Internet DRAFT - draft-ietf-i2nsf-applicability
draft-ietf-i2nsf-applicability
I2NSF Working Group J. Jeong
Internet-Draft Sungkyunkwan University
Intended status: Informational S. Hyun
Expires: March 18, 2020 Myongji University
T. Ahn
Korea Telecom
S. Hares
Huawei
D. Lopez
Telefonica I+D
September 15, 2019
Applicability of Interfaces to Network Security Functions to Network-
Based Security Services
draft-ietf-i2nsf-applicability-18
Abstract
This document describes the applicability of Interface to Network
Security Functions (I2NSF) to network-based security services in
Network Functions Virtualization (NFV) environments, such as
firewall, deep packet inspection, or attack mitigation engines.
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
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This Internet-Draft will expire on March 18, 2020.
Copyright Notice
Copyright (c) 2019 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. I2NSF Framework . . . . . . . . . . . . . . . . . . . . . . . 5
4. Time-dependent Web Access Control Service . . . . . . . . . . 8
5. Intent-based Security Services . . . . . . . . . . . . . . . 13
6. I2NSF Framework with SFC . . . . . . . . . . . . . . . . . . 15
7. I2NSF Framework with SDN . . . . . . . . . . . . . . . . . . 17
7.1. Firewall: Centralized Firewall System . . . . . . . . . . 19
7.2. Deep Packet Inspection: Centralized VoIP/VoLTE Security
System . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.3. Attack Mitigation: Centralized DDoS-attack Mitigation
System . . . . . . . . . . . . . . . . . . . . . . . . . 20
8. I2NSF Framework with NFV . . . . . . . . . . . . . . . . . . 21
9. Security Considerations . . . . . . . . . . . . . . . . . . . 23
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
12.1. Normative References . . . . . . . . . . . . . . . . . . 24
12.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Changes from draft-ietf-i2nsf-applicability-17 . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction
Interface to Network Security Functions (I2NSF) defines a framework
and interfaces for interacting with Network Security Functions
(NSFs). Note that an NSF is defined as software that provides a set
of security-related services, such as (i) detecting unwanted
activity, (ii) blocking or mitigating the effect of such unwanted
activity in order to fulfill service requirements, and (iii)
supporting communication stream integrity and confidentiality
[i2nsf-terminology].
The I2NSF framework allows heterogeneous NSFs developed by different
security solution vendors to be used in the Network Functions
Virtualization (NFV) environment [ETSI-NFV] by utilizing the
capabilities of such NSFs through I2NSF interfaces such as Customer-
Facing Interface [consumer-facing-inf-dm] and NSF-Facing Interface
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[nsf-facing-inf-dm]. In the I2NSF framework, each NSF initially
registers the profile of its own capabilities with the Security
Controller (i.e., network operator management system [RFC8329]) of
the I2NSF system via the Registration Interface
[registration-inf-dm]. This registration enables an I2NSF User
(i.e., network security administrator) to select and use the NSF to
enforce a given security policy. Note that Developer's Management
System (DMS) is management software that provides a vendor's security
service software as a Virtual Network Function (VNF) in an NFV
environment (or middlebox in the legacy network) as an NSF, and
registers the capabilities of an NSF into Security Controller via
Registration Interface for a security service [RFC8329].
Security Controller maintains the mapping between a capability and an
NSF, so it can perform to translate a high-level security policy
received from I2NSF User to a low-level security policy configured
and enforced in an NSF [policy-translation]. Security Controller can
monitor the states and security attacks in NSFs through NSF
monitoring [nsf-monitoring-dm].
This document illustrates the applicability of the I2NSF framework
with five different scenarios:
1. The enforcement of time-dependent web access control.
2. The support of intent-based security services through I2NSF and
Security Policy Translator [policy-translation].
3. The application of I2NSF to a Service Function Chaining (SFC)
environment [RFC7665].
4. The integration of the I2NSF framework with Software-Defined
Networking (SDN) [RFC7149] to provide different security
functionality such as firewalls [opsawg-firewalls], Deep Packet
Inspection (DPI), and Distributed Denial of Service (DDoS) attack
mitigation.
5. The use of Network Functions Virtualization (NFV) [ETSI-NFV] as a
supporting technology.
The implementation of I2NSF in these scenarios has allowed us to
verify the applicability and effectiveness of the I2NSF framework for
a variety of use cases.
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2. Terminology
This document uses the terminology described in [RFC7665], [RFC7149],
[ITU-T.Y.3300], [ONF-SDN-Architecture], [ITU-T.X.800],
[NFV-Terminology], [RFC8329], and [i2nsf-terminology]. In addition,
the following terms are defined below:
o Centralized DDoS-attack Mitigation System: A centralized mitigator
that can establish and distribute access control policy rules into
network resources for efficient DDoS-attack mitigation.
o Centralized Firewall System: A centralized firewall that can
establish and distribute policy rules into network resources for
efficient firewall management.
o Centralized VoIP Security System: A centralized security system
that handles the security functions required for VoIP and VoLTE
services.
o Firewall: A service function at the junction of two network
segments that inspects some suspicious packets that attempt to
cross the boundary. It also rejects any packet that does not
satisfy certain criteria for, for example, disallowed port numbers
or IP addresses.
o Network Function: A functional block within a network
infrastructure that has well-defined external interfaces and well-
defined functional behavior [NFV-Terminology].
o Network Functions Virtualization (NFV): A principle of separating
network functions (or network security functions) from the
hardware they run on by using virtual hardware abstraction
[NFV-Terminology].
o Network Security Function (NSF): Software that provides a set of
security-related services. Examples include detecting unwanted
activity and blocking or mitigating the effect of such unwanted
activity in order to fulfill service requirements. The NSF can
also help in supporting communication stream integrity and
confidentiality [i2nsf-terminology].
o Security Policy Translator (SPT): Software that translates a high-
level security policy for the Consumer-Facing Interface into a
low-level security policy for the NSF-Facing Interface
[policy-translation]. The SPT is a core part of the Security
Controller in the I2NSF system.
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o Service Function Chaining (SFC): The execution of an ordered set
of abstract service functions (i.e., network functions) according
to ordering constraints that must be applied to packets, frames,
and flows selected as a result of classification. The implied
order may not be a linear progression as the architecture allows
for SFCs that copy to more than one branch, and also allows for
cases where there is flexibility in the order in which service
functions need to be applied [RFC7665].
o Software-Defined Networking (SDN): A set of techniques that
enables to directly program, orchestrate, control, and manage
network resources, which facilitates the design, delivery and
operation of network services in a dynamic and scalable manner
[ITU-T.Y.3300].
+------------+
| I2NSF User |
+------------+
^
| Consumer-Facing Interface
v
+-------------------+ Registration +-----------------------+
|Security Controller|<-------------------->|Developer's Mgmt System|
+-------------------+ Interface +-----------------------+
^
| NSF-Facing Interface
v
+----------------+ +---------------+ +-----------------------+
| NSF-1 |-| NSF-2 |...| NSF-n |
| (Firewall) | | (Web Filter) | |(DDoS-Attack Mitigator)|
+----------------+ +---------------+ +-----------------------+
Figure 1: I2NSF Framework
3. I2NSF Framework
This section summarizes the I2NSF framework as defined in [RFC8329].
As shown in Figure 1, an I2NSF User can use security functions by
delivering high-level security policies, which specify security
requirements that the I2NSF user wants to enforce, to the Security
Controller via the Consumer-Facing Interface (CFI)
[consumer-facing-inf-dm].
The Security Controller receives and analyzes the high-level security
policies from an I2NSF User, and identifies what types of security
capabilities are required to meet these high-level security policies.
The Security Controller then identifies NSFs that have the required
security capabilities, and generates low-level security policies for
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each of the NSFs so that the high-level security policies are
eventually enforced by those NSFs [policy-translation]. Finally, the
Security Controller sends the generated low-level security policies
to the NSFs via the NSF-Facing Interface (NFI) [nsf-facing-inf-dm].
As shown in Figure 1, with a Developer's Management System (called
DMS), developers (or vendors) inform the Security Controller of the
capabilities of the NSFs through the Registration Interface (RI)
[registration-inf-dm] for registering (or deregistering) the
corresponding NSFs. Note that the lifecycle management of NSF code
from DMS (e.g., downloading of NSF modules and testing of NSF code)
is out of scope for I2NSF.
The Consumer-Facing Interface can be implemented with the Consumer-
Facing Interface YANG data model [consumer-facing-inf-dm] using
RESTCONF [RFC8040] which befits a web-based user interface for an
I2NSF User to send a Security Controller a high-level security
policy. Data models specified by YANG [RFC6020] describe high-level
security policies to be specified by an I2NSF User. The data model
defined in [consumer-facing-inf-dm] can be used for the I2NSF
Consumer-Facing Interface. Note that an inside attacker at the I2NSF
User can misuse the I2NSF system so that the network system under the
I2NSF system is vulnerable to security attacks. To handle this type
of threat, the Security Controller needs to monitor the activities of
all the I2NSF Users as well as the NSFs through the I2NSF NSF
monitoring functionality [nsf-monitoring-dm]. Note that the
monitoring of the I2NSF Users is out of scope for I2NSF.
The NSF-Facing Interface can be implemented with the NSF-Facing
Interface YANG data model [nsf-facing-inf-dm] using NETCONF [RFC6241]
which befits a command-line-based remote-procedure call for a
Security Controller to configure an NSF with a low-level security
policy. Data models specified by YANG [RFC6020] describe low-level
security policies for the sake of NSFs, which are translated from the
high-level security policies by the Security Controller. The data
model defined in [nsf-facing-inf-dm] can be used for the I2NSF NSF-
Facing Interface.
The Registration Interface can be implemented with the Registration
Interface YANG data model [registration-inf-dm] using NETCONF
[RFC6241] which befits a command-line-based remote-procedure call for
a DMS to send a Security Controller an NSF's capability information.
Data models specified by YANG [RFC6020] describe the registration of
an NSF's capabilities to enforce security services at the NSF. The
data model defined in [registration-inf-dm] can be used for the I2NSF
Registration Interface.
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The I2NSF framework can chain multiple NSFs to implement low-level
security policies with the SFC architecture [RFC7665].
The following sections describe different security service scenarios
illustrating the applicability of the I2NSF framework.
<?xml version="1.0" encoding="UTF-8" ?>
<policy xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-cfi-policy">
<policy-name>block_website</policy-name>
<rule>
<rule-name>block_website_during_working_hours</rule-name>
<event>
<time-information>
<begin-time>09:00</begin-time>
<end-time>18:00</end-time>
</time-information>
</event>
<condition>
<firewall-condition>
<source-target>
<src-target>Staff_Members'_PCs</src-target>
</source-target>
</firewall-condition>
<custom-condition>
<destination-target>
<dest-target>SNS_Websites</dest-target>
</destination-target>
</custom-condition>
</condition>
<action>
<primary-action>drop</primary-action>
</action>
</rule>
</policy>
Figure 2: A High-level Security Policy XML File for Time-based Web
Filter
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<?xml version="1.0" encoding="UTF-8" ?>
<i2nsf-security-policy
xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-policy-rule-for-nsf">
<system-policy>
<system-policy-name>block_website</system-policy-name>
<rules>
<rule-name>block_website_during_working_hours</rule-name>
<time-intervals>
<absolute-time-interval>
<begin-time>09:00</begin-time>
<end-time>18:00</end-time>
</absolute-time-interval>
</time-intervals>
<condition-clause-container>
<packet-security-ipv6-condition>
<pkt-sec-ipv6-src>
<ipv6-address>
<ipv6>2001:DB8:10:1::10</ipv6>
<ipv6>2001:DB8:10:1::20</ipv6>
<ipv6>2001:DB8:10:1::30</ipv6>
</ipv6-address>
</pkt-sec-ipv6-src>
</packet-security-ipv6-condition>
<packet-security-url-category-condition>
<user-defined-category>example1.com</user-defined-category>
<user-defined-category>example2.com</user-defined-category>
<user-defined-category>example3.com</user-defined-category>
<user-defined-category>example4.com</user-defined-category>
</packet-security-url-category-condition>
</condition-clause-container>
<action-clause-container>
<packet-action>
<egress-action>drop</egress-action>
</packet-action>
</action-clause-container>
</rules>
</system-policy>
</i2nsf-security-policy>
Figure 3: A Low-level Security Policy XML File for Time-based Web
Filter
4. Time-dependent Web Access Control Service
This service scenario assumes that an enterprise network
administrator wants to control the staff members' access to a
particular Internet service (e.g., social networking service (SNS))
during business hours. The following is an example high-level
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security policy rule for a web filter that the administrator
requests: Block the staff members' access to SNS websites from 9 AM
(i.e., 09:00) to 6 PM (i.e., 18:00) by dropping their packets.
Figure 2 is a high-level security policy XML code for the web filter
that is sent from the I2NSF User to the Security Controller via the
Consumer-Facing Interface [consumer-facing-inf-dm].
The security policy name is "block_website" with the tag "policy-
name", and the security policy rule name is
"block_website_during_working_hours" with the tag "rule-name". The
filtering event has the time span where the filtering begin time is
the time "09:00" (i.e., 9:00AM) with the tag "begin-time", and the
filtering end time is the time "18:00" (i.e., 6:00PM) with the tag
"end-time". The filtering condition has the source target of
"Staff_Members'_PCs" with the tag "src-target", and the destination
target of "SNS_Websites" with the tag "dest-target".
Assume that "Staff_Members'_PCs" are 2001:DB8:10:1::10,
2001:DB8:10:1::20, and 2001:DB8:10:1::30, and that "SNS_Websites" are
example1.com, example2.com, example3.com, and example4.com, as shown
in Figure 3. Note that Figure 3 is a low-level security policy XML
code for the web filter that is sent from the Security Controller to
an NSF via the NSF-Facing Interface [nsf-facing-inf-dm].
The source target can by translated by the Security Policy Translator
(SPT) in the Security Controller to the IP addresses of computers (or
mobile devices) used by the staff members. Refer to Section 5 for
the detailed description of the SPT. The destination target can also
be translated by the SPT to the actual websites corresponding to the
symbolic website name "SNS_Websites", and then either each website's
URL or the corresponding IP address(es) can be used by both firewall
and web filter. The action is to "drop" the packets satisfying the
above event and condition with the tag "primary-action".
After receiving the high-level security policy, the Security
Controller identifies required security capabilities, e.g., IP
address and port number inspection capabilities and URL inspection
capability. In this scenario, it is assumed that the IP address and
port number inspection capabilities are required to check whether a
received packet is an HTTP-session packet from a staff member, which
is part of an HTTP session generated by the staff member. The URL
inspection capability is required to check whether the target URL of
a received packet is one of the target websites (i.e., example1.com,
example2.com, example3.com, and example4.com) or not.
The Security Controller maintains the security capabilities of each
active NSF in the I2NSF system, which have been reported by the
Developer's Management System via the Registration interface. Based
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on this information, the Security Controller identifies NSFs that can
perform the IP address and port number inspection and URL inspection
through the security policy translation in Section 5. In this
scenario, it is assumed that a firewall NSF has the IP address and
port number inspection capabilities and a web filter NSF has URL
inspection capability.
The Security Controller generates a low-level security policy for the
NSFs to perform IP address and port number inspection, URL
inspection, and time checking, which is shown in Figure 3.
Specifically, the Security Controller may interoperate with an access
control server in the enterprise network in order to retrieve the
information (e.g., IP address in use, company identifier (ID), and
role) of each employee that is currently using the network. Based on
the retrieved information, the Security Controller generates a low-
level security policy to check whether the source IP address of a
received packet matches any one being used by a staff member.
In addition, the low-level security policy's rule (shortly, low-level
security rule) should be able to determine that a received packet
uses either the HTTP protocol without Transport Layer Security (TLS)
[RFC8446] or the HTTP protocol with TLS as HTTPS. The low-level
security rule for web filter checks that the target URL field of a
received packet is equal to one of the target SNS websites (i.e.,
example1.com, example2.com, example3.com, and example4.com), or that
the destination IP address of a received packet is an IP address
corresponding to one of the SNS websites. Note that if HTTPS is used
for an HTTP-session packet, the HTTP protocol header is encrypted, so
the URL information may not be seen from the packet for the web
filtering. Thus, the IP address(es) corresponding to the target URL
needs to be obtained from the certificate in TLS versions prior to
1.3 [RFC8446] or the Server Name Indication (SNI) in a TCP-session
packet in TLS versions without the encrypted SNI [tls-esni]. Also,
to obtain IP address(es) corresponding to a target URL, the DNS name
resolution process can be observed through a packet capturing tool
because the DNS name resolution will translate the target URL into IP
address(es). The IP addresses obtained through either TLS or DNS can
be used by both firewall and web filter for whitelisting or
blacklisting the TCP five-tuples of HTTP sessions.
Finally, the Security Controller sends the low-level security policy
of the IP address and port number inspection to the firewall NSF and
the low-level security policy for URL inspection to the web filter
NSF.
The following describes how the time-dependent web access control
service is enforced by the NSFs of firewall and web filter.
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1. A staff member tries to access one of the target SNS websites
(i.e., example1.com, example2.com, example3.com, and
example4.com) during business hours, e.g., 10 AM.
2. The packet is forwarded from the staff member's device to the
firewall, and the firewall checks the source IP address and port
number. Now the firewall identifies the received packet is an
HTTP-session packet from the staff member.
3. The firewall triggers the web filter to further inspect the
packet, and the packet is forwarded from the firewall to the web
filter. The SFC architecture [RFC7665] can be utilized to
support such packet forwarding in the I2NSF framework.
4. The web filter checks the received packet's target URL field or
its destination IP address corresponding to the target URL, and
detects that the packet is being sent to the server for
example1.com. The web filter then checks that the current time
is within business hours. If so, the web filter drops the
packet, and consequently the staff member's access to one of the
SNS websites (i.e., example1.com, example2.com, example3.com, and
example4.com) during business hours is blocked.
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+------------------------+-------------------------+
| |
| I2NSF User |
| |
+------------------------+-------------------------+
| Consumer-Facing Interface
|
High-level Security Policy
Security |
Controller V
+------------------------+-------------------------+
| Security Policy | |
| Translator | |
| +---------------------+----------------------+ |
| | | | |
| | +-------+--------+ | |
| | | Data Extractor | | |
| | +-------+--------+ | |
| | | Extracted Data from | |
| | V High-level Policy | |
| | +-------+--------+ +------+ | |
| | | Data Converter |<-->|NSF DB| | |
| | +-------+--------+ +------+ | |
| | | Required Data for | |
| | V Target NSFs | |
| | +-------+--------+ | |
| | |Policy Generator| | |
| | +-------+--------+ | |
| | | | |
| +---------------------+----------------------+ |
| | |
+------------------------+-------------------------+
| NSF-Facing Interface
|
Low-level Security Policy
|
V
+------------------------+-------------------------+
| |
| NSF(s) |
| |
+------------------------+-------------------------+
Figure 4: Security Policy Translation and Enforcement in I2NSF System
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5. Intent-based Security Services
I2NSF aims at providing intent-based security services to configure
specific security policies into NSFs with customer-friendly secuirty
policies at a high level. For example, when an I2NSF User submits a
high-level security policy (e.g., web filtering as shown in Figure 2)
to the Security Controller, the Security Policy Tranlator (SPT) in
the Security Controller will translate it into the correspondong low-
level security policy as shown in Figure 3 [policy-translation]. A
security administrator using the I2NSF User can describe a security
policy without the knowledge of the detailed information about
subjects (e.g., source and destination) and objects (e.g., web
traffic) of the security policy's rule(s).
Figure 4 shows the security policy translation and enforcement in the
I2NSF system [policy-translation]. As shown in Figure 4, an I2NSF
User delivers a high-level security policy to the Security Controller
using the Consumer-Facing Interface (denoted as CFI). The high-level
security policy is translated by the SPT in the Security Controller
into the corresponding low-level security policy which is
understandable by target NSF(s). The Security Controller delivers
the low-level security policy to the appropriate NSF(s) to enforce
the policy's rules.
The SPT consists of three modules for security policy translations
such as Data Extractor, Data Converter, and Policy Generator, as
shown in Figure 4. The Data Extractor extracts data from a high-
level security policy delivered by the I2NSF User. The data
correspond to the leaf nodes in the YANG data model for the Consumer-
Facing Interface. In the high-level policy in Figure 2, the data are
the tag values of policy-name, rule-name, begin-time, end-time, src-
target, dest-target, and primary-action. That is, the tag values are
"block_website", "block_website_during_working_hours", "09:00",
"18:00", "Staff_Members'_PCs", "SNS_Websites", and "drop."
The Data Converter converts the extracted high-level policy data
received from the Data Extractor into the corresponding low-level
policy data. The low-level policy data have the capability
information of NSFs to be selected as target NSFs for the required
security service enforcement specified by the high-level security
policy. The tag values in the extracted high-level policy data are
replaced with the tag values in the low-level policy data, which are
the leaf nodes of the YANG data model for the NSF-Facing Interface
(denoted as NFI). The value of each leaf node in CFI is translated
into the value of the corresponding leaf node in NFI. For example,
"block_website" of policy-name in CFI (in Figure 2) is translated
into "block_website" of system-policy-name in NFI (in Figure 3). The
tag values of rule-name, begin-time, end-time, and primary-action in
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CFI are mapped into the same values of rule-name, begin-time, end-
time, and egress-action in NFI. However, the tag values of src-
target and dest-target in CFI are translated into IP addresses and
URLs, respectively, for the sake of NFI. That is,
"Staff_Members'_PCs" of CFI is translated into three IPv6 addresses
such as "2001:DB8:10:1::10", "2001:DB8:10:1::20", and
"2001:DB8:10:1::30" for the sake of NFI. Also, "SNS_Websites" of CFI
is translated into four URLs such as "example1.com", "example2.com",
"example3.com", and "example4.com" for the sake of NFI. In addition
to the data conversion, the Data Converter searches for appropriate
NSFs having capabilities corresponding to the leaf nodes of the YANG
data model for NFI. For the data conversion and NSF search, an NSF
database (denoted as NSF DB) can be consulted, as shown in Figure 4,
because the NSF DB has the capability information of NSFs that the
DMS(s) registered with the Security Controller using the Registration
Interface.
The Policy Generator generates a low-level security policy
corresponding to the low-level policy data made by the Data Converter
per a target NSF. That is, the Policy Generator can build such a
low-level security policy XML file like Figure 3 with the NSF DB
because the NSF DB has the mapping information between the CFI YANG
data model and the NFI YANG data model.
Therefore, by allowing the I2NSF User to express its security policy
without knowing the detailed information of entities for security
policies, the I2NSF can efficiently support the intent-based security
services with the help of the security policy translator along with
the NSF DB.
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+------------+
| I2NSF User |
+------------+
^
| Consumer-Facing Interface
v
+-------------------+ Registration +-----------------------+
|Security Controller|<-------------------->|Developer's Mgmt System|
+-------------------+ Interface +-----------------------+
^ ^
| | NSF-Facing Interface
| |-------------------------
| |
| NSF-Facing Interface |
+-----v-----------+ +------v-------+
| +-----------+ | ------>| NSF-1 |
| |Classifier | | | | (Firewall) |
| +-----------+ | | +--------------+
| +-----+ |<-----| +--------------+
| | SFF | | |----->| NSF-2 |
| +-----+ | | | (DPI) |
+-----------------+ | +--------------+
| .
| .
| .
| +-----------------------+
------>| NSF-n |
|(DDoS-Attack Mitigator)|
+-----------------------+
Figure 5: An I2NSF Framework with SFC
6. I2NSF Framework with SFC
In the I2NSF architecture, an NSF can trigger an advanced security
action (e.g., DPI or DDoS attack mitigation) on a packet based on the
result of its own security inspection of the packet. For example, a
firewall triggers further inspection of a suspicious packet with DPI.
For this advanced security action to be fulfilled, the suspicious
packet should be forwarded from the current NSF to the successor NSF.
SFC [RFC7665] is a technology that enables this advanced security
action by steering a packet with multiple service functions (e.g.,
NSFs), and this technology can be utilized by the I2NSF architecture
to support the advanced security action.
Figure 5 shows an I2NSF framework with the support of SFC. As shown
in the figure, SFC generally requires classifiers and service
function forwarders (SFFs); classifiers are responsible for
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determining which service function path (SFP) (i.e., an ordered
sequence of service functions) a given packet should pass through,
according to pre-configured classification rules, and SFFs perform
forwarding the given packet to the next service function (e.g., NSF)
on the SFP of the packet by referring to their forwarding tables. In
the I2NSF architecture with SFC, the Security Controller can take
responsibilities of generating classification rules for classifiers
and forwarding tables for SFFs. By analyzing high-level security
policies from I2NSF users, the Security Controller can construct SFPs
that are required to meet the high-level security policies, generates
classification rules of the SFPs, and then configures classifiers
with the classification rules over NSF-Facing Interface so that
relevant traffic packets can follow the SFPs. Also, based on the
global view of NSF instances available in the system, the Security
Controller constructs forwarding tables, which are required for SFFs
to forward a given packet to the next NSF over the SFP, and
configures SFFs with those forwarding tables over NSF-Facing
Interface.
To trigger an advanced security action in the I2NSF architecture, the
current NSF appends metadata describing the security capability
required to the suspicious packet via a network service header (NSH)
[RFC8300]. It then sends the packet to the classifier. Based on the
metadata information, the classifier searches an SFP which includes
an NSF with the required security capability, changes the SFP-related
information (e.g., service path identifier and service index
[RFC8300]) of the packet with the new SFP that has been found, and
then forwards the packet to the SFF. When receiving the packet, the
SFF checks the SFP-related information such as the service path
identifier and service index contained in the packet and forwards the
packet to the next NSF on the SFP of the packet, according to its
forwarding table.
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+------------+
| I2NSF User |
+------------+
^
| Consumer-Facing Interface
v
+-------------------+ Registration +-----------------------+
|Security Controller|<-------------------->|Developer's Mgmt System|
+-------------------+ Interface +-----------------------+
^ ^
| | NSF-Facing Interface
| v
| +----------------+ +---------------+ +-----------------------+
| | NSF-1 |-| NSF-2 |...| NSF-n |
| | (Firewall) | | (DPI) | |(DDoS-Attack Mitigator)|
| +----------------+ +---------------+ +-----------------------+
|
|
| SDN Network
+--|----------------------------------------------------------------+
| V NSF-Facing Interface |
| +----------------+ |
| | SDN Controller | |
| +----------------+ |
| ^ |
| | SDN Southbound Interface |
| v |
| +--------+ +------------+ +--------+ +--------+ |
| |Switch-1|-| Switch-2 |-|Switch-3|.......|Switch-m| |
| | | |(Classifier)| | (SFF) | | | |
| +--------+ +------------+ +--------+ +--------+ |
+-------------------------------------------------------------------+
Figure 6: An I2NSF Framework with SDN Network
7. I2NSF Framework with SDN
This section describes an I2NSF framework with SDN for I2NSF
applicability and use cases, such as firewall, deep packet
inspection, and DDoS-attack mitigation functions. SDN enables some
packet filtering rules to be enforced in network forwarding elements
(e.g., switch) by controlling their packet forwarding rules. By
taking advantage of this capability of SDN, it is possible to
optimize the process of security service enforcement in the I2NSF
system. For example, for efficient firewall services, simple packet
filtering can be performed by SDN forwarding elements (e.g.,
switches), and complicated packet filtering based on packet payloads
can be performed by a firewall NSF. This optimized firewall using
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both SDN forwarding elements and a firewall NSF is more efficient
than a firewall where SDN forwarding elements forward all the packets
to a firewall NSF for packet filtering. This is because packets to
be filtered out can be early dropped by SDN forwarding elements
without consuming further network bandwidth due to the forwarding of
the packets to the firewall NSF.
Figure 6 shows an I2NSF framework [RFC8329] with SDN networks to
support network-based security services. In this system, the
enforcement of security policy rules is divided into the SDN
forwarding elements (e.g., a switch running as either a hardware
middle box or a software virtual switch) and NSFs (e.g., a firewall
running in a form of a VNF [ETSI-NFV]). Note that NSFs are created
or removed by the NFV Management and Orchestration (MANO)
[ETSI-NFV-MANO], performing the lifecycle management of NSFs as VNFs.
Refer to Section 8 for the detailed discussion of the NSF lifecycle
management in the NFV MANO for I2NSF. For security policy
enforcement (e.g., packet filtering), the Security Controller
instructs the SDN Controller via NSF-Facing Interface so that SDN
forwarding elements can perform the required security services with
flow tables under the supervision of the SDN Controller.
As an example, let us consider two different types of security rules:
Rule A is a simple packet filtering rule that checks only the IP
address and port number of a given packet, whereas rule B is a time-
consuming packet inspection rule for analyzing whether an attached
file being transmitted over a flow of packets contains malware. Rule
A can be translated into packet forwarding rules of SDN forwarding
elements and thus be enforced by these elements. In contrast, rule B
cannot be enforced by forwarding elements, but it has to be enforced
by NSFs with anti-malware capability. Specifically, a flow of
packets is forwarded to and reassembled by an NSF to reconstruct the
attached file stored in the flow of packets. The NSF then analyzes
the file to check the existence of malware. If the file contains
malware, the NSF drops the packets.
In an I2NSF framework with SDN, the Security Controller can analyze
given security policy rules and automatically determine which of the
given security policy rules should be enforced by SDN forwarding
elements and which should be enforced by NSFs. If some of the given
rules requires security capabilities that can be provided by SDN
forwarding elements, then the Security Controller instructs the SDN
Controller via NSF-Facing Interface so that SDN forwarding elements
can enforce those security policy rules with flow tables under the
supervision of the SDN Controller. Or if some rules require security
capabilities that cannot be provided by SDN forwarding elements but
by NSFs, then the Security Controller instructs relevant NSFs to
enforce those rules.
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The distinction between software-based SDN forwarding elements and
NSFs, which can both run as VNFs, may be necessary for some
management purposes in this system. Note that an SDN forwarding
element (i.e., switch) is a specific type of VNF rather than an NSF
because an NSF is for security services rather than for packet
forwarding. For this distinction, we can take advantage of the NFV
MANO where there is a subsystem that maintains the descriptions of
the capabilities each VNF can offer [ETSI-NFV-MANO]. This subsystem
can determine whether a given software element (VNF instance) is an
NSF or a virtualized SDN switch. For example, if a VNF instance has
anti-malware capability according to the description of the VNF, it
could be considered as an NSF. A VNF onboarding system
[VNF-ONBOARDING] can be used as such a subsystem that maintains the
descriptions of each VNF to tell whether a VNF instance is for an NSF
or for a virtualized SDN switch.
For the support of SFC in the I2NSF framework with SDN, as shown in
Figure 6, network forwarding elements (e.g., switch) can play the
role of either SFC Classifier or SFF, which are explained in
Section 6. Classifier and SFF have an NSF-Facing Interface with
Security Controller. This interface is used to update security
service function chaining information for traffic flows. For
example, when it needs to update an SFP for a traffic flow in an SDN
network, as shown in Figure 6, SFF (denoted as Switch-3) asks
Security Controller to update the SFP for the traffic flow (needing
another security service as an NSF) via NSF-Facing Interface. This
update lets Security Controller ask Classifier (denoted as Switch-2)
to update the mapping between the traffic flow and SFP in Classifier
via NSF-Facing Interface.
The following subsections introduce three use cases from [RFC8192]
for cloud-based security services: (i) firewall system, (ii) deep
packet inspection system, and (iii) attack mitigation system.
7.1. Firewall: Centralized Firewall System
A centralized network firewall can manage each network resource and
apply common rules to individual network elements (e.g., switch).
The centralized network firewall controls each forwarding element,
and firewall rules can be added or deleted dynamically.
A time-based firewall can be enforced with packet filtering rules and
a time span (e.g., work hours). With this time-based firewall, a
time-based security policy can be enforced, as explained in
Section 4. For example, employees at a company are allowed to access
social networking service websites during lunch time or after work
hours.
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7.2. Deep Packet Inspection: Centralized VoIP/VoLTE Security System
A centralized VoIP/VoLTE security system can monitor each VoIP/VoLTE
flow and manage VoIP/VoLTE security rules, according to the
configuration of a VoIP/VoLTE security service called VoIP Intrusion
Prevention System (IPS). This centralized VoIP/VoLTE security system
controls each switch for the VoIP/VoLTE call flow management by
manipulating the rules that can be added, deleted or modified
dynamically.
The centralized VoIP/VoLTE security system can cooperate with a
network firewall to realize VoIP/VoLTE security service.
Specifically, a network firewall performs the basic security check of
an unknown flow's packet observed by a switch. If the network
firewall detects that the packet is an unknown VoIP call flow's
packet that exhibits some suspicious patterns, then it triggers the
VoIP/VoLTE security system for more specialized security analysis of
the suspicious VoIP call packet.
7.3. Attack Mitigation: Centralized DDoS-attack Mitigation System
A centralized DDoS-attack mitigation can manage each network resource
and configure rules to each switch for DDoS-attack mitigation (called
DDoS-attack Mitigator) on a common server. The centralized DDoS-
attack mitigation system defends servers against DDoS attacks outside
the private network, that is, from public networks
[RFC8612][dots-architecture].
Servers are categorized into stateless servers (e.g., DNS servers)
and stateful servers (e.g., web servers). For DDoS-attack
mitigation, the forwarding of traffic flows in switches can be
dynamically configured such that malicious traffic flows are handled
by the paths separated from normal traffic flows in order to minimize
the impact of those malicious traffic on the servers. This flow path
separation can be done by a flow forwarding path management scheme
[dots-architecture][AVANT-GUARD]. This management should consider
the load balance among the switches for the defense against DDoS
attacks.
So far this section has described the three use cases for network-
based security services using the I2NSF framework with SDN networks.
To support these use cases in the proposed data-driven security
service framework, YANG data models described in
[consumer-facing-inf-dm], [nsf-facing-inf-dm], and
[registration-inf-dm] can be used as Consumer-Facing Interface, NSF-
Facing Interface, and Registration Interface, respectively, along
with RESTCONF [RFC8040] and NETCONF [RFC6241].
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+--------------------+
+-------------------------------------------+ | ---------------- |
| I2NSF User (OSS/BSS) | | | NFV | |
+------+------------------------------------+ | | Orchestrator +-+ |
| Consumer-Facing Interface | -----+---------- | |
+------|------------------------------------+ | | | |
| -----+---------- (a) ----------------- | | ----+----- | |
| | Security +-------+ Developer's | | | | | | |
| |Controller(EM)| |Mgmt System(EM)| +-(b)-+ VNFM(s)| | |
| -----+---------- ----------------- | | | | | |
| | NSF-Facing Interface | | ----+----- | |
| ----+----- ----+----- ----+----- | | | | |
| |NSF(VNF)| |NSF(VNF)| |NSF(VNF)| | | | | |
| ----+----- ----+----- ----+----- | | | | |
| | | | | | | | |
+------|-------------|-------------|--------+ | | | |
| | | | | | |
+------+-------------+-------------+--------+ | | | |
| NFV Infrastructure (NFVI) | | | | |
| ----------- ----------- ----------- | | | | |
| | Virtual | | Virtual | | Virtual | | | | | |
| | Compute | | Storage | | Network | | | | | |
| ----------- ----------- ----------- | | ----+----- | |
| +---------------------------------------+ | | | | | |
| | Virtualization Layer | +-----+ VIM(s) +------+ |
| +---------------------------------------+ | | | | |
| +---------------------------------------+ | | ---------- |
| | ----------- ----------- ----------- | | | |
| | | Compute | | Storage | | Network | | | | |
| | | Hardware| | Hardware| | Hardware| | | | |
| | ----------- ----------- ----------- | | | |
| | Hardware Resources | | | NFV Management |
| +---------------------------------------+ | | and Orchestration |
| | | (MANO) |
+-------------------------------------------+ +--------------------+
(a) = Registration Interface
(b) = Ve-Vnfm Interface
Figure 7: I2NSF Framework Implementation with respect to the NFV
Reference Architectural Framework
8. I2NSF Framework with NFV
This section discusses the implementation of the I2NSF framework
using Network Functions Virtualization (NFV).
NFV is a promising technology for improving the elasticity and
efficiency of network resource utilization. In NFV environments,
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NSFs can be deployed in the forms of software-based virtual instances
rather than physical appliances. Virtualizing NSFs makes it possible
to rapidly and flexibly respond to the amount of service requests by
dynamically increasing or decreasing the number of NSF instances.
Moreover, NFV technology facilitates flexibly including or excluding
NSFs from multiple security solution vendors according to the changes
on security requirements. In order to take advantages of the NFV
technology, the I2NSF framework can be implemented on top of an NFV
infrastructure as show in Figure 7.
Figure 7 shows an I2NSF framework implementation based on the NFV
reference architecture that the European Telecommunications Standards
Institute (ETSI) defines [ETSI-NFV]. The NSFs are deployed as VNFs
in Figure 7. The Developer's Management System (DMS) in the I2NSF
framework is responsible for registering capability information of
NSFs into the Security Controller. However, those NSFs are created
or removed by a virtual network function manager (VNFM) in the NFV
MANO that performs the lifecycle management of VNFs. Note that the
lifecycle management of VNFs is out of scope for I2NSF. The Security
Controller controls and monitors the configurations (e.g., function
parameters and security policy rules) of VNFs via the NSF-Facing
Interface along with the NSF monitoring capability
[nsf-facing-inf-dm][nsf-monitoring-dm]. Both the DMS and Security
Controller can be implemented as the Element Managements (EMs) in the
NFV architecture. Finally, the I2NSF User can be implemented as OSS/
BSS (Operational Support Systems/Business Support Systems) in the NFV
architecture that provides interfaces for users in the NFV system.
The operation procedure in the I2NSF framework based on the NFV
architecture is as follows:
1. The VNFM has a set of virtual machine (VM) images of NSFs, and
each VM image can be used to create an NSF instance that provides
a set of security capabilities. The DMS initially registers a
mapping table of the ID of each VM image and the set of
capabilities that can be provided by an NSF instance created from
the VM image into the Security Controller.
2. If the Security Controller does not have any instantiated NSF
that has the set of capabilities required to meet the security
requirements from users, it searches the mapping table
(registered by the DMS) for the VM image ID corresponding to the
required set of capabilities.
3. The Security Controller requests the DMS to instantiate an NSF
with the VM image ID via VNFM.
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4. When receiving the instantiation request, the VNFM first asks the
NFV orchestrator for the permission required to create the NSF
instance, requests the VIM to allocate resources for the NSF
instance, and finally creates the NSF instance based on the
allocated resources.
5. Once the NSF instance has been created by the VNFM, the DMS
performs the initial configurations of the NSF instance and then
notifies the Security Controller of the NSF instance.
6. After being notified of the created NSF instance, the Security
Controller delivers low-level security policy rules to the NSF
instance for policy enforcement.
We can conclude that the I2NSF framework can be implemented based on
the NFV architecture framework. Note that the registration of the
capabilities of NSFs is performed through the Registration Interface
and the lifecycle management for NSFs (VNFs) is performed through the
Ve-Vnfm interface between the DMS and VNFM, as shown in Figure 7.
9. Security Considerations
The same security considerations for the I2NSF framework [RFC8329]
are applicable to this document.
This document shares all the security issues of SDN that are
specified in the "Security Considerations" section of [ITU-T.Y.3300].
The role of the DMS is to provide an I2NSF system with the software
packages or images for NSF execution. The DMS must not access NSFs
in activated status. An inside attacker or a supply chain attacker
at the DMS can seriously weaken the I2NSF system's security. A
malicious DMS is relevant to an insider attack, and a compromised DMS
is relevant to a supply chain attack. A malicious (or compromised)
DMS could register an NSF of its choice in response to a capability
request by the Security Controller. As a result, a malicious DMS can
attack the I2NSF system by providing malicious NSFs with arbitrary
capabilities to include potentially controlling those NSFs in real
time. An unwitting DMS could be compromised and the infrastructure
of the DMS could be coerced into distributing modified NSFs as well.
To deal with these types of threats, an I2NSF system should not use
NSFs from an untrusted DMS or without prior testing. The practices
by which these packages are downloaded and loaded into the system are
out of scope for I2NSF.
I2NSF system operators should audit and monitor interactions with
DMSs. Additionally, the operators should monitor the running NSFs
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through the I2NSF NSF Monitoring Interface [nsf-monitoring-dm] as
part of the I2NSF NSF-Facing Interface. Note that the mechanics for
monitoring the DMSs are out of scope for I2NSF.
10. Acknowledgments
This work was supported by Institute of Information & Communications
Technology Planning & Evaluation (IITP) grant funded by the Korea
MSIT (Ministry of Science and ICT) (R-20160222-002755, Cloud based
Security Intelligence Technology Development for the Customized
Security Service Provisioning).
This work has been partially supported by the European Commission
under Horizon 2020 grant agreement no. 700199 "Securing against
intruders and other threats through a NFV-enabled environment
(SHIELD)". This support does not imply endorsement.
11. Contributors
I2NSF is a group effort. I2NSF has had a number of contributing
authors. The following are considered co-authors:
o Hyoungshick Kim (Sungkyunkwan University)
o Jinyong Tim Kim (Sungkyunkwan University)
o Hyunsik Yang (Soongsil University)
o Younghan Kim (Soongsil University)
o Jung-Soo Park (ETRI)
o Se-Hui Lee (Korea Telecom)
o Mohamed Boucadair (Orange)
12. References
12.1. Normative References
[AVANT-GUARD]
Shin, S., Yegneswaran, V., Porras, P., and G. Gu, "AVANT-
GUARD: Scalable and Vigilant Switch Flow Management in
Software-Defined Networks", ACM CCS, November 2013.
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[consumer-facing-inf-dm]
Jeong, J., Kim, E., Ahn, T., Kumar, R., and S. Hares,
"I2NSF Consumer-Facing Interface YANG Data Model", draft-
ietf-i2nsf-consumer-facing-interface-dm-06 (work in
progress), July 2019.
[dots-architecture]
Mortensen, A., Reddy, T., Andreasen, F., Teague, N., and
R. Compton, "Distributed-Denial-of-Service Open Threat
Signaling (DOTS) Architecture", draft-ietf-dots-
architecture-14 (work in progress), May 2019.
[ETSI-NFV]
"Network Functions Virtualisation (NFV); Architectural
Framework", Available:
https://www.etsi.org/deliver/etsi_gs/
nfv/001_099/002/01.01.01_60/gs_nfv002v010101p.pdf, October
2013.
[ITU-T.Y.3300]
"Framework of Software-Defined Networking",
Available: https://www.itu.int/rec/T-REC-Y.3300-201406-I,
June 2014.
[NFV-Terminology]
"Network Functions Virtualisation (NFV); Terminology for
Main Concepts in NFV", Available:
https://www.etsi.org/deliver/etsi_gs/
NFV/001_099/003/01.02.01_60/gs_nfv003v010201p.pdf,
December 2014.
[nsf-facing-inf-dm]
Kim, J., Jeong, J., Park, J., Hares, S., and Q. Lin,
"I2NSF Network Security Function-Facing Interface YANG
Data Model", draft-ietf-i2nsf-nsf-facing-interface-dm-07
(work in progress), July 2019.
[nsf-monitoring-dm]
Jeong, J., Chung, C., Hares, S., Xia, L., and H. Birkholz,
"I2NSF NSF Monitoring YANG Data Model", draft-ietf-i2nsf-
nsf-monitoring-data-model-01 (work in progress), July
2019.
[ONF-SDN-Architecture]
"SDN Architecture (Issue 1.1)", Available:
https://www.opennetworking.org/wp-
content/uploads/2014/10/TR-
521_SDN_Architecture_issue_1.1.pdf, June 2016.
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[registration-inf-dm]
Hyun, S., Jeong, J., Roh, T., Wi, S., and J. Park, "I2NSF
Registration Interface YANG Data Model", draft-ietf-i2nsf-
registration-interface-dm-05 (work in progress), July
2019.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6241] Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
Bierman, "Network Configuration Protocol (NETCONF)",
RFC 6241, June 2011.
[RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined
Networking: A Perspective from within a Service Provider
Environment", RFC 7149, March 2014.
[RFC7665] Halpern, J. and C. Pignataro, "Service Function Chaining
(SFC) Architecture", RFC 7665, October 2015.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, January 2017.
[RFC8192] Hares, S., Lopez, D., Zarny, M., Jacquenet, C., Kumar, R.,
and J. Jeong, "Interface to Network Security Functions
(I2NSF): Problem Statement and Use Cases", RFC 8192, July
2017.
[RFC8300] Quinn, P., Elzur, U., and C. Pignataro, "Network Service
Header (NSH)", RFC 8300, January 2018.
[RFC8329] Lopez, D., Lopez, E., Dunbar, L., Strassner, J., and R.
Kumar, "Framework for Interface to Network Security
Functions", RFC 8329, February 2018.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, August 2018.
[RFC8612] Mortensen, A., Reddy, T., and R. Moskowitz, "DDoS Open
Threat Signaling (DOTS) Requirements", RFC 8612, May 2019.
12.2. Informative References
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[ETSI-NFV-MANO]
"Network Functions Virtualisation (NFV); Management and
Orchestration", Available:
https://www.etsi.org/deliver/etsi_gs/nfv-
man/001_099/001/01.01.01_60/gs_nfv-man001v010101p.pdf,
December 2014.
[i2nsf-terminology]
Hares, S., Strassner, J., Lopez, D., Xia, L., and H.
Birkholz, "Interface to Network Security Functions (I2NSF)
Terminology", draft-ietf-i2nsf-terminology-08 (work in
progress), July 2019.
[ITU-T.X.800]
"Security Architecture for Open Systems Interconnection
for CCITT Applications", March 1991.
[opsawg-firewalls]
Baker, F. and P. Hoffman, "On Firewalls in Internet
Security", draft-ietf-opsawg-firewalls-01 (work in
progress), October 2012.
[policy-translation]
Jeong, J., Yang, J., Chung, C., and J. Kim, "Security
Policy Translation in Interface to Network Security
Functions", draft-yang-i2nsf-security-policy-
translation-04 (work in progress), July 2019.
[tls-esni]
Rescorla, E., Oku, K., Sullivan, N., and C. Wood,
"Encrypted Server Name Indication for TLS 1.3", draft-
ietf-tls-esni-04 (work in progress), July 2019.
[VNF-ONBOARDING]
"VNF Onboarding", Available:
https://wiki.opnfv.org/display/mano/VNF+Onboarding,
November 2016.
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Appendix A. Changes from draft-ietf-i2nsf-applicability-17
The following changes have been made from draft-ietf-i2nsf-
applicability-17:
o In Section 4, a high-level security policy XML file in Figure 2
and the corresponding low-level security policy XML file Figure 3
are constructed using the Consumer-Facing Interface data model and
the NSF-Facing data model, respectively.
o For the applicability of I2NSF to the real world, Section 5 is
added to support the Intent-based Security Services using I2NSF.
This section explains the security policy translation based on an
I2NSF User's intents on the required security services. Figure 4
shows the archiecture and procedure of the I2NSF security policy
translator.
Authors' Addresses
Jaehoon Paul Jeong
Department of Computer Science and Engineering
Sungkyunkwan University
2066 Seobu-Ro, Jangan-Gu
Suwon, Gyeonggi-Do 16419
Republic of Korea
Phone: +82 31 299 4957
Fax: +82 31 290 7996
EMail: pauljeong@skku.edu
URI: http://iotlab.skku.edu/people-jaehoon-jeong.php
Sangwon Hyun
Department of Computer Engineering
Myongji University
116 Myongji-ro, Cheoin-gu
Yongin 17058
Republic of Korea
Phone: +82 62 230 7473
EMail: shyun@chosun.ac.kr
Jeong, et al. Expires March 18, 2020 [Page 28]
Internet-Draft I2NSF Applicability September 2019
Tae-Jin Ahn
Korea Telecom
70 Yuseong-Ro, Yuseong-Gu
Daejeon 305-811
Republic of Korea
Phone: +82 42 870 8409
EMail: taejin.ahn@kt.com
Susan Hares
Huawei
7453 Hickory Hill
Saline, MI 48176
USA
Phone: +1-734-604-0332
EMail: shares@ndzh.com
Diego R. Lopez
Telefonica I+D
Jose Manuel Lara, 9
Seville 41013
Spain
Phone: +34 682 051 091
EMail: diego.r.lopez@telefonica.com
Jeong, et al. Expires March 18, 2020 [Page 29]
