Networking Working Group L. Ginsberg
Internet-Draft P. Psenak
Intended status: Standards Track S. Previdi
Expires: April 29, 2017 Cisco Systems
M. Pilka
October 26, 2016
Segment Routing Conflict Resolution
draft-ietf-spring-conflict-resolution-02.txt
Abstract
In support of Segment Routing (SR) routing protocols advertise a
variety of identifiers used to define the segments which direct
forwarding of packets. In cases where the information advertised by
a given protocol instance is either internally inconsistent or
conflicts with advertisements from another protocol instance a means
of achieving consistent forwarding behavior in the network is
required. This document defines the policies used to resolve these
occurrences.
Requirements Language
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on April 29, 2017.
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Copyright Notice
Copyright (c) 2016 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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. SR Global Block Inconsistency . . . . . . . . . . . . . . . . 3
3. SR-MPLS Segment Identifier Conflicts . . . . . . . . . . . . 5
3.1. SID Preference . . . . . . . . . . . . . . . . . . . . . 6
3.2. Conflict Types . . . . . . . . . . . . . . . . . . . . . 6
3.2.1. Prefix Conflict . . . . . . . . . . . . . . . . . . . 6
3.2.2. SID Conflict . . . . . . . . . . . . . . . . . . . . 8
3.3. Processing conflicting entries . . . . . . . . . . . . . 9
3.3.1. Policy: Ignore conflicting entries . . . . . . . . . 9
3.3.2. Policy: Preference Algorithm/Quarantine . . . . . . . 10
3.3.3. Policy: Preference algorithm/ignore overlap only . . 10
3.3.4. Preference Algorithm . . . . . . . . . . . . . . . . 10
3.3.5. Example Behavior - Single Topology/Algorithm . . . . 11
3.3.6. Example Behavior - Multiple Topologies . . . . . . . 12
3.3.7. Evaluation of Policy Alternatives . . . . . . . . . . 13
3.3.8. Guaranteeing Database Consistency . . . . . . . . . . 14
4. Scope of SR-MPLS SID Conflicts . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
6. IANA Consideration . . . . . . . . . . . . . . . . . . . . . 15
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Normative References . . . . . . . . . . . . . . . . . . 15
8.2. Informational References . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
Segment Routing (SR) as defined in [SR-ARCH] utilizes forwarding
instructions called "segments" to direct packets through the network.
Depending on the forwarding plane architecture in use, routing
protocols advertise various identifiers which define the permissible
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values which can be used as segments, which values are assigned to
specific prefixes, etc. Where segments have global scope it is
necessary to have non-conflicting assignments - but given that the
advertisements may originate from multiple nodes the possibility
exists that advertisements may be received which are either
internally inconsistent or conflicting with advertisements originated
by other nodes. In such cases it is necessary to have consistent
resolution of conflicts network-wide in order to avoid forwarding
loops.
The problem to be addressed is protocol independent i.e., segment
related advertisements may be originated by multiple nodes using
different protocols and yet the conflict resolution MUST be the same
on all nodes regardless of the protocol used to transport the
advertisements.
The remainder of this document defines conflict resolution policies
which meet these requirements. All protocols which support SR MUST
adhere to the policies defined in this document.
2. SR Global Block Inconsistency
In support of an MPLS dataplane routing protocols advertise an SR
Global Block (SRGB) which defines a set of label ranges reserved for
use by the advertising node in support of SR. The details of how
protocols advertise this information can be found in the protocol
specific drafts e.g., [SR-OSPF], [SR-OSPFv3], and [SR-IS-IS].
However the protocol independent semantics are illustrated by the
following example:
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The originating router advertises the following ranges:
Range 1: (100, 199)
Range 2: (1000, 1099)
Range 3: (500, 599)
The receiving routers concatenate the ranges and build the Segment
Routing Global Block (SRGB) as follows:
SRGB = (100, 199)
(1000, 1099)
(500, 599)
The indeces span multiple ranges:
index=0 means label 100
...
index 99 means label 199
index 100 means label 1000
index 199 means label 1099
...
index 200 means label 500
...
Note that the ranges are an ordered set - what labels are mapped to a
given index depends on the placement of a given label range in the
set of ranges advertised.
For the set of ranges to be usable the ranges MUST be disjoint.
Sender behavior is defined in various SR protocol drafts such as [SR-
IS-IS] which specify that senders MUST NOT advertise overlapping
ranges.
Receivers of SRGB ranges MUST validate the SRGB ranges advertised by
other nodes. If the advertised ranges do not conform to the
restrictions defined in the respective protocol specification
receivers MUST ignore all advertised SRGB ranges from that node.
Operationally the node is treated as though it did not advertise any
SRGB ranges. [SR-MPLS] defines the procedures for mapping global
SIDs to outgoing labels.
Note that utilization of local SIDs (e.g. adjacency SIDs) advertised
by a node is not affected by the state of the advertised SRGB.
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3. SR-MPLS Segment Identifier Conflicts
In support of an MPLS dataplane Segment identifiers (SIDs) are
advertised and associated with a given prefix. SIDs may be
advertised in the prefix reachability advertisements originated by a
routing protocol (PFX) . SIDs may also be advertised by a Segment
Routing Mapping Server (SRMS).
Information in a SID advertisement is used to construct a mapping
entry. A generalized mapping entry can be represented using the
following definitions:
Prf - Preference Value (See Section 3.1)
Pi - Initial prefix
Pe - End prefix
L - Prefix length
Lx - Maximum prefix length (32 for IPv4, 128 for IPv6)
Si - Initial SID value
Se - End SID value
R - Range value (See Note 1)
T - Topology
A - Algorithm
A Mapping Entry is then the tuple: (Prf, Src, Pi/L, Si, R, T, A)
Pe = (Pi + ((R-1) << (Lx-L))
Se = Si + (R-1)
NOTE 1: The SID advertised in a prefix reachability advertisement
always has an implicit range of 1.
Conflicts in SID advertisements may occur as a result of
misconfiguration. Conflicts may occur either in the set of
advertisements originated by a single node or between advertisements
originated by different nodes. Conflicts which occur within the set
of advertisements (P-SID and SRMS) originated by a single node SHOULD
be prevented by configuration validation on the originating node.
When conflicts occur, it is not possible for routers to know which of
the conflicting advertisements is "correct". In order to avoid
forwarding loops and/or blackholes, there is a need for all nodes to
resolve the conflicts in a consistent manner. This in turn requires
that all routers have identical sets of advertisements and that they
all use the same selection algorithm. This document defines
procedures to achieve these goals.
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3.1. SID Preference
If a node acts as an SRMS, it MAY advertise a preference to be
associated with all SRMS SID advertisements sent by that node. The
means of advertising the preference is defined in the protocol
specific drafts e.g., [SR-OSPF], [SR-OSPFv3], and [SR-IS-IS]. The
preference value is an unsigned 8 bit integer with the following
properties:
0 - Reserved value indicating advertisements from that node
MUST NOT be used.
1 - 255 Preference value
Advertisement of a preference value is optional. Nodes which do not
advertise a preference value are assigned a preference value of 128.
All SIDs advertised in prefix reachability advertisements implicitly
have a preference value of 192.
3.2. Conflict Types
Two types of conflicts may occur - Prefix Conflicts and SID
Conflicts. Examples are provided in this section to illustrate these
conflict types.
3.2.1. Prefix Conflict
When different SIDs are assigned to the same prefix we have a "prefix
conflict". Prefix conflicts are specific to mapping entries sharing
the same topology and algorithm.
Example PC1
(192, 192.0.2.120/32, 200, 1, 0, 0)
(192, 192.0.2.120/32, 30, 1, 0, 0)
The prefix 192.0.2.120/32 has been assigned two different SIDs:
200 by the first advertisement
30 by the second advertisement
Example PC2
(192, 2001:DB8::1/128, 400, 1, 2, 0)
(192, 2001:DB8::1/128, 50, 1, 2, 0)
The prefix 2001:DB8::1/128 has been assigned two different SIDs:
400 by the first advertisement
50 by the second advertisement
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Prefix conflicts may also occur as a result of overlapping prefix
ranges.
Example PC3
(128, 192.0.2.1/32, 200, 200, 0, 0)
(128, 192.0.2.121/32, 30, 10, 0, 0)
Prefixes 192.0.2.121/32 - 192.0.2.130/32 are assigned two
different SIDs:
320 through 329 by the first advertisement
30 through 39 by the second advertisement
Example PC4
(128, 2001:DB8::1/128, 400, 200, 2, 0)
(128, 2001:DB8::121/128, 50, 10, 2, 0)
Prefixes 2001:DB8::121/128 - 2001:DB8::130/128 are assigned
two different SIDs:
420 through 429 by the first advertisement
50 through 59 by the second advertisement
Examples PC3 and PC4 illustrate a complication - only part of the
range advertised in the first advertisement is in conflict. It is
logically possible to isolate the conflicting portion and try to use
the non-conflicting portion(s).
A variant of the overlapping prefix range is a case where we have
overlapping prefix ranges but no actual SID conflict.
Example PC5
(128, 192.0.2.1/32, 200, 200, 0, 0)
(128, 192.0.2.121/32, 320, 10, 0, 0)
(128, 2001:DB8::1/128, 400, 200, 2, 0)
(128, 2001:DB8::121/128, 520, 10, 2, 0)
Although there is prefix overlap between the two IPv4 entries (and
the two IPv6 entries) the same SID is assigned to all of the shared
prefixes by the two entries.
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Given two mapping entries:
(Prf, P1/L1, S1, R1, T1, A1) and
(Prf, P2/L2, S2, R2, T2, A2)
where P1 <= P2
a prefix conflict exists if all of the following are true:
1)(T1 == T2) && (A1 == A2)
2)P1 <= P2
3)The prefixes are in the same address family.
2)L1 == L2
3)(P1e >= P2) && ((S1 + (P2 - P1)) != S2)
3.2.2. SID Conflict
When the same SID has been assigned to multiple prefixes we have a
"SID conflict". SID conflicts are independent of address-family,
independent of prefix len, independent of topology, and independent
of algorithm. A SID conflict occurs when a mapping entry which has
previously been checked to have no prefix conflict assigns one or
more SIDs that are assigned by another entry which also has no prefix
conflicts.
Example SC1
(192, 192.0.2.1/32, 200, 1, 0, 0)
(192, 192.0.2.222/32, 200, 1, 0, 0)
SID 200 has been assigned to 192.0.2.1/32 by the
first advertisement.
The second advertisement assigns SID 200 to 192.0.2.222/32.
Example SC2
(192, 2001:DB8::1/128, 400, 1, 2, 0)
(192, 2001:DB8::222/128, 400, 1, 2, 0)
SID 400 has been assigned to 2001:DB8::1/128 by the
first advertisement.
The second advertisement assigns SID 400 to 2001:DB8::222/128
SID conflicts may also occur as a result of overlapping SID ranges.
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Example SC3
(128, 192.0.2.1/32, 200, 200, 0, 0)
(128, 198.51.100.1/32, 300, 10, 0, 0)
SIDs 300 - 309 have been assigned to two different prefixes.
The first advertisement assigns these SIDs
to 192.0.2.101/32 - 192.0.2.110/32.
The second advertisement assigns these SIDs to
198.51.100.1/32 - 198.51.100.10/32.
Example SC4
(128, 2001:DB8::1/128, 400, 200, 2, 0)
(128, 2001:DB8:1::1/128, 500, 10, 2, 0)
SIDs 500 - 509 have been assigned to two different prefixes.
The first advertisement assigns these SIDs to
2001:DB8::101/128 - 2001:DB8::10A/128.
The second advertisement assigns these SIDs to
2001:DB8:1::1/128 - 2001:DB8:1::A/128.
Examples SC3 and SC4 illustrate a complication - only part of the
range advertised in the first advertisement is in conflict.
3.3. Processing conflicting entries
Two general approaches can be used to process conflicting entries.
1. Conflicting entries can be ignored
2. A standard preference algorithm can be used to choose which of
the conflicting entries will be used
The following sections discuss these two approaches in more detail.
Note: This document does not discuss any implementation details i.e.
what type of data structure is used to store the entries (trie, radix
tree, etc.) nor what type of keys may be used to perform lookups in
the database.
3.3.1. Policy: Ignore conflicting entries
In cases where entries are in conflict none of the conflicting
entries are used i.e., the network operates as if the conflicting
advertisements were not present.
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Implementations are required to identify the conflicting entries and
ensure that they are not used.
3.3.2. Policy: Preference Algorithm/Quarantine
For entries which are in conflict properties of the conflicting
advertisements are used to determine which of the conflicting entries
are used in forwarding and which are "quarantined" and not used. The
entire quarantined entry is not used.
This approach requires that conflicting entries first be identified
and then evaluated based on a preference rule. Based on which entry
is preferred this in turn may impact what other entries are
considered in conflict i.e. if A conflicts with B and B conflicts
with C - it is possible that A does NOT conflict with C. Hence if as
a result of the evaluation of the conflict between A and B, entry B
is not used the conflict between B and C will not be detected.
3.3.3. Policy: Preference algorithm/ignore overlap only
A variation of the preference algorithm approach is to quarantine
only the portions of the less preferred entry which actually
conflicts. The original entry is split into multiple ranges. The
ranges which are in conflict are quarantined. The ranges which are
not in conflict are used in forwarding. This approach adds
complexity as the relationship between the derived sub-ranges of the
original mapping entry have to be associated with the original entry
- and every time some change to the advertisement database occurs the
derived sub-ranges have to be recalculated.
3.3.4. Preference Algorithm
The following algorithm is used to select the preferred mapping entry
when a conflict exists. Evaluation is made in the order specified.
Prefix conflicts are evaluated first. SID conflicts are then
evaluated on the Active entries remaining after Prefix Conflicts have
been resolved.
1. Higher preference value wins
2. Smaller range wins
3. IPv6 entry wins over IPv4 entry
4. Longer prefix length wins
5. Smaller algorithm wins
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6. Smaller starting address (considered as an unsigned integer
value) wins
7. Smaller starting SID wins
8. If topology IDs are NOT identical both entries MUST be ignored
As SIDs associated with prefix reachability advertisements have a
preference of 192 while by default SRMS preference is 128, the
default behavior is then to prefer SIDs advertised in prefix
reachability advertisements over SIDs advertised by SRMSs, but an
operator can choose to override this behavior by setting SRMS
preference higher than 192.
Preferring advertisements with smaller range has the nice property
that a single misconfiguration of an SRMS entry with a large range
will not be preferred over a large number of advertisements with
smaller ranges.
Since topology identifiers are locally scoped, it is not possible to
make a consistent choice network wide when all elements of a mapping
entry are identical except for the topology. This is why both
entries MUST be ignored in such cases (Rule #8 above). Note that
Rule #8 only applies when considering SID conflicts since Prefix
conflicts are restricted to a single topology.
3.3.5. Example Behavior - Single Topology/Algorithm
The following mapping entries exist:in the database. For brevity,
Topology/Algorithm is omitted and assumed to be (0,0) in all entries.
1. (192, 192.0.2.1/32, 100, 1)
2. (192, 192.0.2.101/32, 200, 1)
3. (128, 192.0.2.1/32, 400, 255) !Prefix conflict with entries 1 and
2
4. (128, 198.51.100.40/32, 200,1) !SID conflict with entry 2
The table below shows what mapping entries will be used in the
forwarding plane (Active) and which ones will not be used (Excluded)
under the three candidate policies:
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+--------------------------------------------------------------------+
|Policy | Active Entries | Excluded Entries |
+--------------------------------------------------------------------+
|Ignore | |(192,192.0.2.1/32,100,1) |
| | |(192,192.0.2.101/32,200,1) |
| | |(128,192.0.2.1/32,400,255) |
| | |(128,198.51.100.40/32,200,1) |
+--------------------------------------------------------------------+
|Quarantine|(192,192.0.1.1/32,100,1) |(128,192.0.2.1/32,400,255) |
| |(192,192.0.2.101/32,200,1) |(128,198.51.100.40/32,200,1) |
+--------------------------------------------------------------------+
|Overlap- |(192,192.0.2.1/32,100,1) |(128,198.51.100.40/32,200,1) |
| Only |(192,192.0.2.101/32,200,1) |*(128,192.0.2.1/32,400,1) |
| |*(128,192.0.2.2/32,401,99) |*(128,192.0.2.101/32,500,1) |
| |*(128,192.0.2.102/32, |
| | 501,153) | |
+--------------------------------------------------------------------+
* Derived from (128,192.0.2.1/32,400,300)
3.3.6. Example Behavior - Multiple Topologies
When using a preference rule the order in which conflict resolution
is applied has an impact on what entries are usable when entries for
multiple topologies (or algorithms) are present. The following
mapping entries exist in the database:
1. (192, 192.0.2.1/32, 100, 1, 0, 0) !Topology 0
2. (192, 192.0.2.1/32, 200, 1, 0, 0) !Topology 0, Prefix Conflict
with entry #1
3. (192, 198.51.100.40/32, 200,1,1,0) ! Topology 1, SID conflict
with entry 2
The table below shows what mapping entries will be used in the
forwarding plane (Active) and which ones will not be used (Excluded)
under the Quarantine Policy based on the order in which conflict
resolution is applied.
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+------------------------------------------------------------------+
|Order | Active Entries | Excluded Entries |
+------------------------------------------------------------------+
|Prefix- |(192,192.0.2.1/32,100,1,0,0)|(192,192.0.2.101/32,200,1,0)|
|Conflict|(192,198.51.100.40/32,200,1,| |
|First | 1,0) | |
+------------------------------------------------------------------+
|SID- |(192,192.0.2.1/32,100,1,0,0)|(192,192.0.2.101/32,200,1,0)|
|Conflict| |(192,198.51.100.40/32,200,1,|
|First | | 1,0) |
+------------------------------------------------------------------+
This illustrates the advantage of evaluating prefix conflicts within
a given topology (or algorithm) before evaluating topology (or
algorithm) independent SID conflicts. It insures that entries which
will be excluded based on intratopology preference will not prevent a
SID assigned in another topology from being considered Active.
3.3.7. Evaluation of Policy Alternatives
The previous sections have defined three alternatives for resolving
conflicts - ignore, quarantine, and ignore overlap-only.
The ignore policy impacts the greatest amount of traffic as
forwarding to all destinations which have a conflict is affected.
Quarantine allows forwarding for some destinations which have a
conflict to be supported.
Ignore overlap-only maximizes the destinations which will be
forwarded as all destinations covered by some mapping entry
(regardless of range) will be able to use the SID assigned by the
winning range. This alternative increases implementation complexity
as compared to quarantine. Mapping entries with a range greater than
1 which are in conflict with other mapping entries have to internally
be split into 2 or more "derived mapping entries". The derived
mapping entries then fall into two categories - those that are in
conflict with other mapping entries and those which are NOT in
conflict. The former are ignored and the latter are used. Each time
the underived mapping database is updated the derived entries have to
be recomputed based on the updated database. Internal data
structures have to be maintained which maintain the relationship
between the advertised mapping entry and the set of derived mapping
entries. All nodes in the network have to achieve the same behavior
regardless of implementation internals.
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There is then a tradeoff between a goal of maximizing traffic
delivery and the risks associated with increased implementation
complexity.
Consensus of the working group is that maximizing traffic delivery is
the most important deployment consideration - therefore ignore-
overlap-only is specified as the standard policy which MUST be
implemented by all nodes which support SR-MPLS.
3.3.8. Guaranteeing Database Consistency
In order to obtain consistent active entries all nodes in a network
MUST have the same mapping entry database. Mapping entries can be
obtained from a variety of sources.
o SIDs can be configured locally for prefixes assigned to interfaces
on the router itself. Only SIDs which are advertised to protocol
peers can be considered as part of the mapping entry database.
o SIDs can be received in prefix reachability advertisements from
protocol peers. These advertisements may originate from peers
local to the area or be leaked from other areas and/or
redistributed from other routing protocols.
o SIDs can be received from SRMS advertisements - these
advertisements can originate from routers local to the area or
leaked from other areas
o In cases where multiple routing protocols are in use mapping
entries advertised by all routing protocols MUST be included.
4. Scope of SR-MPLS SID Conflicts
The previous section defines the types of SID conflicts and
procedures to resolve such conflicts when using an MPLS dataplane.
The mapping entry database used MUST be populated with entries for
destinations for which the associated SID will be used to derive the
labels installed in the forwarding plane of routers in the network.
This consists of entries associated with intra-domain routes.
There are cases where destinations which are external to the domain
are advertised by protocol speakers running within that network - and
it is possible that those advertisements have SIDs associated with
those destinations. However, if reachability to a destination is
topologically outside the forwarding domain of the protocol instance
then the SIDs for such destinations will never be installed in the
forwarding plane of any router within the domain - so such
advertisements cannot create a SID conflict within the domain. Such
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entries therefore MUST NOT be installed in the database used for
intra-domain conflict resolution.
Consider the case of two sites "A and B" associated with a given
[RFC4364] VPN. Connectivity between the sites is via a provider
backbone. SIDs associated with destinations in Site A will never be
installed in the forwarding plane of routers in Site B. Reachability
between the sites (assuming SR is being used across the backbone)
only requires using a SID associated with a gateway PE. So a
destination in Site A MAY use the same SID as a destination in Site B
without introducing any conflict in the forwarding plane of routers
in Site A.
Such cases are handled by insuring that the mapping entries in the
database used by the procedures defined in the previous section only
include entries associated with advertisements within the site.
5. Security Considerations
The ability to introduce SID conflicts into a deployment may
compromise traffic forwarding. Protocol specific security mechanisms
SHOULD be used to insure that all SID advertisements originate from
trusted sources.
6. IANA Consideration
This document has no actions for IANA.
7. Acknowledgements
The authors would like to thank Jeff Tantsura, Wim Henderickx, and
Bruno Decraene for their careful review and content suggestions.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <http://www.rfc-editor.org/info/rfc4364>.
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[SR-IS-IS]
"IS-IS Extensions for Segment Routing, draft-ietf-isis-
segment-routing-extensions-08(work in progress)", October
2016.
[SR-MPLS] "Segment Routing with MPLS dataplane, draft-ietf-spring-
segment-routing-mpls-05(work in progress)", July 2016.
[SR-OSPF] "OSPF Extensions for Segment Routing, draft-ietf-ospf-
segment-routing-extensions-09(work in progress)", July
2016.
[SR-OSPFv3]
"OSPFv3 Extensions for Segment Routing, draft-ietf-ospf-
ospfv3-segment-routing-extensions-06(work in progress)",
July 2016.
8.2. Informational References
[SR-ARCH] "Segment Routing Architecture, draft-ietf-spring-segment-
routing-09(work in progress)", July 2016.
Authors' Addresses
Les Ginsberg
Cisco Systems
821 Alder Drive
Milpitas, CA 95035
USA
Email: ginsberg@cisco.com
Peter Psenak
Cisco Systems
Apollo Business Center Mlynske nivy 43
Bratislava 821 09
Slovakia
Email: ppsenak@cisco.com
Ginsberg, et al. Expires April 29, 2017 [Page 16]
Internet-Draft sr-conflict-resolution October 2016
Stefano Previdi
Cisco Systems
Via Del Serafico 200
Rome 0144
Italy
Email: sprevidi@cisco.com
Martin Pilka
Email: martin@infobox.sk
Ginsberg, et al. Expires April 29, 2017 [Page 17]
