INTERNET-DRAFT Margaret Cullen
Intended Status: Proposed Standard Painless Security
Updates: 7177, 7178 Donald Eastlake
Mingui Zhang
Dacheng Zhang
Huawei
Expires: April 30, 2017 October 31, 2016
TRILL (Transparent Interconnection of Lots of Links) over IP
<draft-ietf-trill-over-ip-08.txt>
Abstract
The TRILL (Transparent Interconnection of Lots of Links) protocol
supports both point-to-point and multi-access links and is designed
so that a variety of link protocols can be used between TRILL switch
ports. This document standardizes methods for encapsulating TRILL in
IP (v4 or v6) so as to use IP as a TRILL link protocol in a unified
TRILL campus. It updates RFC 7177 and updates RFC 7178.
Status of This Document
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Distribution of this document is unlimited. Comments should be sent
to the authors or the TRILL Working Group mailing list
<dnsext@ietf.org>.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft
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Table of Contents
1. Introduction............................................4
2. Terminology.............................................5
3. Use Cases for TRILL over IP.............................6
3.1 Remote Office Scenario.................................6
3.2 IP Backbone Scenario...................................6
3.3 Important Properties of the Scenarios..................6
3.3.1 Security Requirements................................7
3.3.2 Multicast Handling...................................7
3.3.3 Neighbor Discovery...................................8
4. TRILL Packet Formats....................................9
4.1 General Packet Formats.................................9
4.2 General TRILL Over IP Packet Formats..................10
4.2.1 Without Security....................................10
4.2.2 With Security.......................................10
4.3 QoS Considerations....................................11
4.4 Broadcast Links and Multicast Packets.................12
4.5 TRILL Over IP IS-IS SubNetwork Point of Attachment....13
5. TRILL over IP Encapsulation Formats....................14
5.1 Encapsulation Considerations..........................14
5.2 Encapsulation Agreement...............................15
5.3 Broadcast Link Encapsulation Considerations...........16
5.4 Native Encapsulation..................................17
5.5 VXLAN Encapsulation...................................17
5.6 Other Encapsulations..................................18
6. Handling Multicast.....................................19
7. Use of IPsec and IKEv2.................................20
7.1 Keying................................................20
7.1.1 Pairwise Keying.....................................20
7.1.2 Group Keying........................................21
7.2 Mandatory-to-Implement Algorithms.....................21
8. Transport Considerations...............................22
8.1 Congestion Considerations.............................22
8.2 Recursive Ingress.....................................23
8.3 Fat Flows.............................................24
8.4 MTU Considerations....................................25
8.5 Middlebox Considerations..............................25
9. TRILL over IP Port Configuration.......................27
9.1 Per IP Port Configuration.............................27
9.2 Additional per IP Address Configuration...............27
9.2.1 Native Multicast Configuration......................28
9.2.2 Serial Unicast Configuration........................28
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Table of Contents (continued)
9.2.3 Encapsulation Specific Configuration................28
9.2.3.1 UDP Source Port...................................28
9.2.3.2 VXLAN Configuration...............................29
9.2.3.3 Other Encapsulation Configuration.................29
9.2.4 Security Configuration..............................29
10. Security Considerations...............................30
10.1 IPsec................................................30
10.2 IS-IS Security.......................................31
11. IANA Considerations...................................32
11.1 Port Assignments.....................................32
11.2 Multicast Address Assignments........................32
11.3 Encapsulation Method Support Indication..............32
Normative References......................................34
Informative References....................................36
Acknowledgements..........................................38
Authors' Addresses........................................39
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1. Introduction
TRILL switches (RBridges) are devices that implement the IETF TRILL
protocol [RFC6325] [RFC7177] [RFC7780]. TRILL provides transparent
forwarding of frames within an arbitrary network topology, using
least cost paths for unicast traffic. It supports VLANs and Fine
Grained Labels [RFC7172] as well as multipathing of unicast and
multi-destination traffic. It uses IS-IS [IS-IS] [RFC7176] link state
routing and encapsulation with a hop count.
RBridge ports can communicate with each other over various protocols,
such as Ethernet [RFC6325], pseudowires [RFC7173], or PPP [RFC6361].
This document defines a method for RBridge ports to communicate over
IP (v4 or v6). TRILL over IP allows RBridges to form a single TRILL
campus, or multiple TRILL networks to be connected as a single TRILL
campus via a TRILL over IP backbone.
TRILL over IP connects RBridge ports using IPv4 or IPv6 as a
transport in such a way that the ports with IP connectivity appear to
TRILL to be connected by a single multi-access link. If more than two
RBridge ports are connected via a single TRILL over IP link, any pair
of them can communicate.
To support the scenarios where RBridges are connected via IP paths
(including those over the public Internet) that are not under the
same administrative control as the TRILL campus and/or not physically
secure, this document specifies the use of IPsec [RFC4301]
Encapsulating Security Protocol (ESP) [RFC4303] for security.
To dynamically select a mutually supported TRILL over IP
encapsulation, normally one with good fast path hardware support, a
method is provided for agreement between adjacent TRILL switch ports
as to what encapsulation to use. Alternatively, where a common
encapsulation is supported by the TRILL switch ports on a link, they
can simply be configured to use that encapsulation.
This document updates [RFC7177] and [RFC7178] as described in Section
5 by making adjacency between TRILL over IP ports dependent on having
a method of encapsulation in common and by redefining an interval of
RBridge Channel protocol numbers to indicate encapsulation method
support for TRILL over IP links.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
The following terms and acronyms have the meaning indicated:
DRB - Designated RBridge. The RBridge (TRILL switch) elected to be in
charge of certain aspects of a TRILL link that is not
configured as a point-to-point link [RFC6325] [RFC7177].
ENCAP Hdr - Encapsulation headers in use between the IP Header and
the TRILL Header. See Section 5.
ESP - IPsec Encapsulating Security Protocol [RFC4303].
FGL - Fine Grained Label [RFC7172].
Hdr - Used herein as an abbreviation for "Header".
HKDF - Hash based Key Derivation Function [RFC5869].
MTU - Maximum Transmission Unit.
RBridge - Routing Bridge. An alternative term for a TRILL switch.
SNPA - Sub-Network Point of Attachment.
Sz - The campus wide MTU [RFC6325] [RFC7780].
TRILL - Transparent Interconnection of Lots of Links or Tunneled
Routing in the Link Layer. The protocol specified in [RFC6325],
[RFC7177], [RFC7780], and related RFCs.
TRILL switch - A device implementing the TRILL protocol.
VNI - Virtual Network Identifier. In VXLAN [RFC7348], the VXLAN
Network Identifier.
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3. Use Cases for TRILL over IP
This section introduces two application scenarios (a remote office
scenario and an IP backbone scenario) which cover typical situations
where network administrators may choose to use TRILL over an IP
network to connect TRILL switches.
3.1 Remote Office Scenario
In the Remote Office Scenario, a remote TRILL network is connected to
a TRILL campus across a multihop IP network, such as the public
Internet. The TRILL network in the remote office becomes a part of
TRILL campus, and nodes in the remote office can be attached to the
same VLANs or Fine Grained Labels [RFC7172] as local campus nodes. In
many cases, a remote office may be attached to the TRILL campus by a
single pair of RBridges, one on the campus end, and the other in the
remote office. In this use case, the TRILL over IP link will often
cross logical and physical IP networks that do not support TRILL, and
are not under the same administrative control as the TRILL campus.
3.2 IP Backbone Scenario
In the IP Backbone Scenario, TRILL over IP is used to connect a
number of TRILL networks to form a single TRILL campus. For example,
a TRILL over IP backbone could be used to connect multiple TRILL
networks on different floors of a large building, or to connect TRILL
networks in separate buildings of a multi-building site. In this use
case, there may often be several TRILL switches on a single TRILL
over IP link, and the IP link(s) used by TRILL over IP are typically
under the same administrative control as the rest of the TRILL
campus.
3.3 Important Properties of the Scenarios
There are a number of differences between the above two application
scenarios, some of which drive features of this specification. These
differences are especially pertinent to the security requirements of
the solution, how multicast data frames are handled, and how the
TRILL switch ports discover each other.
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3.3.1 Security Requirements
In the IP Backbone Scenario, TRILL over IP is used between a number
of RBridge ports, on a network link that is in the same
administrative control as the remainder of the TRILL campus. While it
is desirable in this scenario to prevent the association of
unauthorized RBridges, this can be accomplished using existing IS-IS
security mechanisms. There may be no need to protect the data
traffic, beyond any protections that are already in place on the
local network.
In the Remote Office Scenario, TRILL over IP may run over a network
that is not under the same administrative control as the TRILL
network. Nodes on the network may think that they are sending traffic
locally, while that traffic is actually being sent, in an IP tunnel,
over the public Internet. It is necessary in this scenario to protect
the integrity and confidentiality of user traffic, as well as
ensuring that no unauthorized RBridges can gain access to the RBridge
campus. The issues of protecting integrity and confidentiality of
user traffic are addressed by using IPsec for both TRILL IS-IS and
TRILL Data packets between RBridges in this scenario.
3.3.2 Multicast Handling
In the IP Backbone scenario, native IP multicast may be supported on
the TRILL over IP link. If so, it can be used to send TRILL IS-IS and
multicast data packets, as discussed later in this document.
Alternatively, multi-destination packets can be transmitted serially
by IP unicast to the intended recipients.
In the Remote Office Scenario there will often be only one pair of
RBridges connecting a given site and, even when multiple RBridges are
used to connect a Remote Office to the TRILL campus, the intervening
network may not provide reliable (or any) multicast connectivity.
Issues such as complex key management also make it difficult to
provide strong data integrity and confidentiality protections for
multicast traffic. For all of these reasons, the connections between
local and remote RBridges will commonly be treated like point-to-
point links, and all TRILL IS-IS control messages and multicast data
packets that are transmitted between the Remote Office and the TRILL
campus will be serially transmitted by IP unicast, as discussed later
in this document.
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3.3.3 Neighbor Discovery
In the IP Backbone Scenario, TRILL switches that use TRILL over IP
can use the normal TRILL IS-IS Hello mechanisms to discover the
existence of other TRILL switches on the link [RFC7177], and to
establish authenticated communication with them.
In the Remote Office Scenario, an IPsec session will need to be
established before TRILL IS-IS traffic can be exchanged, as discussed
below. In this case, one end will need to be configured to establish
a IPSEC session with the other. This will typically be accomplished
by configuring the TRILL switch or a border device at a Remote Office
to initiate an IPsec session and subsequent TRILL exchanges with a
TRILL over IP-enabled RBridge attached to the TRILL campus.
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4. TRILL Packet Formats
To support TRILL two types of TRILL packets are transmitted between
TRILL switches: TRILL Data packets and TRILL IS-IS packets.
Section 4.1 describes general TRILL packet formats for data and IS-IS
independent of link technology. Section 4.2 specifies general TRILL
over IP packet formats including IPsec ESP encapsulation. Section 4.3
provides QoS Considerations. Section 4.4 discusses broadcast links
and multicast packets. And Section 4.5 provides TRILL IS-IS Hello
SubNetwork Point of Attachment (SNPA) considerations for TRILL over
IP.
4.1 General Packet Formats
The on-the-wire form of a TRILL Data packet in transit between two
neighboring TRILL switch ports is as shown below:
+----------------+----------+----------------+-----------+
| Link Header | TRILL | Native Frame | Link |
| for TRILL Data | Header | Payload | Trailer |
+----------------+----------+----------------+-----------+
The encapsulated Native Frame Payload is similar to an Ethernet frame
with a VLAN tag or Fine Grained Label [RFC7172] but with no trailing
Frame Check Sequence (FCS).
TRILL IS-IS packets are formatted on-the-wire as follows:
+-----------------+---------------+-----------+
| Link Header | TRILL IS-IS | Link |
| for TRILL IS-IS | Payload | Trailer |
+-----------------+---------------+-----------+
The Link Header and Link Trailer in these formats depend on the
specific link technology. The Link Header contains one or more fields
that distinguish TRILL Data from TRILL IS-IS. For example, over
Ethernet, the Link Header for TRILL Data ends with the TRILL
Ethertype while the Link Header for TRILL IS-IS ends with the L2-IS-
IS Ethertype; on the other hand, over PPP, there are no Ethertypes in
the Link Header but PPP protocol code points are included that
distinguish TRILL Data from TRILL IS-IS.
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4.2 General TRILL Over IP Packet Formats
In TRILL over IP, we use an IP (v4 or v6) header followed by an
encapsulation header as the link header. (On the wire, the IP header
will normally be preceded by the lower layer header of a protocol
that is carrying IP; however, this does not concern us at the level
of this document.)
There are multiple IP based encapsulations usable for TRILL over IP
that differ in exactly what appears after the IP header and before
the TRILL Header or the TRILL IS-IS Payload. These encapsulations are
further detailed in Section 5. In the general specification below,
those encapsulation fields will be represented as "ENCAP Hdr".
4.2.1 Without Security
When TRILL over IP link security is not being used, a TRILL over IP
packet on the wire looks like one of the following:
TRILL Data Packet
+---------+-----------+---------+------------------+
| IP | ENCAP Hdr | TRILL | Native frame |
| Header | for Data | Header | Payload |
+---------+-----------+---------+------------------+
<--- link header ---->
TRILL IS-IS Packet
+---------+-----------+-----------------+
| IP | ENCAP Hdr | TRILL IS-IS |
| Header | for IS-IS | Payload |
+---------+-----------+-----------------+
<--- link header ---->
As discussed above and further specified in Section 5, the ENCAP Hdr
indicates whether the packet is TRILL Data or IS-IS.
4.2.2 With Security
TRILL over IP link security uses IPsec Encapsulating Security
Protocol (ESP) in tunnel mode [RFC4303]. Since TRILL over IP always
starts with an IP Header (on the wire this appears after any lower
layer header that might be required), the modifications for IPsec are
independent of the TRILL over IP ENCAP Hdr that occurs after that IP
Header. The resulting packet formats are as follows for IPv4 and
IPv6:
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With IPv4:
+-------------+-----+--------------+-----------+-----------+
| new IP Hdr | ESP | TRILL IP Hdr | ENCAP Hdr | ESP |ESP|
|(any options)| Hdr | (any options)| + payload |Trailer|ICV|
+-------------+-----+--------------+-----------+-----------+
|<---------- encryption ---------->|
|<-------------- integrity ------------->|
With IPv6:
+------+-------+-----+------+--------+-----------+-------+---+
| new |new ext| ESP | orig |orig ext| ENCAP Hdr | ESP |ESP|
|IP Hdr| Hdrs | Hdr |IP Hdr| Hdrs | + payload |Trailer|ICV|
+------+-------+-----+------+--------+-----------+-------+---+
|<----------- encryption ---------->|
|<--------------- integrity ------------->|
As shown above, IP Header options are considered part of the IPv4
Header but are extensions ("ext") of the IPv6 Header. For further
information on the IPsec ESP Hdr, Trailer, and ICV, see [RFC4303] and
Section 7 below. "ENCAP Hdr + payload" is the encapsulation header
(Section 5) and TRILL data or the encapsulation header and IS-IS
payload, that is, the material after the IP Header in the diagram in
Section 4.2.1.
This architecture permits the ESP tunnel end point to be separated
from the TRILL over IP RBridge port (see, for example, Section 1.1.3
of [RFC7296]).
4.3 QoS Considerations
In IP, QoS handling is indicated by the Differentiated Services Code
Point (DSCP [RFC2474] [RFC3168]) in the IP Header. The former Type
of Service (TOS) octet in the IPv4 Header and the Traffic Class octet
in the IPv6 Header has been divided as shown in the following diagram
adapted from [RFC3168]. (TRILL support of ECN is beyond the scope of
this document. See [TRILLECN].)
0 1 2 3 4 5 6 7
+-----+-----+-----+-----+-----+-----+-----+-----+
| DSCP FIELD | ECN FIELD |
+-----+-----+-----+-----+-----+-----+-----+-----+
DSCP: Differentiated Services Codepoint
ECN: Explicit Congestion Notification
Within a TRILL switch, priority is indicated by configuration for
TRILL IS-IS packets and for TRILL Data packets by a three bit (0
through 7) priority field and a Drop Eligibility Indicator bit (see
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Sections 8.2 and 7 of [RFC7780]). (Typically TRILL IS-IS is
configured to use the highest two priorities depending on the IS-IS
PDU.) The priority affects queuing behavior at TRILL switch ports and
may be encoded into the link header, particularly if there could be
priority sensitive devices within the link. For example, if the link
is a bridged LAN, it is commonly encoded into an Outer.VLAN tag's
priority and DEI fields.
TRILL over IP implementations MUST support setting the DSCP value in
the outer IP Header of TRILL packets they send by mapping the TRILL
priority and DEI to the DSCP. They MAY support, for a TRILL Data
packet where the native frame payload is an IP packet, mapping the
DSCP in this inner IP packet to the outer IP Header with the default
for that mapping being to copy the DSCP without change.
The default TRILL priority and DEI to DSCP mapping, which may be
configured per TRILL over IP port, is an follows. Note that the DEI
value does not affect the default mapping and, to provide a
potentially lower priority service than the default priority 0,
priority 1 is considered lower priority than 0. So the priority
sequence from lower to higher priority is 1, 0, 2, 3, 4, 5, 6, 7.
TRILL Priority DEI DSCP Field (Binary/decimal)
-------------- --- -----------------------------
0 0/1 001000 / 8
1 0/1 000000 / 0
2 0/1 010000 / 16
3 0/1 011000 / 24
4 0/1 100000 / 32
5 0/1 101000 / 40
6 0/1 110000 / 48
7 0/1 111000 / 56
4.4 Broadcast Links and Multicast Packets
TRILL supports broadcast links. These are links to which more than
two TRILL switch ports can be attached and where a packet can be
broadcast or multicast from a port to all or a subset of the other
ports on the link as well as unicast to a specific other port on the
link.
As specified in [RFC6325], TRILL Data packets being forwarded between
TRILL switches can be unicast on a link to a specific TRILL switch
port or multicast on a link to all TRILL switch ports. TRILL IS-IS
packets are always multicast to all other TRILL switches on the link
except for IS-IS MTU PDUs, which may be unicast [RFC7177]. This
distinction is not significant if the link is inherently point-to-
point, such as a PPP link; however, on a broadcast link there will be
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a packet outer link address that will be unicast or multicast as
appropriate. For example, over Ethernet links, the Ethernet multicast
addresses All-RBridges and All-IS-IS-RBridges are used for
multicasting TRILL Data and TRILL IS-IS respectively. For details on
TRILL over IP handling of multicast, see Section 6.
4.5 TRILL Over IP IS-IS SubNetwork Point of Attachment
IS-IS routers, such as TRILL switches, establish adjacency through
the exchange of Hello PDUs on a link [IS-IS] [RFC7177]. The Hellos
transmitted out a port indicate what neighbor ports that port can see
on the link by listing what IS-IS refers to as the neighbor port's
SubNetwork Point of Attachment (SNPA). (For an Ethernet link, which
may be a bridged network, the SNPA is the port MAC address.)
In TRILL Hello PDUs on a TRILL over IP link, the IP addresses of the
IP ports connected to that link are their actual SNPA (SubNetwork
Point of Attachment [IS-IS]) addresses and, for IPv6, the 16-byte
IPv6 address is used as the SNPA; however, for easy in re-using code
designed for the common case of 48-bit SNPAs, in TRILL over IPv4 a
48-bit synthetic SNPA that looks like a unicast MAC address is
constructed for use in the SNPA field of TRILL Neighbor TLVs
[RFC7176] [RFC7177] in such Hellos. This synthetic SNPA is derived
from the port IPv4 address is as follows:
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0xFE | 0x00 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 upper half |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 lower half |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This synthetic SNPA (MAC) address has the local (0x02) bit on in the
first byte and so cannot conflict with any globally unique 48-bit
Ethernet MAC. However, when TRILL operates on an IP link, TRILL sees
only IP addresses on that link, not MAC stations, even if the TRILL
over IP Link is being carried over Ethernet. Therefore conflict on
the link between a real MAC address and a TRILL over IP synthetic
SNPA (MAC) address would be impossible in any case.
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5. TRILL over IP Encapsulation Formats
There are a variety of TRILL over IP encapsulation formats possible.
By default TRILL over IP adopts a hybrid encapsulation approach.
There is one format, called "native encapsulation" that MUST be
implemented. Although native encapsulation does not typically have
good fast path support, as a lowest common denominator it can be used
by low bandwidth control traffic to determine a preferred
encapsulation with better performance. In particular, by default, all
TRILL IS-IS Hellos are sent using native encapsulation and those
Hellos are used to determine the encapsulation used for all TRILL
Data packets and all other TRILL IS-IS PDUs (with the exception of
IS-IS MTU-probe and MTU-ack PDUs used to establish adjacency).
Alternatively, the network operator can pre-configure a TRILL over IP
port to use a particular encapsulation chosen for their particular
network's needs and port capabilities. That encapsulation is then
used for all TRILL Data and IS-IS packets on ports so configured.
This is expected to frequently be the case for a managed campus of
TRILL switches.
Section 5.1 discusses general consideration for the TRILL over IP
encapsulation format. Section 5.2 discusses encapsulation agreement.
Section 5.3 discusses broadcast link encapsulation considerations.
The subsequent subsections discuss particular encapsulations.
5.1 Encapsulation Considerations
An encapsulation must provide a method to distinguish TRILL Data
packets and TRILL IS-IS packets, or it is not useful for TRILL. In
addition, the following criteria can be helpful is choosing between
different encapsulations:
a) Fast path support - For most applications, it is highly desirable
to be able to encapsulate/decapsulate TRILL over IP at line speed
so a format where existing or anticipated fast path hardware can
do that is best. This is commonly the dominant consideration.
b) Ease of multi-pathing - The IP path between TRILL over IP ports
may include equal cost multipath routes internal to the IP link so
a method of encapsulation that provides variable fields available
for existing or anticipated fast path hardware multi-pathing is
preferred.
c) Robust fragmentation and re-assembly - The MTU of the IP link may
require fragmentation in which case an encapsulation with robust
fragmentation and re-assembly is important. There are known
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problems with IPv4 fragmentation and re-assembly [RFC6864] which
generally do not apply to IPv6. Some encapsulations can fix these
problems but the encapsulations specified in this document do not.
Therefore, if fragmentation is anticipated with the encapsulations
specified in this document, the use of IPv6 is RECOMMENDED.
d) Checksum strength - Depending on the particular circumstances of
the TRILL over IP link, a checksum provided by the encapsulation
may be a significant factor. Use of IPsec can also provide a
strong integrity check.
5.2 Encapsulation Agreement
TRILL Hellos sent out a TRILL over IP port indicate the
encapsulations that port is willing to support through a mechanism
initially specified in [RFC7178] and [RFC7176] that is hereby
extended. Specifically, RBridge Channel Protocol numbers 0xFD0
through 0xFF7 are redefined to be link technology dependent flags
that, for TRILL over IP, indicate support for different
encapsulations, allowing support for up to 40 encapsulations to be
specified. Support for an encapsulation is indicated in the Hello
PDU in the same way that support for an RBridge Channel was
indicated. (See also section 11.3.) "Support" indicates willingness
to use that encapsulation for TRILL Data and TRILL IS-IS packets
(although TRILL IS-IS Hellos are still sent in native encapsulation
by default unless the port is configured to always use some other
encapsulation).
If, in a TRILL Hello on a TRILL over IP link, support is not
indicated for any encapsulation, then the port from which it was sent
is assumed to support only native encapsulation (see Section 5.4).
An adjacency is formed between two TRILL over IP ports if the
intersection of the sets of encapsulation methods they support is not
null. If that intersection is null, then no adjacency is formed. In
particular, for a TRILL over IP link, the adjacency state machine
MUST NOT advance to the Report state unless the ports share an
encapsulation [RFC7177]. If no encapsulation is shared, the adjacency
state machine remains in the state from which it would otherwise have
transitioned to the Report state.
If any TRILL over IP packet, other than an IS-IS Hello or MTU PDU in
native encapsulation, is received in an encapsulation for which
support is not being indicated by the receiver, that packet MUST be
discarded (see Section 5.3).
If there are two or more encapsulations in common between two
adjacent ports for unicast or the set of adjacent ports for
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multicast, a transmitter is free to choose whichever of the
encapsulations it wishes to use. Thus transmissions between adjacent
ports P1 and P2 could use different encapsulations depending on which
port is transmitting and which is receiving.
It is expected to be the normal case in a well configured network
that all the TRILL over IP ports connected to an IP link (i.e., an IP
network) that are intended to communicate with each other will
support the same encapsulation(s).
5.3 Broadcast Link Encapsulation Considerations
To properly handle TRILL protocol packets on a TRILL over IP link in
the general case, either native IP multicast mode is used on that
link or multicast must be simulated using serial IP unicast, as
discussed in Section 6. (Of course, if the IP link happens to
actually be point-to-point no special provision is needed for
handling IP multicast addressed packets.)
It is possible for the Hellos from a TRILL over IP port P1 to
establish adjacency with multiple other TRILL over IP ports (P2, P3,
...) on a broadcast link. In a well configured network one would
expect all of the IP ports involved to support the same
encapsulation(s); but, for example, if P1 supports multiple
encapsulations, it is possible that P2 and P3, do not have an
encapsulation in common that is supported by P1. [IS-IS] can handle
such non-transitive adjacencies that are reported as specified in
[RFC7177]. This is generally done, albeit with reduced efficiency, by
forwarding through the designated RBridge (router) on the link. Thus
it is RECOMENDED that all TRILL over IP ports on an IP link be
configured to support one encapsulation in common that has good fast
path support.
If serial IP unicast is being used by P1, it can use different
encapsulations for different transmissions.
If native IP multicast is available for use by P1, it can send one
transmission per encapsulation method by which it has a disjoint set
of adjacencies on the link. If the transmitting port has adjacencies
with overlapping sets of ports that are adjacent using different
encapsulations, use of native multicast with different encapsulations
may result in packet duplication. It would always be possible to use
native IP multicast for one encapsulation for which the transmitting
port has adjacencies, perhaps the encapsulation for which it has the
largest number of adjacencies, and serially unicast to other
receivers. These considerations are the reason that a TRILL over IP
port MUST discard any packet received with an encapsulation for which
it has not established an adjacency with the receiver. Otherwise,
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packets would be further duplicated.
5.4 Native Encapsulation
The mandatory to implement "native encapsulation" format of a TRILL
over IP packet, when used without security, is TRILL over UDP as
shown below. This provides simple and direct access by TRILL to the
native datagram service of IP.
+----------+--------+-----------------------+
| IP | UDP | TRILL |
| Header | Header | Payload |
+----------+--------+-----------------------+
Where the UDP Header is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = Entropy | Destination Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TRILL Payload ...
Source Port - see Section 8.3
Destination Port - indicates TRILL Data or IS-IS, see Section
11.1.
UDP Length - as specified in [RFC0768]
UDP Checksum - as specified in [RFC0768]
The TRILL Payload starts with the TRILL Header (not including the
TRILL Ethertype) for TRILL Data packets and starts with the 0x83
Intradomain Routeing Protocol Discriminator byte (thus not including
the L2-IS-IS Ethertype) for TRILL IS-IS packets.
5.5 VXLAN Encapsulation
VXLAN [RFC7348] IP encapsulation of TRILL looks, on the wire, like
TRILL over Ethernet over VXLAN over UDP over IP.
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+--------+--------+--------+----------+-----------+
| IP | UDP | VXLAN | Ethernet | TRILL |
| Header | Header | Header | Header | Payload |
+--------+--------+--------+----------+-----------+
The outer UDP uses a destination port number indicating VXLAN and the
outer UDP source port MAY be used for entropy as with native
encapsulation (see Section 8.3). The VXLAN header after the outer UDP
header adds a 24 bit Virtual Network Identifier (VNI). The Ethernet
header after the VXLAN header and before the TRILL header consists of
source MAC address, destination MAC address, and Ethertype. The
Ethertype distinguishes TRILL Data from TRILL IS-IS. The destination
and source MAC addresses in this Ethernet header are not used.
A TRILL over IP port using VXLAN encapsulation by default uses a VNI
of 1 for TRILL IS-IS traffic and a VNI of 2 for TRILL data traffic
but can be configured as described in Section 9.2.3.1 to use some
other fixed VNIs or to map from VLAN/FGL to VNI.
5.6 Other Encapsulations
It is anticipated that additional TRILL over IP encapsulations will
be specified in future documents and allocated a link technology
specific flag bit as per Section 11.3. A primary consideration for
whether it is worth the effort to specify use of an encapsulation by
TRILL over IP is whether it has good existing or anticipated fast
path support.
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6. Handling Multicast
By default, both TRILL IS-IS packets and multi-destination TRILL Data
packets are sent to an All-RBridges IPv4 or IPv6 IP multicast Address
as appropriate (see Section 11.2); however, a TRILL over IP port may
be configured (see Section 9) to use a different multicast address or
to use serial IP unicast with a list of one or more unicast IP
addresses of other TRILL over IP ports to which multi-destination
packets are sent. In the serial unicast case the outer IP header of
each copy of the packet sent shows an IP unicast destination address
even through the TRILL header has the M bit set to one to indicate
multi-destination. Serial unicast configuration is necessary if the
TRILL over IP port is connected to an IP network that does not
support IP multicast. In any case, unicast TRILL packets (those with
the M bit in the TRILL Header set to zero) are sent by unicast IP.
Even if a TRILL over IP port is configured to send multi-destination
packets with serial unicast, it MUST be prepared to receive IP
multicast TRILL packets. All TRILL over IP ports default to
periodically transmitting appropriate IGMP (IPv4 [RFC3376]) or MLD
(IPv6 [RFC2710]) packets, so that the TRILL multicast IP traffic can
be sent to them, but may be configured not to do so.
Although TRILL fully supports broadcast links with more than 2
RBridges connected to the link there may be good reasons for
configuring TRILL over IP ports to use serial unicast even where
native IP multicast is available. Use of serial unicast provides the
network manager with more precise control over adjacencies and how
TRILL over IP links will be formed in an IP network. In some
networks, unicast is more reliable than multicast. If multiple point-
to-point TRILL over IP connections between two parts of a TRILL
campus are configured, TRILL will in any case spread traffic across
them, treating them as parallel links, and appropriately fail over
traffic if a link fails or incorporate a new link that comes up.
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7. Use of IPsec and IKEv2
All TRILL switches (RBridges) that support TRILL over IP MUST
implement IPsec [RFC4301] and support the use of IPsec Encapsulating
Security Protocol (ESP [RFC4303]) in tunnel mode to secure both TRILL
IS-IS and TRILL Data packets. When IPsec is used to secure a TRILL
over IP link and no IS-IS security is enabled, the IPsec session MUST
be fully established before any TRILL IS-IS or data packets are
exchanged. When there is IS-IS security [RFC5310] provided,
implementers SHOULD use IS-IS security to protect TRILL IS-IS
packets. However, in this case, the IPsec session still MUST be fully
established before any TRILL Data packets transmission, since IS-IS
security does not provide any protection to data packets, and SHOULD
be fully established before any TRILL IS-IS packet transmission other
than IS-IS Hello or MTU PDUs.
All RBridges that support TRILL over IP MUST implement the Internet
Key Exchange Protocol version 2 (IKEv2) for automated key management.
7.1 Keying
The following subsections discuss pairwise and group keying for TRILL
over IP IPsec.
7.1.1 Pairwise Keying
When IS-IS security is in use, IKEv2 SHOULD use a pre-shared key that
incorporates the IS-IS shared key in order to bind the TRILL data
session to the IS-IS session. The pre-shared key that will be used
for IKEv2 exchanges for TRILL over IP is determined as follows:
HKDF-Expand-SHA256 ( IS-IS-key,
"TRILL IP" | P1-System-ID | P1-Port | P2-System-ID | P2-Port )
In the above "|" indicates concatenation, HKDF is as in [RFC5869],
SHA256 is as in [RFC6234], and "TRILL IP" is the eight byte US ASCII
[RFC0020] string indicated. "IS-IS-key" is an IS-IS key usable for
IS-IS security of link local IS-IS PDUs such as Hello, CSNP, and
PSNP. This SHOULD be a link scope IS-IS key. P1-System-ID and
P2-System ID are the six byte System IDs of the two TRILL RBridges,
and P1-Port and P2-Port are the TRILL Port IDs [RFC6325] of the ports
in use on each end. System IDs are guaranteed to be unique within the
TRILL campus. Both of the RBridges involved treat the larger
magnitude System ID, comparing System IDs as unsigned integers, as P1
and the smaller as P2 so both will derive the same key.
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With [RFC5310] there could be multiple keys identified with 16-bit
key IDs. The key ID when an IS-IS key is in use is transmitted in an
IKEv2 ID_KEY_ID identity field [RFC7296] with Identification Data
length of 2 bytes (Payload Length 6 bytes). The Key ID of the IS-IS-
key is used to identify the IKEv2 shared secret derived as above that
is actually used. ID_KEY_ID identity field(s) of other lengths MAY
occur but their use is beyond the scope of this document.
The IS-IS-shared key from which the IKEv2 shared secret is derived
might expire and be updated as described in [RFC5310]. The IKEv2
pre-shared keys derived from an IS-IS shared key MUST expire within a
lifetime no longer than the IS-IS-shared key from which they were
derived. When the IKEv2 shared secret key expires, or earlier, the
IKEv2 Security Association must be rekeyed using a new shared secret
derived from a new IS-IS shared key.
IKEv2 with certificate based security MAY be used but details of
certificate contents and use policy for this application of IKEv2 are
beyond the scope of this document.
7.1.2 Group Keying
In the case of a TRILL over IP port configured as point-to-point (see
Section 4.2.4.1 of [RFC6325]), there is no group keying and the
pairwise keying determined as in Section 7.1.1 is used for multi-
destination TRILL traffic, which is unicast.
In the case of a TRILL over IP port configured as broadcast but where
the port is configured to use serial unicast (see Section 8), there
is no group keying and the pairwise keying determined as in Section
7.1.1 is used for multi-destination TRILL traffic, which is unicast.
The case of a TRILL over IP port configured as broadcast and using
native multicast is beyond the scope of this document. For security
as provided in this document, multicast is handled via serial
unicast.
7.2 Mandatory-to-Implement Algorithms
All RBridges that support TRILL over IP MUST implement IPsec ESP
[RFC4303] in tunnel mode. The implementation requirements for ESP
cryptographic algorithms are as specified for IPsec. That
specification is currently [RFC7321].
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8. Transport Considerations
This section discusses a variety of important transport
considerations.
8.1 Congestion Considerations
Section 3.1.3 of [RFC5405] discussed the congestion implications of
UDP tunnels. As discussed in [RFC5405], because other flows can share
the path with one or more UDP tunnels, congestion control [RFC2914]
needs to be considered.
The default initial determination of the TRILL over IP encapsulation
to be used through the exchange of TRILL IS-IS Hellos is a low
bandwidth process. Hellos are not permitted to be sent any more often
than once per second, and so are very unlikely to cause congestion.
One motivation for including UDP in a TRILL encapsulation is to
improve the use of multipath (such as ECMP) in cases where traffic is
to traverse routers which are able to hash on UDP Port and IP
address. In many cases this may reduce the occurrence of congestion
and improve usage of available network capacity. However, it is also
necessary to ensure that the network, including applications that use
the network, responds appropriately in more difficult cases, such as
when link or equipment failures have reduced the available capacity.
The impact of congestion must be considered both in terms of the
effect on the rest of the network of a UDP tunnel that is consuming
excessive capacity, and in terms of the effect on the flows using the
UDP tunnels. The potential impact of congestion from a UDP tunnel
depends upon what sort of traffic is carried over the tunnel, as well
as the path of the tunnel.
TRILL is used to carry a wide range of traffic. In many cases TRILL
is used to carry IP traffic. IP traffic is generally assumed to be
congestion controlled, and thus a tunnel carrying general IP traffic
(as might be expected to be carried across the Internet) generally
does not need additional congestion control mechanisms. As specified
in [RFC5405]:
"IP-based traffic is generally assumed to be congestion-
controlled, i.e., it is assumed that the transport protocols
generating IP-based traffic at the sender already employ
mechanisms that are sufficient to address congestion on the path.
Consequently, a tunnel carrying IP-based traffic should already
interact appropriately with other traffic sharing the path, and
specific congestion control mechanisms for the tunnel are not
necessary".
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For this reason, where TRILL is sent using UDP and used to carry IP
traffic that is known to be congestion controlled, the UDP paths MAY
be used across any combination of a single or cooperating service
providers or across the general Internet.
However, TRILL is also used to carry traffic that is not necessarily
congestion controlled. For example, TRILL may be used to carry
traffic where specific bandwidth guarantees are provided.
In such cases congestion may be avoided by careful provisioning of
the network and/or by rate limiting of user data traffic. Where TRILL
is carried, directly or indirectly, over UDP over IP, the identity of
each individual TRILL flow is in general lost.
For this reason, where the TRILL traffic is not congestion
controlled, TRILL over UDP/IP MUST only be used within a single
service provider that utilizes careful provisioning (e.g., rate
limiting at the entries of the network while over-provisioning
network capacity) to ensure against congestion, or within a limited
number of service providers who closely cooperate in order to jointly
provide this same careful provisioning. As such, TRILL over UDP/IP
MUST NOT be used as a general TRILL encapsulation over the general
Internet, or over non-cooperating service providers, to carry traffic
that is not congestion-controlled.
Measures SHOULD be taken to prevent non-congestion-controlled TRILL
over UDP/IP traffic from "escaping" to the general Internet, for
example the following:
a. Physical or logical isolation of the TRILL over IP links from the
general Internet.
b. Deployment of packet filters that block the UDP ports assigned for
TRILL-over-UDP.
c. Imposition of restrictions on TRILL over UDP/IP traffic by
software tools used to set up TRILL over UDP paths between
specific end systems (as might be used within a single data
center).
d. Use of a "Managed Circuit Breaker" for the TRILL traffic as
described in [circuit-breaker].
8.2 Recursive Ingress
TRILL is specified to transport data to and from end stations over
Ethernet and IP is frequently transported over Ethernet. Thus, an end
station native data Ethernet frame "EF" might get TRILL ingressed to
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TRILL(EF) that was subsequently sent to a next hop RBridge out a
TRILL over IP over Ethernet port resulting in a packet on the wire of
the form Ethernet(IP(TRILL(EF))). There is a risk of such a packet
being re-ingressed by the same TRILL campus, due to physical or
logical misconfiguration, looping round, being further re-ingressed,
and so on. (Or this might occur through a cycle of TRILL campuses.)
The packet would get discarded if it got too large but if
fragmentation is enabled, it would just keep getting split into
fragments that would continue to loop and grow and re-fragment until
the path was saturated with junk and packets were being discarded due
to queue overflow. The TRILL Header TTL would provide no protection
because each TRILL ingress adds a new TRILL header with a new TTL.
To protect against this scenario, a TRILL over IP port MUST, by
default, test whether a TRILL packet it is about to transmit appears
to be a TRILL ingress of a TRILL over IP over Ethernet packet. That
is, is it of the form TRILL(Ethernet(IP(TRILL(...)))? If so, the
default action of the TRILL over IP output port is to discard the
packet rather than transmit it. However, there are cases where some
level of nested ingress is desired so it MUST be possible to
configure the port to allow such packets.
8.3 Fat Flows
For the purpose of load balancing, it is worthwhile to consider how
to transport TRILL packets over any Equal Cost Multiple Paths (ECMPs)
existing internal to the IP path between TRILL over IP ports.
The ECMP election for the IP traffic could be based, for example with
IPv4, on the quintuple of the outer IP header { Source IP,
Destination IP, Source Port, Destination Port, and IP protocol }.
Such tuples, however, could be exactly the same for all TRILL Data
packets between two RBridge ports, even if there is a huge amount of
data being sent between a variety of ingress and egress RBridges. On
solution to this is to use the UDP Source Port as an entropy field.
(This idea is also introduced in [gre-in-udp].) For example, for
TRILL Data, this entropy field could be based on some hash of the
Inner.MacDA, Inner.MacSA, and Inner.VLAN or Inner.FGL. Unfortunately,
this can conflict with middleboxes inside the TRILL over IP link (see
8.5). Therefore, in order to better support ECMP, a RBridge SHOULD
set the Source Port to a range of values as an entropy field for ECMP
decisions; this range SHOULD be the ephemeral port range
(49152-65535) except that, if there are middleboxes in the path (see
Section 8.5), it MUST be possible to configure the range of different
Source Port values to a sufficiently smaller range to avoid
disrupting connectivity.
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8.4 MTU Considerations
In TRILL each RBridge advertises in its LSP number zero the largest
LSP frame it can accept (but not less than 1,470 bytes) on any of its
interfaces (at least those interfaces with adjacencies to other TRILL
switches in the campus) through the originatingLSPBufferSize TLV
[RFC6325] [RFC7177]. The campus minimum MTU (Maximum Transmission
Unit), denoted Sz, is then established by taking the minimum of this
advertised MTU for all RBridges in the campus. Links that do not meet
the Sz MTU are not included in the routing topology. This protects
the operation of IS-IS from links that would be unable to accommodate
the largest LSPs.
A method of determining originatingLSPBufferSize for an RBridge with
one or more TRILL over IP ports is described in [RFC7780]. However,
if an IP link either can accommodate jumbo frames or is a link on
which IP fragmentation is enabled and acceptable, then it is unlikely
that the IP link will be a constraint on the originatingLSPBufferSize
of an RBridge using the link. On the other hand, if the IP link can
only handle smaller frames and fragmentation is to be avoided when
possible, a TRILL over IP port might constrain the RBridge's
originatingLSPBufferSize.
Because TRILL sets the minimum values of Sz at 1,470 bytes, there may
be links that meet the minimum MTU for the IP protocol (1,280 bytes
for IPv6, 576 bytes for IPv4) on which it would be necessary to
enable fragmentation for safe TRILL use.
The use of TRILL IS-IS MTU PDUs, as specified in Section 5 of
[RFC6325] and in [RFC7177], can provide added assurance of the actual
MTU of a link.
8.5 Middlebox Considerations
This section gives some middlebox considerations for the IP
encapsulations covered by this document, namely native and VXLAN
encapsulation.
The requirements for the usage of the zero UDP Checksum in a UDP
tunnel protocol are detailed in [RFC6936]. These requirements apply
to the TRILL over IP encapsulations specified herein (native and
VXLAN), which are applications of UDP tunnel.
Besides the Checksum, the Source Port number of the UDP header is
also pertinent to the middlebox behavior. Network Address/Port
Translator (NAPT) is the most commonly deployed Network Address
Translation (NAT) device [RFC4787]. For a UDP tunnel protocol, the
NAPT device establishes a NAT session to translate the {private IP
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address, private source port number} tuple to a {public IP address,
public source port number} tuple, and vice versa, for the duration of
the UDP session. This provides the UDP tunnel protocol application
with the "NAT-pass-through" function. NAPT allows multiple internal
hosts to share a single public IP address. The port number, i.e., the
UDP Source Port number, is used as the demultiplexer of the multiple
internal hosts.
However, the above NAPT behavior conflicts with the behavior that the
UDP Source Port number is used as an entropy (See Section 8.3).
Hence, the network operator MUST ensure the TRILL switch ports
sending through local or remote NAPT middleboxes limit the entropy
usage of the UDP Source Port number, possibly to a single value.
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9. TRILL over IP Port Configuration
This section specifies the configuration information needed at a
TRILL over IP port beyond that needed for a general RBridge port.
9.1 Per IP Port Configuration
Each RBridge port used for a TRILL over IP link should have at least
one IP (v4 or v6) address. If no IP address is associated with the
port, perhaps as a transient condition during re-configuration, the
port is disabled. Implementations MAY allow a single port to operate
as multiple IPv4 and/or IPv6 logical ports. Each IP address
constitutes a different logical port and the RBridge with those ports
MUST associate a different Port ID (see Section 4.4.2 of [RFC6325])
with each logical port.
By default a TRILL over IP port discards output packets that fail the
possible recursive ingress test (see Section 10.1) unless configured
to disable that test.
9.2 Additional per IP Address Configuration
The configuration information specified below is per TRILL over IP
port IP address.
The mapping from TRILL packet priority to TRILL over IP
Differentiated Services Code Point (DSCP [RFC2474]) can be
configured. If supported, mapping from an inner DSCP code point, when
the TRILL payload is IP, to the outer TRILL over IP DSCP can be
configured. (See Section 4.3.)
Each TRILL over IP port has a list of acceptable encapsulations it
will use as the basis of adjacency. By default this list consists of
one entry for native encapsulation (see Section 7). Additional
encapsulations MAY be configured and native encapsulation MAY be
removed from this list by configuration. Additional configuration can
be required or possible for specific encapsulations as described in
Section 9.2.3.
Each IP address at a TRILL over IP port uses native IP multicast by
default but may be configured whether to use serial IP unicast
(Section 9.2.2) or native IP multicast (Section 9.2.1). Each IP
address at a TRILL over IP is configured whether or not to use IPsec
(Section 9.2.4).
Regardless of whether they will send IP multicast, TRILL over IP
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ports emit appropriate IGMP (IPv4 [RFC3376]) or MLD (IPv6 [RFC2710])
packets unless configured not to do so. These are sent for the IP
multicast group the port would use if it sent IP multicast.
9.2.1 Native Multicast Configuration
If a TRILL over IP port address is using native IP multicast for
multi-destination TRILL packets (IS-IS and data), by default
transmissions from that IP address use the IP multicast address (IPv4
or IPv6) specified in Section 11.2. The TRILL over IP port may be
configured to use a different IP multicast address for multicasting
packets.
9.2.2 Serial Unicast Configuration
If a TRILL over IP port address has been configured to use serial
unicast for multi-destination packets (IS-IS and data), it should
have associated with it a non-empty list of unicast IP destination
addresses with the same IP version as the version of the port's IP
address (IPv4 or IPv6). Multi-destination TRILL packets are serially
unicast to the addresses in this list. Such a TRILL over IP port will
only be able to form adjacencies [RFC7177] with the RBridges at the
addresses in this list as those are the only RBridges to which it
will send TRILL Hellos. IP packets received from a source IP address
not on the list are discarded.
If this list of destination IP addresses is empty, the port is
disabled.
9.2.3 Encapsulation Specific Configuration
Specific TRILL over IP encapsulation methods may provide for further
configuration as specified below.
9.2.3.1 UDP Source Port
As discussed above, the native starts with a UDP header where the
source UDP port can be used for entropy (Section 8.3). The range of
UDP source port values used defaults to the ephemeral port range
(49152-65535) but can be configured to any other range including to a
single value.
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9.2.3.2 VXLAN Configuration
A TRILL over IP port using VXLAN encapsulation can be configured with
non-default VXLAN Network Identifiers (VNIs) that are used in that
field of the VXLAN header for all TRILL IS-IS and TRILL Data packets
sent using the encapsulation and required in those received using the
encapsulation. The default VNI is 1 for TRILL IS-IS and 2 for TRILL
Data. A TRILL packet received with the an unknown VNI is discarded.
A TRILL over IP port using VXLAN encapsulation can also be configured
to map the Inner.VLAN of a TRILL Data packet being transported to the
value it places in the VNI field and/or to copy the Inner.FGL of a
TRILL Data packet to the VNI field.
9.2.3.3 Other Encapsulation Configuration
Additional encapsulation methods, beyond the native UDP encapsulation
and VXLAN encapsulation specified in this document, are expected to
be specified in future documents and may require further
configuration.
9.2.4 Security Configuration
A TRILL over IP port can be configured, for the case where IS-IS
security [RFC5310] is in use, as to whether or not IPsec must be
fully established and used for any TRILL IS-IS transmissions other
than IS-IS Hello or MTU PDUs (see Section 7). There may also be
configuration whose details are outside the scope of this document
concerning certificate based IPsec or use of shared keys other than
IS-IS based shared key or how to select what IS-IS based shared key
to use.
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10. Security Considerations
TRILL over IP is subject to all of the security considerations for
the base TRILL protocol [RFC6325]. In addition, there are specific
security requirements for different TRILL deployment scenarios, as
discussed in the "Use Cases for TRILL over IP", Section 3 above.
For communication between end stations in a TRILL campus, security
may be possible at three levels: end-to-end security between those
end stations, edge-to-edge security between ingress and egress
RBridges [LinkSec], and link security to protect a TRILL hop. Any
combination of these can be used, including all three.
TRILL over IP link security protects the contents of TRILL Data and
IS-IS packets, including the identities of the end stations for
data and the identities of the edge RBridges, from observers of
the link and transit devices within the link such as bridges or IP
routers, but does not encrypt the link local IP addresses used in
a packet and does not protect against observation by the sending
and receiving RBridges on the link.
Edge-to-edge TRILL security would protect the contents of TRILL data
packets including the identities of the end stations for data from
transit RBridges but does not encrypt the identities of the edge
RBridges involved and does not protect against observation by
those edge RBridges. It is anticipated that edge-to-edge TRILL
security will be covered in future documents.
End-to-end security does not protect the identities of the end
stations or edge RBridge involved but does protect the content of
TRILL data packets from observation by all RBridges or other
intervening devices between the end stations involved. End-to-end
security should always be considered as an added layer of security
to protect any particularly sensitive information from unintended
disclosure. Such end station to end station security is generally
beyond the scope of TRILL
If VXLAN encapsulation is used, the unused Ethernet source and
destination MAC addresses mentioned in Section 5.5, provide a 96 bit
per packet side channel.
10.1 IPsec
This document specifies that all RBridges that support TRILL over IP
links MUST implement IPsec for the security of such links, and makes
it clear that it is both wise and good to use IPsec in all cases
where a TRILL over IP link will traverse a network that is not under
the same administrative control as the rest of the TRILL campus or is
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not secure. IPsec is important, in these cases, to protect the
privacy and integrity of data traffic. However, in cases where IPsec
is impractical due to lack of fast path support, use of TRILL edge-
to-edge security or use by the end stations of end-to-end security
can provide significant security.
Further Security Considerations for IPsec ESP and for the
cryptographic algorithms used with IPsec can be found in the RFCs
referenced by this document.
10.2 IS-IS Security
TRILL over IP is compatible with the use of IS-IS Security [RFC5310],
which can be used to authenticate TRILL switches before allowing them
to join a TRILL campus. This is sufficient to protect against rogue
devices impersonating TRILL switches, but is not sufficient to
protect data packets that may be sent in TRILL over IP outside of the
local network or across the public Internet. To protect the privacy
and integrity of that traffic, use IPsec.
In cases were IPsec is used, the use of IS-IS security may not be
necessary, but there is nothing about this specification that would
prevent using both IPsec and IS-IS security together.
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11. IANA Considerations
IANA considerations are given below.
11.1 Port Assignments
IANA is requested to assign destination UDP Ports for the TRILL IS-IS
and TRILL Data:
UDP Port Protocol Reference
---------- --------------- -----------------
(TBD1) TRILL IS-IS [this document]
(TBD2) TRILL Data [this document]
11.2 Multicast Address Assignments
IANA is requested to assign one IPv4 and one IPv6 multicast address,
as shown below, which correspond to both the All-RBridges and All-IS-
IS-RBridges multicast MAC addresses that have been assigned for
TRILL. Because the low level hardware MAC address dispatch
considerations for TRILL over Ethernet do not apply to TRILL over IP,
one IP multicast address for each version of IP is sufficient.
(Values recommended to IANA in square brackets)
Name IPv4 IPv6
------------ ------------------ --------------------------
All-RBridges TBD3[233.252.14.0] TBD4[FF0X:0:0:0:0:0:0:BAC1]
The hex digit "X" in the IPv6 variable scope address indicates the
scope and defaults to 8. The IPv6 All-RBridges IP address may be used
with other values of X.
11.3 Encapsulation Method Support Indication
The existing "RBridge Channel Protocols" registry is re-named and a
new sub-registry under that registry added as follows:
The TRILL Parameters registry for "RBridge Channel Protocols" is
renamed the "RBridge Channel Protocols and Link Technology Specific
Flags" registry. [this document] is added as a second reference for
this registry. The first part of the table is changed to the
following:
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Range Registration Note
----------- ---------------- ----------------------------
0x002-0x0FF Standards Action
0x100-0xFCF RFC Required allocation of a single value
0x100-0xFCF IESG Approval allocation of multiple values
0xFD0 0xFF7 see Note link technology dependent,
see subregistry
In the existing table of RBridge Channel Protocols, the following
line is changed to two lines as shown:
OLD
0x004-0xFF7 Unassigned
NEW
0x004-0xFCF Unassigned
0xFD0-0xFF7 (link technology dependent, see subregistry)
A new indented subregistry under the re-named "RBridge Channel
Protocols and Link Technology Specific Flags" registry is added as
follows:
Name: TRILL over IP Link Flags
Registration Procedure: Expert Review
Reference: [this document]
Flag Meaning Reference
----------- ------------------------------ ---------
0xFD0 Native encapsulation supported [this document]
0xFD1 VXLAN encapsulation supported [this document]
0xFD2-0xFF7 Unassigned
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Normative References
[IS-IS] - "Intermediate system to Intermediate system routeing
information exchange protocol for use in conjunction with the
Protocol for providing the Connectionless-mode Network Service
(ISO 8473)", ISO/IEC 10589:2002, 2002".
[RFC0020] - Cerf, V., "ASCII format for network interchange", STD 80,
RFC 20, DOI 10.17487/RFC0020, October 1969, <http://www.rfc-
editor.org/info/rfc20>.
[RFC0768] - Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI
10.17487/RFC0768, August 1980, <http://www.rfc-
editor.org/info/rfc768>.
[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>.
[RFC2474] - Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS Field) in
the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474,
December 1998, <http://www.rfc-editor.org/info/rfc2474>.
[RFC2710] - Deering, S., Fenner, W., and B. Haberman, "Multicast
Listener Discovery (MLD) for IPv6", RFC 2710, DOI
10.17487/RFC2710, October 1999, <http://www.rfc-
editor.org/info/rfc2710>.
[RFC2914] - Floyd, S., "Congestion Control Principles", BCP 41, RFC
2914, DOI 10.17487/RFC2914, September 2000, <http://www.rfc-
editor.org/info/rfc2914>.
[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>.
[RFC3376] - Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version 3",
RFC 3376, DOI 10.17487/RFC3376, October 2002, <http://www.rfc-
editor.org/info/rfc3376>.
[RFC4301] - Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, December
2005, <http://www.rfc-editor.org/info/rfc4301>.
[RFC4303] - Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
4303, DOI 10.17487/RFC4303, December 2005, <http://www.rfc-
editor.org/info/rfc4303>.
Margaret Cullen, et al [Page 34]
INTERNET-DRAFT TRILL over IP
[RFC5405] - Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008,
<http://www.rfc-editor.org/info/rfc5304>.
[RFC5310] - Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC
5310, DOI 10.17487/RFC5310, February 2009, <http://www.rfc-
editor.org/info/rfc5310>.
[RFC5869] - Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-
Expand Key Derivation Function (HKDF)", RFC 5869, DOI
10.17487/RFC5869, May 2010, <http://www.rfc-
editor.org/info/rfc5869>.
[RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011,
<http://www.rfc-editor.org/info/rfc6325>.
[RFC7176] - Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt,
D., and A. Banerjee, "Transparent Interconnection of Lots of
Links (TRILL) Use of IS-IS", RFC 7176, DOI 10.17487/RFC7176,
May 2014, <http://www.rfc-editor.org/info/rfc7176>.
[RFC7177] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, H.,
and V. Manral, "Transparent Interconnection of Lots of Links
(TRILL): Adjacency", RFC 7177, DOI 10.17487/RFC7177, May 2014,
<http://www.rfc-editor.org/info/rfc7177>.
[RFC7178] - Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D.
Ward, "Transparent Interconnection of Lots of Links (TRILL):
RBridge Channel Support", RFC 7178, DOI 10.17487/RFC7178, May
2014, <http://www.rfc-editor.org/info/rfc7178>.
[RFC7321] - McGrew, D. and P. Hoffman, "Cryptographic Algorithm
Implementation Requirements and Usage Guidance for
Encapsulating Security Payload (ESP) and Authentication Header
(AH)", RFC 7321, DOI 10.17487/RFC7321, August 2014,
<http://www.rfc-editor.org/info/rfc7321>.
[RFC7348] - Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3 Networks",
RFC 7348, DOI 10.17487/RFC7348, August 2014, <http://www.rfc-
editor.org/info/rfc7348>.
[RFC7780] - Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A.,
Ghanwani, A., and S. Gupta, "Transparent Interconnection of
Lots of Links (TRILL): Clarifications, Corrections, and
Margaret Cullen, et al [Page 35]
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Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016,
<http://www.rfc-editor.org/info/rfc7780>.
Informative References
[RFC4787] - Audet, F., Ed., and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast UDP", BCP
127, RFC 4787, DOI 10.17487/RFC4787, January 2007,
<http://www.rfc-editor.org/info/rfc4787>.
[RFC6234] - Eastlake 3rd, D. and T. Hansen, "US Secure Hash
Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, DOI
10.17487/RFC6234, May 2011, <http://www.rfc-
editor.org/info/rfc6234>.
[RFC6361] - Carlson, J. and D. Eastlake 3rd, "PPP Transparent
Interconnection of Lots of Links (TRILL) Protocol Control
Protocol", RFC 6361, DOI 10.17487/RFC6361, August 2011,
<http://www.rfc-editor.org/info/rfc6361>.
[RFC6864] - Touch, J., "Updated Specification of the IPv4 ID Field",
RFC 6864, DOI 10.17487/RFC6864, February 2013, <http://www.rfc-
editor.org/info/rfc6864>.
[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>.
[RFC7172] - Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R.,
and D. Dutt, "Transparent Interconnection of Lots of Links
(TRILL): Fine-Grained Labeling", RFC 7172, DOI
10.17487/RFC7172, May 2014, <http://www.rfc-
editor.org/info/rfc7172>.
[RFC7173] - Yong, L., Eastlake 3rd, D., Aldrin, S., and J. Hudson,
"Transparent Interconnection of Lots of Links (TRILL) Transport
Using Pseudowires", RFC 7173, DOI 10.17487/RFC7173, May 2014,
<http://www.rfc-editor.org/info/rfc7173>.
[RFC7296] - Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)",
STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014,
<http://www.rfc-editor.org/info/rfc7296>.
[circuit-breaker] - Fairhurst, G., "Network Transport Circuit
Breakers", draft-ietf-tsvwg-circuit-breaker, work in progress.
Margaret Cullen, et al [Page 36]
INTERNET-DRAFT TRILL over IP
[gre-in-udp] - Crabbe, E., Yong, L., and X. Xu, "Generic UDP
Encapsulation for IP Tunneling", draft-yong-tsvwg-gre-in-udp-
encap, work in progress.
[LinkSec] - Eastlake, D., D. Zhang, "TRILL: Link Security", draft-
eastlake-trill-link-security, work in progress.
[TRILLECN] - Eastlake, D., B. Briscoe, "TRILL: ECN (Explicit
Congestion Notification) Support", draft-eastlake-trill-ecn-
support, work in progress.
Margaret Cullen, et al [Page 37]
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Acknowledgements
The following people have provided useful feedback on the contents of
this document: Sam Hartman, Adrian Farrel, and Mohammed Umair.
Some material in Section 10.2 is derived from draft-ietf-mpls-in-udp
by Xiaohu Xu, Nischal Sheth, Lucy Yong, Carlos Pignataro, and
Yongbing Fan.
The document was prepared in raw nroff. All macros used were defined
within the source file.
Margaret Cullen, et al [Page 38]
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Authors' Addresses
Margaret Cullen
Painless Security
14 Summer Street, Suite 202
Malden, MA 02148
USA
Phone: +1-781-605-3459
Email: margaret@painless-security.com
URI: http://www.painless-security.com
Donald Eastlake
Huawei Technologies
155 Beaver Street
Milford, MA 01757
USA
Phone: +1 508 333-2270
Email: d3e3e3@gmail.com
Mingui Zhang
Huawei Technologies
No.156 Beiqing Rd. Haidian District,
Beijing 100095 P.R. China
EMail: zhangmingui@huawei.com
Dacheng Zhang
Huawei Technologies
Email: dacheng.zhang@huawei.com
Copyright, Disclaimer, and Additional IPR Provisions
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This document is subject to BCP 78 and the IETF Trust's Legal
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
Margaret Cullen, et al [Page 39]
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Margaret Cullen, et al [Page 40]