The Locator/ID Separation Protocol (LISP)lispers.netfarinacci@gmail.comvaf.net Internet Consultingvince.fuller@gmail.com1-4-5.netdmm@1-4-5.netCisco Systems170 Tasman DriveSan JoseCAUSAdarlewis@cisco.comUPC/BarcelonaTechCampus Nord, C. Jordi Girona 1-3BarcelonaCatalunyaSpainacabello@ac.upc.eduThis document describes the Data-Plane protocol for the
Locator/ID Separation Protocol (LISP). LISP defines two
namespaces, End-point Identifiers (EIDs) that identify end-hosts
and Routing Locators (RLOCs) that identify network attachment
points. With this, LISP effectively separates control from data,
and allows routers to create overlay networks. LISP-capable
routers exchange encapsulated packets according to EID-to-RLOC
mappings stored in a local Map-Cache.LISP requires no change to either host protocol stacks or
to underlay routers and offers Traffic Engineering,
multihoming and mobility, among other features.This document obsoletes RFC 6830.This document describes the Locator/Identifier Separation
Protocol (LISP). LISP is an encapsulation protocol built around the
fundamental idea of separating the topological location of a network
attachment point from the node's identity . As a result LISP creates two namespaces: Endpoint Identifiers
(EIDs), that are used to identify end-hosts (e.g., nodes or Virtual
Machines) and routable Routing Locators (RLOCs), used to identify
network attachment points. LISP then defines functions for mapping
between the two namespaces and for encapsulating traffic
originated by devices using non-routable EIDs for transport across a
network infrastructure that routes and forwards using RLOCs. LISP
encapsulation uses a dynamic form of tunneling where no static provisioning
is required or necessary.LISP is an overlay protocol that separates control from
Data-Plane, this document specifies the Data-Plane as well as how LISP-capable
routers (Tunnel Routers) exchange packets by encapsulating them to
the appropriate location. Tunnel routers are equipped with a cache,
called Map-Cache, that contains EID-to-RLOC mappings. The Map-Cache
is populated using the LISP Control-Plane protocol .LISP does not require changes to either the host protocol stack or to
underlay routers. By separating the EID from the RLOC space, LISP
offers native Traffic Engineering, multihoming and mobility, among
other features.Creation of LISP was initially motivated by discussions during
the IAB-sponsored Routing and Addressing Workshop held in Amsterdam
in October 2006 (see ).This document specifies the LISP Data-Plane encapsulation and
other LISP forwarding node functionality while specifies the LISP control
plane. LISP deployment guidelines can be found in and describes
considerations for network operational management. Finally, describes the LISP architecture.This document obsoletes RFC 6830.LISP was originally developed to address the Internet-wide
route scaling problem . While there are a
number of approaches of interest for that problem, as LISP as been
developed and refined, a large number of other LISP uses have been
found and are being used. As such, the design and development of
LISP has changed so as to focus on these use cases. The common
property of these uses is a large set of cooperating entities
seeking to communicate over the public Internet or other large
underlay IP infrastructures, while keeping the addressing and
topology of the cooperating entities separate from the underlay
and Internet topology, routing, and addressing.The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in BCP 14 when, and only when, they appear in all capitals,
as shown here.AFI is a term used
to describe an address encoding in a packet. An address family
that pertains to addresses found in Data-Plane headers. See and for details. An AFI
value of 0 used in this specification indicates an unspecified
encoded address where the length of the address is 0 octets
following the 16-bit AFI value of 0.Anycast Address refers to the same
IPv4 or IPv6 address configured
and used on multiple systems at the same time. An EID or RLOC can
be an anycast address in each of their own address spaces.Client-side is a term used in this
document to indicate a connection initiation attempt by an end-system
represented by an EID.An ETR is a router that
accepts an IP packet where the destination address in the "outer"
IP header is one of its own RLOCs. The router strips the "outer"
header and forwards the packet based on the next IP header
found. In general, an ETR receives LISP-encapsulated IP packets
from the Internet on one side and sends decapsulated IP packets to
site end-systems on the other side. ETR functionality does not
have to be limited to a router device. A server host can be the
endpoint of a LISP tunnel as well.The EID-to-RLOC Database is a
distributed database that contains all known EID-Prefix-to-RLOC
mappings. Each potential ETR typically contains a small piece of
the database: the EID-to-RLOC mappings for the EID-Prefixes
"behind" the router. These map to one of the router's own IP
addresses that are routable on the underlay.
Note that there MAY be transient conditions when the EID-Prefix
for the LISP site and Locator-Set for each EID-Prefix may not be the
same on all ETRs. This has no negative implications, since a
partial set of Locators can be used.The EID-to-RLOC Map-Cache is
generally short-lived, on-demand table in an ITR that stores, tracks, and
is responsible for timing out and otherwise validating EID-to-RLOC
mappings. This cache is distinct from the full "database" of
EID-to-RLOC mappings; it is dynamic, local to the ITR(s), and
relatively small, while the database is distributed, relatively
static, and much more widely scoped to LISP nodes.An EID-Prefix is a power-of-two block
of EIDs that are allocated to a site by an address allocation
authority. EID-Prefixes are associated with a set of RLOC
addresses. EID-Prefix allocations can be broken up into smaller
blocks when an RLOC set is to be associated with the larger
EID-Prefix block.An end-system is an IPv4 or IPv6 device
that originates packets with a single IPv4 or IPv6 header. The
end-system supplies an EID value for the destination address field
of the IP header when communicating outside of its routing domain.
An end-system can be a host computer, a switch or router device,
or any network appliance.An EID is a 32-bit (for IPv4) or
128-bit (for IPv6) value that identifies a host. EIDs are generally
only found in the source and destination
address fields of the first (most inner) LISP header of a
packet. The host obtains a destination EID the same way it obtains
a destination address today, for example, through a Domain Name
System (DNS) lookup or Session
Initiation Protocol (SIP) exchange. The
source EID is obtained via existing mechanisms used to set a
host's "local" IP address. An EID used on the public Internet MUST
have the same properties as any other IP address used in that
manner; this means, among other things, that it MUST be
unique. An EID is allocated to a host from an EID-Prefix block
associated with the site where the host is located. An EID can be
used by a host to refer to other hosts. Note that EID blocks MAY
be assigned in a hierarchical manner, independent of the network
topology, to facilitate scaling of the mapping database. In
addition, an EID block assigned to a site MAY have site-local
structure (subnetting) for routing within the site; this structure
is not visible to the underlay routing system. In theory, the bit
string that represents an EID for one device can represent an RLOC
for a different device. When used in discussions with other
Locator/ID separation proposals, a LISP EID will be called an
"LEID". Throughout this document, any references to "EID" refer to
an LEID.An ITR is a router
that resides in a LISP site. Packets sent by sources inside of the
LISP site to destinations outside of the site are candidates for
encapsulation by the ITR. The ITR treats the IP destination
address as an EID and performs an EID-to-RLOC mapping lookup. The
router then prepends an "outer" IP header with one of its routable
RLOCs (in the RLOC space) in the source address field and the
result of the mapping lookup in the destination address field.
Note that this destination RLOC may be an intermediate, proxy
device that has better knowledge of the EID-to-RLOC mapping closer
to the destination EID. In general, an ITR receives IP packets
from site end-systems on one side and sends LISP-encapsulated IP
packets toward the Internet on the other side.LISP header is a term used in this
document to refer to the outer IPv4 or IPv6 header, a UDP header,
and a LISP-specific 8-octet header that follow the UDP header and
that an ITR prepends or an ETR strips.A LISP router is a router that
performs the functions of any or all of the following: ITR, ETR, RTR,
Proxy-ITR (PITR), or Proxy-ETR (PETR).LISP site is a set of routers in an edge
network that are under a single technical administration. LISP
routers that reside in the edge network are the demarcation points
to separate the edge network from the core network. Locator-Status-Bits are
present in the LISP header. They are used by ITRs to inform ETRs
about the up/down status of all ETRs at the local site. These bits
are used as a hint to convey up/down router status and not path
reachability status. The LSBs can be verified by use of one of the
Locator reachability algorithms described in . An ETR MUST rate-limit the action it takes
when it detects changes in the Locator-Status-Bits.A PETR is defined and described
in . A PETR acts like an ETR but does so
on behalf of LISP sites that send packets to destinations at
non-LISP sites.A PITR is defined and described
in . A PITR acts like an ITR but does so
on behalf of non-LISP sites that send packets to destinations at
LISP sites.Recursive Tunneling occurs
when a packet has more than one LISP IP header. Additional layers
of tunneling MAY be employed to implement Traffic Engineering or
other re-routing as needed. When this is done, an additional
"outer" LISP header is added, and the original RLOCs are preserved
in the "inner" header.
An RTR acts like an ETR to remove a LISP header, then acts as an
ITR to prepend a new LISP header. This is known as
Re-encapsulating Tunneling. Doing this allows a packet to be
re-routed by the RTR without adding the overhead of additional
tunnel headers. When using multiple mapping database systems, care
must be taken to not create re- encapsulation loops through
misconfiguration.Route-returnability is an
assumption that the underlying routing system will deliver packets
to the destination. When combined with a nonce that is provided by
a sender and returned by a receiver, this limits off-path data
insertion. A route-returnability check is verified when a message
is sent with a nonce, another message is returned with the same
nonce, and the destination of the original message appears as the
source of the returned message.An RLOC is an IPv4 or IPv6 address of
an Egress Tunnel Router (ETR). An RLOC is the output of an
EID-to-RLOC mapping lookup. An EID maps to zero or more
RLOCs. Typically, RLOCs are numbered from blocks that
are assigned to a site at each point to which it attaches to the
underlay network; where the topology is defined by the connectivity
of provider networks. Multiple RLOCs can be assigned to the same
ETR device or to multiple ETR devices at a site.Server-side is a term used in this
document to indicate that a connection initiation attempt is being
accepted for a destination EID.An xTR is a reference to an ITR or ETR when
direction of data flow is not part of the context description.
"xTR" refers to the router that is the tunnel endpoint and is used
synonymously with the term "Tunnel Router". For example, "An xTR
can be located at the Customer Edge (CE) router" indicates both
ITR and ETR functionality at the CE router.One key concept of LISP is that end-systems operate the same way
they do today. The IP addresses that hosts use for tracking sockets
and connections, and for sending and receiving packets, do not
change. In LISP terminology, these IP addresses are called Endpoint
Identifiers (EIDs).Routers continue to forward packets based on IP destination
addresses. When a packet is LISP encapsulated, these addresses are
referred to as Routing Locators (RLOCs). Most routers along a path
between two hosts will not change; they continue to perform
routing/forwarding lookups on the destination addresses. For routers
between the source host and the ITR as well as routers from the ETR
to the destination host, the destination address is an EID. For the
routers between the ITR and the ETR, the destination address is an
RLOC.Another key LISP concept is the "Tunnel Router". A Tunnel Router
prepends LISP headers on host-originated packets and strips them
prior to final delivery to their destination. The IP addresses in
this "outer header" are RLOCs. During end-to-end packet
exchange between two Internet hosts, an ITR prepends a new LISP
header to each packet, and an ETR strips the new header. The ITR
performs EID-to-RLOC lookups to determine the routing path to the
ETR, which has the RLOC as one of its IP addresses. Some basic rules governing LISP are:End-systems only send to addresses that are EIDs. EIDs are
typically IP addresses assigned to hosts (other types of EID are
supported by LISP, see for further
information). End-systems don't know that addresses are EIDs
versus RLOCs but assume that packets get to their intended
destinations. In a system where LISP is deployed, LISP routers
intercept EID-addressed packets and assist in delivering them
across the network core where EIDs cannot be routed. The
procedure a host uses to send IP packets does not change.LISP routers mostly deal with Routing Locator addresses. See
details in to clarify what is meant by
"mostly".RLOCs are always IP addresses assigned to routers, preferably
topologically oriented addresses from provider CIDR (Classless
Inter-Domain Routing) blocks. When a router originates packets, it MAY use as a source
address either an EID or RLOC. When acting as a host (e.g., when
terminating a transport session such as Secure SHell (SSH),
TELNET, or the Simple Network Management Protocol (SNMP)), it
MAY use an EID that is explicitly assigned for that purpose. An
EID that identifies the router as a host MUST NOT be used as an
RLOC; an EID is only routable within the scope of a site. A
typical BGP configuration might demonstrate this "hybrid"
EID/RLOC usage where a router could use its "host-like" EID to
terminate iBGP sessions to other routers in a site while at the
same time using RLOCs to terminate eBGP sessions to routers
outside the site.Packets with EIDs in them are not expected to be delivered
end-to-end in the absence of an EID-to-RLOC mapping
operation. They are expected to be used locally for intra-site
communication or to be encapsulated for inter-site
communication.EIDs MAY also be structured (subnetted) in a manner suitable
for local routing within an Autonomous System (AS).An additional LISP header MAY be prepended to packets by a
TE-ITR when re-routing of the path for a packet is desired. A
potential use-case for this would be an ISP router that needs to
perform Traffic Engineering for packets flowing through its
network. In such a situation, termed "Recursive Tunneling", an ISP
transit acts as an additional ITR, and the destination RLOC it
uses for the new prepended header would be either a TE-ETR within
the ISP (along an intra-ISP traffic engineered path) or a TE-ETR
within another ISP (an inter-ISP traffic engineered path, where an
agreement to build such a path exists). In order to avoid excessive packet overhead as well as possible
encapsulation loops, this document RECOMMENDS that a maximum of two
LISP headers can be prepended to a packet. For initial LISP
deployments, it is assumed that two headers is sufficient, where
the first prepended header is used at a site for Location/Identity
separation and the second prepended header is used inside a
service provider for Traffic Engineering purposes.Tunnel Routers can be placed fairly flexibly in a multi-AS
topology. For example, the ITR for a particular end-to-end packet
exchange might be the first-hop or default router within a site
for the source host. Similarly, the ETR might be the last-hop
router directly connected to the destination host. Another
example, perhaps for a VPN service outsourced to an ISP by a site,
the ITR could be the site's border router at the service
provider attachment point. Mixing and matching of site-operated,
ISP-operated, and other Tunnel Routers is allowed for maximum
flexibility. Several of the mechanisms in this document are intended for deployment in controlled,
trusted environments, and are insecure for use over the public Internet.
In particular, on the public internet xTRs:MUST set the N, L, E, and V bits in the LISP header () to zero.MUST NOT use Locator-Status-Bits and echo-nonce, as described in for Routing Locator Reachability.
Instead MUST rely solely on control-plane methods.MUST NOT use Gleaning or Locator-Status-Bits and Map-Versioning, as described in to update the EID-to-RLOC Mappings.
Instead relying solely on control-plane methods.This section provides an example of the unicast packet flow,
including also Control-Plane information as specified in . The example also assumes
the following conditions:Source host "host1.abc.example.com" is sending a
packet to "host2.xyz.example.com", exactly as it would if the site was not
not using LISP.Each site is multihomed, so each Tunnel Router has an
address (RLOC) assigned from the service provider address
block for each provider to which that particular Tunnel Router
is attached.The ITR(s) and ETR(s) are directly connected to the source
and destination, respectively, but the source and destination
can be located anywhere in the LISP site.A Map-Request is sent for an external destination when the
destination is not found in the forwarding table or matches a
default route. Map-Requests are sent to the mapping database
system by using the LISP Control-Plane protocol documented in
.Map-Replies are sent on the underlying routing system
topology using the
Control-Plane protocol.Client host1.abc.example.com wants to communicate with
server host2.xyz.example.com:host1.abc.example.com wants to open a TCP connection to
host2.xyz.example.com. It does a DNS lookup on
host2.xyz.example.com. An A/AAAA record is returned. This
address is the destination EID. The locally assigned address
of host1.abc.example.com is used as the source EID. An IPv4
or IPv6 packet is built and forwarded through the LISP site
as a normal IP packet until it reaches a LISP ITR.The LISP ITR must be able to map the destination EID to an
RLOC of one of the ETRs at the destination site. A method
to do this is to send a LISP Map-Request, as specified in
.The mapping system helps forwarding the Map-Request to the
corresponding ETR. When the Map-Request arrives at one of the
ETRs at the destination site, it will process the packet as a
control message.The ETR looks at the destination EID of the Map-Request
and matches it against the prefixes in the ETR's configured
EID-to-RLOC mapping database. This is the list of
EID-Prefixes the ETR is supporting for the site it resides
in. If there is no match, the Map-Request is
dropped. Otherwise, a LISP Map-Reply is returned to the
ITR.The ITR receives the Map-Reply message, parses the message,
and stores the mapping information from the packet. This information
is stored in the ITR's EID-to-RLOC Map-Cache. Note that the
Map-Cache is an on-demand cache. An ITR will manage its
Map-Cache in such a way that optimizes for its resource
constraints.Subsequent packets from host1.abc.example.com to
host2.xyz.example.com will have a LISP header prepended by
the ITR using the appropriate RLOC as the LISP header
destination address learned from the ETR. Note that the
packet MAY be sent to a different ETR than the one that
returned the Map-Reply due to the source site's hashing
policy or the destination site's Locator-Set policy.The ETR receives these packets directly (since the
destination address is one of its assigned IP addresses),
checks the validity of the addresses, strips the LISP header,
and forwards packets to the attached destination host.In order to defer the need for a mapping lookup in the
reverse direction, an ETR can OPTIONALLY create a cache entry
that maps the source EID (inner-header source IP address) to
the source RLOC (outer-header source IP address) in a
received LISP packet. Such a cache entry is termed a
"glean mapping" and only contains a single RLOC for the EID
in question. More complete information about additional
RLOCs SHOULD be verified by sending a LISP Map-Request for
that EID. Both the ITR and the ETR MAY also influence the
decision the other makes in selecting an RLOC.Since additional tunnel headers are prepended, the packet
becomes larger and can exceed the MTU of any link traversed from
the ITR to the ETR. It is RECOMMENDED in IPv4 that packets do not
get fragmented as they are encapsulated by the ITR. Instead, the
packet is dropped and an ICMP Unreachable/Fragmentation-Needed
message is returned to the source.In the case when fragmentation is needed, this specification
RECOMMENDS that implementations provide support for one of the
proposed fragmentation and reassembly schemes. Two existing
schemes are detailed in .Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the
LISP architecture supports IPv4 EIDs with IPv6 RLOCs (where the
inner header is in IPv4 packet format and the outer header is in
IPv6 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner
header is in IPv6 packet format and the outer header is in IPv4
packet format). The next sub-sections illustrate packet formats
for the homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all
4 combinations MUST be supported. Additional types of EIDs are
defined in .As LISP uses UDP encapsulation to carry traffic between xTRs
across the Internet, implementors should be aware of the
provisions of , especially those given in
section 3.1.11 on congestion control for UDP tunneling.Implementors are encouraged to consider UDP checksum usage
guidelines in section 3.4 of when it is
desirable to protect UDP and LISP headers against corruption.The inner header is the header on the datagram
received from the originating host . The
source and destination IP addresses are EIDs.The outer header is a new
header prepended by an ITR. The address fields contain RLOCs
obtained from the ingress router's EID-to-RLOC Cache. The IP
protocol number is "UDP (17)" from . The setting of the Don't Fragment (DF)
bit 'Flags' field is according to rules listed in Sections
and .The UDP header contains an ITR
selected source port when encapsulating a packet. See for details on the hash algorithm used
to select a source port based on the 5-tuple of the inner
header. The destination port MUST be set to the well-known
IANA-assigned port value 4341.The 'UDP Checksum' field SHOULD
be transmitted as zero by an ITR for either IPv4 and IPv6 encapsulation . When a
packet with a zero UDP checksum is received by an ETR, the
ETR MUST accept the packet for decapsulation. When an ITR
transmits a non-zero value for the UDP checksum, it MUST
send a correctly computed value in this field. When an ETR
receives a packet with a non-zero UDP checksum, it MAY
choose to verify the checksum value. If it chooses to
perform such verification, and the verification fails, the
packet MUST be silently dropped. If the ETR chooses not to
perform the verification, or performs the verification
successfully, the packet MUST be accepted for
decapsulation. The handling of UDP zero checksums over IPv6
for all tunneling protocols, including LISP, is subject to
the applicability statement in .The 'UDP Length' field is set for
an IPv4-encapsulated packet to be the sum of the
inner-header IPv4 Total Length plus the UDP and LISP header
lengths. For an IPv6-encapsulated packet, the 'UDP Length'
field is the sum of the inner-header IPv6 Payload Length,
the size of the IPv6 header (40 octets), and the size of the
UDP and LISP headers.The N-bit is the nonce-present bit. When
this bit is set to 1, the low-order 24 bits of the first 32
bits of the LISP header contain a Nonce. See for details. Both N- and V-bits MUST
NOT be set in the same packet. If they are, a decapsulating
ETR MUST treat the 'Nonce/Map-Version' field as having a
Nonce value present.The L-bit is the 'Locator-Status-Bits'
field enabled bit. When this bit is set to 1, the
Locator-Status-Bits in the second 32 bits of the LISP
header are in use.The E-bit is the echo-nonce-request bit.
This bit MUST be ignored and has no meaning when the N-bit
is set to 0. When the N-bit is set to 1 and this bit is set
to 1, an ITR is requesting that the nonce value in the
'Nonce' field be echoed back in LISP-encapsulated packets
when the ITR is also an ETR. See
for details.The V-bit is the Map-Version present
bit. When this bit is set to 1, the N-bit MUST be 0. Refer
to for more details. This
bit indicates that the LISP header is encoded in this
case as:The I-bit is the Instance ID bit. See for more details. When this bit is set
to 1, the 'Locator-Status-Bits' field is reduced to 8 bits
and the high-order 24 bits are used as an Instance ID. If
the L-bit is set to 0, then the low-order 8 bits are
transmitted as zero and ignored on receipt. The format of
the LISP header would look like this:The R-bit is a Reserved and unassigned bit
for future use. It MUST be set to 0 on transmit and MUST be
ignored on receipt.The KK-bits are a 2-bit field used when
encapsulated packets are encrypted. The field is set to 00
when the packet is not encrypted. See for further information.The LISP 'Nonce' field is a 24-bit
value that is randomly generated by an ITR when the N-bit is
set to 1. Nonce generation algorithms are an implementation
matter but are required to generate different nonces when
sending to different RLOCs. The nonce is also used when the E-bit is set to
request the nonce value to be echoed by the other side when
packets are returned. When the E-bit is clear but the N-bit
is set, a remote ITR is either echoing a previously
requested echo-nonce or providing a random nonce. See for more details. Finally, when
both the N and V-bit are not set (N=0, V=0), then both the Nonce
and Map-Version fields are set to 0 and ignored on receipt.When the
L-bit is also set, the 'Locator-Status-Bits' field in the
LISP header is set by an ITR to indicate to an ETR the
up/down status of the Locators in the source site. Each RLOC
in a Map-Reply is assigned an ordinal value from 0 to n-1
(when there are n RLOCs in a mapping entry). The
Locator-Status-Bits are numbered from 0 to n-1 from the
least significant bit of the field. The field is 32 bits
when the I-bit is set to 0 and is 8 bits when the I-bit is
set to 1. When a Locator-Status-Bit is set to 1, the ITR is
indicating to the ETR that the RLOC associated with the bit
ordinal has up status. See for
details on how an ITR can determine the status of the ETRs
at the same site. When a site has multiple EID-Prefixes
that result in multiple mappings (where each could have a
different Locator-Set), the Locator-Status-Bits setting in
an encapsulated packet MUST reflect the mapping for the
EID-Prefix that the inner-header source EID address
matches (longest-match). If the LSB for an anycast Locator is set to 1, then
there is at least one RLOC with that address, and the ETR is
considered 'up'.When doing ITR/PITR encapsulation:The outer-header 'Time to Live' field (or 'Hop Limit'
field, in the case of IPv6) SHOULD be copied from the
inner-header 'Time to Live' field. The outer-header IPv4 'Differentiated Services Code Point'
(DSCP) field or the 'Traffic Class' field, in the case of
IPv6, SHOULD be copied from the inner-header IPv4 DSCP field or
'Traffic Class' field in the case of IPv6, to the
outer-header. Guidelines for this can be found at .The IPv4 'Explicit Congestion Notification' (ECN) field and bits
6 and 7 of the IPv6 'Traffic Class' field requires special
treatment in order to avoid discarding indications of
congestion as specified in .When doing ETR/PETR decapsulation:The inner-header IPv4 'Time to Live' field or 'Hop Limit'
field in the case of IPv6, MUST be copied from the
outer-header 'Time to Live'/'Hop Limit' field, when the 'Time to Live'/'Hop Limit'
value of the outer header is less than the 'Time to Live'/'Hop Limit'
value of the inner header. Failing to perform this check
can cause the 'Time to Live'/'Hop Limit' of the inner header to increment
across encapsulation/decapsulation cycles. This check is
also performed when doing initial encapsulation, when a
packet comes to an ITR or PITR destined for a LISP site.The outer-header IPv4 'Differentiated Services Code Point'
(DSCP) field or the 'Traffic Class' field in the case of
IPv6, SHOULD be copied from the outer-header IPv4 DSCP field or
'Traffic Class' field in the case of IPv6, to the
inner-header. Guidelines for this can be found at .The IPv4 'Explicit Congestion Notification' (ECN) field and bits
6 and 7 of the IPv6 'Traffic Class' field, requires special
treatment in order to avoid discarding indications of
congestion as specified in . Note
that implementations exist that copy the 'ECN' field from
the outer header to the inner header even though does not recommend this behavior. It is
RECOMMENDED that implementations change to support the
behavior in .Note that if an ETR/PETR is also an ITR/PITR and chooses to
re-encapsulate after decapsulating, the net effect of this
is that the new outer header will carry the same Time to
Live as the old outer header minus 1.Copying the Time to Live (TTL) serves two purposes:
first, it preserves the distance the host intended the packet to
travel; second, and more importantly, it provides for
suppression of looping packets in the event there is a loop of
concatenated tunnels due to misconfiguration.Some xTRs and PxTRs performs re-encapsulation operations
and need to treat the 'Explicit Congestion Notification' (ECN)
in a special way. Because the re-encapsulation operation is a
sequence of two operations, namely a decapsulation followed by
an encapsulation, the ECN bits MUST be treated as described
above for these two operations.
The LISP dataplane protocol is not backwards compatible with
and does not have explicit support for introducing
future protocol changes (e.g. an explicit version field). However,
the LISP control plane allows an ETR to register
dataplane capabilities by means of new LCAF types .
In this way an ITR can be made aware of the dataplane capabilities
of an ETR, and encapsulate accordingly. The specification of the new
LCAF types, new LCAF mechanisms, and their use, is out of the
scope of this document.
ITRs and PITRs maintain an on-demand cache, referred as LISP
EID-to-RLOC Map-Cache, that contains mappings from EID-prefixes
to locator sets. The cache is used to encapsulate packets from
the EID space to the corresponding RLOC network attachment point.When an ITR/PITR receives a packet from inside of the LISP
site to destinations outside of the site a longest-prefix match
lookup of the EID is done to the Map-Cache.When the lookup succeeds, the Locator-Set retrieved from the
Map-Cache is used to send the packet to the EID's topological
location.If the lookup fails, the ITR/PITR needs to retrieve the
mapping using the LISP Control-Plane protocol . While the mapping is being retrieved,
the ITR/PITR can either drop or buffer the packets. This document does not have specific
recommendations about the action to be taken.
It is up to the deployer to consider whether or not it is desirable to buffer packets
and deploy a LISP implementation that offers the desired behaviour. Once the mapping is resolved
it is then stored in the local Map-Cache to forward subsequent packets addressed to
the same EID-prefix.The Map-Cache is a local cache of mappings, entries are
expired based on the associated Time to live. In addition,
entries can be updated with more current information, see for further information on
this. Finally, the Map-Cache also contains reachability
information about EIDs and RLOCs, and uses LISP reachability
information mechanisms to determine the reachability of RLOCs,
see for the specific mechanisms.This section proposes two mechanisms to deal with
packets that exceed the path MTU between the ITR and ETR.It is left to the implementor to decide if the stateless or
stateful mechanism SHOULD be implemented. Both or neither can be
used, since it is a local decision in the ITR regarding how
to deal with MTU issues, and sites can interoperate with differing
mechanisms.Both stateless and stateful mechanisms also apply to
Re-encapsulating and Recursive Tunneling, so any actions
below referring to an ITR also apply to a TE-ITR.An ITR stateless solution to handle MTU issues is described as
follows:Define H to be the size, in octets, of the outer header an ITR
prepends to a packet. This includes the UDP and LISP header lengths.Define L to be the size, in octets, of the maximum-sized packet
an ITR can send to an ETR without the need for the ITR or any
intermediate routers to fragment the packet.
The network administrator of the LISP deployment has to determine
what is the suitable value of L so to make sure that no MTU issues arise.Define an architectural constant S for the maximum size of a
packet, in octets, an ITR MUST receive from the source so the
effective MTU can be met. That is, L = S + H.When an ITR receives a packet from a site-facing interface and
adds H octets worth of encapsulation to yield a packet size
greater than L octets (meaning the received packet size was
greater than S octets from the source), it resolves the MTU issue
by first splitting the original packet into 2 equal-sized
fragments. A LISP header is then prepended to each fragment. The
size of the encapsulated fragments is then (S/2 + H), which is
less than the ITR's estimate of the path MTU between the ITR and
its correspondent ETR.When an ETR receives encapsulated fragments, it treats them
as two individually encapsulated packets. It strips the LISP
headers and then forwards each fragment to the destination host of
the destination site. The two fragments are reassembled at
the destination host into the single IP datagram that was
originated by the source host. Note that reassembly can happen
at the ETR if the encapsulated packet was fragmented at or after the
ITR.This behavior MUST be performed by the ITR only when the source
host originates a packet with the 'DF' field of the IP header set
to 0. When the 'DF' field of the IP header is set to 1, or the
packet is an IPv6 packet originated by the source host, the ITR
will drop the packet when the size (adding in the size of the
encapsulation header) is greater than L and send an ICMPv4 ICMP
Unreachable/Fragmentation-Needed or ICMPv6 "Packet Too Big"
message to the source with a value of S, where S is (L - H).When the outer-header encapsulation uses an IPv4 header, an
implementation SHOULD set the DF bit to 1 so ETR fragment
reassembly can be avoided. An implementation MAY set the DF
bit in such headers to 0 if it has good reason to believe
there are unresolvable path MTU issues between the sending ITR
and the receiving ETR.This specification RECOMMENDS that L be defined as 1500.
Additional information about in-network MTU and fragmentation issues can be found at .An ITR stateful solution to handle MTU issues is described as
follows:The ITR will keep state of the effective MTU for each Locator
per Map-Cache entry. The effective MTU is what the core network
can deliver along the path between the ITR and ETR.When an IPv4-encapsulated packet with the DF bit set to 1, exceeds what the core network
can deliver, one of the intermediate routers on the path will
send an an ICMPv4
Unreachable/Fragmentation-Needed to the ITR, respectively. The
ITR will parse the ICMP message to determine which Locator is
affected by the effective MTU change and then record the new
effective MTU value in the Map-Cache entry.When a packet is received by the ITR from a source inside
of the site and the size of the packet is greater than the
effective MTU stored with the Map-Cache entry associated with
the destination EID the packet is for, the ITR will send an
ICMPv4 ICMP Unreachable/Fragmentation-Needed message back to the source. The packet size
advertised by the ITR in the ICMP message is the effective
MTU minus the LISP encapsulation length.Even though this mechanism is stateful, it has advantages over
the stateless IP fragmentation mechanism, by not involving the
destination host with reassembly of ITR fragmented packets.Please note that and , which describe the use
of ICMP packets for PMTU discovery, can behave suboptimally in the
presence of ICMP black holes or off-path attackers that spoof ICMP.
Possible mitigations include ITRs and ETRs cooperating on MTU probe
packets (, ), or ITRs
storing the beginning of large packets to verify that they match
the echoed packet in ICMP Frag Needed/PTB.There are several cases where segregation is needed at the
EID level. For instance, this is the case for deployments
containing overlapping addresses, traffic isolation policies
or multi-tenant virtualization. For these and other scenarios
where segregation is needed, Instance IDs are used.An Instance ID can be carried in a LISP-encapsulated
packet. An ITR that prepends a LISP header will copy a
24-bit value used by the LISP router to uniquely identify
the address space. The value is copied to the 'Instance ID'
field of the LISP header, and the I-bit is set to 1.When an ETR decapsulates a packet, the Instance ID from the
LISP header is used as a table identifier to locate the
forwarding table to use for the inner destination EID
lookup.For example, an 802.1Q VLAN tag or VPN identifier could be
used as a 24-bit Instance ID. See
for LISP VPN use-case details. Please note that the Instance ID
is not protected, an on-path attacker can modify the tags and for instance,
allow communicatons between logically isolated VLANs.Participants within a LISP deployment must agree
on the meaning of Instance ID values. The source and destination EIDs
MUST belong to the same Instance ID.
Instance ID SHOULD NOT be used with overlapping IPv6 EID addresses.The Map-Cache contains the state used by ITRs and PITRs to
encapsulate packets. When an ITR/PITR receives a packet from
inside the LISP site to a destination outside of the site a
longest-prefix match lookup of the EID is done to the
Map-Cache (see ). The lookup
returns a single Locator-Set containing a list of RLOCs
corresponding to the EID's topological location. Each RLOC in
the Locator-Set is associated with a 'Priority' and 'Weight',
this information is used to select the RLOC to
encapsulate.The RLOC with the lowest 'Priority' is selected. An RLOC
with 'Priority' 255 means that MUST NOT be used for
forwarding. When multiple RLOCs have the same 'Priority' then
the 'Weight' states how to load balance traffic among them.
The value of the 'Weight' represents the relative weight of
the total packets that match the mapping entry.The following are different scenarios for choosing
RLOCs and the controls that are available:The server-side returns one RLOC. The client-side can only
use one RLOC. The server-side has complete control of the
selection.The server-side returns a list of RLOCs where a subset
of the list has the same best Priority. The client can only use
the subset list according to the
weighting assigned by the server-side. In this case, the
server-side controls both the subset list and load-splitting
across its members. The client-side can use RLOCs outside
of the subset list if it determines that the subset
list is unreachable (unless RLOCs are set to a Priority of 255).
Some sharing of control exists: the server-side determines
the destination RLOC list and load distribution while the
client-side has the option of using alternatives to this list if
RLOCs in the list are unreachable.The server-side sets a Weight of zero for the RLOC subset
list. In this case, the client-side can choose how the traffic
load is spread across the subset list. See for details on load-sharing mechanisms.
Control is shared by the server-side determining the list and
the client-side determining load distribution. Again, the
client can use alternative RLOCs if the server-provided list
of RLOCs is unreachable.Either side (more likely the server-side ETR) decides to "glean"
the RLOCs. For example, if the server-side ETR gleans RLOCs,
then the client-side ITR gives the client-side ITR responsibility
for bidirectional RLOC reachability and preferability. Server-side
ETR gleaning of the client-side ITR RLOC is done by caching the
inner-header source EID and the outer-header source RLOC of
received packets. The client-side ITR controls how traffic is
returned and can alternate using an outer-header source RLOC,
which then can be added to the list the server-side ETR uses
to return traffic. Since no Priority or Weights are provided
using this method, the server-side ETR MUST assume that each
client-side ITR RLOC uses the same best Priority with a Weight
of zero. In addition, since EID-Prefix encoding cannot be conveyed
in data packets, the EID-to-RLOC Cache on Tunnel Routers can grow
to be very large. Gleaning has several important considerations.
A "gleaned" Map-Cache entry is only stored and used for a RECOMMENDED period of 3 seconds,
pending verification. Verification MUST be performed by
sending a Map-Request to the source EID (the inner-header IP source
address) of the received encapsulated packet. A reply to this
"verifying Map-Request" is used to fully populate the Map-Cache entry
for the "gleaned" EID and is stored and used for the time indicated
from the 'TTL' field of a received Map-Reply. When a verified Map-
Cache entry is stored, data gleaning no longer occurs for subsequent
packets that have a source EID that matches the EID-Prefix of the
verified entry. This "gleaning" mechanism MUST NOT be used over
the public Internet and SHOULD only be used in trusted and closed
deployments. Refer to for security issues regarding this
mechanism.RLOCs that appear in EID-to-RLOC Map-Reply messages are
assumed to be reachable when the R-bit for the Locator record is set
to 1. When the R-bit is set to 0, an ITR or PITR MUST NOT
encapsulate to the RLOC. Neither the information contained in
a Map-Reply nor that stored in the mapping database system
provides reachability information for RLOCs. Note that
reachability is not part of the mapping system and is
determined using one or more of the Routing Locator
reachability algorithms described in the next section.Several Data-Plane mechanisms for determining RLOC
reachability are currently defined. Please note that
additional Control-Plane based reachability mechanisms are
defined in .An ETR MAY examine the Locator-Status-Bits in the LISP
header of an encapsulated data packet received from an
ITR. If the ETR is also acting as an ITR and has
traffic to return to the original ITR site, it can use
this status information to help select an RLOC.When an ETR receives an encapsulated packet from an ITR,
the source RLOC from the outer header of the packet is likely
to be reachable. Please note that in some scenarios the
RLOC from the outer header can be an spoofable field.An ITR/ETR pair can use the 'Echo-Noncing' Locator
reachability algorithms described in this section.When determining Locator up/down reachability by
examining the Locator-Status-Bits from the LISP-encapsulated
data packet, an ETR will receive up-to-date status from an
encapsulating ITR about reachability for all ETRs at the
site. CE-based ITRs at the source site can determine
reachability relative to each other using the site IGP as
follows:Under normal circumstances, each ITR will advertise
a default route into the site IGP.If an ITR fails or if the upstream link to its PE
fails, its default route will either time out or be
withdrawn.Each ITR can thus observe the presence or lack of a
default route originated by the others to determine the
Locator-Status-Bits it sets for them.When ITRs at the site are not deployed in CE routers, the IGP
can still be used to determine the reachability of Locators,
provided they are injected into the IGP. This is
typically done when a /32 address is configured on a loopback
interface. RLOCs listed in a Map-Reply are numbered with ordinals
0 to n-1. The Locator-Status-Bits in a LISP-encapsulated
packet are numbered from 0 to n-1 starting with the least
significant bit. For example, if an RLOC listed in the 3rd
position of the Map-Reply goes down (ordinal value 2),
then all ITRs at the site will clear the 3rd least
significant bit (xxxx x0xx) of the 'Locator-Status-Bits'
field for the packets they encapsulate.When an xTR decides to use 'Locator-Status-Bits'
to affect reachability information, it acts as follows:
ETRs decapsulating a packet will check for any change in
the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the
ETR, if acting also as an ITR, will refrain from encapsulating
packets to an RLOC that is indicated as down. It will only resume
using that RLOC if the corresponding Locator-Status-Bit
returns to a value of 1. Locator-Status-Bits are associated with a Locator-Set
per EID-Prefix. Therefore, when a Locator becomes unreachable, the
Locator-Status-Bit that corresponds to that Locator's position in the
list returned by the last Map-Reply will be set to zero for that
particular EID-Prefix.
Locator-Status-Bits MUST NOT be used
over the public Internet and SHOULD only be used in trusted
and closed deployments. In addition Locator-Status-Bits
SHOULD be coupled with Map-Versioning ()
to prevent race conditions where Locator-Status-Bits are interpreted as
referring to different RLOCs than intended. Refer to
for security issues regarding this mechanism.If an ITR encapsulates a packet to an ETR and the packet is
received and decapsulated by the ETR, it is implied but not
confirmed by the ITR that the ETR's RLOC is reachable. In
most cases, the ETR can also reach the ITR but cannot assume
this to be true, due to the possibility of path asymmetry. In
the presence of unidirectional traffic flow from an ITR to an
ETR, the ITR SHOULD NOT use the lack of return traffic as an
indication that the ETR is unreachable. Instead, it MUST use
an alternate mechanism to determine reachability.The security considerations of
related to data-plane reachability applies to the data-plane
RLOC reachability mechanisms described in this section.When data flows bidirectionally between Locators from
different sites, a Data-Plane mechanism called "nonce
echoing" can be used to determine reachability between an ITR
and ETR. When an ITR wants to solicit a nonce echo, it sets
the N- and E-bits and places a 24-bit nonce in the LISP header of the next
encapsulated data packet.When this packet is received by the ETR, the encapsulated
packet is forwarded as normal. When the ETR is an xTR
(co-located as an ITR), it then sends a data packet to the
ITR (when it is an xTR co-located as an ETR), it includes the
nonce received earlier with the N-bit set and E-bit
cleared. The ITR sees this "echoed nonce" and knows that the
path to and from the ETR is up.The ITR will set the E-bit and N-bit for every packet it
sends while in the echo-nonce-request state. The time the
ITR waits to process the echoed nonce before it determines
the path is unreachable is variable and is a choice left for
the implementation.If the ITR is receiving packets from the ETR but does not
see the nonce echoed while being in the echo-nonce-request
state, then the path to the ETR is unreachable. This decision
MAY be overridden by other Locator reachability
algorithms. Once the ITR determines that the path to the ETR
is down, it can switch to another Locator for that
EID-Prefix.Note that "ITR" and "ETR" are relative terms here. Both
devices MUST be implementing both ITR and ETR functionality
for the echo nonce mechanism to operate.The ITR and ETR MAY both go into the echo-nonce-request
state at the same time. The number of packets sent or the
time during which echo nonce requests are sent is an
implementation-specific setting. In this case, an xTR
receiving the echo-nonce-request packets will suspend
the echo-nonce-request state and setup a 'echo-nonce-request-state' timer.
After the 'echo-nonce-request-state' timer expires it will resume
the echo-nonce-request state.This mechanism does not completely solve the forward path
reachability problem, as traffic may be unidirectional. That
is, the ETR receiving traffic at a site MAY not be the same
device as an ITR that transmits traffic from that site, or
the site-to-site traffic is unidirectional so there is no ITR
returning traffic.The echo-nonce algorithm is bilateral. That is, if one
side sets the E-bit and the other side is not enabled for
echo-noncing, then the echoing of the nonce does not occur
and the requesting side may erroneously consider the Locator
unreachable. An ITR SHOULD set the E-bit in an
encapsulated data packet when it knows the ETR is enabled for
echo-noncing. This is conveyed by the E-bit in the
Map-Reply message.Many implementations default to not advertising they are
echo-nonce capable in Map-Reply messages and so RLOC-probing tends
to be used for RLOC reachability.The echo-nonce mechanism MUST NOT be used
over the public Internet and MUST only be used in trusted
and closed deployments. Refer to for
security issues regarding this mechanism.A site MAY be multihomed using two or more ETRs. The hosts
and infrastructure within a site will be addressed using one
or more EID-Prefixes that are mapped to the RLOCs of the
relevant ETRs in the mapping system. One possible failure
mode is for an ETR to lose reachability to one or more of the
EID-Prefixes within its own site. When this occurs when the
ETR sends Map-Replies, it can clear the R-bit associated with
its own Locator. And when the ETR is also an ITR, it can clear
its Locator-Status-Bit in the encapsulation data header.It is recognized that there are no simple solutions to the
site partitioning problem because it is hard to know which
part of the EID-Prefix range is partitioned and which Locators
can reach any sub-ranges of the EID-Prefixes. Note that this
is not a new problem introduced by the LISP architecture. The
problem exists today when a multihomed site uses BGP to
advertise its reachability upstream.When an ETR provides an EID-to-RLOC mapping in a
Map-Reply message that is stored in the Map-Cache of a
requesting ITR, the Locator-Set for the EID-Prefix MAY
contain different Priority and Weight values for each
locator address. When more than one best Priority Locator
exists, the ITR can decide how to load-share traffic against
the corresponding Locators.The following hash algorithm MAY be used by an ITR to
select a Locator for a packet destined to an EID for the
EID-to-RLOC mapping:Either a source and destination address hash or the
traditional 5-tuple hash can be used. The traditional
5-tuple hash includes the source and destination
addresses; source and destination TCP, UDP, or Stream
Control Transmission Protocol (SCTP) port numbers; and the
IP protocol number field or IPv6 next-protocol fields of a
packet that a host originates from within a LISP
site. When a packet is not a TCP, UDP, or SCTP packet, the
source and destination addresses only from the header are
used to compute the hash.Take the hash value and divide it by the number of
Locators stored in the Locator-Set for the EID-to-RLOC
mapping.The remainder will yield a value of 0 to "number of
Locators minus 1". Use the remainder to select the Locator
in the Locator-Set.The specific hash algorithm the ITR uses for load-sharing
is out of scope for this document and does not prevent
interoperability.The Source port SHOULD be the same for all packets belonging to the
same flow. Also note that when a packet is LISP encapsulated, the source
port number in the outer UDP header needs to be set. Selecting
a hashed value allows core routers that are attached to Link
Aggregation Groups (LAGs) to load-split the encapsulated
packets across member links of such LAGs. Otherwise, core
routers would see a single flow, since packets have a source
address of the ITR, for packets that are originated by
different EIDs at the source site. A suggested setting for the
source port number computed by an ITR is a 5-tuple hash
function on the inner header, as described above. The source
port SHOULD be the same for all packets belonging to the same
flow.Many core router implementations use a 5-tuple hash to decide
how to balance packet load across members of a LAG. The 5-tuple
hash includes the source and destination addresses of the packet
and the source and destination ports when the protocol number in
the packet is TCP or UDP. For this reason, UDP encoding is
used for LISP encapsulation. In this scenario, when the outer header is IPv6, the flow label MAY also be
set following the procedures specified in . When the inner header
is IPv6 then the flow label is not zero, it MAY be used to compute the hash.Since the LISP architecture uses a caching scheme to
retrieve and store EID-to-RLOC mappings, the only way an ITR
can get a more up-to-date mapping is to re-request the
mapping. However, the ITRs do not know when the mappings
change, and the ETRs do not keep track of which ITRs
requested its mappings. For scalability reasons, it is
desirable to maintain this approach but need to provide a
way for ETRs to change their mappings and inform the sites
that are currently communicating with the ETR site using
such mappings.This section defines two Data-Plane mechanism for updating
EID-to-RLOC mappings. Additionally, the Solicit-Map Request
(SMR) Control-Plane updating mechanism is specified in .Locator-Status-Bits (LSB) can also be used to keep track of the
Locator status (up or down) when EID-to-RLOC mappings are changing. When LSB are used in a LISP deployment, all LISP tunnel routers MUST implement both ITR and ETR capabilities (therefore all tunnel routers are effectively xTRs). In this section the term "source xTR" is used to refer to the xTR setting the LSB and "destination xTR" is used to refer to the xTR receiving the LSB. The procedure is as follows:
First, when a Locator record is added or removed from the Locator-Set, the source xTR
will signal this by sending a Solicit-Map Request (SMR) Control-Plane message to the destination xTR. At this point the source xTR MUST NOT use LSB (L-bit = 0) since the
destination xTR site has outdated information. The source xTR will setup a 'use-LSB' timer.Second and as defined in ,
upon reception of the SMR message the destination xTR will retrieve the updated
EID-to-RLOC mappings by sending a Map-Request.And third, when the 'use-LSB' timer expires, the source xTR can use again LSB with the destination xTR to signal the Locator status (up or down).
The specific value for the 'use-LSB' timer depends on the LISP deployment, the 'use-LSB' timer needs to be large enough
for the destination xTR to retreive the updated EID-to-RLOC mappings. A RECOMMENDED value for the 'use-LSB' timer is 5 minutes.When there is unidirectional packet flow between an ITR and
ETR, and the EID-to-RLOC mappings change on the ETR, it needs to
inform the ITR so encapsulation to a removed Locator can stop
and can instead be started to a new Locator in the
Locator-Set.An ETR, when it sends Map-Reply messages, conveys its
own Map-Version Number. This is known as the Destination
Map-Version Number. ITRs include the Destination
Map-Version Number in packets they encapsulate to the
site. When an ETR decapsulates a packet and detects that the
Destination Map-Version Number is less than the current
version for its mapping, the SMR procedure described in
occurs.An ITR, when it encapsulates packets to ETRs, can convey
its own Map-Version Number. This is known as the Source
Map-Version Number. When an ETR decapsulates a packet and
detects that the Source Map-Version Number is greater than the
last Map-Version Number sent in a Map-Reply from the ITR's site,
the ETR will send a Map-Request to one of the ETRs for the source
site.A Map-Version Number is used as a sequence number per
EID-Prefix, so values that are greater are considered to be
more recent. A value
of 0 for the Source Map-Version Number or the Destination
Map-Version Number conveys no versioning information, and an
ITR does no comparison with previously received Map-Version
Numbers.A Map-Version Number can be included in Map-Register messages
as well. This is a good way for the Map-Server to assure that
all ETRs for a site registering to it will be synchronized
according to Map-Version Number.Map-Version requires that ETRs within the LISP site are synchronized
with respect to the Map-Version Number, EID-prefix and the set and status (up/down)
of the RLOCs. The use of Map-Versioning without proper synchronization may cause
traffic disruption. The synchronization protocol is out-of-the-scope of this document, but MUST
keep ETRs synchronized within a 1 minute window.Map-Versioning MUST NOT be used over the public Internet and
SHOULD only be used in trusted and closed deployments. Refer to
for security issues regarding this mechanism.See for a more
detailed analysis and description of Database
Map-Versioning.A multicast group address, as defined in the original Internet
architecture, is an identifier of a grouping of topologically
independent receiver host locations. The address encoding itself
does not determine the location of the receiver(s). The multicast
routing protocol, and the network-based state the protocol creates,
determine where the receivers are located.In the context of LISP, a multicast group address is both an
EID and a Routing Locator. Therefore, no specific semantic or
action needs to be taken for a destination address, as it would
appear in an IP header. Therefore, a group address that
appears in an inner IP header built by a source host will be
used as the destination EID. The outer IP header (the
destination Routing Locator address), prepended by a LISP
router, can use the same group address as the destination
Routing Locator, use a multicast or unicast Routing Locator
obtained from a Mapping System lookup, or use other means to
determine the group address mapping.With respect to the source Routing Locator address, the ITR
prepends its own IP address as the source address of the outer
IP header, just like it would if the destination EID was a
unicast address. This source Routing Locator address, like any
other Routing Locator address, MUST be routable on the underlay.There are two approaches for LISP-Multicast, one that uses
native multicast routing in the underlay with no support from
the Mapping System and the other that uses only unicast routing
in the underlay with support from the Mapping System. See and , respectively,
for details. Details for LISP-Multicast and interworking with
non-LISP sites are described in and
.LISP is designed to be very "hardware-based forwarding
friendly". A few implementation techniques can be used to
incrementally implement LISP:When a tunnel-encapsulated packet is received by an
ETR, the outer destination address may not be the address
of the router. This makes it challenging for the control
plane to get packets from the hardware. This may be
mitigated by creating special Forwarding Information Base
(FIB) entries for the EID-Prefixes of EIDs served by the
ETR (those for which the router provides an RLOC
translation). These FIB entries are marked with a flag
indicating that Control-Plane processing SHOULD be
performed. The forwarding logic of testing for particular
IP protocol number values is not necessary. There are a
few proven cases where no changes to existing deployed
hardware were needed to support the LISP Data-Plane.On an ITR, prepending a new IP header consists of adding
more octets to a MAC rewrite string and prepending the
string as part of the outgoing encapsulation
procedure. Routers that support Generic Routing Encapsulation
(GRE) tunneling or 6to4 tunneling
may already support this
action.A packet's source address or interface the
packet was received on can be used to select VRF
(Virtual Routing/Forwarding). The VRF's routing table
can be used to find EID-to-RLOC mappings.For performance issues related to Map-Cache management, see
.In what follows we highlight security
considerations that apply when LISP is deployed in environments such
as those specified in .The optional mechanisms of gleaning is offered to directly obtain
a mapping from the LISP encapsulated packets. Specifically, an xTR
can learn the EID-to-RLOC mapping by inspecting the source RLOC and
source EID of an encapsulated packet, and insert this new mapping
into its Map-Cache. An off-path attacker can spoof the source EID
address to divert the traffic sent to the victim's spoofed EID. If
the attacker spoofs the source RLOC, it can mount a DoS attack by
redirecting traffic to the spoofed victim's RLOC, potentially
overloading it.The LISP Data-Plane defines several mechanisms to monitor RLOC
Data-Plane reachability, in this context Locator-Status Bits,
Nonce-Present and Echo-Nonce bits of the LISP encapsulation header
can be manipulated by an attacker to mount a DoS attack. An off-path
attacker able to spoof the RLOC and/or nonce of a victim's xTR can
manipulate such mechanisms to declare false information about the
RLOC's reachability status.For example of such attacks, an off-path attacker can exploit the
echo-nonce mechanism by sending data packets to an ITR with a random
nonce from an ETR's spoofed RLOC. Note the attacker must guess a
valid nonce the ITR is requesting to be echoed within a small window
of time. The goal is to convince the ITR that the ETR's RLOC is
reachable even when it may not be reachable. If the attack is
successful, the ITR believes the wrong reachability status of the
ETR's RLOC until RLOC-probing detects the correct status. This time
frame is on the order of 10s of seconds. This specific attack can
be mitigated by preventing RLOC spoofing in the network by deploying
uRPF BCP 38 . In addition and in order to exploit
this vulnerability, the off-path attacker must send echo-nonce
packets at high rate. If the nonces have never been requested by the
ITR, it can protect itself from erroneous reachability attacks.A LISP-specific uRPF check is also possible. When decapsulating,
an ETR can check that the source EID and RLOC are valid EID-to-RLOC
mappings by checking the Mapping System.Map-Versioning is a Data-Plane mechanism used to signal a peering
xTR that a local EID-to-RLOC mapping has been updated, so that the
peering xTR uses LISP Control-Plane signaling message to retrieve a
fresh mapping. This can be used by an attacker to forge the
map-versioning field of a LISP encapsulated header and force an
excessive amount of signaling between xTRs that may overload them.Locator-Status-Bits, echo-nonce and map-versioning MUST NOT be used
over the public Internet and SHOULD only be used in trusted
and closed deployments. In addition Locator-Status-Bits
SHOULD be coupled with map-versioning to prevent race conditions
where Locator-Status-Bits are interpreted as referring to different RLOCs than intended.LISP implementations and deployments which permit outer header fragments
of IPv6 LISP encapsulated packets as a means of dealing with MTU issues
should also use implementation techniques in ETRs to prevent this
from being a DoS attack vector. Limits on the number of fragments
awaiting reassembly at an ETR, RTR, or PETR, and the rate of admitting
such fragments may be used.Considerations for network management tools exist so the LISP
protocol suite can be operationally managed. These mechanisms can
be found in and .For implementation considerations, the following changes have been made
to this document since RFC 6830 was published:It is no longer mandated that a maximum number of 2 LISP
headers be prepended to a packet. If there is a application need
for more than 2 LISP headers, an implementation can support
more. However, it is RECOMMENDED that a maximum of two LISP
headers can be prepended to a packet.The 3 reserved flag bits in the LISP header have been allocated
for . The low-order 2 bits of the 3-bit
field (now named the KK bits) are used as a key identifier. The 1
remaining bit is still documented as reserved and unassigned.Data-Plane gleaning for creating map-cache entries has been
made optional. Any ITR implementations that depend on or assume the
remote ETR is gleaning should not do so. This does not create any
interoperability problems since the control-plane map-cache
population procedures are unilateral and are the typical method
for map-cache population.The bulk of the changes to this document which reduces its
length are due to moving the LISP control-plane messaging and
procedures to .This section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of values related to this
Data-Plane LISP specification, in accordance with BCP 26 .The IANA registry has allocated UDP port number 4341 for the
LISP Data-Plane. IANA has updated the description for UDP port
4341 as follows:Endpoints and Endpoint names: A Proposed
Address Family NumbersIANAAn initial thank you goes to Dave Oran for planting the seeds for
the initial ideas for LISP. His consultation continues to provide
value to the LISP authors.A special and appreciative thank you goes to Noel Chiappa for
providing architectural impetus over the past decades on separation
of location and identity, as well as detailed reviews of the LISP
architecture and documents, coupled with enthusiasm for making LISP
a practical and incremental transition for the Internet.The original authors would like to gratefully acknowledge many people who
have contributed discussions and ideas to the making of this
proposal. They include Scott Brim, Andrew Partan, John Zwiebel,
Jason Schiller, Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay
Gill, Geoff Huston, David Conrad, Mark Handley, Ron Bonica, Ted
Seely, Mark Townsley, Chris Morrow, Brian Weis, Dave McGrew, Peter
Lothberg, Dave Thaler, Eliot Lear, Shane Amante, Ved Kafle, Olivier
Bonaventure, Luigi Iannone, Robin Whittle, Brian Carpenter, Joel
Halpern, Terry Manderson, Roger Jorgensen, Ran Atkinson, Stig
Venaas, Iljitsch van Beijnum, Roland Bless, Dana Blair, Bill Lynch,
Marc Woolward, Damien Saucez, Damian Lezama, Attilla De Groot,
Parantap Lahiri, David Black, Roque Gagliano, Isidor Kouvelas,
Jesper Skriver, Fred Templin, Margaret Wasserman, Sam Hartman,
Michael Hofling, Pedro Marques, Jari Arkko, Gregg Schudel, Srinivas
Subramanian, Amit Jain, Xu Xiaohu, Dhirendra Trivedi, Yakov Rekhter,
John Scudder, John Drake, Dimitri Papadimitriou, Ross Callon, Selina
Heimlich, Job Snijders, Vina Ermagan, Fabio Maino, Victor Moreno,
Chris White, Clarence Filsfils, Alia Atlas, Florin Coras and Alberto
Rodriguez.This work originated in the Routing Research Group (RRG) of the
IRTF. An individual submission was converted into the IETF LISP
working group document that became this RFC.The LISP working group would like to give a special thanks to
Jari Arkko, the Internet Area AD at the time that the set of LISP
documents were being prepared for IESG last call, and for his
meticulous reviews and detailed commentaries on the 7 working group
last call documents progressing toward standards-track RFCs.The current authors would like to give a sincere thank you to the
people who help put LISP on standards track in the IETF. They
include Joel Halpern, Luigi Iannone, Deborah Brungard, Fabio Maino,
Scott Bradner, Kyle Rose, Takeshi Takahashi, Sarah Banks, Pete Resnick,
Colin Perkins, Mirja Kuhlewind, Francis Dupont, Benjamin Kaduk, Eric
Rescorla, Alvaro Retana, Alexey Melnikov, Alissa Cooper, Suresh
Krishnan, Alberto Rodriguez-Natal, Vina Ermagen, Mohamed Boucadair,
Brian Trammell, Sabrina Tanamal, and John Drake. The contributions
they offered greatly added to the security, scale, and robustness of
the LISP architecture and protocols.[RFC Editor: Please delete this section on publication as RFC.]Posted November 2019.Fixed how LSB behave in the presence of new/removed locators.Added ETR synchronization requirements when using Map-Versioning.Fixed a large set of minor comments and edits.Posted April 2019 post telechat.Made editorial corrections per Warren's suggestions.Put in suggested text from Luigi that Mirja agreed with.LSB, Echo-Nonce and Map-Versioning SHOULD be only used in closed environments.Removed paragraph stating that Instance-ID can be 32-bit in the control-plane.6831/8378 are now normative.Rewritten Security Considerations according to the changes.Stated that LSB SHOULD be coupled with Map-Versioning.Posted late October 2018.Changed description about "reserved" bits to state "reserved
and unassigned".Posted mid October 2018.Added more to the Security Considerations section with discussion
about echo-nonce attacks.Posted mid October 2018.Final editorial changes for Eric and Ben.Posted early October 2018.Added an applicability statement in section 1 to address security
concerns from Telechat.Posted early October 2018.Changes to reflect comments post Telechat.Posted late-September 2018.Changes to reflect comments from Sep 27th Telechat.Posted late-September 2018.Fix old reference to RFC3168, changed to RFC6040.Posted late-September 2018.More editorial changes.Posted mid-September 2018.Changes to reflect comments from Secdir review (Mirja).Posted September 2018.Indicate in the "Changes since RFC 6830" section why the document
has been shortened in length.Make reference to RFC 8085 about UDP congestion control.More editorial changes from multiple IESG reviews.Posted late August 2018.Distinguish the message type names between ICMP for IPv4 and
ICMP for IPv6 for handling MTU issues.Posted August 2018.Final editorial changes before RFC submission for Proposed
Standard.Added section "Changes since RFC 6830" so implementers are informed
of any changes since the last RFC publication.Posted July 2018 IETF week.Put obsolete of RFC 6830 in Intro section in addition to abstract.Posted March IETF Week 2018.Clarified that a new nonce is required per RLOC.Removed 'Clock Sweep' section. This text must be placed in a
new OAM document.Some references changed from normative to informativePosted July 2018.Fixed Luigi editorial comments to ready draft for RFC status.Posted March 2018.Removed sections 16, 17 and 18 (Mobility, Deployment and
Traceroute considerations). This text must be placed in a new
OAM document.Posted March 2018.Updated section 'Router Locator Selection' stating that the
Data-Plane MUST follow what's stored in the Map-Cache
(priorities and weights).Section 'Routing Locator Reachability': Removed bullet point
2 (ICMP Network/Host Unreachable),3 (hints from BGP),4 (ICMP
Port Unreachable),5 (receive a Map-Reply as a response) and RLOC
probing Removed 'Solicit-Map Request'.Posted January 2018.Add more details in section 5.3 about DSCP processing during
encapsulation and decapsulation.Added clarity to definitions in the Definition of Terms section
from various commenters.Removed PA and PI definitions from Definition of Terms section.More editorial changes.Removed 4342 from IANA section and move to RFC6833 IANA section.Posted January 2018.Remove references to research work for any protocol mechanisms.Document scanned to make sure it is RFC 2119 compliant.Made changes to reflect comments from document WG shepherd Luigi
Iannone.Ran IDNITs on the document.Posted November 2017.Rephrase how Instance-IDs are used and don't refer to addresses.Posted October 2017.Put RTR definition before it is used.Rename references that are now working group drafts.Remove "EIDs MUST NOT be used as used by a host to refer to
other hosts. Note that EID blocks MAY LISP RLOCs".Indicate what address-family can appear in data packets.ETRs may, rather than will, be the ones to send Map-Replies.Recommend, rather than mandate, max encapsulation headers to 2.Reference VPN draft when introducing Instance-ID.Indicate that SMRs can be sent when ITR/ETR are in the same node.Clarify when private addresses can be used.Posted August 2017.Make it clear that a Re-encapsulating Tunnel Router is an RTR.Posted July 2017.Changed reference of IPv6 RFC2460 to RFC8200.Indicate that the applicability statement for UDP zero checksums
over IPv6 adheres to RFC6936.Posted May 2017.Move the control-plane related codepoints in the IANA Considerations
section to RFC6833bis.Posted April 2017.Reflect some editorial comments from Damien Sausez.Posted March 2017.Include references to new RFCs published.Change references from RFC6833 to RFC6833bis.Clarified LCAF text in the IANA section.Remove references to "experimental".Posted December 2016.Created working group document from draft-farinacci-lisp
-rfc6830-00 individual submission. No other changes made.