Internet DRAFT - draft-ietf-l2vpn-ipls
draft-ietf-l2vpn-ipls
L2VPN Working Group Himanshu Shah
Internet-Draft Ciena Corp
Intended Status: Historic
Eric Rosen
Francois Le Faucheur
Giles Heron
Cisco Systems
October 30, 2014
IP-Only LAN Service (IPLS)
draft-ietf-l2vpn-ipls-16.txt
Status of this Memo
This document is not an Internet Standards Track specificaion; it
is published for the historical record.
This document defines a Historic Document for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG).
Not all documents approved by the IESG are a candidate for any
level of Internet Standard; see section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6348.
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), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on April 30, 2015
Shah, el Expires April 2015 Page 1
Internet Draft draft-ietf-l2vpn-ipls-16.txt
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Abstract
A Virtual Private LAN Service (VPLS) is used to interconnect
systems across a wide-area or metropolitan-area network, making it
appear that they are on a private LAN. The systems which are
interconnected may themselves be LAN switches. If, however, they
are IP hosts or IP routers, certain simplifications to the operation
of the VPLS are possible. We call this simplified type of VPLS an
"IP-only LAN Service" (IPLS). In an IPLS, as in a VPLS, LAN
interfaces are run in promiscuous mode, and frames are forwarded
based on their destination MAC addresses. However, the maintenance
of the MAC forwarding tables is done via signaling, rather than via
the MAC address learning procedures specified in [IEEE 802.1D].
This draft specifies the protocol extensions and procedures for
support of the IPLS service.
The original intent was to provide an alternate solution to VPLS
for those PE routers that were not capable of learning MAC address
through data plane. This became a non-issue with newer hardware.
The concepts put forth by this draft are still valuable and are
adopted in one form or other by newer work such as Ethernet VPN
in L2VPN Working Group and possible data center applications. At
this point, no further action is planned to update this document
and is published simply as a historic record of the ideas.
Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
Shah, et al. Expires April 2015 Page 2
Internet Draft draft-ietf-l2vpn-ipls-16.txt
Table of Contents
Copyright Notice .................................................... 1
Abstract.............................................................. 2
1.0 Contributing Authors ............................................. 3
2.0 Overview.......................................................... 4
2.1 Terminology ..................................................... 7
3.0 Topology.......................................................... 8
4.0 Configuration..................................................... 9
5.0 Discovery........................................................ 10
5.1 CE discovery ................................................... 10
5.1.1 IPv4 based CE discovery ..................................... 10
5.1.2 Ipv6 based CE discovery [RFC 4861] .......................... 10
6.0 Pseudowire Creation.............................................. 11
6.1 Receive Unicast Multipoint-to-point Pseudowire ................. 11
6.2 Receive Multicast Multipoint-to-point Pseudowire ............... 11
6.3 Send Multicast Replication tree ................................ 12
7.0 Signaling........................................................ 13
7.1 IPLS PW Signaling .............................................. 13
7.2 IPv6 Capability Advertisement .................................. 17
7.3 Signaling Advertisement Processing ............................. 18
8. IANA Considerations............................................... 19
8.1. LDP Status messages ........................................... 19
8.2. Interface Parameters .......................................... 19
9.0 Forwarding....................................................... 19
9.1 Non-IP or non-ARP traffic ...................................... 19
9.2 Unicast IP Traffic ............................................. 20
9.3 Broadcasts and Multicast IP Traffic ............................ 20
9.4 ARP Traffic .................................................... 20
9.6 Encapsulation .................................................. 23
10.0 Attaching to IPLS via ATM or FR............................... 23
11.0 VPLS vs IPLS.................................................... 23
12.0 IP Protocols.................................................... 24
13.0 Dual Homing with IPLS........................................... 25
14.0 Proxy ARP function.............................................. 25
14.1 ARP Proxy - Responder ......................................... 25
14.2 ARP Proxy - Generator ......................................... 25
15.0 Data Center Applicability ...................................... 25
16.0 Acknowledgements................................................ 26
17.0 Security Considerations......................................... 27
17.1 Control plane security ........................................ 27
17.2 Data plane security ........................................... 28
18.0 References...................................................... 29
18.1 Normative References .......................................... 29
18.2 Informative References ........................................ 29
19.0 Author's Address................................................ 30
1.0 Contributing Authors
Shah, et al. Expires April 2015 Page 3
Internet Draft draft-ietf-l2vpn-ipls-16.txt
This document is the combined effort of the following individuals
and many others who have carefully reviewed this document and
provided the technical clarifications.
K. Arvind Fortress
Vach Kompella/Mathew Bocci Alcatel/Lucent
Shane Amante Apple
2.0 Overview
As emphasized in [VPLS], Ethernet has become popular as an access
technology in Metropolitan and Wide Area Networks. [VPLS] describes
how geographically dispersed customer LANs can be interconnected
over a service provider's network. The VPLS service is provided by
Provider Edge (PE) devices that connect Customer Edge (CE) devices.
The VPLS architecture provides this service by incorporating
bridging functions such as MAC address learning in the PE devices.
Provider Edge platforms are designed primarily to be IP routers,
rather than to be LAN switches. To add VPLS capability to a PE
router, one has to add MAC address learning capabilities, along with
aging and other mechanisms native to Ethernet switches. This may be
fairly complex to add to the forwarding plane architecture of an IP
router. As discussed in [L2VPN-FWK], in scenarios where the CE
devices are NOT LAN switches, but rather are IP hosts or IP routers,
it is possible to provide the VPLS service without requiring MAC
address learning and aging on the PE. Instead, a PE router has to
have the capability to match the destination MAC address in a packet
received from a CE to an outbound pseudowire. The requirements for
the IPLS service are described in [L2VPN-REQTS]. The purpose of this
document is to specify a solution optimized for IPLS.
IPLS provides a VPLS-like service using PE routers that are not
designed to perform general LAN bridging functions. One must be
willing to accept the restriction that an IPLS be used for IP
traffic only, and not used to interconnect CE devices that are
themselves LAN switches. This is an acceptable restriction in many
environments, given that IP is the predominant type of traffic in
today's networks.
The original intent was to provide an alternate solution to VPLS
for those PE routers that were not capable of learning MAC address
through data plane. This became non-issue with newer hardware.
The concepts put forth by this draft are still valuable and are
adopted in one form or other by newer work such as Ethernet VPN
in L2VPN Working Group and possible data center applications. At
this point, no further action is planned to update this document
and is published simply as a historic record of the ideas.
Shah, et al. Expires April 2015 Page 4
Internet Draft draft-ietf-l2vpn-ipls-16.txt
In IPLS, a PE device implements multi-point LAN connectivity for IP
traffic using the following key functions:
1. CE Address Discovery: Each Provider Edge (PE) device discovers
MAC address of the locally attached Customer Edge (CE) IP
devices, for each IPLS instance configured on the PE device. In
some configurations, PE also learns the IP address of the CE
device (when performing ARP proxy functions, described later in
the document).
2. Pseudowire (PW) for Unicast Traffic: For each locally attached
CE device in a given IPLS instance, a PE device sets up a
pseudowire (PW-LSP) to each of the other PEs that supports the
same IPLS instance.
For instance, if PEx and PEy both support IPLS I, and PEy is
locally attached to CEa and CEb, PEy will initiate the setup of
two pseudowires between itself and PEx. One of these will be
used to carry unicast traffic from any of PEx's CE devices to
CEa. The other will be used to carry unicast traffic from any
of PEx's CE devices to CEb.
Note that these pseudowires carry traffic only in one
direction. Further, while the pseudowire implicitly identifies
the destination CE of the traffic, it does not identify the
source CE; packets from different source CEs bound to the same
destination CE are sent on a single pseudowire.
3. Pseudowires for Multicast Traffic: In addition, every PE
supporting a given IPLS instance will set up a special
'multicast pseudowire' to every other PE in that IPLS instance.
If, in the above example, one of PEx's CE devices sends a
multicast packet, PEx would forward the multicast packet to PEy
on the special 'multicast' pseudowire. PEy would then send a
copy of that packet to CEa and a copy to CEb.
The 'multicast' pseudowire carries Ethernet frames of
multicast/broadcast IP, ARP and ICMP (Inverse) Neighbor
Discovery (ND/IND) packets for IPv6. Thus when a PE sends a
multicast packet across the network, it sends one copy to each
remote PE (supporting the given IPLS instance). If a
particular remote PE has more than one CE device in that IPLS
instance, the remote PE must replicate the packet and send one
copy to each of its local CEs.
As with the pseudowires that are used for unicast traffic,
packets travel in only one direction on these pseudowires, and
packets from different sources may be freely intermixed.
Shah, et al. Expires April 2015 Page 5
Internet Draft draft-ietf-l2vpn-ipls-16.txt
4. Signaling: The necessary pseudowires can be set up and
maintained using the LDP-based signaling procedures described
in [PWE3-CONTROL].
A PE may assign the same label to each of the unicast
pseudowires that lead to a given CE device, in effect creating
a multipoint-to-point pseudowire.
Similarly, a PE may assign the same label to each of the
'multicast' pseudowires for a given IPLS instance, in effect
creating a multipoint-to-point pseudowire.
When setting up a pseudowire to be used for unicast traffic,
the PE must also signal the MAC address of the corresponding CE
device. It should also, optionally, advertise IP address of the
local CE device, especially when ARP proxy function is
configured or simply for operational management purposes.
Similarly, for IPv6 support, PE may optionally advertise the
IPv6 addresses of the local CE device.
5. ARP Packet Forwarding: ARP packets [ARP] are forwarded from
attachment circuit (AC) to 'multicast' pseudowires in the
Ethernet frame format as described by [PWE3-ETH].The following
rules are observed when processing ARP packets,
a. Both broadcast (request) and unicast (response) ARP
packets are sent over the 'multicast' pseudowire.
b. When an ARP packet is received from an AC, the packet is
copied to control plane for learning MAC address of the
CE. Optionally, IP address is also learned to record the
association of IP and MAC address.
c. All Ethernet packets, including ARP packets, received from
'multicast' pseudowire are forwarded out to all the ACs
associated with the IPLS instance. These packets are not
copied to control plane.
6. ICMP IPv6 ND/IND related Packet Forwarding: (Inverse) Neighbor
Discovery (ND/IND) IPv6 packets from an AC are replicated and a
copy is sent to other ACs and to 'multicast' PWs associated
with the IPLS instance in the native Ethernet format,
unchanged. A copy is also submitted to Control Plane to learn
the MAC address and optionally corresponding IPv6 addresses.
7. Multicast IP packet forwarding: An IP Ethernet frame received
from an AC is replicated to other ACs and the 'multicast'
pseudowires associated with the IPLS instance. An IP Ethernet
frame received from a 'multicast' pseudowire is replicated to
all the egress ACs associated with the IPLS instance.
Shah, et al. Expires April 2015 Page 6
Internet Draft draft-ietf-l2vpn-ipls-16.txt
8. Unicast IP packet forwarding: An IP packet received from the AC
is forwarded based on the MAC DA lookup in the forwarding
table. If a match is found, the packet is forwarded to the
associated egress interface. If the egress interface is unicast
pseudowire, the packet is sent without MAC header. If the
egress interface is a local AC the Ethernet frame is forwarded
as such. An IP packet received from the unicast pseudowire is
forwarded to egress AC with MAC header prepended. The MAC DA is
derived from the forwarding table while MAC SA is the MAC
address of the PE.
Both VPLS [VPLS] and IPLS require the ingress PE to forward a frame
based on its destination MAC address. However, two key differences
between VPLS and IPLS can be noted from the above description:
. In VPLS, MAC entries are placed in the Forwarding Information
Base (FIB) of the ingress PE as a result of MAC address
learning (which occurs in the data plane) while in IPLS MAC
entries are placed in the FIB as a result of pseudowire
signaling operations (control plane).
. In VPLS, the egress PE looks up a frame's destination MAC
address to determine the egress AC; in IPLS, the egress AC is
determined entirely by the ingress PW-label.
The following sections describe the details of the IPLS scheme.
2.1 Terminology
IPLS IP-only LAN service (a type of Virtual Private
LAN Service that is restricted to IP traffic
only).
mp2p PW Multipoint-to-Point Pseudowire. A pseudowire
that carries traffic from remote PE devices to
a PE device that signals the pseudowire. The
signaling PE device advertises the same PW-
label to all remote PE devices that participate
in the IPLS service instance. In IPLS, for a
given IPLS instance, an mp2p PW used for IP
unicast traffic is established by a PE for each
CE device locally attached to that PE. It is a
unidirectional tree whose leaves consist of the
remote PE peers (which connect at least one AC
associated with the same IPLS instance) and
whose root is the signaling PE. Traffic flows
from the leaves towards the root.
Multicast PW Multicast/broadcast Pseudowire. A special kind
of mp2p PW that carries IP multicast/broadcast
traffic, all ARP frames and ICMP (I)ND frames
for IPv6. In the IPLS architecture, for each
IPLS instance supported by a PE, that PE device
establishes exactly one multicast PW. Multicast
PW uses Ethernet encapsulation.
Shah, et al. Expires April 2015 Page 7
Internet Draft draft-ietf-l2vpn-ipls-16.txt
Unicast PW Unicast Pseudowire carries IP unicast packets.
A PE creates unicast PW for each locally
attached CE. The unicast PW uses IP Layer2
transport encapsulation.
CE Customer Edge device. In this document, a CE is
any IP node (host or router) connected to the
IPLS LAN service.
Replication Tree The collection of all multicast PWs and ACs
that are members of an IPLS service instance on
a given PE. When a PE receives a
multicast/broadcast packet from an AC, the PE
device sends a copy of the packet to every
multicast pseudowire and AC of the replication
tree, excluding the AC on which the packet was
received. When a PE receives a packet from a
multicast PW, the PE device sends a copy of the
packet to all the ACs of the replication tree
and never to other PWs.
(I)ND (Inverse) Neighbor Discovery in IPv6 uses ICMP
packets. It is a protocol that uses Neighbor
solicitation/Advertisement PDUs.
RS Router Solicitation. Hosts generate all router
multicast ICMP packet to discover IPv6 router
on the local link.
RA Router Advertisement. Router generates all
multicast ICMP packet to advertise its presence
on the link. A unicast response is also sent
when RS is received.
NS Neighbor Solicitation in IPv6 uses (multicast)
ICMP packets to resolve IPv6 interface address
to MAC address association.
NA Neighbor Advertisement in IPv6 uses (unicast)
ICMP packets to respond to NS.
3.0 Topology
The Customer Edge (CE) devices are IP nodes (hosts or routers) that
are connected to PE devices either directly, or via an Ethernet
network. We assume that the PE/CE connection may be regarded by the
PE as an "interface" to which one or more CEs are attached. This
interface may be a physical LAN interface or a VLAN. The Provider
Edge (PE) routers are MPLS Label Edge Routers (LERs) that serve as
pseudowire endpoints.
Shah, et al. Expires April 2015 Page 8
Internet Draft draft-ietf-l2vpn-ipls-16.txt
+----+ +----+
+ S1 +---+ ........................... +---| S2 |
+----+ | | . . | +----+
IPa | | +----+ +----+ | IPe
+ +---| PE1|---MPLS and/or IP---| PE2|---+
/ \ +----+ |Network +----+ |
+----+ +---+ . | . | +----+
+ S1 + | S1| . +----+ . +---| S2 |
+----+ +---+ ..........| PE3|........... +----+
IPb IPc +----+ IPf
|
|
+----+
| S3 |
+----+
IPd
In the above diagram, an IPLS instance is shown with three sites:
site S1, site S2 and site S3. In site S3, the CE device is directly
connected to its PE. In the other two sites, there are multiple CEs
connected to a single PE. More precisely, the CEs at these sites are
on an Ethernet (switched at site 1 and shared at site 2) network (or
VLAN), and the PE is attached to that same Ethernet network or
VLAN). We impose the following restriction: if one or more CEs
attach to a PE by virtue of being on a common LAN or VLAN, there
MUST NOT be more than one PE on that LAN or VLAN.
PE1, PE2 and PE3 are shown as connected via an MPLS network;
however, other tunneling technologies, such as GRE, L2TPv3, etc.,
could also be used to carry the pseudowires.
An IPLS instance is a single broadcast domain, such that each IP end
station (e.g., IPa) appears to be co-located with other IP end
stations (e.g., IPb through IPf) on the same subnet. The IPLS
service is transparent to the CE devices and requires no changes to
them.
4.0 Configuration
Each PE router is configured with one or more IPLS service
instances, and each IPLS service instance is associated with a
unique VPN-Id. For a given IPLS service instance, a set of ACs is
identified. Each AC can be associated with only one IPLS instance.
An AC, in this document, is either a customer-facing Ethernet port,
or a particular VLAN (identified by an IEEE 802.1Q VLAN ID) on a
customer-facing Ethernet port.
The PE router can optionally be configured with a local MAC address
to be used as source MAC address when IP packets are forwarded from
Shah, et al. Expires April 2015 Page 9
Internet Draft draft-ietf-l2vpn-ipls-16.txt
a pseudowire to an AC. By default, a PE uses the MAC address of the
customer-facing Ethernet interface for this purpose.
5.0 Discovery
The discovery process includes:
. Remote PE discovery
. VPN (i.e., IPLS) membership discovery
. IP CE end station discovery
This draft does not discuss the remote PE discovery or VPN
membership discovery. This information can either be user configured
or can be obtained using auto-discovery techniques described in
[L2VPN-SIG] or other methods. However, the discovery of the CE is an
important operational step in the IPLS model and is described below.
5.1 CE discovery
Each PE actively detects the presence of local CEs by snooping IP
and ARP frames received over the ACs. When an AC configured in an
IPLS instance becomes operational, it enters the CE discovery phase.
In this phase, the PE examines each multicast/broadcast Ethernet
frame. For link-local IP frames (for example IGP
discovery/multicast/broadcast packets typically 224.0.0.x addresses
[RFC-1112]), the CE's (source) MAC address is extracted from the
Ethernet header and the (source) IP address is obtained from the IP
header.
For each CE, the PE maintains the following tuple: <Attachment
Circuit identification info, VPN-Id, MAC address, IP address
(optional)>.
5.1.1 IPv4 based CE discovery
As indicated earlier, a copy of ARP frames received over the AC is
submitted to the control plane. The PE learns MAC address and
optionally IP address of the CE from the source address fields of
the ARP PDU.
Once a CE is discovered, its status is monitored continuously by
examining the received ARP frames and by periodically generating ARP
requests. The absence of an ARP response from a CE after a
configurable number of ARP requests is interpreted as loss of
connectivity with the CE.
5.1.2 Ipv6 based CE discovery [RFC 4861]
A copy of Neighbor and Router Discovery frames received over the AC
are submitted to the control plane in the PE.
Shah, et al. Expires April 2015 Page 10
Internet Draft draft-ietf-l2vpn-ipls-16.txt
If the PE receives a Neighbor Solicitation message, and the source
IP address of the message is not the unspecified address, the PE
learns the MAC address and optionally IP address of the CE.
If the PE receives an unsolicited Neighbor Advertisement message,
the PE learns the source MAC address and optionally the IP address
of the CE.
If the PE receives a Router Solicitation, and the source IP address
of the message is not the unspecified address, the PE learns source
MAC address and optionally the IP address of the CE.
If the PE receives a Router Advertisement, it learns source MAC
address and optionally the IP address of the CE.
The PE will periodically generate Neighbor Solicitation messages for
the IP address of the CE as a means of verifying the continued
existence of the address and its MAC address binding. The absence of
a response from the CE device for a given number of retries could be
interpreted as a loss of connectivity with the CE.
6.0 Pseudowire Creation
6.1 Receive Unicast Multipoint-to-point Pseudowire
As the PE discovers each locally attached CE, a unicast multipoint-
to-point pseudowire (mp2p PW) associated exclusively with that CE is
created by distributing the MAC address and optionally IP address of
the CE along with a PW-Label to all the remote PE peers that
participate in the same IPLS instance. Note that the same value of a
PW-label SHOULD be distributed to all the remote PE peers for a
given CE. The mp2p PW thus created is used by remote PEs to send
unicast IP traffic to a specific CE.
(The same functionality can be provided by a set of point-to-point
PWs, and the PE is not required to send the same PW-label to all the
other PEs. For convenience, however, we will use the term mp2p PWs,
which may be implemented using a set of point-to-point PWs.)
The PE forwards a frame received over this mp2p PW to the associated
AC.
The unicast pseudowire uses IP Layer2 Transport encapsulation as
define in [PWE3-CONTROL].
6.2 Receive Multicast Multipoint-to-point Pseudowire
When a PE is configured to participate in an IPLS instance, it
advertises a 'multicast' PW-label to every other PE that is a member
Shah, et al. Expires April 2015 Page 11
Internet Draft draft-ietf-l2vpn-ipls-16.txt
of the same IPLS. The advertised PW-label value is the same for each
PE, which creates an mp2p pseudowire. There is only one such
multicast mp2p PW per PE for each IPLS instance and this pseudowire
is used exclusively to carry IP multicast/broadcast, ARP traffic and
(inverse) Neighbor Discovery packets for IPv6 from the remote PEs to
this PE for this IPLS instance.
Note that no special functionality is expected from this pseudowire.
We call it a 'multicast' pseudowire because we use it to carry
multicast and broadcast IP, ARP and IPv6 Neighbor Discovery traffic.
The pseudowire itself need not provide any different service than
any of the unicast pseudowires.
In particular, the Receive multicast mp2p PW does not perform any
replication of frames itself. Rather, it is there to signify to the
PE that the PE may need to replicate a copy of a frame received over
this mp2p PW onto all the AC that are associated with the IPLS
instance of the mp2p PW.
The multicast mp2p pseudowire is considered the principle pseudowire
in the bundle of mp2p pseudowires that consist of one multicast mp2p
pseudowire and a variable number of unicast mp2p pseudowires for a
given IPLS instance. In a principle role, multicast PW represents
the IPLS instance. The life of all unicast PWs in the IPLS instance
depends on the existence of the multicast PW. If, for some reasons,
multicast PW cease to exist, all the associated unicast pseudowires
in the bundle are removed.
The multicast pseudowire uses Ethernet encapsulation as defined in
[PWE3-ETH].
The use of pseudowires which are specially optimized for multicast
is for further study.
6.3 Send Multicast Replication tree
The PE creates a send replication tree for each IPLS instance, which
consists of the collection of all ACs and all the 'multicast'
pseudowires of the IPLS instance.
Any ARP, Neighbor Discovery or multicast IP Ethernet frame received
over an AC is replicated to the other ACs and to the mp2p multicast
pseudowire of the send replication tree. The send replication tree
deals mostly with broadcast/multicast Ethernet MAC frames. One
exception to this is unicast ARP and IPv6 Neighbor Discovery frame,
the processing of which is described in the following section.
Any Ethernet frame received over the multicast PW is replicated to
all the ACs of the send replication tree of the IPLS instance
associated with the incoming PW label. One exception is unicast ARP
Shah, et al. Expires April 2015 Page 12
Internet Draft draft-ietf-l2vpn-ipls-16.txt
and Neighbor Discovery frame used for IPv6, the processing of which
is described in the following section.
7.0 Signaling
[PWE3-CONTROL] uses the Label Distribution Protocol (LDP) to
exchange PW-FECs in the Label Mapping message in a downstream
unsolicited mode. The PW-FEC comes in two forms; PWid and
Generalized PWid FEC elements. These FEC elements define some fields
that are common between them. The discussions below refer to these
common fields for IPLS related extensions. Note that the use of
multipoint to point and unidirectional characteristics of the PW
makes BGP as the ideal candidate for PW-FEC signaling. The use of
BGP for such purposes is for future study.
7.1 IPLS PW Signaling
An IPLS carries IP packets as payload over its unicast pseudowires
and Ethernet packet as payload over its multicast pseudowire. The
PW-type to be used for unicast pseudowire is the IP PW, defined in
[PWE3-CONTROL] as IP Layer2 Transport. The PW-type to be used for
multicast pseudowire is the Ethernet PW as defined in [PWE3-ETH].
The PW-Type values for these encapsulations are defined in [PWE3-
IANA].
When processing a received PW FEC, the PE matches the PW Id with the
locally configured PW Id for the IPLS instance. If the PW type is
Ethernet, the PW-FEC is for multicast PW. If the PW type is 'IP
Layer2 transport', the PW FEC is for unicast PW.
For unicast PW, PE must check the presence of MAC address TLV in the
optional parameter fields of the Label Mapping message. If this
parameter is absent, a Label Release message must be issued with a
Status Code meaning "MAC Address of the CE is absent" [note: Status
Code 0x000000XX is pending IANA allocation], to reject the
establishment of the unicast PW with the remote PE.
The PE may optionally include IP address TLV based on the user
configuration for advertising of the IP addresses of the local CE.
The processing of the address list TLV is as follows.
o If a pseudowire is configured for AC with IPv4 CEs only, the
PE should advertise address list tlv with address family type
to be of IPv4 address. The PE should process the IPv4 address
list TLV as described in this document.
o If a pseudowire is configured for AC with both IPv4 and IPv6
CEs, the PE should advertise IPv6 capability using the
procedures described in Section below.
Shah, et al. Expires April 2015 Page 13
Internet Draft draft-ietf-l2vpn-ipls-16.txt
o If a PE does not receive any IP address list TLV or IPv6
capability advertisement, it MAY assume IPv4 behavior.
The IPLS uses the Address List TLV as defined in [RFC 5036] to
signal the MAC (and optionally IP) address of the local CE. There
are two TLVs defined below; IP Address TLV and MAC Address TLV. MAC
address TLV must be included in the optional parameter field of the
Label Mapping message when establishing the unicast IP PW for IPLS.
When configured to support specific type of IP traffic (IPv4 or
IPv6), the PE augments verification of the type of traffic PW will
carry using the Address Family Type value. If there is a mismatch
between the received Address Family value and the expectation of
IPLS instance to which the PW belongs, the PE must issue a Label
Release message with a Status Code meaning "IP Address type
mismatch" (Status Code 0x0000004A) to reject the PW establishment.
Encoding of the IP Address TLV is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| Address List (0x0101) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Family | CE's IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CE's IP Address | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length
When Address Family is IPV4, Length is equal to 6 bytes;
2 bytes for address family and 4 bytes of IP address. The
length is 18 bytes when address family is IPv6, 2 bytes for
address family and 16 bytes of IP address.
Address Family
Two octet quantity containing a value from the ADDRESS FAMILY
NUMBERS from ADDRESS FAMILY NUMBERS in [ADDR-IANA] that encodes
the addresses contained in the Addresses field.
IP Address of the CE
IP address of the CE attached to the advertising PE. The
encoding of the individual address depends on the Address
Family.
The following address encodings are defined by this version of the
protocol:
Address Family Address Encoding
IPv4 (1) 4 octet full IPv4 address
Shah, et al. Expires April 2015 Page 14
Internet Draft draft-ietf-l2vpn-ipls-16.txt
IPv6 (2) 16 octet full IPv6 address
Note that more than one instance of the IP address TLV may exist,
especially when support for IPv6 is configured.
Shah, et al. Expires April 2015 Page 15
Internet Draft draft-ietf-l2vpn-ipls-16.txt
Encoding of the MAC Address TLV is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| Address List (0x0101) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Family | CE's MAC address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Length
The length field is set to value 8 (2 for address family, 6 for
MAC address)
Address Family
Two octet quantity containing a value from ADDRESS FAMILY
NUMBERS in [ADDR-IANA] that encodes the addresses contained in
the Addresses field.
CE's MAC Address
MAC address of the CE attached to the advertising PE. The
encoding of the individual address depends on the Address
Family.
The following address encodings are defined by this version of the
protocol:
Address Family Address Encoding
MAC (6) 6 octet full Ethernet MAC address
The IPv4 address of the CE is also supplied in the optional
parameters field of the LDP Notification message along with the PW
FEC. The LDP Notification message is used to signal any change in
the status of the CE's IPv4 address.
Note that Notification message does not apply to MAC address TLV
since an update to MAC address of the CE should result in label
withdraw followed by establishment of new PW with new MAC address of
the CE. However, advertisement of IP address(es) of the CE is
optional and changes may become known after the establishment of
unicast PW.
Shah, et al. Expires April 2015 Page 16
Internet Draft draft-ietf-l2vpn-ipls-16.txt
The encoding of the LDP Notification message is as follows.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Notification (0x0001) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status (TLV) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address List TLV (as defined above) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PWId FEC or Generalized ID FEC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Status TLV status code is set to 0x0000002C "IP address of CE",
to indicate that IP Address update follows. Since this notification
does not refer to any particular message the Message Id, and Message
Type fields are set to 0.
The PW FEC TLV SHOULD NOT include the interface parameters as they
are ignored in the context of this message.
7.2 IPv6 Capability Advertisement
A 'Stack Capability' Interface Parameter sub-TLV is signaled by the
two PEs so that they can agree which stack(s) they should be using.
It is assumed by default that the IP PW will always be capable of
carrying IPv4 packets. Thus this capability sub-TLV is used to
indicate if other stacks need to be supported concurrently with
IPv4.
The 'Stack Capability' sub-TLV is part of the interface parameters
of the PW FEC. The proposed format for the Stack Capability
interface parameter sub-TLV is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parameter ID | Length | Stack Capability |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Parameter ID = 0x16
Length = 4
Stack capability = 0x000X to indicate IPv6 stack capability
Shah, et al. Expires April 2015 Page 17
Internet Draft draft-ietf-l2vpn-ipls-16.txt
The Value of Stack capability is dependent on the PW type context.
For IP PW type, a setting of 0x000X indicates IPv6 stack capability.
A PE that supports IPv6 on an IP PW MUST signal the stack capability
sub-TLV in the initial label mapping message for the PW. The PE
nodes compare the value advertised by the remote PE with the local
configuration and only use a capability which is advertised by both.
If a PE that supports IPv6 does not receive a 'stack capability'
sub-TLV from the far-end PE in the initial label mapping message, or
one is received but it is set to a reserved value, the PE MUST send
an unsolicited release for the PW label with the LDP status code
meaning "IP Address type mismatch" (Status Code 0x0000004A).
The behavior of a PE that does not understand an interface parameter
sub-TLV is specified in RFC4447 [PWE3-CONTROL].
7.3 Signaling Advertisement Processing
A PE should process a received [PWE3-CONTROL] advertisement with PW-
type of IP Layer2 transport for IPLS as follows,
- Verify the IPLS VPN membership by matching the VPN-Id
signaled in the AGI field or the PW-ID field with all the
VPN-Ids configured in the PE. Discard and release the PW
label if VPN-Id is not found.
- Program the Forwarding Information Base (FIB) such that when
a unicast IP packet is received from an AC with its
destination MAC address matching the advertised MAC address,
the packet is forwarded out over the tunnel to the
advertising PE with the advertised PW-label as the inner
label.
A PE should process a received [PWE3-CONTROL] advertisement with the
PW type of Ethernet for IPLS as follows,
- Verify the IPLS VPN membership by matching the VPN-Id
signaled in the AGI field or the PW-ID field with all the
VPN-Ids configured in the PE. Discard and release the PW
label if VPN-Id is not found.
- Add the PW-label to the send broadcast replication tree for
the VPN-Id. This enables sending a copy of a
multicast/broadcast IP Ethernet frame or ARP Ethernet frame
or Neighbor Discovery frames from the AC to this pseudowire.
Shah, et al. Expires April 2015 Page 18
Internet Draft draft-ietf-l2vpn-ipls-16.txt
8. IANA Considerations
Since this document is being published as historic record, no
requests for IANA code points are necessary. However, if in
future, interest to pursue this proposal arises, the following
requests for IANA codes would become necessary.
8.1. LDP Status messages
This document uses new LDP status code. IANA already maintains a
registry of name "STATUS CODE NAME SPACE" defined by [RFC 5036]. The
following value is suggested for assignment:
0x000000XX "MAC Address of CE is absent"
8.2. Interface Parameters
This document proposes a new Interface Parameters sub-TLV, to be
assigned from the 'Pseudowire Interface Parameters Sub-TLV type
Registry'. The following value is suggested for the Parameter ID:
0xXX "Stack capability"
IANA is also requested to set up a registry of "L2VPN PE stack
capabilities". This is a 16 bit field. Stack capability values
0x000X is specified in Section 7. of this document. The remaining
bitfield values (0x0002,..,0x8000) are to be assigned by IANA using
the "IETF Consensus" policy defined in [RFC 5226].
L2VPN PE Stack Capabilities:
Bit (Value) Description
=============== ==========================================
Bit 0 (0x000X) - IPv6 stack capability
Bit 1 (0x000X) - Reserved
Bit 2 (0x000X) - Reserved
.
.
.
Bit 14 (0xX000) - Reserved
Bit 15 (0xX000) - Reserved
9.0 Forwarding
9.1 Non-IP or non-ARP traffic
In an IPLS VPN, a PE forwards only IP and ARP traffic. All other
frames are dropped silently. If the CEs must pass non-IP traffic to
each other, they must do so through IP tunnels that terminate at the
CEs themselves.
Shah, et al. Expires April 2015 Page 19
Internet Draft draft-ietf-l2vpn-ipls-16.txt
9.2 Unicast IP Traffic
In IPLS, IP traffic is forwarded from the AC to the PW based on the
destination MAC address of the layer 2 frame (and not based on the
IP Header).
The PE identifies the FIB associated with an IPLS instance based on
the AC or the PW label. When a frame is received from an AC, the PE
uses the destination MAC address as the lookup key. When a frame is
received from a PW, the PE uses the PW-Label as the lookup key. The
frame is dropped if the lookup fails.
For IPv6 support, the unicast IP ICMP frame of Neighbor Discovery
Protocol [RFC 4861] is bi-casted; one copy is submitted to the
control plane and other copy to the PW, based on the destination MAC
address.
9.3 Broadcasts and Multicast IP Traffic
When the destination MAC address is either a broadcast or multicast,
a copy of the frame is sent to the control plane for CE discovery
purposes (see section 5.1). It is important to note that stricter
rate-limiting criteria is applied to frames sent to the control
plane, in order to avoid overwhelming it under adverse conditions
such as Denial of Service attack. The service provider should also
provide a configurable limitation to prevent overflowing of the
learned source addresses in a given IPLS instance. Also, caution
must be used such that only link local multicasts and broadcast IP
packets are sent to control plane.
When a multicast/broadcast IP packet is received from an AC, the PE
replicates it onto the Send Multicast Replication Tree (See section
6.3). When a multicast/broadcast IP Ethernet frame is received from
a pseudowire, the PE forwards a copy of the frame to all the ACs
associated with the respective IPLS VPN instance. Note that
'multicast' PW uses Ethernet encapsulation and hence does not
require additional header manipulations.
9.4 ARP Traffic
When a broadcast ARP frame is received over the AC, a copy of the
frame is sent to the control plane for CE discovery purposes. The PE
replicates the frame onto the Send Multicast Replication Tree (see
section 6.3), which results into a copy to be delivered to all the
remote PEs on the 'multicast' PW and other local CEs through the
egress ACs.
When a broadcast Ethernet ARP frame is received over the 'multicast'
PW, a copy of the Ethernet ARP frame is sent to all the ACs
associated with the IPLS instance.
Shah, et al. Expires April 2015 Page 20
Internet Draft draft-ietf-l2vpn-ipls-16.txt
When a unicast Ethernet ARP frame is received over the AC, a copy of
the frame is sent to the control plane for CE discovery
purposes. The PE may optionally do MAC DA lookup in the forwarding
table and send the ARP frame to a specific egress interface (AC or
'multicast' PW to a remote PE) or replicate the frame onto the Send
Multicast Replication Tree (see section 6.3).
When a unicast ARP Ethernet frame is received over the 'multicast'
PW, PE may optionally do MAC DA lookup in the forwarding table and
forward it to the AC where the CE is located. If the CE is not
accessible through any local AC, the frame is dropped. Conversely,
the PE may simply forward the frame to all the ACs associated with
that IPLS instance without any lookup in the forwarding table.
9.5 Discovery of IPv6 CE devices
A PE device that supports IPv6 MUST be capable of,
- Intercepting ICMPv6 Neighbor Discovery [RFC 4861] packets
received over the AC.
- Record the IPv6 interface addresses and CE link-layer addresses
present in these packets
- Forward them towards the original destination
A PE device may also intercept Router Discovery packets in order to
discover the link layer address and IPv6 interface address(es) of
the CE. Following sections describe the details.
The PE device MUST learn the link-layer address of the local CE and
be able to use it when forwarding traffic between CEs. The PE MAY
also wish to monitor the source link-layer address of data packets
received from the CE, and discard packets not matching its learned
CE link-layer address. The PE device may also optionally learn a
list of CE IPv6 interface addresses for its directly-attached CE.
9.5.1. Processing of Neighbor Solicitations
When a broadcast Neighbor Solicitation frame is received over the
AC, a copy of the frame is sent to the control plane for CE
discovery purposes. The PE replicates the frame onto the Send
Multicast Replication Tree (see section 6.3), which results in a
copy to be delivered to all the remote PEs on the 'multicast' PW and
other local CEs through the egress ACs. The PE may optionally learn
an IPv6 interface address (If provided - this will not be the case
for Duplicate Address Detection) when present.
Shah, et al. Expires April 2015 Page 21
Internet Draft draft-ietf-l2vpn-ipls-16.txt
When a broadcast Ethernet Neighbor Solicitation frame is received
over the 'multicast' PW, a copy is sent to all the ACs associated
with the IPLS instance.
9.5.2 Processing of Neighbor Advertisements
When a unicast Neighbor Advertisement is received over the AC, a
copy of the frame is sent to the control plane for the CE discovery
purposes. The PE may optionally do MAC DA lookup in the forwarding
table and send the Neighbor Advertisement frame to a specific egress
interface (AC or 'multicast' PW to a remote PE) or replicate the
frame onto the Send Multicast Replication Tree (see section 6.3).
Optionally, PE could learn the IPv6 Interface address of the CE.
When a unicast Neighbor Advertisement frame is received over the
'multicast' PW, PE may optionally do MAC DA lookup in the forwarding
table and forward it to the AC where the CE is located. If the CE is
not accessible through any local AC, the frame is dropped.
Conversely, the PE may simply forward the frame to all the ACs
associated with that IPLS instance without any lookup in the
forwarding table.
9.5.3 Processing of Inverse Neighbor Solicitations and Advertisement
Inverse Neighbor Discovery is typically used on non-broadcast links,
but are allowed on broadcast links too [RFC 3122]. PE may optionally
intercept Inverse Neighbor Solicitation and Advertisement and learn
MAC and IPv6 interface address list of the attached CE from the copy
of the frame sent to the control plane. The PE may optionally do MAC
DA lookup in the forwarding table and send another copy of the frame
to a specific egress interface (AC or 'multicast' PW to a remote PE)
or replicate the frame onto the Send Multicast Replication Tree (see
section 6.3).
9.5.4 Processing of Router Solicitations and Advertisements
Router Solicitations (RS) are multicast while Router Advertisement
(RA) can be unicast or multicast Ethernet frames. The PE could
optionally intercept RS and RA frames and send a copy to control
plane. The PE may learn the MAC address and a list of interface
addresses for the attached CE.
For unicast RA, the PE may optionally do MAC DA lookup in the
forwarding table and send the Neighbor Advertisement frame to a
specific egress interface (AC or 'multicast' PW to a remote PE) or
replicate the frame onto the Send Multicast Replication Tree (see
section 6.3). The multicast RA and RS Ethernet frames are replicated
using the Send Multicast Replication Tree as described in section
6.3.
Shah, et al. Expires April 2015 Page 22
Internet Draft draft-ietf-l2vpn-ipls-16.txt
9.6 Encapsulation
The Ethernet MAC header of a unicast IP packet received from an AC
is stripped before forwarding the frame to the unicast pseudowire.
However, the MAC header is retained for the following cases,
. when a frame is unicast or broadcast IP packet that is directed
to one or more local AC(s).
. when a frame is a broadcast IP packet
. when a frame is an ARP packet
. when a frame is Neighbor/Router Solicitation/Advertisement
An IP frame received over a unicast pseudowire is prepended with a
MAC header before transmitting it on the appropriate AC(s). The
fields in the MAC header are filled in as follows:
- The destination MAC address is the MAC address associated
with the PW label in the FIB
- The source MAC address is the PE's own local MAC address or a
MAC address which has been specially configured on the PE for
this use.
- The Ethernet Type field is 0x0800 if IPv4 or 0x86DD if IPv6
[RFC 2464]
- The frame may be IEEE802.1Q tagged based on the VLAN
information associated with the AC.
An FCS is appended to the frame.
10.0 Attaching to IPLS via ATM or FR
In addition to (i) an Ethernet port and a (ii) combination of
Ethernet port and a VLAN ID, an AC to IPLS may also be (iii) an ATM
or FR VC carrying encapsulated bridged Ethernet frames or (iv) the
combination of an ATM or FR VC and a VLAN ID.
The ATM/FR VC is just used as a way to transport Ethernet frames
between a customer site and the PE. The PE terminates the ATM/FR VC
and operates on the encapsulated Ethernet frames exactly as if those
were received on a local Ethernet interface. When a frame is
propagated from pseudowire to a ATM or FR VC the PE prepends the
Ethernet frame with the appropriate bridged encapsulation header as
defined in [RFC 2684] and [RFC 2427] respectively. Operation of an
IPLS over ATM/FR VC is exactly as described above, with the
exception that the AC is then identified via the ATM VCI/VPI or
Frame Relay DLCI (instead of via a local Ethernet port ID), or a
combination of those with a VLAN ID.
11.0 VPLS vs IPLS
The VPLS approach proposed in [VPLS] provides VPN services for IP as
well as other protocols. The IPLS approach described in this draft
is similar to VPLS in many respects:
Shah, et al. Expires April 2015 Page 23
Internet Draft draft-ietf-l2vpn-ipls-16.txt
- It provides a Provider Provisioned Virtual LAN service with
multipoint capability where a CE connected via a single
attachment circuit can reach many remote CEs
- It appears as a broadcast domain and a single subnet
- forwarding is based on destination MAC addresses
However, unlike VPLS, IPLS is restricted to IP traffic only. By
restricting the scope of the service to the predominant type of
traffic in today's environment, IPLS eliminates the need for service
provider edge routers to implement some bridging functions such as
MAC address learning in the data path (by, instead, distributing MAC
information in the control plane). Thus this solution offers a
number of benefits:
- Facilitates Virtual LAN services in instances where PE
devices cannot or cannot efficiently (or are specifically
configured not to) perform MAC address learning.
- Unknown Unicast frames are never flooded as would be the case
in VPLS.
- Encapsulation is more efficient (MAC header is stripped) for
unicast IP packets while traversing the backbone network.
- PE devices are not burdened with the processing overhead
associated with traditional bridging (e.g., STP processing,
etc.). Note, however, that some of these overheads (e.g., STP
processing) could optionally be turned-off with a VPLS
solution in the case where it is known that only IP devices
are interconnected.
- Loops (perhaps through backdoor links) are minimized since a
PE could easily reject (via label release) a duplicate IP to
MAC address advertisement.
- Greater control over CE topology distribution.
12.0 IP Protocols
The solution described in this document offers IPLS service for IPv4
and IPv6 traffic only. For this reason, the MAC Header is not
carried over the unicast pseudowire. It is reconstructed by the PE
when receiving a packet from a unicast pseudowire and the Ethertype
0x0800 or 0x86DD is used in the MAC Header since IPv4 or IPv6
respectively, is assumed.
However, this solution may be extended to carry other types of
important traffic such as ISIS , which does not use Ethernet-II,
EtherType based header. In order to permit the propagation of such
packets correctly, one may create a separate set of pseudowires, or
pass protocol information in the "control word" of a "multiprotocol"
pseudowire, or encapsulate the Ethernet MAC Header in the
pseudowire. The selection of appropriate multiplexing/demultiplexing
schemes is the subject of future study. The current document focuses
on IPLS service for IPv4 and IPv6 traffic.
Shah, et al. Expires April 2015 Page 24
Internet Draft draft-ietf-l2vpn-ipls-16.txt
13.0 Dual Homing with IPLS
As stated in previous sections, IPLS prohibits connection of a
common LAN or VLAN to more than one PE. However, the CE device
itself can connect to more than one instance of IPLS through two
separate LAN or VLAN connections to separate PEs. To the CE IP
device, these separate connections appear as connections to two IP
subnets. The failure of reachability through one subnet is then
resolved via the other subnet using IP routing protocols.
14.0 Proxy ARP function
The earlier version of this proposal used IP-PW to carry both the
broadcast/multicast and unicast IP traffic. It also discussed how PE
proxy functionality responds to the ARP requests of the local CE on
behalf of remote CE. The current version of the draft eliminated
these functions and instead uses Ethernet PW to carry broadcast,
multicast and ARP frames to remote PEs. The motivation to use
Ethernet PW and propagate ARP frames in the current version is to
support configuration like back-to-back IPLS (similar to Inter
AS option-A configurations in [RFC 4364]).
The termination and controlled propagation of ARP frames is still a
desirable option for security, DoS and other purposes. For these
reasons, we re-introduce the ARP Proxy [PROXY-ARP] function in this
revision as an optional feature. Following sections describe this
option.
14.1 ARP Proxy - Responder
As a local configuration, a PE can enable ARP Proxy responder
function. In this mode, local PE responds to ARP requests received
over the Attachment Circuit via learnt IP and MAC address
associations, which are advertised by the remote PEs. In addition,
PE may utilize local policies to determine if ARP requests should be
responded based on the source of the ARP request, rate at which the
ARP requests are generated, etc. In a nutshell, when this feature is
enabled, ARP requests are not propagated to remote PE routers that
are members of the same IPLS instance.
14.2 ARP Proxy - Generator
As a local configuration, a PE can enable ARP Proxy generator
function. In this mode, the PE generates ARP request for each IP and
MAC address associations received from the remote PEs. The remote
CE's IP and MAC address is used as the source information in the ARP
request while the destination IP address in the request is obtained
from the local configuration (that is, user needs to configure an IP
address when this feature is enabled). The ARP request is sent on
Shah, et al. Expires April 2015 Page 25
Internet Draft draft-ietf-l2vpn-ipls-16.txt
the Attachment Circuits that have ARP Proxy Generator enabled and is
associated with the given IPLS instance.
In addition, the PE may utilize local policies to determine which
IP/MAC addresses are candidate for ARP request generation.
The ARP Proxy Generator feature is required to support back-to-back
IPLS configuration when any member of the IPLS instance is using ARP
Proxy Responder function. An example of a back-to-back IPLS is a
configuration where PE-1 (ASBR) in an IPLS cloud in one Autonomous
System (say, AS-1) is connected via an Attachment Circuit to another
PE-2 (ASBR) in an IPLS cloud in another Autonomous System (say, AS-
2) where each PE appears as CE to each other. Such configuration is
described in [RFC 4364] as option-A for inter-AS connectivity. The
Proxy ARP responder feature prevents propagation of ARP requests to
PE-1 (ASBR) in AS-1. This necessitates that PE-1 (ASBR) in AS-1
generate ARP request on behalf of each CE connected to the IPLS
instance in AS-1 as a mean to 'advertise' the reachability to IPLS
cloud in AS-2
15.0 Data Center Applicability
The resurgence of interest in providing IP/MPLS based solution for
Data Center Networks (DCN) deserves another look at the IPLS
methodologies described in this document. The key requirement of
DCN to permit VM mobility within or across DCN necessiates
extending the reachability of IP subnet over a LAN, transparently.
In addition, VMs tendency to generate frequent gratutious ARPs
for location discovery necessiates a solution that curbs broadcasts
closest to the source.
The IPLS solution facilitates VM mobility by the PE closest to
the new location signaling the MAC address to all remote peers.
In addition, control-plane based MAC learning mechanisms prevent
flooding of unknown unicast across DCN. The optional ARP proxy
mechanisms further reduces ARP broadcast floods by preventing
its reach across local PE.
16.0 Acknowledgements
Authors would like to thank Alp Dibirdi from Alcatel, Xiahou from
Huawei and other L2VPN working group members for their valuable
comments.
Shah, et al. Expires April 2015 Page 26
Internet Draft draft-ietf-l2vpn-ipls-16.txt
17.0 Security Considerations
A more comprehensive description of the security issues involved in
L2VPNs are covered in [VPN-SEC]. Most of the security issues can be
avoided through implementation of appropriate guards. The security
aspect of this solution is addressed for two planes; control plane
and data plane.
17.1 Control plane security
The control plane security pertains to establishing the LDP
connection, pseudo-wire establishment and CE's IP and MAC address
distribution. The LDP connection between two trusted PEs can be
achieved by each PE verifying the incoming connection against the
configured peer's address and authenticating the LDP messages by
verifying keyed digests. The pseudo-wire establishments between two
secure LDP peers do not pose security issue but mis-wiring could
occur due to configuration error. Some checks, such as, proper
pseudo-wire type and other pseudo-wire options may prevent mis-
wiring due to configuration errors.
The learning of the appropriate CE's IP and MAC address can be a
security issue. It is expected that the local attachment circuit to
CE be physically secured. If this is a concern, the PE must be
configured with CE's IP and MAC address. During each ARP frame
processing, PE must verify the received information against the
configuration before accepting. This prevents theft of service,
denial of service to a subscriber or DoS attacks to all subscribers
by malicious use of network services.
The IPLS also provides MAC anti spoofing by preventing the use of
already known MAC address. For instance, if a PE has already learned
a presence of a CE through local connection or from another PE, and
subsequently an advertisement for the same MAC and/or IP address is
received from a different PE, the receiving PE can terminate service
to that CE (either through label release and/or removing the ARP
entry from the FIB) and raise the alarm.
The IPLS learns and distributes CE reachability through the control
plane. This provides greater control over CE topology distribution
through application of local policies.
Shah, et al. Expires April 2015 Page 27
Internet Draft draft-ietf-l2vpn-ipls-16.txt
17.2 Data plane security
The data traffic between CE and PE is not encrypted and it is
possible that in an insecure environment, a malicious user may tap
into the CE to PE connection and could conduct an active or passive
attack. An example of an active attack would be generating traffic
using the spoofed destination MAC address on the Ethernet Attachment
Circuit and a passive attack could include targeted or passive
monitoring between the CE and PE. In order to avoid such hijacking,
local PE may verify the source MAC address of the received frame
against the MAC address of the admitted connection. The frame is
forwarded to PW only when authenticity is verified. When spoofing is
detected, PE must severe the connection with the local CE, tear down
the PW and start over.
Each IPLS instance uses its own FIB. This prevents leaking of one
customer data into another.
Shah, et al. Expires April 2015 Page 28
Internet Draft draft-ietf-l2vpn-ipls-16.txt
18.0 References
18.1 Normative References
[ARP] RFC 826, STD 37, D. Plummer, "An Ethernet Address Resolution
Protocol".
[PWE3-CONTROL] L. Martini et al., "Pseudowire Setup and Maintenance
using LDP", RFC 4447.
[PWE3-IANA] L. Martini et al,. "IANA Allocations for pseudo Wire
Edge to Edge Emulation (PWE3)", RFC 4446.
[PWE3-ETH] Martini et al., "Encapsulation Methods for Transport of
Ethernet over MPLS Networks", RFC 4448.
[VPLS] Lasserre et al, "Virtual Private LAN Service Using LDP", RFC
4762, January 2007.
[RFC 5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, October 2007.
[IEEE 802.1D] ISO/IEC 10038, ANSI/IEEE Std 802.1D-1993, "MAC
Bridges".
[RFC 4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC 2464] Crawford, M., "Transmission of IPv6 packets over
Ethernet Networks", RFC 2464, December 1998.
[RFC 3122] Conta, A., "Extensions to IPv6 Neighbor Discovery for
Inverse Discovery Specification", RFC 3122, June 2001.
[RFC 5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
Shah, et al. Expires Novemeber 2014 Page 29
Internet Draft draft-ietf-l2vpn-ipls-16.txt
18.2 Informative References
[L2VPN-FWK] Andersson, L., Ed., and E. Rosen, Ed., "Framework for
Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664,
September 2006.
[PROXY-ARP] RFC 925, J. Postel, "Multi-LAN Address Resolution".
[L2VPN-REQTS] Augustyn, W. et.al "Service Requirements for Layer 2
Provider Provisioned Virtual Private Networks",
RFC 4665, September 2006.
[L2VPN-SIG] Rosen et al., "Provisioning, Autodiscovery, and
signaling in L2VPN", RFC 6074, Jan 2011.
[RFC-1112] Deering, S., "Host Extensions for IP Multicasting", RFC
1112, August, 1989.
[RFC 2684] Grossman, et al., "Multiprotocol Encapsulation over ATM
Adaptation Layer 5", September 1999.
[RFC 2427] Brown, et al., "Multiprotocol Interconnect over Frame
Relay", September 1998.
[RFC 4364] Rosen et al., "BGP/MPLS IP Virtual Private Network
(VPNs)", February 2006.
[VPN-SEC] Fang, L., "Security framework for Provider Provisioned
Virtual Private Networks", RFC 4111, July 2005.
[ADDR-IANA] http://www.iana.org/assignments/address-family-numbers/
address-family-numbers.xhtml
Shah, et al. Expires Novemeber 2014 Page 30
Internet Draft draft-ietf-l2vpn-ipls-16.txt
18.0 Author's Address
Himanshu Shah
Ciena Corp
3939 North 1st Street,
San Jose, CA 95110
Email: hshah@ciena.com
Eric Rosen
Cisco Systems
300 Apollo Drive,
Chelmsford, MA 01824
Email: erosen@cisco.com
Giles Heron
Cisco Systems
Email: giheron@cisco.com
Francois Le Faucheur
Cisco Systems, Inc.
Village d'Entreprise Green Side - Batiment T3
400, Avenue de Roumanille
06410 Biot-Sophia Antipolis, France
Email: flefauch@cisco.com
Shah, et al. Expires Novemeber 2014 Page 31
