Network Working Group D. Farinacci
Internet-Draft V. Fuller
Intended status: Standards Track D. Meyer
Expires: September 27, 2017 D. Lewis
Cisco Systems
A. Cabellos (Ed.)
UPC/BarcelonaTech
March 26, 2017
The Locator/ID Separation Protocol (LISP)
draft-ietf-lisp-rfc6830bis-01
Abstract
This document describes the Locator/ID Separation Protocol (LISP)
data-plane encapsulation protocol. 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. The
map-cache is populated by the LISP Control-Plane protocol
[I-D.ietf-lisp-rfc6833bis].
LISP requires no change to either host protocol stacks or to underlay
routers and offers Traffic Engineering, multihoming and mobility,
among other features.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on September 27, 2017.
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Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4
3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4
4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . 11
5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . 13
5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 14
5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 15
5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . 16
6. LISP EID-to-RLOC Map-Cache . . . . . . . . . . . . . . . . . 20
7. Dealing with Large Encapsulated Packets . . . . . . . . . . . 20
7.1. A Stateless Solution to MTU Handling . . . . . . . . . . 21
7.2. A Stateful Solution to MTU Handling . . . . . . . . . . . 22
8. Using Virtualization and Segmentation with LISP . . . . . . . 22
9. Routing Locator Selection . . . . . . . . . . . . . . . . . . 23
10. Routing Locator Reachability . . . . . . . . . . . . . . . . 24
10.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . . 27
10.2. RLOC-Probing Algorithm . . . . . . . . . . . . . . . . . 28
11. EID Reachability within a LISP Site . . . . . . . . . . . . . 29
12. Routing Locator Hashing . . . . . . . . . . . . . . . . . . . 29
13. Changing the Contents of EID-to-RLOC Mappings . . . . . . . . 30
13.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . . 31
13.2. Solicit-Map-Request (SMR) . . . . . . . . . . . . . . . 32
13.3. Database Map-Versioning . . . . . . . . . . . . . . . . 33
14. Multicast Considerations . . . . . . . . . . . . . . . . . . 34
15. Router Performance Considerations . . . . . . . . . . . . . . 35
16. Mobility Considerations . . . . . . . . . . . . . . . . . . . 36
16.1. Slow Mobility . . . . . . . . . . . . . . . . . . . . . 36
16.2. Fast Mobility . . . . . . . . . . . . . . . . . . . . . 36
16.3. LISP Mobile Node Mobility . . . . . . . . . . . . . . . 37
17. LISP xTR Placement and Encapsulation Methods . . . . . . . . 37
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17.1. First-Hop/Last-Hop xTRs . . . . . . . . . . . . . . . . 38
17.2. Border/Edge xTRs . . . . . . . . . . . . . . . . . . . . 39
17.3. ISP Provider Edge (PE) xTRs . . . . . . . . . . . . . . 39
17.4. LISP Functionality with Conventional NATs . . . . . . . 40
17.5. Packets Egressing a LISP Site . . . . . . . . . . . . . 40
18. Traceroute Considerations . . . . . . . . . . . . . . . . . . 41
18.1. IPv6 Traceroute . . . . . . . . . . . . . . . . . . . . 42
18.2. IPv4 Traceroute . . . . . . . . . . . . . . . . . . . . 42
18.3. Traceroute Using Mixed Locators . . . . . . . . . . . . 42
19. Security Considerations . . . . . . . . . . . . . . . . . . . 43
20. Network Management Considerations . . . . . . . . . . . . . . 44
21. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44
21.1. LISP ACT and Flag Fields . . . . . . . . . . . . . . . . 44
21.2. LISP Address Type Codes . . . . . . . . . . . . . . . . 44
21.3. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . 45
21.4. LISP Key ID Numbers . . . . . . . . . . . . . . . . . . 45
22. References . . . . . . . . . . . . . . . . . . . . . . . . . 45
22.1. Normative References . . . . . . . . . . . . . . . . . . 45
22.2. Informative References . . . . . . . . . . . . . . . . . 48
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 52
Appendix B. Document Change Log . . . . . . . . . . . . . . . . 52
B.1. Changes to draft-ietf-lisp-rfc6830bis-01 . . . . . . . . 53
B.2. Changes to draft-ietf-lisp-rfc6830bis-00 . . . . . . . . 53
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53
1. Introduction
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 [CHIAPPA]. 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 numbering spaces and for encapsulating traffic originated by
devices using non-routable EIDs for transport across a network
infrastructure that routes and forwards using RLOCs.
LISP is an overlay protocol that separates control from data-plane,
this document specifies the data-plane, 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
[I-D.ietf-lisp-rfc6833bis].
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LISP does not require changes to either 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 [RFC4984])
This document specifies the LISP data-plane encapsulation and other
xTR functionality while [I-D.ietf-lisp-rfc6833bis] specifies the LISP
control plane. LISP deployment guidelines can be found in [RFC7215]
and [RFC6835] describes considerations for network operational
management. Finally, [I-D.ietf-lisp-introduction] describes the LISP
architecture.
2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Definition of Terms
Provider-Independent (PI) Addresses: PI addresses are an address
block assigned from a pool where blocks are not associated with
any particular location in the network (e.g., from a particular
service provider) and are therefore not topologically aggregatable
in the routing system.
Provider-Assigned (PA) Addresses: PA addresses are an address block
assigned to a site by each service provider to which a site
connects. Typically, each block is a sub-block of a service
provider Classless Inter-Domain Routing (CIDR) [RFC4632] block and
is aggregated into the larger block before being advertised into
the global Internet. Traditionally, IP multihoming has been
implemented by each multihomed site acquiring its own globally
visible prefix. LISP uses only topologically assigned and
aggregatable address blocks for RLOCs, eliminating this
demonstrably non-scalable practice.
Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6
[RFC2460] address of an Egress Tunnel Router (ETR). An RLOC is
the output of an EID-to-RLOC mapping lookup. An EID maps to one
or more RLOCs. Typically, RLOCs are numbered from topologically
aggregatable blocks that are assigned to a site at each point to
which it attaches to the global Internet; where the topology is
defined by the connectivity of provider networks, RLOCs can be
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thought of as PA addresses. Multiple RLOCs can be assigned to the
same ETR device or to multiple ETR devices at a site.
Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for
IPv6) value used 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) [RFC1034]
lookup or Session Initiation Protocol (SIP) [RFC3261] 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 globally
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. EIDs MUST NOT be used as
LISP RLOCs. 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 global routing system. In theory, the bit string
that represents an EID for one device can represent an RLOC for a
different device. As the architecture is realized, if a given bit
string is both an RLOC and an EID, it must refer to the same
entity in both cases. 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.
EID-Prefix: 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 that make up
a "database mapping". EID-Prefix allocations can be broken up
into smaller blocks when an RLOC set is to be associated with the
larger EID-Prefix block. A globally routed address block (whether
PI or PA) is not inherently an EID-Prefix. A globally routed
address block MAY be used by its assignee as an EID block. The
converse is not supported. That is, a site that receives an
explicitly allocated EID-Prefix may not use that EID-Prefix as a
globally routed prefix. This would require coordination and
cooperation with the entities managing the mapping infrastructure.
Once this has been done, that block could be removed from the
globally routed IP system, if other suitable transition and access
mechanisms are in place. Discussion of such transition and access
mechanisms can be found in [RFC6832] and [RFC7215].
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End-system: 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 globally (i.e., outside of its routing
domain). An end-system can be a host computer, a switch or router
device, or any network appliance.
Ingress Tunnel Router (ITR): 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 globally routable
RLOCs 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.
Specifically, when a service provider prepends a LISP header for
Traffic Engineering purposes, the router that does this is also
regarded as an ITR. The outer RLOC the ISP ITR uses can be based
on the outer destination address (the originating ITR's supplied
RLOC) or the inner destination address (the originating host's
supplied EID).
TE-ITR: A TE-ITR is an ITR that is deployed in a service provider
network that prepends an additional LISP header for Traffic
Engineering purposes.
Egress Tunnel Router (ETR): 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.
TE-ETR: A TE-ETR is an ETR that is deployed in a service provider
network that strips an outer LISP header for Traffic Engineering
purposes.
xTR: 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
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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.
LISP Router: A LISP router is a router that performs the functions
of any or all of the following: ITR, ETR, Proxy-ITR (PITR), or
Proxy-ETR (PETR).
EID-to-RLOC Map-Cache: The EID-to-RLOC map-cache is a 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 global in scope.
EID-to-RLOC Database: The EID-to-RLOC Database is a global
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
globally visible IP addresses. The same database mapping entries
MUST be configured on all ETRs for a given site. In a steady
state, the EID-Prefixes for the site and the Locator-Set for each
EID-Prefix MUST be the same on all ETRs. Procedures to enforce
and/or verify this are outside the scope of this document. Note
that there MAY be transient conditions when the EID-Prefix for the
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.
Recursive Tunneling: 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. Any references to tunnels in this specification refer to
dynamic encapsulating tunnels; they are never statically
configured.
Re-encapsulating Tunnels: Re-encapsulating Tunneling occurs when an
ETR removes a LISP header, then acts as an ITR to prepend another
LISP header. Doing this allows a packet to be re-routed by the
re-encapsulating router without adding the overhead of additional
tunnel headers. Any references to tunnels in this specification
refer to dynamic encapsulating tunnels; they are never statically
configured. When using multiple mapping database systems, care
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must be taken to not create re-encapsulation loops through
misconfiguration.
LISP Header: 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.
Address Family Identifier (AFI): AFI is a term used to describe an
address encoding in a packet. An address family currently
pertains to an IPv4 or IPv6 address. See [AFN] and [RFC3232] 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.
Negative Mapping Entry: A negative mapping entry, also known as a
negative cache entry, is an EID-to-RLOC entry where an EID-Prefix
is advertised or stored with no RLOCs. That is, the Locator-Set
for the EID-to-RLOC entry is empty or has an encoded Locator count
of 0. This type of entry could be used to describe a prefix from
a non-LISP site, which is explicitly not in the mapping database.
There are a set of well-defined actions that are encoded in a
Negative Map-Reply.
Data-Probe: A Data-Probe is a LISP-encapsulated data packet where
the inner-header destination address equals the outer-header
destination address used to trigger a Map-Reply by a decapsulating
ETR. In addition, the original packet is decapsulated and
delivered to the destination host if the destination EID is in the
EID-Prefix range configured on the ETR. Otherwise, the packet is
discarded. A Data-Probe is used in some of the mapping database
designs to "probe" or request a Map-Reply from an ETR; in other
cases, Map-Requests are used. See each mapping database design
for details. When using Data-Probes, by sending Map-Requests on
the underlying routing system, EID-Prefixes must be advertised.
However, this is discouraged if the core is to scale by having
less EID-Prefixes stored in the core router's routing tables.
Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A
PITR acts like an ITR but does so on behalf of non-LISP sites that
send packets to destinations at LISP sites.
Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A
PETR acts like an ETR but does so on behalf of LISP sites that
send packets to destinations at non-LISP sites.
Route-returnability: Route-returnability is an assumption that the
underlying routing system will deliver packets to the destination.
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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.
LISP site: 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.
Client-side: Client-side is a term used in this document to indicate
a connection initiation attempt by an EID. The ITR(s) at the LISP
site are the first to get involved in obtaining database Map-Cache
entries by sending Map-Request messages.
Server-side: Server-side is a term used in this document to indicate
that a connection initiation attempt is being accepted for a
destination EID. The ETR(s) at the destination LISP site are the
first to send Map-Replies to the source site initiating the
connection. The ETR(s) at this destination site can obtain
mappings by gleaning information from Map-Requests, Data-Probes,
or encapsulated packets.
Locator-Status-Bits (LSBs): 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 Section 10.
Anycast Address: Anycast Address is a term used in this document to
refer 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.
4. Basic Overview
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
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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:
o End-systems only send to addresses that are EIDs. They 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.
o EIDs are typically IP addresses assigned to hosts.
o Other types of EID are supported by LISP, see [RFC8060] for
further information.
o LISP routers mostly deal with Routing Locator addresses. See
details in Section 4.1 to clarify what is meant by "mostly".
o RLOCs are always IP addresses assigned to routers, preferably
topologically oriented addresses from provider CIDR (Classless
Inter-Domain Routing) blocks.
o 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.
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o 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.
o EID-Prefixes are likely to be hierarchically assigned in a manner
that is optimized for administrative convenience and to facilitate
scaling of the EID-to-RLOC mapping database. The hierarchy is
based on an address allocation hierarchy that is independent of
the network topology.
o 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 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 mandates 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.
4.1. Packet Flow Sequence
This section provides an example of the unicast packet flow,
including also control-plane information as specified in
[I-D.ietf-lisp-rfc6833bis]. The example also assumes the following
conditions:
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o Source host "host1.abc.example.com" is sending a packet to
"host2.xyz.example.com", exactly what host1 would do if the site
was not using LISP.
o 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.
o 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.
o Map-Requests are sent to the mapping database system by using the
LISP control-plane protocol documented in
[I-D.ietf-lisp-rfc6833bis]. A Map-Request is sent for an external
destination when the destination is not found in the forwarding
table or matches a default route.
o Map-Replies are sent on the underlying routing system topology
using the [I-D.ietf-lisp-rfc6833bis] control-plane protocol.
Client host1.abc.example.com wants to communicate with server
host2.xyz.example.com:
1. 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.
2. The LISP ITR must be able to map the destination EID to an RLOC
of one of the ETRs at the destination site. The specific method
used to do this is not described in this example. See
[I-D.ietf-lisp-rfc6833bis] for further information.
3. The ITR sends a LISP Map-Request as specified in
[I-D.ietf-lisp-rfc6833bis]. Map-Requests SHOULD be rate-limited.
4. 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.
5. 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
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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.
6. The ITR receives the Map-Reply message, parses the message (to
check for format validity), 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.
7. 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.
8. 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.
9. 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 "gleaned" 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.
5. LISP Encapsulation Details
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 Too Big message is returned to the source.
This specification RECOMMENDS that implementations provide support
for one of the proposed fragmentation and reassembly schemes. Two
existing schemes are detailed in Section 7.
Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP
architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner
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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 [RFC8060].
5.1. LISP IPv4-in-IPv4 Header Format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| IHL |Type of Service| Total Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Identification |Flags| Fragment Offset |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OH | Time to Live | Protocol = 17 | Header Checksum |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Source Routing Locator |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | Destination Routing Locator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L |N|L|E|V|I|R|K|K| Nonce/Map-Version |
I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S / | Instance ID/Locator-Status-Bits |
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| IHL |Type of Service| Total Length |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Identification |Flags| Fragment Offset |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IH | Time to Live | Protocol | Header Checksum |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Source EID |
\ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | Destination EID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IHL = IP-Header-Length
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5.2. LISP IPv6-in-IPv6 Header Format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| Traffic Class | Flow Label |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Payload Length | Next Header=17| Hop Limit |
v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
O + +
u | |
t + Source Routing Locator +
e | |
r + +
| |
H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
d | |
r + +
| |
^ + Destination Routing Locator +
| | |
\ + +
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Source Port = xxxx | Dest Port = 4341 |
UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\ | UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L |N|L|E|V|I|R|K|K| Nonce/Map-Version |
I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
S / | Instance ID/Locator-Status-Bits |
P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ |Version| Traffic Class | Flow Label |
/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ | Payload Length | Next Header | Hop Limit |
v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
I + +
n | |
n + Source EID +
e | |
r + +
| |
H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
d | |
r + +
| |
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^ + Destination EID +
\ | |
\ + +
\ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
5.3. Tunnel Header Field Descriptions
Inner Header (IH): The inner header is the header on the datagram
received from the originating host. The source and destination IP
addresses are EIDs [RFC0791] [RFC2460].
Outer Header: (OH) 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 [RFC0768]. The setting of the Don't Fragment (DF) bit
'Flags' field is according to rules listed in Sections 7.1 and
7.2.
UDP Header: The UDP header contains an ITR selected source port when
encapsulating a packet. See Section 12 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.
UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero
by an ITR for either IPv4 [RFC0768] or IPv6 encapsulation
[RFC6935] [RFC6936]. 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
checksums for all tunneling protocols, including LISP, is under
active discussion within the IETF. When that discussion
concludes, any necessary changes will be made to align LISP with
the outcome of the broader discussion.
UDP Length: 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.
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N: 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 Section 10.1 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.
L: 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.
x 1 x x 0 x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|R|K|K| Nonce/Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Locator-Status-Bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E: 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
Section 10.1 for details.
V: The V-bit is the Map-Version present bit. When this bit is set to
1, the N-bit MUST be 0. Refer to Section 13.3 for more details.
This bit indicates that the LISP header is encoded in this
case as:
0 x 0 1 x x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID/Locator-Status-Bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
I: The I-bit is the Instance ID bit. See Section 8 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:
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x x x x 1 x x x
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|L|E|V|I|R|K|K| Nonce/Map-Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID | LSBs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
R: The R-bit is a Reserved bit for future use. It MUST be set to 0
on transmit and MUST be ignored on receipt.
KK: The KK-bits are a 2-bit field used when encapsualted packets are
encrypted. The field is set to 00 when the packet is not
encrypted. See [RFC8061] for further information.
LISP Nonce: 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
destinations. However, the same nonce can be used for a period of
time to the same destination. 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
Section 10.1 for more details.
LISP Locator-Status-Bits (LSBs): 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
Section 10 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. 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:
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o 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.
o The outer-header 'Type of Service' field (or the 'Traffic Class'
field, in the case of IPv6) SHOULD be copied from the inner-header
'Type of Service' field (with one exception; see below).
When doing ETR/PETR decapsulation:
o The inner-header 'Time to Live' field (or 'Hop Limit' field, in
the case of IPv6) SHOULD be copied from the outer-header 'Time to
Live' field, when the Time to Live value of the outer header is
less than the Time to Live value of the inner header. Failing to
perform this check can cause the Time to Live 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.
o The inner-header 'Type of Service' field (or the 'Traffic Class'
field, in the case of IPv6) SHOULD be copied from the outer-header
'Type of Service' field (with one exception; see below).
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. See Section 18.3 for TTL exception handling for
traceroute packets.
The Explicit Congestion Notification ('ECN') field occupies bits 6
and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic
Class' field [RFC3168]. The 'ECN' field requires special treatment
in order to avoid discarding indications of congestion [RFC3168].
ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner
header to the outer header. Re-encapsulation MUST copy the 2-bit
'ECN' field from the stripped outer header to the new outer header.
If the 'ECN' field contains a congestion indication codepoint (the
value is '11', the Congestion Experienced (CE) codepoint), then ETR
decapsulation MUST copy the 2-bit 'ECN' field from the stripped outer
header to the surviving inner header that is used to forward the
packet beyond the ETR. These requirements preserve CE indications
when a packet that uses ECN traverses a LISP tunnel and becomes
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marked with a CE indication due to congestion between the tunnel
endpoints.
6. LISP EID-to-RLOC Map-Cache
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 [I-D.ietf-lisp-rfc6833bis]. The
mapping 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 Section 13 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
Section 10 for the specific mechanisms.
7. Dealing with Large Encapsulated Packets
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.
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7.1. A Stateless Solution to MTU Handling
An ITR stateless solution to handle MTU issues is described as
follows:
1. 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.
2. 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.
3. 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 is performed by the ITR 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 is greater than L and send an ICMP 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.
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7.2. A Stateful Solution to MTU Handling
An ITR stateful solution to handle MTU issues is described as follows
and was first introduced in [OPENLISP]:
1. 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.
2. When an IPv6-encapsulated packet, or 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
ICMP Too Big message to the ITR. 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.
3. 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 ICMP Too Big message
back to the source. The packet size advertised by the ITR in the
ICMP Too Big 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.
8. Using Virtualization and Segmentation with LISP
When multiple organizations inside of a LISP site are using private
addresses [RFC1918] as EID-Prefixes, their address spaces MUST remain
segregated due to possible address duplication. An Instance ID in
the address encoding can aid in making the entire AFI-based address
unique. See IANA Considerations (Section 21.2) for details on
possible address encodings.
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.
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For example, an 802.1Q VLAN tag or VPN identifier could be used as a
24-bit Instance ID.
The Instance ID that is stored in the mapping database when LISP-DDT
[I-D.ietf-lisp-ddt] is used is 32 bits in length. That means the
control-plane can store more instances than a given data-plane can
use. Multiple data-planes can use the same 32-bit space as long as
the low-order 24 bits don't overlap among xTRs.
9. Routing Locator Selection
Both the client-side and server-side may need control over the
selection of RLOCs for conversations between them. This control is
achieved by manipulating the 'Priority' and 'Weight' fields in EID-
to-RLOC Map-Reply messages. Alternatively, RLOC information MAY be
gleaned from received tunneled packets or EID-to-RLOC Map-Request
messages.
The following are different scenarios for choosing RLOCs and the
controls that are available:
o The server-side returns one RLOC. The client-side can only use
one RLOC. The server-side has complete control of the selection.
o 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.
o The server-side sets a Weight of 0 for the RLOC subset list. In
this case, the client-side can choose how the traffic load is
spread across the subset list. Control is shared by the server-
side determining the list and the client determining load
distribution. Again, the client can use alternative RLOCs if the
server-provided list of RLOCs is unreachable.
o Either side (more likely the server-side ETR) decides not to send
a Map-Request. For example, if the server-side ETR does not send
Map-Requests, it gleans RLOCs from the client-side ITR, giving the
client-side ITR responsibility for bidirectional RLOC reachability
and preferability. Server-side ETR gleaning of the client-side
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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.
o A "gleaned" Map-Cache entry, one learned from the source RLOC of a
received encapsulated packet, is only stored and used for a few
seconds, pending verification. Verification is 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
is OPTIONAL.
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.
10. Routing Locator Reachability
Several mechanisms for determining RLOC reachability are currently
defined:
1. 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.
2. An ITR may receive an ICMP Network Unreachable or Host
Unreachable message for an RLOC it is using. This indicates that
the RLOC is likely down. Note that trusting ICMP messages may
not be desirable, but neither is ignoring them completely.
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Implementations are encouraged to follow current best practices
in treating these conditions.
3. An ITR that participates in the global routing system can
determine that an RLOC is down if no BGP Routing Information Base
(RIB) route exists that matches the RLOC IP address.
4. An ITR may receive an ICMP Port Unreachable message from a
destination host. This occurs if an ITR attempts to use
interworking [RFC6832] and LISP-encapsulated data is sent to a
non-LISP-capable site.
5. An ITR may receive a Map-Reply from an ETR in response to a
previously sent Map-Request. The RLOC source of the Map-Reply is
likely up, since the ETR was able to send the Map-Reply to the
ITR.
6. When an ETR receives an encapsulated packet from an ITR, the
source RLOC from the outer header of the packet is likely up.
7. An ITR/ETR pair can use the Locator reachability algorithms
described in this section, namely Echo-Noncing or RLOC-Probing.
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:
o Under normal circumstances, each ITR will advertise a default
route into the site IGP.
o 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.
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.
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When an ETR decapsulates a packet, it 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.
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.
When ITRs receive ICMP Network Unreachable or Host Unreachable
messages as a method to determine unreachability, they will refrain
from using Locators that are described in Locator lists of Map-
Replies. However, using this approach is unreliable because many
network operators turn off generation of ICMP Destination Unreachable
messages.
If an ITR does receive an ICMP Network Unreachable or Host
Unreachable message, it MAY originate its own ICMP Destination
Unreachable message destined for the host that originated the data
packet the ITR encapsulated.
Also, BGP-enabled ITRs can unilaterally examine the RIB to see if a
locator address from a Locator-Set in a mapping entry matches a
prefix. If it does not find one and BGP is running in the Default-
Free Zone (DFZ), it can decide to not use the Locator even though the
Locator-Status-Bits indicate that the Locator is up. In this case,
the path from the ITR to the ETR that is assigned the Locator is not
available. More details are in [I-D.meyer-loc-id-implications].
Optionally, an ITR can send a Map-Request to a Locator, and if a Map-
Reply is returned, reachability of the Locator has been determined.
Obviously, sending such probes increases the number of control
messages originated by Tunnel Routers for active flows, so Locators
are assumed to be reachable when they are advertised.
This assumption does create a dependency: Locator unreachability is
detected by the receipt of ICMP Host Unreachable messages. When a
Locator has been determined to be unreachable, it is not used for
active traffic; this is the same as if it were listed in a Map-Reply
with Priority 255.
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The ITR can test the reachability of the unreachable Locator by
sending periodic Requests. Both Requests and Replies MUST be rate-
limited. Locator reachability testing is never done with data
packets, since that increases the risk of packet loss for end-to-end
sessions.
When an ETR decapsulates a packet, it knows that it is reachable from
the encapsulating ITR because that is how the packet arrived. 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.
10.1. Echo Nonce Algorithm
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 [RFC4086] 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 next sends a data packet to the
ITR, 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
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nonce requests are sent is an implementation-specific setting.
However, when an ITR is in the echo-nonce-request state, it can echo
the ETR's nonce in the next set of packets that it encapsulates and
subsequently continue sending echo-nonce-request packets.
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 only 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.
Note that other Locator reachability mechanisms are being researched
and can be used to compliment or even override the echo nonce
algorithm. See the next section for an example of control-plane
probing.
10.2. RLOC-Probing Algorithm
RLOC-Probing is a method that an ITR or PITR can use to determine the
reachability status of one or more Locators that it has cached in a
Map-Cache entry. The probe-bit of the Map-Request and Map-Reply
messages is used for RLOC-Probing.
RLOC-Probing is done in the control plane on a timer basis, where an
ITR or PITR will originate a Map-Request destined to a locator
address from one of its own locator addresses. A Map-Request used as
an RLOC-probe is NOT encapsulated and NOT sent to a Map-Server or to
the mapping database system as one would when soliciting mapping
data. The EID record encoded in the Map-Request is the EID-Prefix of
the Map-Cache entry cached by the ITR or PITR. The ITR may include a
mapping data record for its own database mapping information that
contains the local EID-Prefixes and RLOCs for its site. RLOC-probes
are sent periodically using a jittered timer interval.
When an ETR receives a Map-Request message with the probe-bit set, it
returns a Map-Reply with the probe-bit set. The source address of
the Map-Reply is set according to the procedure described in
[I-D.ietf-lisp-rfc6833bis]. The Map-Reply SHOULD contain mapping
data for the EID-Prefix contained in the Map-Request. This provides
the opportunity for the ITR or PITR that sent the RLOC-probe to get
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mapping updates if there were changes to the ETR's database mapping
entries.
There are advantages and disadvantages of RLOC-Probing. The greatest
benefit of RLOC-Probing is that it can handle many failure scenarios
allowing the ITR to determine when the path to a specific Locator is
reachable or has become unreachable, thus providing a robust
mechanism for switching to using another Locator from the cached
Locator. RLOC-Probing can also provide rough Round-Trip Time (RTT)
estimates between a pair of Locators, which can be useful for network
management purposes as well as for selecting low delay paths. The
major disadvantage of RLOC-Probing is in the number of control
messages required and the amount of bandwidth used to obtain those
benefits, especially if the requirement for failure detection times
is very small.
Continued research and testing will attempt to characterize the
tradeoffs of failure detection times versus message overhead.
11. EID Reachability within a LISP Site
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. This problem is under investigation with
the expectation that experiments will tell us more. 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.
12. Routing Locator Hashing
When an ETR provides an EID-to-RLOC mapping in a Map-Reply message to
a requesting ITR, the Locator-Set for the EID-Prefix may contain
different Priority 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.
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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:
1. 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.
2. Take the hash value and divide it by the number of Locators
stored in the Locator-Set for the EID-to-RLOC mapping.
3. 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.
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.
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.
13. Changing the Contents of EID-to-RLOC Mappings
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, we want
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.
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When adding a new Locator record in lexicographic order to the end of
a Locator-Set, it is easy to update mappings. We assume that new
mappings will maintain the same Locator ordering as the old mapping
but will just have new Locators appended to the end of the list. So,
some ITRs can have a new mapping while other ITRs have only an old
mapping that is used until they time out. When an ITR has only an
old mapping but detects bits set in the Locator-Status-Bits that
correspond to Locators beyond the list it has cached, it simply
ignores them. However, this can only happen for locator addresses
that are lexicographically greater than the locator addresses in the
existing Locator-Set.
When a Locator record is inserted in the middle of a Locator-Set, to
maintain lexicographic order, the SMR procedure in Section 13.2 is
used to inform ITRs and PITRs of the new Locator-Status-Bit mappings.
When a Locator record is removed from a Locator-Set, ITRs that have
the mapping cached will not use the removed Locator because the xTRs
will set the Locator-Status-Bit to 0. So, even if the Locator is in
the list, it will not be used. For new mapping requests, the xTRs
can set the Locator AFI to 0 (indicating an unspecified address), as
well as setting the corresponding Locator-Status-Bit to 0. This
forces ITRs with old or new mappings to avoid using the removed
Locator.
If many changes occur to a mapping over a long period of time, one
will find empty record slots in the middle of the Locator-Set and new
records appended to the Locator-Set. At some point, it would be
useful to compact the Locator-Set so the Locator-Status-Bit settings
can be efficiently packed.
We propose here three approaches for Locator-Set compaction: one
operational mechanism and two protocol mechanisms. The operational
approach uses a clock sweep method. The protocol approaches use the
concept of Solicit-Map-Requests and Map-Versioning.
13.1. Clock Sweep
The clock sweep approach uses planning in advance and the use of
count-down TTLs to time out mappings that have already been cached.
The default setting for an EID-to-RLOC mapping TTL is 24 hours. So,
there is a 24-hour window to time out old mappings. The following
clock sweep procedure is used:
1. 24 hours before a mapping change is to take effect, a network
administrator configures the ETRs at a site to start the clock
sweep window.
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2. During the clock sweep window, ETRs continue to send Map-Reply
messages with the current (unchanged) mapping records. The TTL
for these mappings is set to 1 hour.
3. 24 hours later, all previous cache entries will have timed out,
and any active cache entries will time out within 1 hour. During
this 1-hour window, the ETRs continue to send Map-Reply messages
with the current (unchanged) mapping records with the TTL set to
1 minute.
4. At the end of the 1-hour window, the ETRs will send Map-Reply
messages with the new (changed) mapping records. So, any active
caches can get the new mapping contents right away if not cached,
or in 1 minute if they had the mapping cached. The new mappings
are cached with a TTL equal to the TTL in the Map-Reply.
13.2. Solicit-Map-Request (SMR)
Soliciting a Map-Request is a selective way for ETRs, at the site
where mappings change, to control the rate they receive requests for
Map-Reply messages. SMRs are also used to tell remote ITRs to update
the mappings they have cached.
Since the ETRs don't keep track of remote ITRs that have cached their
mappings, they do not know which ITRs need to have their mappings
updated. As a result, an ETR will solicit Map-Requests (called an
SMR message) from those sites to which it has been sending
encapsulated data for the last minute. In particular, an ETR will
send an SMR to an ITR to which it has recently sent encapsulated
data.
An SMR message is simply a bit set in a Map-Request message. An ITR
or PITR will send a Map-Request when they receive an SMR message.
Both the SMR sender and the Map-Request responder MUST rate-limit
these messages. Rate-limiting can be implemented as a global rate-
limiter or one rate-limiter per SMR destination.
The following procedure shows how an SMR exchange occurs when a site
is doing Locator-Set compaction for an EID-to-RLOC mapping:
1. When the database mappings in an ETR change, the ETRs at the site
begin to send Map-Requests with the SMR bit set for each Locator
in each Map-Cache entry the ETR caches.
2. A remote ITR that receives the SMR message will schedule sending
a Map-Request message to the source locator address of the SMR
message or to the mapping database system. A newly allocated
random nonce is selected, and the EID-Prefix used is the one
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copied from the SMR message. If the source Locator is the only
Locator in the cached Locator-Set, the remote ITR SHOULD send a
Map-Request to the database mapping system just in case the
single Locator has changed and may no longer be reachable to
accept the Map-Request.
3. The remote ITR MUST rate-limit the Map-Request until it gets a
Map-Reply while continuing to use the cached mapping. When
Map-Versioning as described in Section 13.3 is used, an SMR
sender can detect if an ITR is using the most up-to-date database
mapping.
4. The ETRs at the site with the changed mapping will reply to the
Map-Request with a Map-Reply message that has a nonce from the
SMR-invoked Map-Request. The Map-Reply messages SHOULD be rate-
limited. This is important to avoid Map-Reply implosion.
5. The ETRs at the site with the changed mapping record the fact
that the site that sent the Map-Request has received the new
mapping data in the Map-Cache entry for the remote site so the
Locator-Status-Bits are reflective of the new mapping for packets
going to the remote site. The ETR then stops sending SMR
messages.
For security reasons, an ITR MUST NOT process unsolicited Map-
Replies. To avoid Map-Cache entry corruption by a third party, a
sender of an SMR-based Map-Request MUST be verified. If an ITR
receives an SMR-based Map-Request and the source is not in the
Locator-Set for the stored Map-Cache entry, then the responding Map-
Request MUST be sent with an EID destination to the mapping database
system. Since the mapping database system is a more secure way to
reach an authoritative ETR, it will deliver the Map-Request to the
authoritative source of the mapping data.
When an ITR receives an SMR-based Map-Request for which it does not
have a cached mapping for the EID in the SMR message, it MAY not send
an SMR-invoked Map-Request. This scenario can occur when an ETR
sends SMR messages to all Locators in the Locator-Set it has stored
in its map-cache but the remote ITRs that receive the SMR may not be
sending packets to the site. There is no point in updating the ITRs
until they need to send, in which case they will send Map-Requests to
obtain a Map-Cache entry.
13.3. Database Map-Versioning
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
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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
Section 13.2 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.
See [RFC6834] for a more detailed analysis and description of
Database Map-Versioning.
14. Multicast Considerations
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
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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 globally routable.
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 [RFC6831] and
[I-D.ietf-lisp-signal-free-multicast], respectively, for details.
Details for LISP-Multicast and interworking with non-LISP sites are
described in [RFC6831] and [RFC6832].
15. Router Performance Considerations
LISP is designed to be very "hardware-based forwarding friendly". A
few implementation techniques can be used to incrementally implement
LISP:
o 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.
o 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 [RFC2784] or 6to4
tunneling [RFC3056] may already support this action.
o 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.
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For performance issues related to map-cache management, see
Section 19.
16. Mobility Considerations
There are several kinds of mobility, of which only some might be of
concern to LISP. Essentially, they are as follows.
16.1. Slow Mobility
A site wishes to change its attachment points to the Internet, and
its LISP Tunnel Routers will have new RLOCs when it changes upstream
providers. Changes in EID-to-RLOC mappings for sites are expected to
be handled by configuration, outside of LISP.
An individual endpoint wishes to move but is not concerned about
maintaining session continuity. Renumbering is involved. LISP can
help with the issues surrounding renumbering [RFC4192] [LISA96] by
decoupling the address space used by a site from the address spaces
used by its ISPs [RFC4984].
16.2. Fast Mobility
Fast endpoint mobility occurs when an endpoint moves relatively
rapidly, changing its IP-layer network attachment point. Maintenance
of session continuity is a goal. This is where the Mobile IPv4
[RFC5944] and Mobile IPv6 [RFC6275] [RFC4866] mechanisms are used and
primarily where interactions with LISP need to be explored, such as
the mechanisms in [I-D.portoles-lisp-eid-mobility] when the EID moves
but the RLOC is in the network infrastructure.
In LISP, one possibility is to "glean" information. When a packet
arrives, the ETR could examine the EID-to-RLOC mapping and use that
mapping for all outgoing traffic to that EID. It can do this after
performing a route-returnability check, to ensure that the new
network location does have an internal route to that endpoint.
However, this does not cover the case where an ITR (the node assigned
the RLOC) at the mobile-node location has been compromised.
Mobile IP packet exchange is designed for an environment in which all
routing information is disseminated before packets can be forwarded.
In order to allow the Internet to grow to support expected future
use, we are moving to an environment where some information may have
to be obtained after packets are in flight. Modifications to IP
mobility should be considered in order to optimize the behavior of
the overall system. Anything that decreases the number of new EID-
to-RLOC mappings needed when a node moves, or maintains the validity
of an EID-to-RLOC mapping for a longer time, is useful.
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In addition to endpoints, a network can be mobile, possibly changing
xTRs. A "network" can be as small as a single router and as large as
a whole site. This is different from site mobility in that it is
fast and possibly short-lived, but different from endpoint mobility
in that a whole prefix is changing RLOCs. However, the mechanisms
are the same, and there is no new overhead in LISP. A map request
for any endpoint will return a binding for the entire mobile prefix.
If mobile networks become a more common occurrence, it may be useful
to revisit the design of the mapping service and allow for dynamic
updates of the database.
The issue of interactions between mobility and LISP needs to be
explored further. Specific improvements to the entire system will
depend on the details of mapping mechanisms. Mapping mechanisms
should be evaluated on how well they support session continuity for
mobile nodes. See [I-D.farinacci-lisp-predictive-rlocs] for more
recent mechanisms which can provide near-zero packet loss during
handoffs.
16.3. LISP Mobile Node Mobility
A mobile device can use the LISP infrastructure to achieve mobility
by implementing the LISP encapsulation and decapsulation functions
and acting as a simple ITR/ETR. By doing this, such a "LISP mobile
node" can use topologically independent EID IP addresses that are not
advertised into and do not impose a cost on the global routing
system. These EIDs are maintained at the edges of the mapping system
in LISP Map-Servers and Map-Resolvers) and are provided on demand to
only the correspondents of the LISP mobile node.
Refer to [I-D.meyer-lisp-mn] for more details for when the EID and
RLOC are co-located in the roaming node.
17. LISP xTR Placement and Encapsulation Methods
This section will explore how and where ITRs and ETRs can be placed
in the network and will discuss the pros and cons of each scenario.
For a more detailed networkd design deployment recommendation, refer
to [RFC7215].
There are two basic deployment tradeoffs to consider: centralized
versus distributed caches; and flat, Recursive, or Re-encapsulating
Tunneling. When deciding on centralized versus distributed caching,
the following issues should be considered:
o Are the xTRs spread out so that the caches are spread across all
the memories of each router? A centralized cache is when an ITR
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keeps a cache for all the EIDs it is encapsulating to. The packet
takes a direct path to the destination Locator. A distributed
cache is when an ITR needs help from other Re-Encapsulating Tunnel
Routers (RTRs) because it does not store all the cache entries for
the EIDs it is encapsulating to. So, the packet takes a path
through RTRs that have a different set of cache entries.
o Should management "touch points" be minimized by only choosing a
few xTRs, just enough for redundancy?
o In general, using more ITRs doesn't increase management load,
since caches are built and stored dynamically. On the other hand,
using more ETRs does require more management, since EID-Prefix-to-
RLOC mappings need to be explicitly configured.
When deciding on flat, Recursive, or Re-Encapsulating Tunneling, the
following issues should be considered:
o Flat tunneling implements a single encapsulation path between the
source site and destination site. This generally offers better
paths between sources and destinations with a single encapsulation
path.
o Recursive Tunneling is when encapsulated traffic is again further
encapsulated in another tunnel, either to implement VPNs or to
perform Traffic Engineering. When doing VPN-based tunneling, the
site has some control, since the site is prepending a new
encapsulation header. In the case of TE-based tunneling, the site
may have control if it is prepending a new tunnel header, but if
the site's ISP is doing the TE, then the site has no control.
Recursive Tunneling generally will result in suboptimal paths but
with the benefit of steering traffic to parts of the network that
have more resources available.
o The technique of Re-Encapsulation ensures that packets only
require one encapsulation header. So, if a packet needs to be re-
routed, it is first decapsulated by the RTR and then Re-
Encapsulated with a new encapsulation header using a new RLOC.
The next sub-sections will examine where xTRs and RTRs can reside in
the network.
17.1. First-Hop/Last-Hop xTRs
By locating xTRs close to hosts, the EID-Prefix set is at the
granularity of an IP subnet. So, at the expense of more EID-Prefix-
to-RLOC sets for the site, the caches in each xTR can remain
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relatively small. But caches always depend on the number of non-
aggregated EID destination flows active through these xTRs.
With more xTRs doing encapsulation, the increase in control traffic
grows as well: since the EID granularity is greater, more Map-
Requests and Map-Replies are traveling between more routers.
The advantage of placing the caches and databases at these stub
routers is that the products deployed in this part of the network
have better price-memory ratios than their core router counterparts.
Memory is typically less expensive in these devices, and fewer routes
are stored (only IGP routes). These devices tend to have excess
capacity, both for forwarding and routing states.
LISP functionality can also be deployed in edge switches. These
devices generally have layer-2 ports facing hosts and layer-3 ports
facing the Internet. Spare capacity is also often available in these
devices.
17.2. Border/Edge xTRs
Using Customer Edge (CE) routers for xTR placement allows the EID
space associated with a site to be reachable via a small set of RLOCs
assigned to the CE-based xTRs for that site.
This offers the opposite benefit of the first-hop/last-hop xTR
scenario: the number of mapping entries and network management touch
points is reduced, allowing better scaling.
One disadvantage is that fewer network resources are used to reach
host endpoints, thereby centralizing the point-of-failure domain and
creating network choke points at the CE xTR.
Note that more than one CE xTR at a site can be configured with the
same IP address. In this case, an RLOC is an anycast address. This
allows resilience between the CE xTRs. That is, if a CE xTR fails,
traffic is automatically routed to the other xTRs using the same
anycast address. However, this comes with the disadvantage where the
site cannot control the entrance point when the anycast route is
advertised out from all border routers. Another disadvantage of
using anycast Locators is the limited advertisement scope of /32 (or
/128 for IPv6) routes.
17.3. ISP Provider Edge (PE) xTRs
The use of ISP PE routers as xTRs is not the typical deployment
scenario envisioned in this specification. This section attempts to
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capture some of the reasoning behind this preference for implementing
LISP on CE routers.
The use of ISP PE routers for xTR placement gives an ISP, rather than
a site, control over the location of the ETRs. That is, the ISP can
decide whether the xTRs are in the destination site (in either CE
xTRs or last-hop xTRs within a site) or at other PE edges. The
advantage of this case is that two encapsulation headers can be
avoided. By having the PE be the first router on the path to
encapsulate, it can choose a TE path first, and the ETR can
decapsulate and Re-Encapsulate for a new encapsuluation path to the
destination end site.
An obvious disadvantage is that the end site has no control over
where its packets flow or over the RLOCs used. Other disadvantages
include difficulty in synchronizing path liveness updates between CE
and PE routers.
As mentioned in earlier sections, a combination of these scenarios is
possible at the expense of extra packet header overhead; if both site
and provider want control, then Recursive or Re-Encapsulating Tunnels
are used.
17.4. LISP Functionality with Conventional NATs
LISP routers can be deployed behind Network Address Translator (NAT)
devices to provide the same set of packet services hosts have today
when they are addressed out of private address space.
It is important to note that a locator address in any LISP control
message MUST be a globally routable address and therefore SHOULD NOT
contain [RFC1918] addresses. If a LISP xTR is configured with
private RLOC addresses, they MUST be used only in the outer IP header
so the NAT device can translate properly. Otherwise, EID addresses
MUST be translated before encapsulation is performed when LISP VPNs
are not in use. Both NAT translation and LISP encapsulation
functions could be co-located in the same device.
17.5. Packets Egressing a LISP Site
When a LISP site is using two ITRs for redundancy, the failure of one
ITR will likely shift outbound traffic to the second. This second
ITR's cache may not be populated with the same EID-to-RLOC mapping
entries as the first. If this second ITR does not have these
mappings, traffic will be dropped while the mappings are retrieved
from the mapping system. The retrieval of these messages may
increase the load of requests being sent into the mapping system.
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18. Traceroute Considerations
When a source host in a LISP site initiates a traceroute to a
destination host in another LISP site, it is highly desirable for it
to see the entire path. Since packets are encapsulated from the ITR
to the ETR, the hop across the tunnel could be viewed as a single
hop. However, LISP traceroute will provide the entire path so the
user can see 3 distinct segments of the path from a source LISP host
to a destination LISP host:
Segment 1 (in source LISP site based on EIDs):
source host ---> first hop ... next hop ---> ITR
Segment 2 (in the core network based on RLOCs):
ITR ---> next hop ... next hop ---> ETR
Segment 3 (in the destination LISP site based on EIDs):
ETR ---> next hop ... last hop ---> destination host
For segment 1 of the path, ICMP Time Exceeded messages are returned
in the normal manner as they are today. The ITR performs a TTL
decrement and tests for 0 before encapsulating. Therefore, the ITR's
hop is seen by the traceroute source as having an EID address (the
address of the site-facing interface).
For segment 2 of the path, ICMP Time Exceeded messages are returned
to the ITR because the TTL decrement to 0 is done on the outer
header, so the destinations of the ICMP messages are the ITR RLOC
address and the source RLOC address of the encapsulated traceroute
packet. The ITR looks inside of the ICMP payload to inspect the
traceroute source so it can return the ICMP message to the address of
the traceroute client and also retain the core router IP address in
the ICMP message. This is so the traceroute client can display the
core router address (the RLOC address) in the traceroute output. The
ETR returns its RLOC address and responds to the TTL decrement to 0,
as the previous core routers did.
For segment 3, the next-hop router downstream from the ETR will be
decrementing the TTL for the packet that was encapsulated, sent into
the core, decapsulated by the ETR, and forwarded because it isn't the
final destination. If the TTL is decremented to 0, any router on the
path to the destination of the traceroute, including the next-hop
router or destination, will send an ICMP Time Exceeded message to the
source EID of the traceroute client. The ICMP message will be
encapsulated by the local ITR and sent back to the ETR in the
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originated traceroute source site, where the packet will be delivered
to the host.
18.1. IPv6 Traceroute
IPv6 traceroute follows the procedure described above, since the
entire traceroute data packet is included in the ICMP Time Exceeded
message payload. Therefore, only the ITR needs to pay special
attention to forwarding ICMP messages back to the traceroute source.
18.2. IPv4 Traceroute
For IPv4 traceroute, we cannot follow the above procedure, since IPv4
ICMP Time Exceeded messages only include the invoking IP header and
8 octets that follow the IP header. Therefore, when a core router
sends an IPv4 Time Exceeded message to an ITR, all the ITR has in the
ICMP payload is the encapsulated header it prepended, followed by a
UDP header. The original invoking IP header, and therefore the
identity of the traceroute source, is lost.
The solution we propose to solve this problem is to cache traceroute
IPv4 headers in the ITR and to match them up with corresponding IPv4
Time Exceeded messages received from core routers and the ETR. The
ITR will use a circular buffer for caching the IPv4 and UDP headers
of traceroute packets. It will select a 16-bit number as a key to
find them later when the IPv4 Time Exceeded messages are received.
When an ITR encapsulates an IPv4 traceroute packet, it will use the
16-bit number as the UDP source port in the encapsulating header.
When the ICMP Time Exceeded message is returned to the ITR, the UDP
header of the encapsulating header is present in the ICMP payload,
thereby allowing the ITR to find the cached headers for the
traceroute source. The ITR puts the cached headers in the payload
and sends the ICMP Time Exceeded message to the traceroute source
retaining the source address of the original ICMP Time Exceeded
message (a core router or the ETR of the site of the traceroute
destination).
The signature of a traceroute packet comes in two forms. The first
form is encoded as a UDP message where the destination port is
inspected for a range of values. The second form is encoded as an
ICMP message where the IP identification field is inspected for a
well-known value.
18.3. Traceroute Using Mixed Locators
When either an IPv4 traceroute or IPv6 traceroute is originated and
the ITR encapsulates it in the other address family header, one
cannot get all 3 segments of the traceroute. Segment 2 of the
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traceroute cannot be conveyed to the traceroute source, since it is
expecting addresses from intermediate hops in the same address format
for the type of traceroute it originated. Therefore, in this case,
segment 2 will make the tunnel look like one hop. All the ITR has to
do to make this work is to not copy the inner TTL to the outer,
encapsulating header's TTL when a traceroute packet is encapsulated
using an RLOC from a different address family. This will cause no
TTL decrement to 0 to occur in core routers between the ITR and ETR.
19. Security Considerations
Security considerations for LISP are discussed in [RFC7833], in
addition [I-D.ietf-lisp-sec] provides authentication and integrity to
LISP mappings.
A complete LISP threat analysis can be found in [RFC7835], in what
follows we provide a summary.
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 of a victim's xTR can manipulate such
mechanisms to declare a set of RLOCs unreachable. This can be used
also, for instance, to declare only one RLOC reachable with the aim
of overload it.
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.
Most of the attack vectors can be mitigated with careful deployment
and configuration, information learned opportunistically (such as LSB
or gleaning) should be verified with other reachability mechanisms.
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In addition, systematic rate-limitation and filtering is an effective
technique to mitigate attacks that aim to overload the control-plane.
20. Network Management Considerations
Considerations for network management tools exist so the LISP
protocol suite can be operationally managed. These mechanisms can be
found in [RFC7052] and [RFC6835].
21. IANA Considerations
This section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of values related to the LISP
specification, in accordance with BCP 26 [RFC5226].
There are four namespaces (listed in the sub-sections below) in LISP
that have been registered.
o LISP IANA registry allocations should not be made for purposes
unrelated to LISP routing or transport protocols.
o The following policies are used here with the meanings defined in
BCP 26: "Specification Required", "IETF Review", "Experimental
Use", and "First Come First Served".
21.1. LISP ACT and Flag Fields
New ACT values [I-D.ietf-lisp-rfc6833bis] can be allocated through
IETF review or IESG approval. Four values have already been
allocated by this specification [I-D.ietf-lisp-rfc6833bis].
In addition, LISP has a number of flag fields and reserved fields,
such as the LISP header flags field (Section 5.3). New bits for
flags in these fields can be implemented after IETF review or IESG
approval, but these need not be managed by IANA.
21.2. LISP Address Type Codes
LISP Canonical Address Format (LCAF) [RFC8060] is an 8-bit field that
defines LISP-specific encodings for AFI value 16387. LCAF encodings
are used for specific use-cases where different address types for
EID-records and RLOC-records are required.
The IANA registry "LISP Canonical Address Format (LCAF) Types" is
used for LCAF types, the registry for LCAF types use the
Specification Required policy [RFC5226]. Initial values for the
registry as well as further information can be found in [RFC8060].
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21.3. LISP UDP Port Numbers
The IANA registry has allocated UDP port numbers 4341 and 4342 for
lisp-data and lisp-control operation, respectively. IANA has updated
the description for UDP ports 4341 and 4342 as follows:
lisp-data 4341 udp LISP Data Packets
lisp-control 4342 udp LISP Control Packets
21.4. LISP Key ID Numbers
The following Key ID values are defined by this specification as used
in any packet type that references a 'Key ID' field:
Name Number Defined in
-----------------------------------------------
None 0 n/a
HMAC-SHA-1-96 1 [RFC2404]
HMAC-SHA-256-128 2 [RFC4868]
Number values are in the range of 0 to 65535. The allocation of
values is on a first come first served basis.
22. References
22.1. Normative References
[I-D.ietf-lisp-ddt]
Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A.
Smirnov, "LISP Delegated Database Tree", draft-ietf-lisp-
ddt-09 (work in progress), January 2017.
[I-D.ietf-lisp-introduction]
Cabellos-Aparicio, A. and D. Saucez, "An Architectural
Introduction to the Locator/ID Separation Protocol
(LISP)", draft-ietf-lisp-introduction-13 (work in
progress), April 2015.
[I-D.ietf-lisp-rfc6833bis]
Fuller, V., Farinacci, D., and A. Cabellos-Aparicio,
"Locator/ID Separation Protocol (LISP) Control-Plane",
draft-ietf-lisp-rfc6833bis-00 (work in progress), December
2016.
[I-D.ietf-lisp-sec]
Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D.
Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-12
(work in progress), November 2016.
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[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
DOI 10.17487/RFC0768, August 1980,
<http://www.rfc-editor.org/info/rfc768>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<http://www.rfc-editor.org/info/rfc791>.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
<http://www.rfc-editor.org/info/rfc1918>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2404] Madson, C. and R. Glenn, "The Use of HMAC-SHA-1-96 within
ESP and AH", RFC 2404, DOI 10.17487/RFC2404, November
1998, <http://www.rfc-editor.org/info/rfc2404>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
of Explicit Congestion Notification (ECN) to IP",
RFC 3168, DOI 10.17487/RFC3168, September 2001,
<http://www.rfc-editor.org/info/rfc3168>.
[RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced
by an On-line Database", RFC 3232, DOI 10.17487/RFC3232,
January 2002, <http://www.rfc-editor.org/info/rfc3232>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<http://www.rfc-editor.org/info/rfc4086>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <http://www.rfc-editor.org/info/rfc4632>.
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[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
384, and HMAC-SHA-512 with IPsec", RFC 4868,
DOI 10.17487/RFC4868, May 2007,
<http://www.rfc-editor.org/info/rfc4868>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5496] Wijnands, IJ., Boers, A., and E. Rosen, "The Reverse Path
Forwarding (RPF) Vector TLV", RFC 5496,
DOI 10.17487/RFC5496, March 2009,
<http://www.rfc-editor.org/info/rfc5496>.
[RFC5944] Perkins, C., Ed., "IP Mobility Support for IPv4, Revised",
RFC 5944, DOI 10.17487/RFC5944, November 2010,
<http://www.rfc-editor.org/info/rfc5944>.
[RFC6115] Li, T., Ed., "Recommendation for a Routing Architecture",
RFC 6115, DOI 10.17487/RFC6115, February 2011,
<http://www.rfc-editor.org/info/rfc6115>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <http://www.rfc-editor.org/info/rfc6275>.
[RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID
Separation Protocol (LISP) Map-Versioning", RFC 6834,
DOI 10.17487/RFC6834, January 2013,
<http://www.rfc-editor.org/info/rfc6834>.
[RFC6836] Fuller, V., Farinacci, D., Meyer, D., and D. Lewis,
"Locator/ID Separation Protocol Alternative Logical
Topology (LISP+ALT)", RFC 6836, DOI 10.17487/RFC6836,
January 2013, <http://www.rfc-editor.org/info/rfc6836>.
[RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID
Separation Protocol (LISP) MIB", RFC 7052,
DOI 10.17487/RFC7052, October 2013,
<http://www.rfc-editor.org/info/rfc7052>.
[RFC7214] Andersson, L. and C. Pignataro, "Moving Generic Associated
Channel (G-ACh) IANA Registries to a New Registry",
RFC 7214, DOI 10.17487/RFC7214, May 2014,
<http://www.rfc-editor.org/info/rfc7214>.
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[RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo-
Pascual, J., and D. Lewis, "Locator/Identifier Separation
Protocol (LISP) Network Element Deployment
Considerations", RFC 7215, DOI 10.17487/RFC7215, April
2014, <http://www.rfc-editor.org/info/rfc7215>.
[RFC7833] Howlett, J., Hartman, S., and A. Perez-Mendez, Ed., "A
RADIUS Attribute, Binding, Profiles, Name Identifier
Format, and Confirmation Methods for the Security
Assertion Markup Language (SAML)", RFC 7833,
DOI 10.17487/RFC7833, May 2016,
<http://www.rfc-editor.org/info/rfc7833>.
[RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID
Separation Protocol (LISP) Threat Analysis", RFC 7835,
DOI 10.17487/RFC7835, April 2016,
<http://www.rfc-editor.org/info/rfc7835>.
[RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol
(LISP) Data-Plane Confidentiality", RFC 8061,
DOI 10.17487/RFC8061, February 2017,
<http://www.rfc-editor.org/info/rfc8061>.
22.2. Informative References
[AFN] IANA, "Address Family Numbers", August 2016,
<http://www.iana.org/assignments/address-family-numbers>.
[CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed",
1999,
<http://mercury.lcs.mit.edu/~jnc/tech/endpoints.txt>.
[I-D.farinacci-lisp-predictive-rlocs]
Farinacci, D. and P. Pillay-Esnault, "LISP Predictive
RLOCs", draft-farinacci-lisp-predictive-rlocs-01 (work in
progress), November 2016.
[I-D.ietf-lisp-signal-free-multicast]
Moreno, V. and D. Farinacci, "Signal-Free LISP Multicast",
draft-ietf-lisp-signal-free-multicast-02 (work in
progress), October 2016.
[I-D.meyer-lisp-mn]
Farinacci, D., Lewis, D., Meyer, D., and C. White, "LISP
Mobile Node", draft-meyer-lisp-mn-16 (work in progress),
December 2016.
Farinacci, et al. Expires September 27, 2017 [Page 48]
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[I-D.meyer-loc-id-implications]
Meyer, D. and D. Lewis, "Architectural Implications of
Locator/ID Separation", draft-meyer-loc-id-implications-01
(work in progress), January 2009.
[I-D.portoles-lisp-eid-mobility]
Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino,
F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a
Unified Control Plane", draft-portoles-lisp-eid-
mobility-01 (work in progress), October 2016.
[LISA96] Lear, E., Tharp, D., Katinsky, J., and J. Coffin,
"Renumbering: Threat or Menace?", Usenix Tenth System
Administration Conference (LISA 96), October 1996.
[OPENLISP]
Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP
Implementation Report", Work in Progress, July 2008.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<http://www.rfc-editor.org/info/rfc2784>.
[RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains
via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February
2001, <http://www.rfc-editor.org/info/rfc3056>.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
DOI 10.17487/RFC3261, June 2002,
<http://www.rfc-editor.org/info/rfc3261>.
[RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic
Key Management", BCP 107, RFC 4107, DOI 10.17487/RFC4107,
June 2005, <http://www.rfc-editor.org/info/rfc4107>.
[RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for
Renumbering an IPv6 Network without a Flag Day", RFC 4192,
DOI 10.17487/RFC4192, September 2005,
<http://www.rfc-editor.org/info/rfc4192>.
Farinacci, et al. Expires September 27, 2017 [Page 49]
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[RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route
Optimization for Mobile IPv6", RFC 4866,
DOI 10.17487/RFC4866, May 2007,
<http://www.rfc-editor.org/info/rfc4866>.
[RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report
from the IAB Workshop on Routing and Addressing",
RFC 4984, DOI 10.17487/RFC4984, September 2007,
<http://www.rfc-editor.org/info/rfc4984>.
[RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480,
February 2012, <http://www.rfc-editor.org/info/rfc6480>.
[RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for
Routing Protocols (KARP) Design Guidelines", RFC 6518,
DOI 10.17487/RFC6518, February 2012,
<http://www.rfc-editor.org/info/rfc6518>.
[RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The
Locator/ID Separation Protocol (LISP) for Multicast
Environments", RFC 6831, DOI 10.17487/RFC6831, January
2013, <http://www.rfc-editor.org/info/rfc6831>.
[RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller,
"Interworking between Locator/ID Separation Protocol
(LISP) and Non-LISP Sites", RFC 6832,
DOI 10.17487/RFC6832, January 2013,
<http://www.rfc-editor.org/info/rfc6832>.
[RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation
Protocol Internet Groper (LIG)", RFC 6835,
DOI 10.17487/RFC6835, January 2013,
<http://www.rfc-editor.org/info/rfc6835>.
[RFC6837] Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to
Routing Locator (RLOC) Database", RFC 6837,
DOI 10.17487/RFC6837, January 2013,
<http://www.rfc-editor.org/info/rfc6837>.
[RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
UDP Checksums for Tunneled Packets", RFC 6935,
DOI 10.17487/RFC6935, April 2013,
<http://www.rfc-editor.org/info/rfc6935>.
Farinacci, et al. Expires September 27, 2017 [Page 50]
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[RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
for the Use of IPv6 UDP Datagrams with Zero Checksums",
RFC 6936, DOI 10.17487/RFC6936, April 2013,
<http://www.rfc-editor.org/info/rfc6936>.
[RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060,
February 2017, <http://www.rfc-editor.org/info/rfc8060>.
Farinacci, et al. Expires September 27, 2017 [Page 51]
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Appendix A. Acknowledgments
An 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 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.
Appendix B. Document Change Log
[RFC Editor: Please delete this section on publication as RFC.]
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B.1. Changes to draft-ietf-lisp-rfc6830bis-01
o Posted March 2017.
o Include references to new RFCs published.
o Change references from RFC6833 to RFC6833bis.
o Clarified LCAF text in the IANA section.
o Remove references to "experimental".
B.2. Changes to draft-ietf-lisp-rfc6830bis-00
o Posted December 2016.
o Created working group document from draft-farinacci-lisp
-rfc6830-00 individual submission. No other changes made.
Authors' Addresses
Dino Farinacci
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA
EMail: farinacci@gmail.com
Vince Fuller
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA
EMail: vince.fuller@gmail.com
Dave Meyer
Cisco Systems
170 Tasman Drive
San Jose, CA
USA
EMail: dmm@1-4-5.net
Farinacci, et al. Expires September 27, 2017 [Page 53]
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Darrel Lewis
Cisco Systems
170 Tasman Drive
San Jose, CA
USA
EMail: darlewis@cisco.com
Albert Cabellos
UPC/BarcelonaTech
Campus Nord, C. Jordi Girona 1-3
Barcelona, Catalunya
Spain
EMail: acabello@ac.upc.edu
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