if the
respective bit is set. Included options MUST be in the same order
as these bits are listed. The bits denote the following options:
bit Option
----- ------------------------
T Transit Oif-List Count
s Stub Oif-List Count
m Minimum Speed Link
M Maximum Speed Link
d Domain Count
n Node Count
D Diameter Count
z TZ Count
See Section 3.1 for details on the different options. The
unallocated bits are reserved. Any unknown bits MUST be set to 0
when a message is sent, and treated as 0 (ignored) when received.
This means that unknown options that are denoted by unknown bits
are ignored.
By using this bitmap we can specify at most 16 options. If there
becomes a need for more than 16 options, one can define a new
option that contains a bitmap that can then be used to specify
which further options are present. The last bit in the current
bitmap could be used for that option. However, the exact
definition of this is left for future documents.
Options: This field contains options. Which options are present is
determined by the flag bits. As new flags and options may be
defined in the future, any unknown/reserved flags MUST be ignored,
and any additional trailing options MUST be ignored. See
Section 3.1 for details on the options defined in this document.
3.1. Options
There are several options defined in this document. For each option,
there is also a related flag that shows whether the option is
present. See the Options Bitmap above for a list of the options and
their respective bits. Each option has a fixed size. Note that
there are no alignment requirements for the options, so an
implementation cannot assume they are aligned.
Transit Oif-List Count: This is filled in by a router sending a
Join/Prune message indicating the number of transit links on the
multicast distribution tree. The value is the number of oifs
(outgoing interfaces) for the multicast route that have been
joined by PIM plus the sum of the values advertised by each of the
downstream PIM routers that have joined on this oif. Length is 4
octets.
Stub Oif-List Count: This is filled in by a router sending a Join/
Prune message indicating the number of stub links (links where
there are host members) on the multicast distribution tree. The
value is the number of oifs for the multicast route that have been
joined by IGMP or MLD plus the sum of the values advertised by
each of the downstream PIM routers that have joined on this oif.
Length is 4 octets.
Minimum Speed Link: This contains the minimum bandwidth rate for any
link in the oif-list and is encoded as specified in Section 3.1.1.
The sender of a Join/Prune message takes the minimum value for
each link in the oif-list for the multicast route. If this value
is less than the value stored for the multicast route (the
smallest value received from downstream joiners), then the value
should be reset and sent in a Join/Prune message. Otherwise, the
value should remain unchanged. This, together with the Maximum
Speed Link option, provides a way to obtain the lowest- and
highest-speed links for the multicast distribution tree. Length
is 2 octets.
Maximum Speed Link: This contains the maximum bandwidth rate for any
link in the oif-list and is encoded as specified in Section 3.1.1.
The sender of a Join/Prune message takes the maximum value for
each link in the oif-list for the multicast route. If this value
is greater than the value stored for the multicast route (the
largest value received from downstream joiners), then the value
should be reset and sent in a Join/Prune message. Otherwise, the
value should remain unchanged. This, together with the Minimum
Speed Link option, provides a way to obtain the lowest- and
highest-speed links for the multicast distribution tree. Length
is 2 octets.
Domain Count: This indicates the number of routing domains the
distribution tree traverses. A router should increment this value
if it is sending a Join/Prune message over a link that traverses a
domain boundary. For this to work, an implementation needs a way
of knowing that a neighbor or an interface is in a different
domain. There is no standard way of doing this. Length is 1
octet.
Node Count: This indicates the number of routers on the distribution
tree. Each router will sum up all the Node Counts from all
joiners on all oifs and increment by 1 before including this value
in the Join/Prune message. Length is 1 octet.
Diameter Count: This indicates the longest length of any given
branch of the tree in router hops. Each router that sends a Join
increments the max value received by all downstream joiners by 1.
Length is 1 octet.
TZ Count: This indicates the number of time zones the distribution
tree traverses. A router should increment this value if it is
sending a Join/Prune message over a link that traverses a time
zone. This can be a configured link attribute, or using other
means to determine the time zone is acceptable. Length is 1
octet.
3.1.1. Link Speed Encoding
The speed is encoded using 2 octets as follows: 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Exponent | Significand | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Using this format, the speed of the link is Significand * 10 ^ Exponent kbps. This allows specifying link speeds with up to 3 decimal digits precision and speeds from 1 kbps to 10 ^ 67 kbps. A computed speed of 0 kbps means the link speed is < 1 kbps. Here are some examples of how this is used: Link Speed Exponent Significand ------------ ---------- ------------- 500 kbps 0 500 500 kbps 2 5 155 Mbps 3 155 40 Gpbs 6 40 100 Gpbs 6 100 100 Gpbs 8 13.2. Example Message Layouts
Here, we will give a few examples to illustrate the use of flags and options. A minimum-size message has no option flags set and looks like this: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |F|E| Attr_Type | Length = 6 | Effective MTU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unalloc/Reserved |P|a|t|A|S|0|0|0|0|0|0|0|0| Unalloc/Rsrvd | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A message containing all the options defined in this document would
look like this:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|E| Attr_Type | Length = 18 | Effective MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unalloc/Reserved |P|a|t|A|S|1|1|1|1|1|1|1|1| Unalloc/Rsrvd |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transit Oif-List Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stub Oif-List Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum Speed Link | Maximum Speed Link |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Domain Count | Node Count | Diameter Count| TZ Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A message containing only Stub Oif-List Count and Node Count would
look like this:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|F|E| Attr_Type | Length = 9 | Effective MTU |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unalloc/Reserved |P|a|t|A|S|0|1|0|0|0|1|0|0| Unalloc/Rsrvd |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stub Oif-List Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Node count |
+-+-+-+-+-+-+-+-+
4. How to Use Pop-Count Encoding
A router supporting this mechanism MUST, unless administratively
disabled, include the PIM Join Attribute option in its PIM Hellos.
See [RFC5384] and "PIM-Hello Options" on [PIM-REG] for details.
It is RECOMMENDED that implementations allow for administrative
control of whether to make use of this mechanism. Implementations
MAY also allow further control of what information to store and send
upstream.
It is very important to note that any changes to the values maintained by this mechanism MUST NOT trigger a new Join/Prune message. Due to the periodic nature of PIM, the values can be accurately obtained at 1-minute intervals (or whatever Join/Prune interval used). When a router removes a link from an oif-list, it needs to be able to reevaluate the values that it will advertise upstream. This happens when an oif-list entry is timed out or a Prune is received. It is RECOMMENDED that the Join Attribute defined in this document be used only for entries in the join-list part of the Join/Prune message. If the attribute is used in the prune-list, an implementation MUST ignore it and process the Prune as if the attribute were not present. It is also RECOMMENDED that join suppression be disabled on a LAN when Pop-Count is used. It is RECOMMENDED that, when triggered Join/Prune messages are sent by a downstream router, the accounting information not be included in the message. This way, when convergence is important, avoiding the processing time to build an accounting record in a downstream router and processing time to parse the message in the upstream router will help reduce convergence time. If an upstream router receives a Join/ Prune message with no accounting data, it SHOULD NOT interpret the message as a trigger to clear or reset the accounting data it has cached.5. Implementation Approaches
This section offers some non-normative suggestions for how Pop-Count may be implemented. An implementation can decide how the accounting attributes are maintained. The values can be stored as part of the multicast route data structure by combining the local information it has with the joined information on a per-oif basis. So, when it is time to send a Join/Prune message, the values stored in the multicast route can be copied to the message. Or, an implementation could store the accounting values per oif and, when a Join/Prune message is sent, it can combine the oifs with its local information. Then, the combined information can be copied to the message.
When a downstream joiner stops joining, accounting values cached must be evaluated. There are two approaches that can be taken. One is to keep values learned from each joiner, so when the joiner goes away, the count/max/min values are known and the combined value can be adjusted. The other approach is to set the value to 0 for the oif, and then start accumulating new values as subsequent Joins are received. The same issue arises when an oif is removed from the oif-list. Keeping per-oif values allows you to adjust the per-route values when an oif goes away. Or, alternatively, a delay for reporting the new set a values from the route can occur while all oif values are zeroed (where accumulation of new values from subsequent Joins cause repopulation of values and a new max/min/count can be reevaluated for the route).6. Caveats
This specification requires each router on a multicast distribution tree to support this specification or else the accounting attributes for the tree will not be known. However, if there is a contiguous set of routers downstream in the distribution tree, they can maintain accounting information for the sub-tree. If there is a set of contiguous routers supporting this specification upstream on the multicast distribution tree, accounting information will be available, but it will not represent an accurate assessment of the entire tree. Also, it will not be clear how much of the distribution tree the accounting information covers.7. IANA Considerations
A new PIM-Hello Option type, 29, has been assigned by IANA. Although the length is specified as 0 in this specification, non-zero length is allowed, so IANA has listed the length as being variable. A new PIM Join Attribute type, 3, has been assigned by IANA.8. Security Considerations
The use of this specification requires some additional processing of PIM Join/Prune messages. However, the additional amount of processing is fairly limited, so this is not believed to be a significant concern.
The use of this mechanism includes information like the number of receivers. This information is assumed to not be of a sensitive nature. If an operator has concerns about revealing this information to upstream routers or other routers/hosts that may potentially inspect this information, there should be a way to disable the mechanism or, alternatively, more detailed control of what information to include.9. Acknowledgments
The authors would like to thank John Zwiebel, Amit Jain, and Clayton Wagar for their review comments on the initial versions of this document. Adrian Farrel did a detailed review of the document and proposed textual changes that have been incorporated. Further review and comments were provided by Thomas Morin and Zhaohui (Jeffrey) Zhang.10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006. [RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano, "Bidirectional Protocol Independent Multicast (BIDIR- PIM)", RFC 5015, October 2007. [RFC5384] Boers, A., Wijnands, I., and E. Rosen, "The Protocol Independent Multicast (PIM) Join Attribute Format", RFC 5384, November 2008.10.2. Informative References
[AMT] Bumgardner, G., "Automatic Multicast Tunneling", Work in Progress, June 2012. [PIM-REG] IANA, "Protocol Independent Multicast (PIM) Parameters", <http://www.iana.org/assignments/pim-parameters>.
Authors' Addresses
Dino Farinacci Cisco Systems Tasman Drive San Jose, CA 95134 USA EMail: dino@cisco.com Greg Shepherd Cisco Systems Tasman Drive San Jose, CA 95134 USA EMail: gjshep@gmail.com Stig Venaas Cisco Systems Tasman Drive San Jose, CA 95134 USA EMail: stig@cisco.com Yiqun Cai Microsoft 1065 La Avenida Mountain View, CA 94043 USA EMail: yiqunc@microsoft.com