Network Working Group Q. Sun
Internet-Draft C. Xie
Intended status: Informational China Telecom
Expires: January 4, 2018 Y. Lee
Comcast
M. Chen
FreeBit
T. Li
Tsinghua University
I. Farrer
Deutsche Telekom AG
July 3, 2017
Deployment Considerations for Lightweight 4over6
draft-ietf-softwire-lightweight-4over6-deployment-01
Abstract
Lightweight 4over6 is a mechanism for providing IPv4 services to
clients connected to a single-stack IPv6 network. The architecture
is similar to DS-Lite, but the network address translation function
is relocated from the tunnel concentrator to the tunnel client, hence
reducing the amount of state which must be maintained in the
concentrator to a per-customer level. This document discusses the
applicability, describes various deployment models and provides
deployment considerations for Lightweight 4over6.
Status of This Memo
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 4, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Deployment Models . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Top-Down Deployment Model . . . . . . . . . . . . . . . . 4
2.2. Bottom-Up Deployment Model . . . . . . . . . . . . . . . 5
2.3. Campus Deployment . . . . . . . . . . . . . . . . . . . . 5
3. Overall Deployment Considerations . . . . . . . . . . . . . . 5
3.1. IP Addressing and Routing . . . . . . . . . . . . . . . . 5
3.1.1. IPv4 Routing . . . . . . . . . . . . . . . . . . . . 5
3.1.2. IPv6 Routing . . . . . . . . . . . . . . . . . . . . 6
3.2. lwB4 Configuration . . . . . . . . . . . . . . . . . . . 6
3.2.1. DHCPv6 Based Provisioning . . . . . . . . . . . . . . 6
3.2.2. DHCPv4 over DHCPv6 Based Provisioning . . . . . . . . 7
3.2.3. PCP Based Provisioning . . . . . . . . . . . . . . . 7
3.2.4. NETCONF/YANG Based Provisioning . . . . . . . . . . . 7
3.2.5. Other lwB4 Configuation Considerations . . . . . . . 7
3.3. lwAFTR Discovery . . . . . . . . . . . . . . . . . . . . 8
3.4. Impacts on Accouting . . . . . . . . . . . . . . . . . . 8
4. lwAFTR Deployment Considerations . . . . . . . . . . . . . . 8
4.1. Logging at the lwAFTR . . . . . . . . . . . . . . . . . . 9
4.2. MTU and Fragmentation Considerations . . . . . . . . . . 9
4.3. Reliability Considerations of lwAFTR . . . . . . . . . . 9
4.4. Location of lwAFTRs in the Network . . . . . . . . . . . 10
4.5. Path Consistency Consideration . . . . . . . . . . . . . 10
5. lwB4 Deployment Considerations . . . . . . . . . . . . . . . 11
5.1. NAT Traversal Issues . . . . . . . . . . . . . . . . . . 11
5.2. Static Port Forwarding Configuration . . . . . . . . . . 11
6. DS-Lite Compatibility Consideration . . . . . . . . . . . . . 12
6.1. Case 1: Integrated Network Element with Lightweight
4over6 and DS-Lite AFTR Scenario . . . . . . . . . . 12
6.2. Case 2: DS-Lite Coexistent scenario with Separated AFTR . 13
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
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8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
Appendix A. China Telecom Experimental Results . . . . . . . . . 17
A.1. Experimental Environment . . . . . . . . . . . . . . . . 18
A.2. Experimental Results . . . . . . . . . . . . . . . . . . 19
A.3. Conclusions . . . . . . . . . . . . . . . . . . . . . . . 20
Appendix B. Tsinghua University Experimental Result . . . . . . 20
B.1. Experimental Environment . . . . . . . . . . . . . . . . 20
B.2. Experimental Results . . . . . . . . . . . . . . . . . . 21
B.3. Conclusion . . . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
Lightweight 4over6 [RFC7596] (lw4o6) is an extension to DS-Lite
[RFC6333] which simplifies the AFTR module by relocating the NAPT
function among B4 elements located at the subscriber's premises. In
the lw4o6 architecture, the functional elements are referred to as
the lwB4 and lwAFTR.
The lwB4 is provisioned with an IPv6 address, a public IPv4 address
and a port-set. It performs port-restricted NAPT on subscriber's
packets using the provisioned public IPv4 address and port-set. IPv4
packets are routed between the lwB4 and the lwAFTR encapsulated in an
IPv4 in IPv6 Softwire. The lwAFTR maintains one binding entry per-
subscriber, consisting of the lwB4's IPv6 tunnel endpoint, IPv4
address and port-set. Section 4.4 of [RFC6346] provides more detail
of this mechanism.
This can bring a number of advantages when compared to DS-Lite:
o Per-subscriber configuration allows for the operator to provision
each subscriber according to their specific service requirements.
o The logging requirements to meet regulatory requirements may be
reduced as it is only necessary to log when a subscriber is
provisioned or de-provisioned in the lwAFTR. This relaxes the
need for logging on a per-session, or per port block allocation.
o In some lw4o6 deployment topologies, the removal of per-session
state means that it is possible to have very large parallelisation
of lwAFTR elements. This offers excellent scaling and resilience.
o This mechanism preserves the dynamic feature of IPv4/IPv6 address
binding as in DS-Lite, so it has no coupling between IPv6 address
and IPv4 address/port-set as any full stateless solution
([RFC6052] or [RFC7597]) requires.
The terminology used in this document follows the definitions and
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abbreviations from [RFC6333] and [RFC7596].
2. Deployment Models
Lightweight 4over6 is suitable for operators who would like to free
any correlation of the IPv6 address with IPv4 address and port-set,
as the IPv4 addressing is an overlay to the IPv6 addressing
architecture. Thus, IPv6 addressing is completely flexible to fit
other deployment requirements, e.g., auto-configuration, service
classification, user management, QoS support, etc.
Lightweight 4over6 can be deployed in a residential ISP network
(depicted in Figure 1). In this scenario, a lwB4 acquires an IPv4
address and a port-set alongside IPv6 provisioning, including an
address for the lwAFTR. It then establishes an IPv4-in-IPv6 softwire
to the lwAFTR. The lwB4 function may be implemented in a CPE
providing IPv4 services for a home network, or directly in a host.
The lwAFTR holds a table with the bindings between the lwB4's IPv6
addresses and their allocated IPv4 addresses + port sets. The
supporting system is used to syncronise the lwB4 and lwAFTR binding
information. It may also be used for logging and user management.
+---------------+
| Supporting |
| System |
+-------+-------+
|
+---------------+-------------+
| |
+---------+ +------+---+ |
| Host | | lwB4 | _ _ |
| |--| |=======( ` )=======+----+----+ +-----------+
+---------+ +----------+ ( ) _ | | | IPv4 |
( IPv6 ) ) | lwAFTR |---| Internet |
+---------+ +------+---+ ( Network ) | | | |
| Host |--| lwB4 |====( ( ) ====+---------+ +-----------+
| | | | `(_, __)
+---------+ +----------+
Figure 1 Architectural Overview
2.1. Top-Down Deployment Model
In the top-down deployment model, the supporting system holds the
overall binding table for the network. It uses this to pre-provision
the local binding table entries for the lwAFTR and also provision
lwB4s with the correct configuration (e.g. using DHCPv6 or PCP).
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With this method, one binding table entry can be present on lwAFTRs
and stateless failover can be achieved.
2.2. Bottom-Up Deployment Model
In the bottom-up model, the client is first provisioned with the
relevant paramters necessary for building the softwire. It then
attempts to send traffic to the lwAFTR.
On receipt of lwB4 traffic which does not have an existing binding-
table entry, one is dynamically created. The lwAFTR reports the new
binding entry to the supporting system.
[I-D.ietf-behave-syslog-nat-logging] or
[I-D.ietf-behave-ipfix-nat-logging] may be used for this purpose. In
this way, the lwAFTR can determine the binding by its own and there
is little impact on existing network architecture.
2.3. Campus Deployment
Lightweight 4over6 can also be deployed in a campus or enterprise
network, (depicted in Figure 2). In this scenario, a lwB4 acts as a
gateway router for a number of hosts. The lwB4 is first provisioned
with an IPv4 address and port-set. It then establishes an IPv4-in-
IPv6 softwire using the IPv6 address to deliver IPv4 services to its
connected host via the lwAFTR in the network. A network management
system could be used to receive statistic information of the network
equipments, such as the binding table, network load, and connected
device. NETCONF [RFC6241] could be used for syncronising lwB4's IPv6
address and its allocated IPv4 address + port set with the lwAFTR.
The network management system may keep the binding information as
well for logging and user management.
3. Overall Deployment Considerations
3.1. IP Addressing and Routing
In Lightweight 4over6, there is no inter-dependency between the IPv4
and IPv6 addressing schemes. This allows for complete flexibilty in
addressing architecture.
3.1.1. IPv4 Routing
The IPv4 addresses/prefixes that are allocated to customer's lwB4s
are advertised to the IPv4 Internet as being reachable via the
lwAFTR(s). If multiple lwAFTRs are all serving the same set of
lwB4s, all will advertise the same IPv4 reachable routes.
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3.1.2. IPv6 Routing
The lwAFTR provides a /128 IPv6 tunnel endpoint address which is
advertsed to the lwB4s. If multiple lwAFTRs are all serving the same
set of lwB4s, all will advertise the same IPv6 tunnel endpoing
address.
The lwB4's IPv6 addressing and routing, there are no specific
topological limitations. An existing IPv6 address and routing
architecture should not be affected. For example, in PPPoE scenario,
a CPE could obtain a prefix via DHCPv6 prefix delegation, and the
hosts behind CPE would get its own IPv6 addresses within the prefix
through SLAAC or DHCPv6 statefully. This IPv6 address assignment
procedure has nothing to do with restricted IPv4 address allocation.
It is worth noting that if the Top-Down provisioning model is chosen,
then there must be determinism in the local address that the lwB4
uses for building its tunnel. This is so that the binding entry for
the lwB4 can be pre-provisioned in the lwAFTR. [RFC7598] offers a
solution for this using the 'bind-ipv6-prefix' field is used to
inform the lwB4 which configured prefix to use. The suffix is then
created according to Section 6 of [RFC7597].
3.2. lwB4 Configuration
In lw4o6, each lwB4 will get its restricted IPv4 address and a port-
set after successful user authentication process and IPv6
provisioning process. This assignment can been achieved using a
number of methods:
o DHCPv6 Softwire S46 Option [RFC7598]
o DHCPv4 over DHCPv6 [RFC7341], [RFC7618] and
[I-D.ietf-dhc-dhcp4o6-saddr-opt]
o PCP [RFC7753]
o NETCONF/YANG [I-D.ietf-softwire-yang]
3.2.1. DHCPv6 Based Provisioning
[RFC7598] describes a set of DHCPv6 options used for provisioning
lw4o6 clients. OPTION_S46_CONT_LW (96) is a DHCPv6 contatiner
option, which can hold the IPv6 of the lwAFTR (OPTION_S46_BR (90)),
the lwB4's IPv4 address and IPv6 prefix hint (OPTION_S46_V4V6BIND
(92)), and port set information (OPTION_S46_PORTPARAMS (93)).
In this model, the DHCPv6 server needs to be pre-provisioned with the
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client configuration. Therefore, this approach is better suited to
client configurations that will be long-lived.
DHCPv6 based provisioning can also be used in conjunction with a AAA
server. [I-D.ietf-softwire-map-radius] decribes this function.
3.2.2. DHCPv4 over DHCPv6 Based Provisioning
An operator may use DHCPv4 to provision IPv4 address to the lwB4. In
a typical deployment, the DHCP server is a centralized DHCP server
and lwAFTR is the DHCP relay agent to relay the dhcp messages to the
server over unicast. Rarely DHCP server will collocate with the
lwAFTR to provision IPv4 resources to the lwB4.
3.2.3. PCP Based Provisioning
Operator may also use PCP Port-set Option to provision IPv4 address
and port-set to the lwB4. In a typical deployment, PCP server will
collocate with lwAFTR, and the subscriber's binding can be determined
by lwAFTR. The PCP request should be sent to the lwAFTR's tunnel
end-point address. It is not common that PCP server will be
centralized deployed in which the lwAFTR is the PCP proxy to relay
PCP requests.
3.2.4. NETCONF/YANG Based Provisioning
Operators using NETCONF to manage customer devices can provision
lw4o6 using [I-D.ietf-softwire-yang].
3.2.5. Other lwB4 Configuation Considerations
Some operators may offer different service level agreements (SLA) to
users that some users may require more ports then others. In this
deployment scenario, the operator can implement differentiated
policies in provisioning system specified to a user's lwB4 or a group
of lwB4s to allocate a certain range of port-set. The lwAFTR may
also run multiple instances with different port-set sizes to build
the mapping table.
It is also worth noting the compatibility between lw4o6 and Public
IPv4 over IPv6 [RFC7040]. When a lw4o6 client is provisioned with a
'full' IPv4 address (i.e. with no port-set or a port-set that allows
the use of all of the L4 ports), then the A+P routing model is no
longer used by the lwAFTR as traffic is routed on the IPv4 address
only. This function can be useful when a subscriber usses protocols
which do not have L4 ports.
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3.3. lwAFTR Discovery
The lwB4 needs to discover the lwAFTR's IPv6 address before it is
able to set up the softwire tunnel and provide any IPv4 services.
This address can be learned through an out-of-band channel, static
configuration, or dynamic configuration. In practice, Lightweight
4over6 lwB4 can use the same DHCPv6 option [RFC6334] to discover the
FQDN of the lwAFTR.
When Lightweight 4over6 is deployed in the same place with DS-Lite,
either different FQDNs can be configured for Lightweight 4over6 and
DS-Lite separately or different DHCPv6 options can be used for
Lightweight 4over6 [RFC7598] and DS-Lite. More detailed
considerations on DS-Lite compatibility will be discussed in
Section 6.
The lw4o6 DHCPv6 option (OPTION_S46_LW_CONT (96)) can contain
OPTION_S46_BR (90) which holds the v6 address of the lwAFTR.
3.4. Impacts on Accouting
In lw4o6, the accounting impact due to the tunneling protocol is the
same with DS-Lite (see section 6.2 of [RFC6908]). However, since in
lw4o6, the IPv4 service is only available after port-set allocation,
if operators regard IPv4 service as a on-demand value-added service,
e.g. IPv6 connectivity is offered by default, while IPv4
connectivity will be offered untill a subscriber requires, etc., IPv4
service accounting should start after port-set allocation has
completed.
It should be noted that in common with all A+P mechanisms, lw4o6 can
not performing per-session logging in the way that CGN based
solutions do.
4. lwAFTR Deployment Considerations
As Lightweight 4over6 is an extension to DS-Lite, both technologies
share similar deployment considerations. For example: the interface
considerations, lawful intercept considerations, blacklisting a
shared IPv4 Address, AFTR policies, and impacts on accounting
processes described in [RFC6908] are also applicable here. This
document only discusses addtional considerations specific to
Lightweight 4over6.
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4.1. Logging at the lwAFTR
In lw4o6, operators only log one entry per subscriber. Each log
needs to include subscriber's IPv6 address used for the softwire, the
public IPv4 address and the allocated port-set, and the start and end
times that the binding entry was valid for.
To ensure consistency of the logged information, the port set
algorithm implemented in lw4o6 lwAFTR needs to be synchronized with
the one implemented in the logging system. For example, if
contiguous port-set algorithm is adopted in the lwAFTR, the same
algorithm needs to be applied for the logging system.
Since the binding in lwAFTR does not log sessions as they are set up,
operators should be aware that lw4o6 does not provided a mechanism
for destination-specific logging.
4.2. MTU and Fragmentation Considerations
As Lightweight 4over6 uses a tunneling protocol, the same
considerations regarding fragmentation and reassembly as for DS-Lite
[RFC6908] are applicable. In order to avoid the problems that are
associated with fragmentation, it is advisable to ensure that the MTU
across the IPv6 domain between the lwB4 and lwAFTR is large enough to
allow for the transportation of IPv4 packets plus the 40-byte
overhead for IPv6 encapsulation.
4.3. Reliability Considerations of lwAFTR
Operators may deploy multiple lwAFTRs for robustness, reliability,
and load balancing. In lw4o6, subscriber to IPv4 and port-set
mapping needs to be pre-provisioned in the lwAFTR before an IPv4
service can be provided.
For redundancy, one or more backup lwAFTR can have the subscriber
bindings already provisioned, e.g. as part of the top-down
provisioning process described above. In this case, the provisioning
system is responsible for ensuring that the binding tables of the
lwAFTRS are consistent. In this case, as customer traffic arriving
or returning through either of the lwAFTRs will be processed in the
same way, an active/active redundancy model is possbile.
A second option, which could be more suitable for bottom-up
provisioning, is for the bindings to be replicated between the
primary lwAFTR and the backup lwAFTR. When the primary lwAFTR fails,
the backup lwAFTR has the necessary binding table entries to
correctly forward subscriber traffic. In this mode, the internal
hosts are not required to re-initiate the bindings with the external
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hosts. In lw4o6, as the number of binding states have been greatly
reduced compared to DS-Lite, it is reasonable to adopt Hot Standby
mode when there are only two lwAFTRs (a primary and a backup lwAFTR).
However, if the number of lwAFTRs is larger than two, it is not
scalable to deploy using hot standby mode since each two of the
lwAFTRs should to syncronize the binding states.
4.4. Location of lwAFTRs in the Network
lwAFTR(s) can be deployed in a centralized or a distributed manner.
For a centralized deployment, the lwAFTR(s) are locacate in central
aggregation points in the network, such as a core site, the exit
point from a MAN etc. As the lwAFTR provides the gateway between the
IPv6 and IPv4 networks, it allows single stack IPv6 to be deployed in
the access part of the network.
In a distributed deployment, lwAFTR function is integrated with the
BRAS/SR. Since newly emerging customers might be distributed in the
whole Metro area, we have to deploy lwAFTR on all BRAS/SRs. This
will cost a lot in the initial phase of the IPv6 transition period.
This model also has the drawback of requiring both IPv4 and IPv6 to
the BRAS/Service Router devices and so is unsuitable for providers
wishing to build a single stack IPv6 only core.
4.5. Path Consistency Consideration
In Lightweight 4over6, if the binding state is not syncronized among
multiple lwAFTRs, the lwAFTR in which the subscriber's binding state
is stored should be exactly the one to service the subscriber.
Otherwise, there will be no match in the lwAFTR. This can be
achieved by using a unique IPv6 tunnel endpoint address and
corresponding reachable public IPv4 customer prefix for each lwAFTR.
If multiple lwAFTRs are deployed for resilience or scalability, using
the top-down provisioning model, all of the lwAFTRs in this cluster
will share the same IPv6 tunnel endpoint and set of reachable
prefixes. In this case, any packet arriving at any of the cluster
members will be processed in the same way. However, it is worth
considering using ECMP with flow-hashing so that a single customer's
traffic will be processed by the same lwAFTR. This will reduce the
change of packet re-ordering.
In Lightweight 4over6, if the binding state is not syncronized among
multiple lwAFTRs, the lwAFTR in which the subscriber's binding state
is stored should be exactly the one to service the subscriber.
Otherwise, there will be no match in lwAFTR. This requires the
provionsion packets (either using DHCPv4-over-DHCPv6 or PCP Port-set)
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should arrive at the same lwAFTR as the subsquent IP-in-IP traffic.
If multiple lwAFTRs are using the same Tunnel End Point address and
there are intermediate routers between lwB4 and lwAFTR, there might
be a problem when intermediate routers perform ECMP based on L4 hash
for the plain provionsion packets while doing L3 hash for subsequent
IP-in-IP traffic. In this case, it is recommended that the
provisioning packet is sent over IPv6 tunnel so that intermediate
routers can only process ECMP using L3 hash.
5. lwB4 Deployment Considerations
For the lwB4, the DNS Deployment Considerations and B4 Remote
Management in [RFC6908] can also be applied here. In this section,
only additional considerations relevant to lw4o6 are discussed.
5.1. NAT Traversal Issues
In lw4o6, as the subscriber's traffic source port will be restricted
to the port-set allocated from the provisioning system, there will be
an impact on some NAT traversal mechanisms. For example, in UPnP
1.0, the external port number that can be used by a remote peer is
selected by a UPnP client in end host. If the client randomly
selects a port number which dos not fall in that valid port-set, the
UPnP process will fail.
This is likely to happen because an end-host does not have knowledge
of the port-set which has been allocated to the lwB4. More detailed
experimental results can be found in
[I-D.deng-aplusp-experiment-results]. This problem will not exist in
UPnP 2.0 because the end-host's UPnP client in the will negotiate the
external port number with the server. Another way is to implement a
mechanism (e.g. [RFC7753]) in end host to fetch the allocated port-
set from the lwB4. The UPnP client can then select the port number
within the port-set.
5.2. Static Port Forwarding Configuration
Currently, some externally initiated applications rely on manual
configuration to reserve a port in the CPE. The restricted port-set
used by the lwB4 may be problematic for manual port forwarding
configuration. It is recommended that the port-set allocated from
the provioning system should be visible to the user (e.g. via the
configuration interface of a HGW which implements the lwB4 function),
which can be used as a hint for subscribers to add port forwarding
mapping.
It should also be noted that the well-known ports are not generally
allocated to a lwB4, unless the client is being allocated a full IPv4
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address with no address sharing ([RFC7596], Section 5.1). If the
user wishes to make a service running on an end-host using a well-
known port externally accessible, it is necessary to configure the
lwB4's port-forwarding to re-map the well-known port to a port taken
from the allocated port-set.
6. DS-Lite Compatibility Consideration
Lightweight 4over6 can be either deployed as a complete solution, or
in conjuction with DS-Lite. Since Lightweight 4over6 does not any
have extra requirement on IPv6 addressing, it can use use the same
addressing scheme with DS-Lite, together with routing policy, user
management policy, etc. Besides, the bottom-up model has quite
similar requirement and workflow on the supporting system with DS-
Lite. Therefore, it is suitable for operators to deploy
incrementally in existing DS-Lite network
6.1. Case 1: Integrated Network Element with Lightweight 4over6 and DS-
Lite AFTR Scenario
In this case, DS-Lite has been deployed in the network. Later in the
deployment schedule, the operator decided to implement Lightweight
4over6 lwAFTR function in the same network element (depicted in
Figure3, below). Therefore, the same network element needs to
support both transition mechanisms.
There are two options to distinguish the traffic from two transition
mechanisms.
The first one is to distinguish using the client's source IPv4
address. The IPv4 address from Lightweight 4over6 is public address
as NAT has been done in the lwB4, and IPv4 address for DS-lite is
private address as NAT will be done on AFTR. When the network
element receives an encapsulated packet, it would de-capsulate packet
and apply the transition mechanism based on the IPv4 source address
in the packet. This requires the network element to examine every
packet and may introduce significant extra load to the network
element. However, both the B4 element and Lightweight 4over6 lwB4
can use the same DHCPv6 option [RFC6334] with the same FQDN of the
AFTR and lwAFTR.
The second one is to distinguish using the destination's tunnel IPv6
address. One network element can run separated instances for
Lightweight 4over6 and DS-Lite with different tunnel addresses. Then
B4 element and Lightweight 4over6 lwB4 can use the same DHCPv6 option
[RFC6334] with different FQDNs pointing to corresponding tunnel
addresses. This requires the supporting system should distinguish
different types of users when assigning the FQDNs in DHCPv6 process.
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Another option is to use a new DHCPv6 option [RFC7598] to discover
the lwAFTR's FQDN.
+---------------+--------------|
+ | |
+---------+ +------+---+ +--+--+ |
| Host | | LW 4over6| | | |
| |--| lwB4 | ======-| BNG | === +-------------+ +-----------+
+---------+ +----------+ +--|--+ |LW 4over6 | | IPv4 |
|lwAFTR/ |---| Internet |
+---------+ +------+---+ +--+--+ |DS-Lite AFTR | | |
| Host |--| DS-Lite | =======| | ====+-------------+ +-----------+
| | | B4 | | BNG | |
+---------+ +----------+ +--|--+ |
+ | |
+---------------+--------------+
Figure 3 DS-Lite Coexistence scenario with Integrated AFTR
6.2. Case 2: DS-Lite Coexistent scenario with Separated AFTR
This is similar to Case 1. The difference is the lwAFTR and AFTR
functions won't be co-located in the same network element (depicted
in Figure4). This use case decouples the functions to allow more
flexible deployment. For example, an operator may deploy AFTR closer
to the edge and lwAFTR closer to the core. Moreover, it does not
require the network element to pre-configure with the CPE's IPv6
addresses. An operator can deploy more AFTR and lwAFTR at needed.
However, this requires the B4 and lwB4 to discover the corresponding
network element. In this case, B4 element and Lightweight 4over6
lwB4 can still use [RFC6334] with different FQDNs pointing to
corresponding tunnel end-point addresses, and the supporting system
should distinguish different types of users.
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+------------------+-----------------|
| | |
+---------+ +------+---+ +------+-----+ |
| Host |__| LW 4over6| | BNG | |
| | | lwB4 |=======|DS-Lite AFTR|=====+------------+ +----------+
+---------+ +----------+ +------+-----+ | lw4o6 | | IPv4 |
| lwAFTR |---| Internet |
+---------+ +------+---+ +------+-----+ | | | |
| Host |__| DS-Lite |=======| BNG |=====+------------+ +----------+
| | | B4 | |DS-Lite AFTR| |
+---------+ +----------+ +------+-----+ |
| | |
+------------------+-----------------+
Figure 4 DS-Lite Co-existence scenario with Seperated AFTR/lwAFTR
7. Acknowledgements
TBD
8. References
[I-D.bajko-pripaddrassign]
Bajko, G., Savolainen, T., Boucadair, M., and P. Levis,
"Port Restricted IP Address Assignment", draft-bajko-
pripaddrassign-04 (work in progress), April 2012.
[I-D.cui-softwire-b4-translated-ds-lite]
Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
Farrer, "Lightweight 4over6: An Extension to the DS-Lite
Architecture", draft-cui-softwire-b4-translated-ds-lite-11
(work in progress), February 2013.
[I-D.deng-aplusp-experiment-results]
Deng, X., Boucadair, M., and F. Telecom, "Implementing A+P
in the provider's IPv6-only network", draft-deng-aplusp-
experiment-results-00 (work in progress), March 2011.
[I-D.ietf-behave-ipfix-nat-logging]
Sivakumar, S. and R. Penno, "IPFIX Information Elements
for logging NAT Events", draft-ietf-behave-ipfix-nat-
logging-13 (work in progress), January 2017.
[I-D.ietf-behave-syslog-nat-logging]
Chen, Z., Zhou, C., Tsou, T., and T. Taylor, "Syslog
Format for NAT Logging", draft-ietf-behave-syslog-nat-
logging-06 (work in progress), January 2014.
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[I-D.ietf-dhc-dhcp4o6-saddr-opt]
Farrer, I., Sun, Q., Cui, Y., and L. Sun, "DHCPv4 over
DHCPv6 Source Address Option", draft-ietf-dhc-dhcp4o6-
saddr-opt-00 (work in progress), March 2017.
[I-D.ietf-pcp-base]
Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)", draft-ietf-pcp-
base-29 (work in progress), November 2012.
[I-D.ietf-softwire-dslite-deployment]
Lee, Y., Maglione, R., Williams, C., Jacquenet, C., and M.
Boucadair, "Deployment Considerations for Dual-Stack
Lite", draft-ietf-softwire-dslite-deployment-08 (work in
progress), January 2013.
[I-D.ietf-softwire-map-radius]
Jiang, S., Fu, Y., Liu, B., Deacon, P., Xie, C., and T.
Li, "RADIUS Attribute for Softwire Address plus Port based
Mechanisms", draft-ietf-softwire-map-radius-12 (work in
progress), May 2017.
[I-D.ietf-softwire-yang]
Sun, Q., Wang, H., Cui, Y., Farrer, I., Zoric, S.,
Boucadair, M., and R. Asati, "A YANG Data Model for IPv4-
in-IPv6 Softwires", draft-ietf-softwire-yang-01 (work in
progress), October 2016.
[I-D.lee-softwire-lw4over6-failover]
Lee, Y., Qiong, Q., and C. Liu, "Simple Failover Mechanism
for Lightweight 4over6", draft-lee-softwire-
lw4over6-failover-01 (work in progress), July 2013.
[I-D.sun-softwire-lw4over6-dhcpv6]
Xie, C., Qiong, Q., Lee, Y., Tsou, T., and P. Wu, "Dynamic
Host Configuration Protocol for IPv6 (DHCPv6) Option for
Lightweight 4over6", draft-sun-softwire-lw4over6-dhcpv6-00
(work in progress), July 2013.
[I-D.zhou-dime-4over6-provisioning]
Zhou, C., Taylor, T., Qiong, Q., and M. Boucadair,
"Attribute-Value Pairs For Provisioning Customer Equipment
Supporting IPv4-Over-IPv6 Transitional Solutions", draft-
zhou-dime-4over6-provisioning-05 (work in progress),
September 2014.
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[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>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010,
<http://www.rfc-editor.org/info/rfc6052>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<http://www.rfc-editor.org/info/rfc6241>.
[RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
Stack Lite Broadband Deployments Following IPv4
Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
<http://www.rfc-editor.org/info/rfc6333>.
[RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
RFC 6334, DOI 10.17487/RFC6334, August 2011,
<http://www.rfc-editor.org/info/rfc6334>.
[RFC6346] Bush, R., Ed., "The Address plus Port (A+P) Approach to
the IPv4 Address Shortage", RFC 6346,
DOI 10.17487/RFC6346, August 2011,
<http://www.rfc-editor.org/info/rfc6346>.
[RFC6431] Boucadair, M., Levis, P., Bajko, G., Savolainen, T., and
T. Tsou, "Huawei Port Range Configuration Options for PPP
IP Control Protocol (IPCP)", RFC 6431,
DOI 10.17487/RFC6431, November 2011,
<http://www.rfc-editor.org/info/rfc6431>.
[RFC6908] Lee, Y., Maglione, R., Williams, C., Jacquenet, C., and M.
Boucadair, "Deployment Considerations for Dual-Stack
Lite", RFC 6908, DOI 10.17487/RFC6908, March 2013,
<http://www.rfc-editor.org/info/rfc6908>.
[RFC7040] Cui, Y., Wu, J., Wu, P., Vautrin, O., and Y. Lee, "Public
IPv4-over-IPv6 Access Network", RFC 7040,
DOI 10.17487/RFC7040, November 2013,
<http://www.rfc-editor.org/info/rfc7040>.
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[RFC7341] Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I.
Farrer, "DHCPv4-over-DHCPv6 (DHCP 4o6) Transport",
RFC 7341, DOI 10.17487/RFC7341, August 2014,
<http://www.rfc-editor.org/info/rfc7341>.
[RFC7596] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
Farrer, "Lightweight 4over6: An Extension to the Dual-
Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
July 2015, <http://www.rfc-editor.org/info/rfc7596>.
[RFC7597] Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
Murakami, T., and T. Taylor, Ed., "Mapping of Address and
Port with Encapsulation (MAP-E)", RFC 7597,
DOI 10.17487/RFC7597, July 2015,
<http://www.rfc-editor.org/info/rfc7597>.
[RFC7598] Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec,
W., Bao, C., Yeh, L., and X. Deng, "DHCPv6 Options for
Configuration of Softwire Address and Port-Mapped
Clients", RFC 7598, DOI 10.17487/RFC7598, July 2015,
<http://www.rfc-editor.org/info/rfc7598>.
[RFC7600] Despres, R., Jiang, S., Ed., Penno, R., Lee, Y., Chen, G.,
and M. Chen, "IPv4 Residual Deployment via IPv6 - A
Stateless Solution (4rd)", RFC 7600, DOI 10.17487/RFC7600,
July 2015, <http://www.rfc-editor.org/info/rfc7600>.
[RFC7618] Cui, Y., Sun, Q., Farrer, I., Lee, Y., Sun, Q., and M.
Boucadair, "Dynamic Allocation of Shared IPv4 Addresses",
RFC 7618, DOI 10.17487/RFC7618, August 2015,
<http://www.rfc-editor.org/info/rfc7618>.
[RFC7753] Sun, Q., Boucadair, M., Sivakumar, S., Zhou, C., Tsou, T.,
and S. Perreault, "Port Control Protocol (PCP) Extension
for Port-Set Allocation", RFC 7753, DOI 10.17487/RFC7753,
February 2016, <http://www.rfc-editor.org/info/rfc7753>.
Appendix A. China Telecom Experimental Results
We have deployed Lightweight 4over6 in our operational network of
HuNan province, China. It is designed for broadband access network,
and different versions of the lwB4 function have been implemented
including a Linksys device, a software client for Windows XP, Windows
Vista and Windows 7.
It can be integrated with existing dial-up mechanisms such as PPPoE,
etc. The major objectives listed below aimed to verify the
functionality and performance of Lightweight 4over6:
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o Verify how to deploy Lightweight 4over6 in a practical network.
o Verify the impact of applications with Lightweight 4over6.
o Verify the performance of Lightweight 4over6.
A.1. Experimental Environment
The network topology for this experiment is depicted in Figure 5.
+--------+
+-----+ +-------+ | Syslog |
|Host1+--+lwB4 |----+ | Server |
+-----+ +-------+ | +---+----+ ---------
| /------\ | // \\
| // \\ | / \
+-----+ +-------+ +-+--+ | IPv6 | +---+----+ | |
|Host2+--|lwB4 |----+BRAS+--| Network |---|lwAFTR +-+ IPv4 Internet +
+-----+ +-------+ +-+--+ \\ // +--------+ | |
| \--+---/ (PCP Server) \ /
| | \\ //
+-----+ +-------+ | | ---------
|Host3+--+lwB4 +----+ |
+-----+ +-------+ | ---------
| // \\
| / \
| | |
+--------------------+ IPv6 Internet +
| |
\ /
\\ //
---------
Figure 5 China Telecom Lightweight 4over6 Experiment Topology
In this deployment model, the lwAFTR is co-located with an extended
PCP server to assign port-restricted IPv4 addresses and port-sets to
lwB4s. It also triggers subscriber-based logging event to a
centrilized syslog server. IPv6 address pools for subscribers have
been distributed to BRASs for configuration, while the available
public IPv4 address pools are configured by the centralized lwAFTR
with a default address sharing ratio. It is rather flexible for IPv6
addressing and routing, and there is little impact on existing IPv6
architecture.
In our experiment, lwB4 will firstly get its IPv6 address and
delegated prefix through PPPoE, and then initiate a PCP-extended
request to get public IPv4 address and its valid port set. The
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lwAFTR will thus create a subscriber-based state accordingly, and
notify the syslog server with {IPv6 address, IPv4 address, port set,
timestamp}.
A.2. Experimental Results
In our trial, we mainly focused on application and performance tests.
The applications tested include web (HTTP/HTTPS), email, instant
messaging, FTP, telnet, SSH, video, Video Camera, P2P, online gaming,
and VoIP.
For the performance tests, we measured the number of concurrent
session and throughput performance.
The experimental results are listed as follows:
+--------------------+----------------------+-----------------------+
| Application Type | Test Result |Port Number Occupation |
+--------------------+----------------------+-----------------------+
| Web | OK | normal websites: 10~20|
| | IE, Firefox, Chrome | Ajex Flash webs: 30~40|
+--------------------+----------------------+-----------------------+
| Video | ok, web based or | 30~40 |
| | client based | |
+--------------------+----------------------+-----------------------+
| Instant Message | OK | |
| | QQ, MSN, gtalk, skype| 8~20 |
+--------------------+----------------------+-----------------------+
| P2P | OK | lower speed: 20~600 |
| |utorrent,emule,xunlei | (per seed) |
| | | higher speed: 150~300 |
+--------------------+----------------------+-----------------------+
| FTP | need ALG for active | 2 |
| | mode, flashxp | |
+--------------------+----------------------+-----------------------+
| SSH, TELNET | OK |1 for SSH, 3 for telnet|
+--------------------+----------------------+-----------------------+
| online game | OK for QQ, flash game| 20~40 |
+--------------------+----------------------+-----------------------+
Figure 6 China Telecom Lightweight 4over6 Experiment Results
The performance tests for the lwAFTR are taken using a PC. Due to
limitations of the PC hardware, the overall throughput is limited to
around 800 Mbps. However, it can still support more than one hundred
million concurrent sessions.
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A.3. Conclusions
From the experiment, we reached the following conclusions:
o Lightweight 4over6 has good scalability. As it is a lightweight
solution that only maintains per-subscription state information,
it can easily support a large amount of concurrent subscribers.
o Lightweight 4over6 can be deployed rapidly. No modifications to
the existing addressing and routing system in our operational
network was necessary. Logging of customer address allocations
was easy to implement.
o Lightweight 4over6 can support the majority of current IPv4
applications commonly in use.
Appendix B. Tsinghua University Experimental Result
Lightweight 4over6 has been deployed in the campus of Tsinghua
University, China. DHCPv4o6 [RFC7341] is used for dynamically
provisioning the lwB4's IPv4 address and port set [RFC7618].
Wireless APs for Lightweight 4over6, were deployed, covering a large
portion of the campus, allowing mobile devices to connect to the
lwB4. We also deployed a lwB4 gateway in some of our buildings so
that end device could connect directly to the lwB4. Users access the
IPv4 Internet through the China Next Generation Internet (CNGI) IPv6
Network.
B.1. Experimental Environment
The network topology for this experiment is depicted in Figure 7.
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+-----+ ------- ---------
|Host1+---+ / \ // \\
+-----+ | // \\ / \
+-----+ | +--------+ | CNGI IPv6 | +--------+ | |
|Host2+---+--+lwB4(AP)+--+--| Network |--+ lwAFTR +---+ IPv4 Internet +
+-----+ | +--------+ | \\ // +--------+ | |
+-----+ | | \ / (DHCP4o6 Server) \ /
|Host3+---+ | --+---- \\ //
+-----+ | | ---------
| |
+-----+ | | ---------
|Host4+---+ | | // \\
+-----+ | +------+ | | / \
+---+lwB4 +---+ | | |
+-----+ | +------+ +-----------------------+ IPv6 Internet +
|Host5+---+ | |
+-----+ \ /
\\ //
---------
Figure 7 Tsinghua University Lightweight 4over6 Experiment Topology
In this deployment model, the lwAFTR is co-located with a DHCP4o6
server to assign port-restricted IPv4 addresses and port-sets to the
lwB4. The lwAFTR snoops the DHCPv4 over DHCPv6 messages generated or
received by the DHCP4o6 server and updates its binding table
accordingly.
In our experiment, the lwB4 receives its IPv6 address through static
or dynamic configuration. It then sends a DHCP4o6 request to the
lwAFTR device to get the public IPv4 address and valid port-set. The
lwAFTR will add the IPv6 address, IPv4 address, and port-set
information of the lwB4 into its binding table.
B.2. Experimental Results
In the Tsinghua University experiment, the performance of various
applications were tested including web (HTTP/HTTPS), email, instant
messaging, FTP, telnet, SSH, video, Video Camera, P2P, online gaming,
and VoIP. We also tested different terminal devices including PC/
laptop computers, and cell phone. These devices used different
operating systems, including Windows 7, MacOS, Android, and Apple
IOS.
The experimental results were as follows:
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+-----------------+------------------------+---------------------+------+
|Application Type | Test Applications | Test Subjects |Result|
+-----------------+------------------------+---------------------+------+
| Web | IE, Chrome, Sougou |Browse websites, | OK |
| | |download files | |
+-----------------+------------------------+---------------------+------+
| Video | Youku, pptv, qqlive |VOD, live video | OK |
| |(Web based,client based)| | |
+-----------------+------------------------+---------------------+------+
| P2P | Bittorrent, xunlei |Download files | OK |
+-----------------+------------------------+---------------------+------+
| Ping/tracert | Command line |Ping/tracert URL | OK |
+-----------------+------------------------+---------------------+------+
| TELNET/SSH | Putty, secureCRT |Telnet/SSH login | OK |
+-----------------+------------------------+---------------------+------+
| Email | 126, QQ, hotmail |Send/receive email | OK |
| |(Web based,client based)| | |
+-----------------+------------------------+---------------------+------+
| Cloud storage | Baidu Cloud |Upload/download files| OK |
+-----------------+------------------------+---------------------+------+
|Instant messaging| Skype, QQ |Send/receive messages| OK |
+-----------------+------------------------+---------------------+------+
|Online gaming | QQ game |Enter game | OK |
+-----------------+------------------------+---------------------+------+
|Online payment | JD, Taobao |Complete payment | OK |
+-----------------+------------------------+---------------------+------+
Figure 8 Tsinghua University Lightweight 4over6 experimental result
B.3. Conclusion
Lightweight 4over6 supports the majority of current IPv4 applications
and services. The user experience of using Lightweight 4over6 is no
different from using the native IPv4 network. It can satisfy the
IPv4 network service demands of IPv6 network users.
Authors' Addresses
Qiong Sun
China Telecom
Room 708, No.118, Xizhimennei Street
Beijing 100035
P.R.China
Phone: +86-10-58552936>
Email: sunqiong@ctbri.com.cn
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Chongfeng Xie
China Telecom
Room 708, No.118, Xizhimennei Street
Beijing 100035
P.R.China
Phone: +86-10-58552116>
Email: xiechf@ctbri.com.cn
Yiu L. Lee
Comcast
One Comcast Center
Philadelphia, PA 19103
USA
Email: yiu_lee@cable.comcast.com
Maoke Chen
FreeBit Co., Ltd.
13F E-space Tower, Maruyama-cho 3-6
Shibuya-ku, Tokyo 150-0044
Japan
Email: fibrib@gmail.com
Tianxiang Li
Tsinghua University
Beijing 100084
P.R.China
Phone: +86-10-6278-5822
Email: peter416733@gmail.com
Ian Farrer
Deutsche Telekom AG
Bonn 53227
Germany
Email: ian.farrer@telekom.de
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