6man Working Group S. Krishnan
Internet-Draft A. Kavanagh
Intended status: Standards Track B. Varga
Expires: March 24, 2011 Ericsson
S. Ooghe
Alcatel-Lucent
E. Nordmark
Oracle
September 20, 2010
Line identification in IPv6 Router Solicitation messages
draft-krishnan-6man-rs-mark-08
Abstract
In Ethernet based aggregation networks, several subscriber premises
may be logically connected to the same interface of an edge router.
This document proposes a method for the edge router to identify the
subscriber premises using the contents of the received Router
Solicitation messages. The applicability is limited to the N:1 VLAN
allocation model.
Status of this Memo
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This Internet-Draft will expire on March 24, 2011.
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Conventions used in this document . . . . . . . . . . . . 5
2. Issues with identifying the subscriber in an N:1 VLAN model . 6
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Basic operation . . . . . . . . . . . . . . . . . . . . . . . 6
5. Access Node Behavior . . . . . . . . . . . . . . . . . . . . . 6
5.1. On receiving a Router Solicitation from the end-device . . 6
5.2. On receiving a Router Advertisement from the Edge
Router . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2.1. Identifying tunneled Router Advertisements . . . . . . 7
5.3. On detecting a subscriber circuit coming up . . . . . . . 7
6. Edge Router Behavior . . . . . . . . . . . . . . . . . . . . . 8
6.1. On receiving a Tunneled Router Solicitation from the
Access Node . . . . . . . . . . . . . . . . . . . . . . . 8
6.2. On sending a Router Advertisement towards the
end-device . . . . . . . . . . . . . . . . . . . . . . . . 8
6.3. Sending periodic unsolicited Router Advertisements
towards the end-device . . . . . . . . . . . . . . . . . . 8
7. Line Identification Destination Option (LIO) . . . . . . . . . 9
8. Interactions with Secure Neighbor Discovery . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
10. Security Considerations . . . . . . . . . . . . . . . . . . . 10
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
12. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
DSL is a widely deployed access technology for Broadband Access for
Next Generation Networks. While traditionally DSL access networks
were PPP based some networks are migrating from the traditional PPP
access model into a pure IP-based Ethernet aggregated access
environment. Architectural and topological models of an Ethernet
aggregation network in context of DSL aggregation are described in
[TR101].
+----+ +----+ +----------+
|Host|---| RG |----| |
+----+ +----+ | |
| AN |\
+----+ +----+ | | \
|Host|---| RG |----| | \
+----+ +----+ +----------+ \ +----------+
\ | |
+-------------+ | |
| Aggregation | | Edge |
| Network |-------| Router |
+-------------+ | |
/ | |
+----------+ / +----------+
| | /
+----+ +----+ | | /
|Host|---| RG |----| AN |/
+----+ +----+ | |
| |
+----------+
Figure 1: Broadband Forum Network Architecture
One of the Ethernet and GPON aggregation models specified in this
document bridges sessions from multiple user ports behind a DSL
Access Node (AN), also referred to as a DSLAM, into a single VLAN in
the aggregation network. This is called the N:1 VLAN allocation
model.
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+----------+
| |
| |
| AN |\
| | \
| | \ VLANx
+----------+ \ +----------+
\ | |
+-------------+ | |
| Aggregation | VLANx | Edge |
| Network |-------| Router |
+-------------+ | |
/ | |
+----------+ / +----------+
| | / VLANx
| | /
| AN |/
| |
| |
+----------+
Figure 2: n:1 VLAN model
1.1. Terminology
1:1 VLAN It is a broadband network deployment
scenario where each user port is mapped to
a different VLAN on the Edge Router. The
uniqueness of the mapping is maintained in
the Access Node and across the Aggregation
Network.
N:1 VLAN It is a broadband network deployment
scenario where multiple user ports are
mapped to the same VLAN on the Edge Router.
The user ports may be located in the same
or different Access Nodes.
AN A DSL or GPON Access Node. The Access Node
terminates the phyiscal layer (e.g. DSL
termination function or GPON termination
function), may physically aggregate other
nodes implementing such functionality, or
may perform both functions at the same
time. This node contains at least one
standard Ethernet interface that serves as
its "northbound" interface into which it
aggregates traffic from several user ports
or Ethernet-based "southbound" interfaces.
It does not implement an IPv6 stack but
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performs some limited inspection/
modification of IPv6 packets.
Aggregation Network The part of the network stretching from the
Access Nodes to the Edge Router. In the
context of this document the aggregation
network is considered to be Ethernet based,
providing standard Ethernet interfaces at
the edges, for connecting the Access Nodes
and Broadband Network. It is comprised of
ethernet switches that provide very limited
IP functionality (e.g. IGMP snooping, MLD
snooping etc.).
Edge Router The Edge Router, also known as the
Broadband Network Gateway (BNG) is the
first IPv6 hop for the user. In the cases
where the RG is bridged, the BNG acts as
the default router for the hosts behind the
RG. In cases where the RG is routed, the
BNG acts as the default router for the RG
itself. This node implements IPv6 router
functionality.
GPON Gigabit-capable Passive Optical Network is
an optical access network that has been
introduced into the Broadband Forum
architecture in [TR156]
Host A node that implements IPv6 host
functionality.
RG A residential gateway device. It can be a
Layer 3 (routed) device similar to one
specified in or a Layer 2 (bridged) device.
The residential gateway for Broadband Forum
networks is defined in [TR124]
End-device A node that sends Router Solicitations and
processes received Router Advertisements.
When a Layer 3 RG is used it is considered
an end-device in the context of this
document. When a Layer 2 RG is used, the
host behind the RG is considered to be an
end-device in the context of this document.
1.2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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2. Issues with identifying the subscriber in an N:1 VLAN model
In a DSL or GPON based fixed Broadband Network, IPv6 end-devices are
connected to an Access Node (AN). These end-devices today will
typically send a Router Solicitation Message to the Edge Router, to
which the Edge Router responds with a Router Advertisement message.
The Router Advertisement typically contains a prefix that the end-
devices will use to automatically configure an IPv6 Address. Upon
sending the Router Solicitation message the node connecting the end-
device on the access circuit, typically an Access Node (AN), would
forward the RS to the Edge Router upstream over a switched network.
However, in such Ethernet-based aggregation networks, several
subscriber premises may be connected to the same interface of an edge
router (e.g. on the same VLAN). However, the edge router requires
some information to identify the end-device on the circuit the end-
device is connected on. To accomplish this, the AN needs to add line
identification information to the Router Solicitation message and
forward this to the Edge Router. This is analogous to the case where
DHCP is being used, and the line identification information is
inserted by a DHCP relay agent. This document proposes a method for
the edge router to identify the subscriber premises using the
contents of the received Router Solicitation messages.
3. Applicability
The line identification destination option is intended to be used
only for the N:1 VLAN deployment model. For the other VLAN
deployment models line identification can be achieved differently.
4. Basic operation
This document recommends tunneling Neighbor discovery packets inside
another IPv6 packet that uses a destination option to convey line
identification information. The Neighbor discovery packets are left
unmodified inside the encapsulating IPv6 packet. In particular, the
Hop Limit field of the ND message is not decremented when the packet
is being tunneled. This is because ND messages whose Hop Limit is
not 255 will be discarded by the receiver of such messages.
5. Access Node Behavior
5.1. On receiving a Router Solicitation from the end-device
When an end-device sends out a Router Solicitation, it is received by
the access node. The AN then tunnels the received Router
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Solicitation in a newly created IPv6 datagram with the Line
Identification Option (LIO). The AN forms a new IPv6 datagram whose
payload is the received Router Solicitation message as described in
[RFC2473] except that the Hop Limit field of the Router Solicitation
message MUST NOT be decremented. If the AN has an IPv6 address, it
SHOULD use this address in the Source Address field of the outer IPv6
datagram. Otherwise it MUST use the unspecified address as the
Source Address of the outer IPv6 datagram. The destination address
of the outer IPv6 datagram MUST be copied from the destination
address of the tunneled RS. The AN MUST insert a destination options
header between the outer IPv6 header and the payload. It MUST insert
a LIO destination option and set the line identification field of the
option to contain the circuit identifier corresponding to the logical
access loop port of the Access Node from which the RS was initiated.
5.2. On receiving a Router Advertisement from the Edge Router
When the edge router sends out a tunneled router advertisement in
response to the RS, it is received by the access node. If there is
an LIO option present, the AN MUST use the line identification data
of the LIO option to identify the subscriber agent circuit of the
Access Node on which the RA should be sent. The AN MUST then remove
the outer IPv6 header of this tunneled RA and multicast the inner
packet (the original RA) on this specific subscriber circuit.
5.2.1. Identifying tunneled Router Advertisements
The Access Node can identify tunneled RAs by installing filters based
on the destination address of the outer packets, and the presence of
a destination option header with an LIO destination option.
5.3. On detecting a subscriber circuit coming up
RSs initiated by end-devices as described in Section 5.1 may be lost
due to lack of connectivity between the access node and the end-
device. To ensure that the end-device will receive an RA, the AN
needs to trigger the sending of periodic RAs on the edge router. For
this purpose, the AN needs to inform the edge router that a
subscriber circuit has come up. When the access node detects that a
subscriber circuit has come up, it MUST create a Router Solicitation
message as described in Section 6.3.7 of [RFC4861]. It MUST use the
unspecified address as the source address of this RS. It MUST then
tunnel this RS towards the edge router as described in Section 5.1.
In case there are connectivity issues between the AN and the edge
router, the RSes initiated by the AN can be lost. The AN MAY
continue retransmitting the Router Solicitations for a given LIO
until it receives an RA for that specific LIO.
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Alternately, the AN can send this notification about the subscriber
circuit coming up using a out-of-band mechanism with acknowledgements
like ANCP, if such mechanism is available.
6. Edge Router Behavior
6.1. On receiving a Tunneled Router Solicitation from the Access Node
When the edge router receives a tunneled Router Solicitation
forwarded by the access node, it needs to check if there is an LIO
destination option present in the outer datagram. The edge router
can use the contents of the line identification field to lookup the
addressing information and policy that need to be applied to the line
from which the Router Solicitation was received. The edge router
MUST then process the inner RS message as specified in [RFC4861]
6.2. On sending a Router Advertisement towards the end-device
When the edge router sends out a Router Advertisement in response to
a tunneled RS that included an LIO option, it MUST tunnel the Router
Advertisement in a newly created IPv6 datagram with the Line
Identification Option (LIO). The edge router creates the Router
Advertisement message as described in Section 6.2.3 of [RFC4861].
The edge router may use the contents of the LIO in the received
router solicitation to determine the contents of this router
advertisement(es. The Edge Router then forms a new IPv6 datagram,
whose payload is the Router Advertisement message, as described in
[RFC2473] except that the Hop Limit field of the Router Advertisement
message MUST NOT be decremented. The Edge router MUST use a link-
local IPv6 address on the outgoing interface in the Source Address
field of the outer IPv6 datagram. The destination address of the
outer IPv6 datagram MUST be set to [KNOWN_VALUE_X, say fe80::0] .
The edge router MUST insert a destination options header between the
outer IPv6 header and the payload. It MUST insert a LIO destination
option and set the line identification field of the option to contain
the circuit identifier corresponding to the logical access loop port
of the Access Node to which the RA MUST be sent. The IPv6
destination address of the inner RA MUST be set to the all-nodes
multicast address. The link-layer destination address of the
tunneled RA MUST be set to the unicast link-layer address of the
Access Node that sent the tunneled Router Solicitation which is being
responded to.
6.3. Sending periodic unsolicited Router Advertisements towards the
end-device
After sending a tunneled Router Advertisement as specified in
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Section 6.2 in response to a received RS, the edge router MUST store
the mapping between the LIO and the prefixes contained in the Router
Advertisement. It should then initiate periodic sending of
unsolicited Router Advertisements as described in Section 6.2.3. of
[RFC4861] . The Router Advertisements MUST be created and tunneled
as described in Section 6.2. The edge router MAY stop sending Router
Advertisements if it receives a notification from the AN that the
subscriber circuit has gone down. This notification can be received
out-of-band using a mechanism such as ANCP.
7. Line Identification Destination Option (LIO)
The Line Identification Destination Option (LIO) is a destination
option that can be included in IPv6 datagrams that tunnel Router
Solicitation and Router Advertisement messages. Multiple Line
Identification destination options MUST NOT be present in the same
IPv6 datagram. The LIO has an alignment requirement of (none).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Line Identification...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Line Identification Destination Option Layout
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Option Type
8-bit identifier of the type of option. The option identifier
for the line identification option will be allocated by the IANA.
Option Length
8-bit unsigned integer. The length of the option (excluding
the Option Type and Option Length fields). The value 0 is
considered invalid.
LineIDLen
Length of the Line Identification field in number of octets.
Line Identification
Variable length data inserted by the Access Node describing the
subscriber agent circuit identifier corresponding to the logical
access loop port of the Access Node from which the RS was
initiated.
8. Interactions with Secure Neighbor Discovery
Since the SEND [RFC3971] protected RS/RA packets are not modified in
anyway by the mechanism described in this document, there are no
issues with SEND verification.
9. Acknowledgements
The authors would like to thank Margaret Wasserman, Mark Townsley,
David Miles, John Kaippallimalil, Eric Levy-Abegnoli, Thomas Narten,
Olaf Bonness, Thomas Haag, Wojciech Dec, Brian Haberman, Ole Troan,
Hemant Singh, Jari Arkko and Joel Halpern for reviewing this document
and suggesting changes.
10. Security Considerations
The line identification information inserted by the access node or
the edge router is not protected. This means that this option may be
modified, inserted, or deleted without being detected. In order to
ensure validity of the contents of the line identification field, the
network between the access node and the edge router needs to be
trusted.
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11. IANA Considerations
This document defines a new IPv6 destination option for carrying line
identification. IANA is requested to assign a new destination option
type in the Destination Options registry maintained at
http://www.iana.org/assignments/ipv6-parameters
<TBA> Line Identification Option [RFCXXXX]
The act bits for this option need to be 10 and the chg bit needs to
be 0.
12. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, December 1998.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[TR101] Broadband Forum, "Migration to Ethernet-based DSL
aggregation", <http://www.broadband-forum.org/technical/
download/TR-101.pdf>.
[TR124] Broadband Forum, "Functional Requirements for Broadband
Residential Gateway Devices", <http://
www.broadband-forum.org/technical/download/
TR-124_Issue-2.pdf>.
[TR156] Broadband Forum, "Using GPON Access in the context of TR-
101", <http://www.broadband-forum.org/technical/download/
TR-156.pdf>.
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Authors' Addresses
Suresh Krishnan
Ericsson
8400 Blvd Decarie
Town of Mount Royal, Quebec
Canada
Email: suresh.krishnan@ericsson.com
Alan Kavanagh
Ericsson
8400 Blvd Decarie
Town of Mount Royal, Quebec
Canada
Email: alan.kavanagh@ericsson.com
Balazs Varga
Ericsson
Email: balazs.a.varga@ericsson.com
Sven Ooghe
Alcatel-Lucent
Copernicuslaan 50
2018 Antwerp,
Belgium
Phone:
Email: sven.ooghe@alcatel-lucent.com
Erik Nordmark
Oracle
17 Network Circle
Menlo Park, CA 94025
USA
Email: erik.nordmark@oracle.com
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