Network Working Group M. Wasserman
Internet-Draft Painless Security
Intended status: Standards Track D. Eastlake
Expires: August 6, 2015 Huawei Technologies
D. Zhang
Alibaba
February 2, 2015
Transparent Interconnection of Lots of Links (TRILL) over IP
draft-ietf-trill-over-ip-02.txt
Abstract
The Transparent Interconnection of Lots of Links (TRILL) protocol is
implemented by devices called TRILL Switches or RBridges (Routing
Bridges). TRILL 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.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 6, 2015.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Requirements Terminology . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Use Cases for TRILL over IP . . . . . . . . . . . . . . . . . 3
3.1. Remote Office Scenario . . . . . . . . . . . . . . . . . 4
3.2. IP Backbone Scenario . . . . . . . . . . . . . . . . . . 4
3.3. Important Properties of the Scenarios . . . . . . . . . . 4
3.3.1. Security Requirements . . . . . . . . . . . . . . . . 4
3.3.2. Multicast Handling . . . . . . . . . . . . . . . . . 5
3.3.3. RBridge Neighbor Discovery . . . . . . . . . . . . . 5
4. TRILL Packet Formats . . . . . . . . . . . . . . . . . . . . 5
5. Link Protocol Specifics . . . . . . . . . . . . . . . . . . . 6
6. RBridge IP Port Configuration . . . . . . . . . . . . . . . . 7
6.1. Per IP Port Configuration . . . . . . . . . . . . . . . . 7
6.2. Additional per IP Address Cofiguration . . . . . . . . . 8
6.2.1. Native Multicast Configuration . . . . . . . . . . . 8
6.2.2. Serial Unicast Configuration . . . . . . . . . . . . 8
6.2.3. Security Configuration . . . . . . . . . . . . . . . 8
7. TRILL over IP Format . . . . . . . . . . . . . . . . . . . . 9
8. Handling Multicast . . . . . . . . . . . . . . . . . . . . . 10
9. Use of IPsec . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Default Pre-Shared Keys . . . . . . . . . . . . . . . . . 11
10. Transport Considerations . . . . . . . . . . . . . . . . . . 12
10.1. Recursive Ingress . . . . . . . . . . . . . . . . . . . 12
10.2. Fat Flows . . . . . . . . . . . . . . . . . . . . . . . 12
10.3. Congestion Considerations . . . . . . . . . . . . . . . 13
10.4. MTU Considerations . . . . . . . . . . . . . . . . . . . 14
11. Middlebox Considerations . . . . . . . . . . . . . . . . . . 15
12. Security Considerations . . . . . . . . . . . . . . . . . . . 15
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
13.1. Port Assignments . . . . . . . . . . . . . . . . . . . . 16
13.2. Multicast Address Assignments . . . . . . . . . . . . . 16
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
15.1. Normative References . . . . . . . . . . . . . . . . . . 17
15.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Requirements 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].
2. Introduction
TRILL switches (RBridges) are devices that implement the IETF TRILL
protocol [RFC6325] [RFC7176] [RFC7177].
RBridges provide transparent forwarding of frames within an arbitrary
network topology, using least cost paths for unicast traffic. They
support not only VLANs and Fine Grained Labels [RFC7172] but also
multipathing of unicast and multi-destination traffic. They use IS-
IS link state routing and encapsulation with a hop count.
Ports on different RBridges can communicate with each other over
various link types, such as Ethernet [RFC6325], pseudowires
[RFC7173], or PPP [RFC6361].
This document defines a method for RBridges to communicate over IP
(v4 or v6). TRILL over IP will allow Internet-connected RBridges to
form a single TRILL campus, or multiple TRILL over IP networks within
a campus 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 appear to TRILL to be
connected by a single multi-access link. Therefore, 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
(such as 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 [RFC4303] to secure all or part of
such paths.
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.
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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 logical
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.
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 rogue
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
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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 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 unicast.
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 unicast, as discussed later in
this document.
3.3.3. RBridge Neighbor Discovery
In the IP Backbone Scenario, RBridges that use TRILL over IP will use
the normal TRILL IS-IS Hello mechanisms to discover the existence of
other RBridges on the link [RFC7177], and to establish authenticated
communication with those RBridges.
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 RBridge 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.
4. TRILL Packet Formats
To support the TRILL base protocol standard [RFC6325], two types of
packets will be transmitted between RBridges: TRILL Data packets and
TRILL IS-IS packets.
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The on-the-wire form of a TRILL Data packet in transit between two
neighboring RBridges is as shown below:
+--------------+----------+----------------+-----------+
| TRILL Data | TRILL | Native Frame | Link |
| Link Header | Header | Payload | Trailer |
+--------------+----------+----------------+-----------+
Where the Encapsulated Native Frame Payload is similar to Ethernet
frame format 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:
+--------------+---------------+-----------+
| TRILL IS-IS | TRILL IS-IS | Link |
| Link Header | 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 TRILL Data Link Header ends with the TRILL
Ethertype while the TRILL IS-IS Link Header ends with the L2-IS-IS
Ethertype; on the other hand, over PPP, there are no Ethertypes but
PPP protocol code points are included that distinguish TRILL Data
from TRILL IS-IS.
In TRILL over IP, we will use UDP/IP (v4 or v6) as the link header,
and the TRILL packet type will be determined based on the UDP
destination port number. In TRILL over IP, no Link Trailer is
specified, although one may be added when the resulting IP packets
are encapsulated for transmission on a network (e.g. Ethernet).
5. Link Protocol Specifics
TRILL Data packets can be unicast to a specific RBridge or multicast
to all RBridges on the link. TRILL IS-IS packets are always
multicast to all other RBridge on the link (except for MTU PDUs,
which may be unicast [RFC7177]). On Ethernet links, the Ethernet
multicast address All-RBridges is used for TRILL Data and All-IS-IS-
RBridges for TRILL IS-IS.
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To properly handle TRILL base protocol packets on a TRILL over IP
link, either native multicast mode must be used on that link, or
multicast must be simulated using serial unicast, as discussed below.
In TRILL Hello PDUs used on TRILL IP links, the IP addresses of the
connected IP ports are their real SNPA (SubNetwork Point of
Attachment [IS-IS]) addresses and, for IPv6, the 16-byte IPv6 address
is used; however, for easy of code re-use designed for common 48-bit
SNPAs, for 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] on the link. This synthetic SNPA 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, at the IP level, where TRILL operates on an
IP link, there are only IP stations, not MAC stations, so conflict on
the link with a real MAC address would be impossible in any case.
6. RBridge IP Port Configuration
This section specifies the configuration information needed at a
TRILL over IP port beyond that needed for a general RBridge port.
6.1. 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 with each logical port.
By default an RBridge IP port discards output packets that fail the
possible recursive ingress test (see Section 10.1) unless configured
to disable that test.
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6.2. Additional per IP Address Cofiguration
The configuration information specified below is per IP address at a
TRILL over IP port.
Each IP address at a TRILL over IP port uses native IP multicast by
default but may be configured whether to use serial unicast
(Section 6.2.2) or native multicast (Section 6.2.1). Each IP address
at a TRILL over IP is configured whether or not to use IPsec
(Section 6.2.3).
6.2.1. Native Multicast Configuration
If a TRILL 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 appropriate IP multicast address (IPv4
or IPv6) specified in Section 13.2. The RBridge IP port may be
configured to use a different IP multicast address or multi-
destination packets.
6.2.2. 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. 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.
If the list is empty, there is no way to transmit a multi-destination
TRILL over IP packet such as a TRILL Hello. Thus it is impossible to
achieve adjacency [RFC7177] or if adjacency had been achieved
(perhaps the list was non-empty and has just been configured to be
empty), no way to maintain such adjacency. Thus, in the empty list
case, TRILL Data multi-destination packets cannot be sent and TRILL
Data unicast packets will not start flowing or, if they are already
flowing, will soon cease.
6.2.3. Security Configuration
... tbd ...
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7. TRILL over IP Format
The general format of a TRILL over IP packet without security is
shown below.
+----------+--------+-----------------------+
| 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 10.2
Destination Port - indicates TRILL Data or IS-IS, see Section 14
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.
TRILL over IP link security uses IPsec Encapsulating Security
Protocol (ESP) in tunnel mode. The resulting packet format is as
follows for IPv4 and IPv6:
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------------------------------------------------------------
IPv4 | new IP hdr | | orig IP hdr | |TRILL| ESP | ESP|
|(any options)| ESP | (any options) |UDP|Data |Trailer| ICV|
------------------------------------------------------------
|<--------- encryption ---------->|
|<------------- integrity ------------->|
-------------------------------------------------------------
IPv6 | new |new ext | | orig |orig ext | |TRILL| ESP | ESP|
|IP hdr| hdrs |ESP|IP hdr| hdrs |UDP|Data |Trailer| ICV|
------------------------------------------------------------.
|<--------- encryption ----------->|
|<------------ integrity ------------->|
This architecture permits the ESP tunnel termination to be separated
from the TRILL over IP RBridge port and, for example, placed at a
physical or administrative security boundary. If two or more RBridge
TRILL over IP ports are communicate securely using IPsec, there are
three possibilities:
(a) For all ports involved, the IPsec implementation is integrated
with the RBridge port. In this case it is straightforward to use the
default and negotiations specified herein for keying and algorithms.
(b) Some of the IPsec implementations are integrated with an RBridge
port and some are not. For example, on a point-to-point TRILL over
IP link, IPsec could be integrated with the RBridge port at one end
but implemented in a separate appliances that could be separated by
IP routers from the TRILL over IP RBridge port at the other end. In
this case mechanisms beyond the scope of this document may be
required to communicate default or negotiated keying or algorithms
between such separate appliances and the RBridge port for which they
are providing TRILL over IP security services.
(c) For all ports involved, the IPsec implementation is in a separate
appliance. In this case, if adequate security is provided, the
appliances MAY negotiation IPsec keying and algorithms as they see
fit. Alternatively, the specifications of this document for keying
and algorithms are used and mechanisms beyond the scope of this
document may be required to communicate default or negotiated keying
or algorithms between such separate appliances and the RBridge port
for which they are providing TRILL over IP security services
8. Handling Multicast
By default, both TRILL IS-IS packets and multi-destination TRILL Data
packets are sent to an All-RBridges IPv4 or IPv6 multicast Address as
appropriate (see Section 13.2); however, a TRILL over IP port may be
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configured (see Section 6) to use serial unicast with a list of one
or more unicast IP addresses of other TRILL over IP ports to which
multi-destination packets are sent. Such configuration is necessary
if the TRILL over IP port is connected to an IP network that does not
support IP multicast. In both cases, unicast TRILL data packets
would be sent by unicast IP.
When a TRILL over IP port is using IP multicast, it MUST periodically
transmit appropriate IGMP (IPv4 [RFC3376]) or MLD (IPv6 [RFC2710])
packets so that the TRILL multicast IP traffic will be sent to it.
Although TRILL fully supports broadcast links with more than 2
RBridges connected to the link, even where native IP multicast is
available, there may be good reasons for configuring TRILL over IP
ports to use serial unicast. In some networks, unicast is more
reliable than multicast. If multiple unicast connections between
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 ceases to operate or
incorporate a new link that comes up.
9. Use of IPsec
All RBridges that support TRILL over IP MUST implement IPsec and
support the use of IPsec Encapsulating Security Protocol (ESP) 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, people may select to use IS-IS security to protect TRILL
IS-IS packets. However, in this case, the IPsec session still MUST
be fully established before any data packets transmission since IS-IS
security does not provide any protection to data packets.
... TBD ...
9.1. Default Pre-Shared Keys
The default pre-shared keyes for IPsec usage are derived as follows:
HMAC-SHA256 ("TRILL IP"| IS-IS-shared key )
In the above "|" indicates concatenation, HMAC-SHA256 is as described
in [FIPS180] [RFC6234] and "TRILL IP" is the eight byte US ASCII
[RFC0020] string indicated. IS-IS-shared key is a link (or wider
scope) IS-IS key usable for IS-IS security of link local IS-IS local
PDUs such as Hello, CSNP, and PSNP. With [RFC5310]there could be
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multiple keys identified with 16-bit key IDs. In this case, the Key
ID of IS-IS-shared key is also used to identify the derived key.
10. Transport Considerations
This section discusses a variety of transport considerations.
10.1. Recursive Ingress
TRILL is designed to transport end station traffic to and from end
stations over IEEE 802.3 and IP is frequently transported over IEEE
802.3 or similar protocols. Thus, an end station native data frame
EF might get TRILL ingressed to TRILL(EF) which was then sent on a
TRILL over IP over an 802.3 link resulting in an 802.3 frame of the
form 802.3(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, etc.
The packet might 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 Header and TTL.
To protect against this scenario, a TRILL over IP port MUST by,
default, test whether a TRILL packet it is about to send is, in fact
a TRILL ingress of a TRILL over IP over 802.3 or the like packets.
That is, is it of the form TRILL(802.3(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.
10.2. Fat Flows
For the purpose of load balancing, it is worthwhile to consider how
to transport the TRILL packets over the Equal Cost Multiple Paths
(ECMPs) existing in the IP path.
The ECMP election for the IP traffics could be based, at least for
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.
Therefore, in order to better support ECMP, a RBridge SHOULD set the
Source Port as an entropy field for ECMP decisions. (This idea is
also introduced in [I-D.yong-tsvwg-gre-in-udp-encap].For example, for
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TRILL Data this entropy field could be based on the Inner.MacDA,
Inner.MacSA, and Inner.VLAN or Inner.FGL.
10.3. 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.
One motivation for encapsulating TRILL in UDP 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".
For this reason, where TRILL is tunneled through UDP and used to
carry IP traffic that is known to be congestion controlled, the UDP
tunnels MAY be used across any combination of a single or cooperating
service providers or across the general Internet.
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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 USP/IP
MUST NOT be used 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 [I-D.ietf-tsvwg-circuit-breaker].
10.4. 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
RBridges in the campus) through the originatingLSPBufferSize TLV
[RFC6325] [RFC7177]. The campus minimum MTU, 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 some LSPs.
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A method of determining originatingLSPBufferSize for an RBridge with
one or more TRILL over IP portsis described in [RFC7180]. 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, theoretically 68 bytes for
IPv4) on which it would be necessary to enable fragmentation for
TRILL use.
The optional use of TRILL IS-IS MTU PDUs, as specified in [RFC6325]
and [RFC7177] can provide added assurance of the actual MTU of a
link.
11. Middlebox Considerations
... TBD ...
12. 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 above.
This document specifies that all RBridges that support TRILL over IP
MUST implement IPsec, 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 not physically secure. IPsec
is necessary, in these cases to protect the privacy and integrity of
data traffic.
TRILL over IP is completely compatible with the use of IS-IS Security
[RFC5310], which can be used to authenticate RBridges before allowing
them to join a TRILL campus. This is sufficient to protect against
rogue RBridges, but is not sufficient to protect data packets that
may be sent in IP outside of the local network, or even 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. In cases where
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both types of security are enabled, by default, a key derived from
the IS-IS key will be used for IPsec.
13. IANA Considerations
IANA considerations are given below.
13.1. Port Assignments
IANA has allocated the following destination UDP Ports for the TRILL
IS-IS and Data channels:
UDP Port Protocol
(TBD) TRILL IS-IS Channel
(TBD) TRILL Data Channel
13.2. Multicast Address Assignments
IANA has allocated one IPv4 and one IPv6 multicast address, as shown
below, which correspond to the All-RBridges and All-IS-IS-RBridges
multicast MAC addresses that the IEEE Registration Authority has
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:]
Name IPv4 IPv6
All-RBridges 233.252.14.0 FF0X:0:0:0:0:0:0:205
Note: when these IPv4 and IPv6 multicast addresses are used and the
resulting IP frame is sent over Ethernet, the usual IP derived MAC
address is used.
[Need to discuss scopes for IPv6 multicast (the "X" in the addresses)
somewhere. Default to "site" scope but MUST be configurable?]
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14. Acknowledgements
This document was written using the xml2rfc tool described in RFC
2629 [RFC2629].
The following people have provided useful feedback on the contents of
this document: Sam Hartman, Adrian Farrel.
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.
15. References
15.1. Normative References
[FIPS180] ""Secure Hash Standard (SHS)", United States of American,
National Institute of Science and Technology, Federal
Information Processing Standard (FIPS) 180-4", March 2012.
[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", RFC 20,
October 1969.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast
Listener Discovery (MLD) for IPv6", RFC 2710, October
1999.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, RFC
2914, September 2000.
[RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
Thyagarajan, "Internet Group Management Protocol, Version
3", RFC 3376, October 2002.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
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[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
4303, December 2005.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, February 2009.
[RFC5405] Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
for Application Designers", BCP 145, RFC 5405, November
2008.
[RFC6325] Perlman, R., Eastlake, D., Dutt, D., Gai, S., and A.
Ghanwani, "Routing Bridges (RBridges): Base Protocol
Specification", RFC 6325, July 2011.
[RFC7176] Eastlake, D., Senevirathne, T., Ghanwani, A., Dutt, D.,
and A. Banerjee, "Transparent Interconnection of Lots of
Links (TRILL) Use of IS-IS", RFC 7176, May 2014.
[RFC7177] Eastlake, D., Perlman, R., Ghanwani, A., Yang, H., and V.
Manral, "Transparent Interconnection of Lots of Links
(TRILL): Adjacency", RFC 7177, May 2014.
[RFC7180] Eastlake, D., Zhang, M., Ghanwani, A., Manral, V., and A.
Banerjee, "Transparent Interconnection of Lots of Links
(TRILL): Clarifications, Corrections, and Updates", RFC
7180, May 2014.
15.2. Informative References
[I-D.ietf-tsvwg-circuit-breaker]
Fairhurst, G., "Network Transport Circuit Breakers",
draft-ietf-tsvwg-circuit-breaker-00 (work in progress),
September 2014.
[I-D.yong-tsvwg-gre-in-udp-encap]
Crabbe, E., Yong, L., and X. Xu, "Generic UDP
Encapsulation for IP Tunneling", draft-yong-tsvwg-gre-in-
udp-encap-02 (work in progress), October 2013.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC6234] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234, May 2011.
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[RFC6361] Carlson, J. and D. Eastlake, "PPP Transparent
Interconnection of Lots of Links (TRILL) Protocol Control
Protocol", RFC 6361, August 2011.
[RFC7172] Eastlake, D., Zhang, M., Agarwal, P., Perlman, R., and D.
Dutt, "Transparent Interconnection of Lots of Links
(TRILL): Fine-Grained Labeling", RFC 7172, May 2014.
[RFC7173] Yong, L., Eastlake, D., Aldrin, S., and J. Hudson,
"Transparent Interconnection of Lots of Links (TRILL)
Transport Using Pseudowires", RFC 7173, May 2014.
Authors' Addresses
Margaret Wasserman
Painless Security
356 Abbott Street
North Andover, MA 01845
USA
Phone: +1 781 405-7464
Email: mrw@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
Dacheng Zhang
Alibaba
Beijing, Chao yang District
P.R. China
Email: dacheng.zdc@alibaba-inc.com
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