Network Working Group S. Previdi, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track K. Raza
Expires: January 21, 2018 D. Dukes
Cisco Systems, Inc.
J. Leddy
B. Field
Comcast
D. Voyer
D. Bernier
Bell Canada
S. Matsushima
Softbank
I. Leung
Rogers Communications
J. Linkova
Google
E. Aries
Facebook
T. Kosugi
NTT
E. Vyncke
Cisco Systems, Inc.
D. Lebrun
Universite Catholique de Louvain
D. Steinberg
Steinberg Consulting
R. Raszuk
Bloomberg
July 20, 2017
IPv6 Segment Routing Header (SRH)
draft-ietf-6man-segment-routing-header-07
Abstract
Segment Routing (SR) allows a node to steer a packet through a
controlled set of instructions, called segments, by prepending an SR
header to the packet. A segment can represent any instruction,
topological or service-based. SR allows to enforce a flow through
any path (topological, or application/service based) while
maintaining per-flow state only at the ingress node to the SR domain.
Segment Routing can be applied to the IPv6 data plane with the
addition of a new type of Routing Extension Header. This draft
describes the Segment Routing Extension Header Type and how it is
used by SR capable nodes.
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Requirements Language
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 21, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Segment Routing Documents . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Data Planes supporting Segment Routing . . . . . . . . . 4
2.2. SRv6 Segment . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Segment Routing (SR) Domain . . . . . . . . . . . . . . . 5
2.3.1. SR Domain in a Service Provider Network . . . . . . . 6
2.3.2. SR Domain in a Overlay Network . . . . . . . . . . . 7
3. Segment Routing Extension Header (SRH) . . . . . . . . . . . 8
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3.1. SRH TLVs . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1.1. Ingress Node TLV . . . . . . . . . . . . . . . . . . 11
3.1.2. Egress Node TLV . . . . . . . . . . . . . . . . . . . 12
3.1.3. Opaque Container TLV . . . . . . . . . . . . . . . . 13
3.1.4. Padding TLV . . . . . . . . . . . . . . . . . . . . . 13
3.1.5. HMAC TLV . . . . . . . . . . . . . . . . . . . . . . 14
3.1.6. NSH Carrier TLV . . . . . . . . . . . . . . . . . . . 15
3.2. SRH and RFC2460 behavior . . . . . . . . . . . . . . . . 16
4. SRH Functions . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1. Endpoint Function (End) . . . . . . . . . . . . . . . . . 16
4.2. End.X: Endpoint with Layer-3 cross-connect . . . . . . . 17
5. SR Nodes . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1. Source SR Node . . . . . . . . . . . . . . . . . . . . . 18
5.2. Transit Node . . . . . . . . . . . . . . . . . . . . . . 19
5.3. SR Segment Endpoint Node . . . . . . . . . . . . . . . . 20
6. Security Considerations . . . . . . . . . . . . . . . . . . . 20
6.1. Threat model . . . . . . . . . . . . . . . . . . . . . . 21
6.1.1. Source routing threats . . . . . . . . . . . . . . . 21
6.1.2. Applicability of RFC 5095 to SRH . . . . . . . . . . 21
6.1.3. Service stealing threat . . . . . . . . . . . . . . . 22
6.1.4. Topology disclosure . . . . . . . . . . . . . . . . . 22
6.1.5. ICMP Generation . . . . . . . . . . . . . . . . . . . 22
6.2. Security fields in SRH . . . . . . . . . . . . . . . . . 23
6.2.1. Selecting a hash algorithm . . . . . . . . . . . . . 24
6.2.2. Performance impact of HMAC . . . . . . . . . . . . . 25
6.2.3. Pre-shared key management . . . . . . . . . . . . . . 25
6.3. Deployment Models . . . . . . . . . . . . . . . . . . . . 26
6.3.1. Nodes within the SR domain . . . . . . . . . . . . . 26
6.3.2. Nodes outside of the SR domain . . . . . . . . . . . 26
6.3.3. SR path exposure . . . . . . . . . . . . . . . . . . 27
6.3.4. Impact of BCP-38 . . . . . . . . . . . . . . . . . . 27
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
7.1. Segment Routing Header TLVs Register . . . . . . . . . . 28
8. Manageability Considerations . . . . . . . . . . . . . . . . 28
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 28
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
11.1. Normative References . . . . . . . . . . . . . . . . . . 29
11.2. Informative References . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Segment Routing Documents
Segment Routing terminology is defined in
[I-D.ietf-spring-segment-routing].
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The network programming paradigm
[I-D.filsfils-spring-srv6-network-programming] defines the basic
functions associated to an SRv6 SID.
Segment Routing use cases are described in [RFC7855] and
[I-D.ietf-spring-ipv6-use-cases].
Segment Routing protocol extensions are defined in
[I-D.ietf-isis-segment-routing-extensions], and
[I-D.ietf-ospf-ospfv3-segment-routing-extensions].
2. Introduction
Segment Routing (SR), defined in [I-D.ietf-spring-segment-routing],
allows a node to steer a packet through a controlled set of
instructions, called segments, by prepending an SR header to the
packet. A segment can represent any instruction, topological or
service-based. SR allows to enforce a flow through any path
(topological or service/application based) while maintaining per-flow
state only at the ingress node to the SR domain. Segments can be
derived from different components: IGP, BGP, Services, Contexts,
Locators, etc. The list of segment forming the path is called the
Segment List and is encoded in the packet header.
SR allows the use of strict and loose source based routing paradigms
without requiring any additional signaling protocols in the
infrastructure hence delivering an excellent scalability property.
The source based routing model described in
[I-D.ietf-spring-segment-routing] is inherited from the ones proposed
by [RFC1940] and [RFC2460]. The source based routing model offers
the support for explicit routing capability.
2.1. Data Planes supporting Segment Routing
Segment Routing (SR), can be instantiated over MPLS
([I-D.ietf-spring-segment-routing-mpls]) and IPv6. This document
defines its instantiation over the IPv6 data-plane based on the use-
cases defined in [I-D.ietf-spring-ipv6-use-cases].
This document defines a new type of Routing Header (originally
defined in [RFC2460]) called the Segment Routing Header (SRH) in
order to convey the Segment List in the packet header as defined in
[I-D.ietf-spring-segment-routing]. Mechanisms through which segment
are known and advertised are outside the scope of this document.
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2.2. SRv6 Segment
An SRv6 Segment is a 128-bit value. "SRv6 SID" or simply "SID" are
often used as a shorter reference for "SRv6 Segment".
An SRv6-capable node N maintains a "My Local SID Table". This table
contains all the local SRv6 segments explicitly instantiated at node
N. N is the parent node for these SID's.
A local SID of N could be an IPv6 address of a local interface of N
but it does not have to. Most often, a local SID is not an address
of a local interface of N. The My Local SID Table is thus not
populated by default with all the addresses of a node.
An illustration is provided in
[I-D.filsfils-spring-srv6-network-programming].
Every SRv6 local SID instantiated has a specific instruction bounded
to it.
This information is stored in the "My Local SID Table". The "My
Local SID Table" has three main purposes:
o Define which local SID's are explicitly instantiated.
o Specify which instruction is bound to each of the instantiated
SID's.
o Store the parameters associated to such instruction (i.e. OIF,
NextHop,...).
A node may receive a packet with an SRv6 SID in the DA without an
SRH. In such case the packet should still be processed by the
Segment Routing engine.
2.3. Segment Routing (SR) Domain
We define the concept of the Segment Routing Domain (SR Domain) as
the set of nodes participating into the source based routing model.
These nodes may be connected to the same physical infrastructure
(e.g.: a Service Provider's network) as well as nodes remotely
connected to each other (e.g.: an enterprise VPN or an overlay).
A non-exhaustive list of examples of SR Domains is:
o The network of an operator, service provider, content provider,
enterprise including nodes, links and Autonomous Systems.
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o A set of nodes connected as an overlay over one or more transit
providers. The overlay nodes exchange SR-enabled traffic with
segments belonging solely to the overlay routers (the SR domain).
None of the segments in the SR-enabled packets exchanged by the
overlay belong to the transit networks
The source based routing model through its instantiation of the
Segment Routing Header (SRH) defined in this document equally applies
to all the above examples.
It is assumed in this document that the SRH is added to the packet by
its source, consistently with the source routing model defined in
[RFC2460]. For example:
o At the node originating the packet (host, server).
o At the ingress node of an SR domain where the ingress node
receives an IPv6 packet and encapsulates it into an outer IPv6
header followed by a Segment Routing header.
2.3.1. SR Domain in a Service Provider Network
The following figure illustrates an SR domain consisting of an
operator's network infrastructure.
(-------------------------- Operator 1 -----------------------)
( )
( (-----AS 1-----) (-------AS 2-------) (----AS 3-------) )
( ( ) ( ) ( ) )
A1--(--(--11---13--14-)--(-21---22---23--24-)--(-31---32---34--)--)--Z1
( ( /|\ /|\ /| ) ( |\ /|\ /|\ /| ) ( |\ /|\ /| \ ) )
A2--(--(/ | \/ | \/ | ) ( | \/ | \/ | \/ | ) ( | \/ | \/ | \)--)--Z2
( ( | /\ | /\ | ) ( | /\ | /\ | /\ | ) ( | /\ | /\ | ) )
( ( |/ \|/ \| ) ( |/ \|/ \|/ \| ) ( |/ \|/ \| ) )
A3--(--(--15---17--18-)--(-25---26---27--28-)--(-35---36---38--)--)--Z3
( ( ) ( ) ( ) )
( (--------------) (------------------) (---------------) )
( )
(-------------------------------------------------------------)
Figure 1: Service Provider SR Domain
Figure 1 describes an operator network including several ASes and
delivering connectivity between endpoints. In this scenario, Segment
Routing is used within the operator networks and across the ASes
boundaries (all being under the control of the same operator). In
this case segment routing can be used in order to address use cases
such as end-to-end traffic engineering, fast re-route, egress peer
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engineering, data-center traffic engineering as described in
[RFC7855], [I-D.ietf-spring-ipv6-use-cases] and
[I-D.ietf-spring-resiliency-use-cases].
Typically, an IPv6 packet received at ingress (i.e.: from outside the
SR domain), is classified according to network operator policies and
such classification results into an outer header with an SRH applied
to the incoming packet. The SRH contains the list of segment
representing the path the packet must take inside the SR domain.
Thus, the SA of the packet is the ingress node, the DA (due to SRH
procedures described in Section 5) is set as the first segment of the
path and the last segment of the path is the egress node of the SR
domain.
The path may include intra-AS as well as inter-AS segments. It has
to be noted that all nodes within the SR domain are under control of
the same administration. When the packet reaches the egress point of
the SR domain, the outer header and its SRH are removed so that the
destination of the packet is unaware of the SR domain the packet has
traversed.
The outer header with the SRH is no different from any other
tunneling encapsulation mechanism and allows a network operator to
implement traffic engineering mechanisms so to efficiently steer
traffic across his infrastructure.
2.3.2. SR Domain in a Overlay Network
The following figure illustrates an SR domain consisting of an
overlay network over multiple operator's networks.
(--Operator 1---) (-----Operator 2-----) (--Operator 3---)
( ) ( ) ( )
A1--(--11---13--14--)--(--21---22---23--24--)--(-31---32---34--)--C1
( /|\ /|\ /| ) ( |\ /|\ /|\ /| ) ( |\ /|\ /| \ )
A2--(/ | \/ | \/ | ) ( | \/ | \/ | \/ | ) ( | \/ | \/ | \)--C2
( | /\ | /\ | ) ( | /\ | /\ | /\ | ) ( | /\ | /\ | )
( |/ \|/ \| ) ( |/ \|/ \|/ \| ) ( |/ \|/ \| )
A3--(--15---17--18--)--(--25---26---27--28--)--(-35---36---38--)--C3
( ) ( | | | ) ( )
(---------------) (--|----|---------|--) (---------------)
| | |
B1 B2 B3
Figure 2: Overlay SR Domain
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Figure 2 describes an overlay consisting of nodes connected to three
different network operators and forming a single overlay network
where Segment routing packets are exchanged.
The overlay consists of nodes A1, A2, A3, B1, B2, B3, C1, C2 and C3.
These nodes are connected to their respective network operator and
form an overlay network.
Each node may originate packets with an SRH which contains, in the
segment list of the SRH or in the DA, segments identifying other
overlay nodes. This implies that packets with an SRH may traverse
operator's networks but, obviously, these SRHs cannot contain an
address/segment of the transit operators 1, 2 and 3. The SRH
originated by the overlay can only contain address/segment under the
administration of the overlay (e.g. address/segments supported by A1,
A2, A3, B1, B2, B3, C1,C2 or C3).
In this model, the operator network nodes are transit nodes and,
according to [RFC2460], MUST NOT inspect the routing extension header
since they are not the DA of the packet.
It is a common practice in operators networks to filter out, at
ingress, any packet whose DA is the address of an internal node and
it is also possible that an operator would filter out any packet
destined to an internal address and having an extension header in it.
This common practice does not impact the SR-enabled traffic between
the overlay nodes as the intermediate transit networks never see a
destination address belonging to their infrastructure. These SR-
enabled overlay packets will thus never be filtered by the transit
operators.
In all cases, transit packets (i.e.: packets whose DA is outside the
domain of the operator's network) will be forwarded accordingly
without introducing any security concern in the operator's network.
This is similar to tunneled packets.
3. Segment Routing Extension Header (SRH)
A new type of the Routing Header (originally defined in [RFC2460]) is
defined: the Segment Routing Header (SRH) which has a new Routing
Type, (suggested value 4) to be assigned by IANA.
The Segment Routing Header (SRH) is defined as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Entry | Flags | Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[0] (128 bits IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
...
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[n] (128 bits IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// //
// Optional Type Length Value objects (variable) //
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Next Header: 8-bit selector. Identifies the type of header
immediately following the SRH.
o Hdr Ext Len: 8-bit unsigned integer, is the length of the SRH
header in 8-octet units, not including the first 8 octets.
o Routing Type: TBD, to be assigned by IANA (suggested value: 4).
o Segments Left. Defined in [RFC2460], it contains the index, in
the Segment List, of the next segment to inspect. Segments Left
is decremented at each segment.
o Last Entry: contains the index, in the Segment List, of the last
element of the Segment List.
o Flags: 8 bits of flags. Following flags are defined:
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0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|U|P|O|A|H| U |
+-+-+-+-+-+-+-+-+
U: Unused and for future use. SHOULD be unset on transmission
and MUST be ignored on receipt.
P-flag: Protected flag. Set when the packet has been rerouted
through FRR mechanism by an SR endpoint node.
O-flag: OAM flag. When set, it indicates that this packet is
an operations and management (OAM) packet.
A-flag: Alert flag. If present, it means important Type Length
Value (TLV) objects are present. See Section 3.1 for details
on TLVs objects.
H-flag: HMAC flag. If set, the HMAC TLV is present and is
encoded as the last TLV of the SRH. In other words, the last
36 octets of the SRH represent the HMAC information. See
Section 3.1.5 for details on the HMAC TLV.
o Tag: tag a packet as part of a class or group of packets, e.g.,
packets sharing the same set of properties.
o Segment List[n]: 128 bit IPv6 addresses representing the nth
segment in the Segment List. The Segment List is encoded starting
from the last segment of the path. I.e., the first element of the
segment list (Segment List [0]) contains the last segment of the
path, the second element contains the penultimate segment of the
path and so on.
o Type Length Value (TLV) are described in Section 3.1.
3.1. SRH TLVs
This section defines TLVs of the Segment Routing Header.
Type Length Value (TLV) contain optional information that may be used
by the node identified in the DA of the packet. It has to be noted
that the information carried in the TLVs is not intended to be used
by the routing layer. Typically, TLVs carry information that is
consumed by other components (e.g.: OAM) than the routing function.
Each TLV has its own length, format and semantic. The code-point
allocated (by IANA) to each TLV defines both the format and the
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semantic of the information carried in the TLV. Multiple TLVs may be
encoded in the same SRH.
The "Length" field of the TLV is primarily used to skip the TLV while
inspecting the SRH in case the node doesn't support or recognize the
TLV codepoint. The "Length" defines the TLV length in octets and not
including the "Type" and "Length" fields.
The following TLVs are defined in this document:
Ingress Node TLV
Egress Node TLV
Opaque TLV
Padding TLV
HMAC TLV
NSH Carrier TLV
Additional TLVs may be defined in the future.
3.1.1. Ingress Node TLV
The Ingress Node TLV is optional and identifies the node this packet
traversed when entered the SR domain. The Ingress Node TLV has
following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | RESERVED | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Ingress Node (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: to be assigned by IANA (suggested value 1).
o Length: 18.
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o RESERVED: 8 bits. SHOULD be unset on transmission and MUST be
ignored on receipt.
o Flags: 8 bits. No flags are defined in this document. SHOULD be
set to 0 on transmission and MUST be ignored on receipt.
o Ingress Node: 128 bits. Defines the node where the packet is
expected to enter the SR domain. In the encapsulation case
described in Section 2.3.1, this information corresponds to the SA
of the encapsulating header.
3.1.2. Egress Node TLV
The Egress Node TLV is optional and identifies the node this packet
is expected to traverse when exiting the SR domain. The Egress Node
TLV has following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | RESERVED | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Egress Node (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: to be assigned by IANA (suggested value 2).
o Length: 18.
o RESERVED: 8 bits. SHOULD be unset on transmission and MUST be
ignored on receipt.
o Flags: 8 bits. No flags are defined in this document. SHOULD be
set to 0 on transmission and MUST be ignored on receipt.
o Egress Node: 128 bits. Defines the node where the packet is
expected to exit the SR domain. In the encapsulation case
described in Section 2.3.1, this information corresponds to the
last segment of the SRH in the encapsulating header.
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3.1.3. Opaque Container TLV
The Opaque Container TLV is optional and has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | RESERVED | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Opaque Container (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: to be assigned by IANA (suggested value 3).
o Length: 18.
o RESERVED: 8 bits. SHOULD be unset on transmission and MUST be
ignored on receipt.
o Flags: 8 bits. No flags are defined in this document. SHOULD be
set to 0 on transmission and MUST be ignored on receipt.
o Opaque Container: 128 bits of opaque data not relevant for the
routing layer. Typically, this information is consumed by a non-
routing component of the node receiving the packet (i.e.: the node
in the DA).
3.1.4. Padding TLV
The Padding TLV is optional and with the purpose of aligning the SRH
on a 8 octet boundary. The Padding TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Padding (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Padding (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: to be assigned by IANA (suggested value 4).
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o Length: 1 to 7
o Padding: from 1 to 7 octets of padding. Padding bits have no
semantic. They SHOULD be set to 0 on transmission and MUST be
ignored on receipt.
The following applies to the Padding TLV:
o Padding TLV is optional and MAY only appear once in the SRH. If
present, it MUST have a length between 1 and 7 octets.
o The Padding TLV is used in order to align the SRH total length on
the 8 octet boundary.
o When present, the Padding TLV MUST appear as the last TLV before
the HMAC TLV (if HMAC TLV is present).
o When present, the Padding TLV MUST have a length from 1 to 7 in
order to align the SRH total lenght on a 8-octet boundary.
o When a router inspecting the SRH encounters the Padding TLV, it
MUST assume that no other TLV (other than the HMAC) follow the
Padding TLV.
3.1.5. HMAC TLV
HMAC TLV is optional and contains the HMAC information. The HMAC TLV
has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HMAC Key ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| //
| HMAC (32 octets) //
| //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: to be assigned by IANA (suggested value 5).
o Length: 38.
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o RESERVED: 2 octets. SHOULD be unset on transmission and MUST be
ignored on receipt.
o HMAC Key ID: 4 octets.
o HMAC: 32 octets.
o HMAC and HMAC Key ID usage is described in Section 6
The Following applies to the HMAC TLV:
o When present, the HMAC TLV MUST be encoded as the last TLV of the
SRH.
o If the HMAC TLV is present, the SRH H-Flag (Figure 4) MUST be set.
o When the H-flag is set in the SRH, the router inspecting the SRH
MUST find the HMAC TLV in the last 38 octets of the SRH.
3.1.6. NSH Carrier TLV
The NSH Carrier TLV is a container used in order to carry TLVs that
have been defined in [I-D.ietf-sfc-nsh]. The NSH Carrier TLV has the
following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// NSH Carried Object //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: to be assigned by IANA (suggested value 6).
o Length: the total length of the TLV.
o Flags: 8 bits. No flags are defined in this document. SHOULD be
set to 0 on transmission and MUST be ignored on receipt.
o NSH Carried Object: the content of the TLV which consists of the
NSH data as defined in [I-D.ietf-sfc-nsh].
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3.2. SRH and RFC2460 behavior
The SRH being a new type of the Routing Header, it also has the same
properties:
SHOULD only appear once in the packet.
Only the router whose address is in the DA field of the packet
header MUST inspect the SRH.
Therefore, Segment Routing in IPv6 networks implies that the segment
identifier (i.e.: the IPv6 address of the segment) is moved into the
DA of the packet.
The DA of the packet changes at each segment termination/completion
and therefore the final DA of the packet MUST be encoded as the last
segment of the path.
4. SRH Functions
Segment Routing architecture, as defined in
[I-D.ietf-spring-segment-routing] defines a segment as an instruction
or, more generally, a set of instructions (function).
[I-D.filsfils-spring-srv6-network-programming] defines the basic
functions associated with SRv6 SID's.
In this section we review two of these functions that may be
associated to a segment:
o End: the endpoint (End) function is the base of the source routing
paradigm. It consists of updating the DA with the next segment
and forward the packet accordingly.
o End.X: The endpoint layer-3 cross-connect function.
More functions are defined in
[I-D.filsfils-spring-srv6-network-programming].
4.1. Endpoint Function (End)
The Endpoint function (End) is the most basic function.
When the endpoint node receives a packet destined to DA "S" and S is
an entry in the MyLocalSID table and the function associated with S
in that entry is "End" then the endpoint does:
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1. IF SegmentsLeft > 0 THEN
2. decrement SL
3. update the IPv6 DA with SRH[SL]
4. FIB lookup on updated DA
5. forward accordingly to the matched entry
6. ELSE
7. drop the packet
It has to be noted that:
o The End function performs the FIB lookup in the forwarding table
of the ingress interface.
o If the FIB lookup matches a multicast state, then the related
Reverse Path Forwarding (RPF) check must be considered successful.
o An SRv6-capable node MUST include the FlowLabel of the IPv6 header
in its hash computation for ECMP load-balancing.
o By default, a local SID bound to the End function does not allow
the decapsulation of an outer header. As a consequence, an End
SID cannot be the last SID of an SRH and cannot be the DA of a
packet without SRH.
o If the decapsulation is desired, then another function must be
bound to the SID (e.g., End.DX6 defined in
[I-D.filsfils-spring-srv6-network-programming]). This prevents
any unintentional decapsulation by the segment endpoint node. The
details of the advertisement of a SID in the control plane are
outside the scope of this document (e.g.,
[I-D.previdi-idr-segment-routing-te-policy],
[I-D.dawra-bgp-srv6-vpn] and [I-D.bashandy-isis-srv6-extensions].
4.2. End.X: Endpoint with Layer-3 cross-connect
When the endpoint node receives a packet destined to DA "S" and S is
an entry in the MyLocalSID table and the function associated with S
in that entry is "End.X" then the endpoint does:
1. IF SegmentsLeft > 0 THEN
2. decrement SL
3. update the IPv6 DA with SRH[SL]
4. forward to layer-3 adjacency bound to the SID "S"
5. ELSE
6. drop the packet
It has to be noted that:
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o If an array of layer-3 adjacencies is bound to the End.X SID, then
one entry of the array is selected based on a hash of the packet's
header (at least SA, DA, Flow Label).
o An End.X function does not allow decaps. An End.X SID cannot be
the last SID of an SRH and cannot be the DA of a packet without
SRH.
o The End.X function is required to express any traffic-engineering
policy.
o The End.X function is the SRv6 instantiation of a Adjacency SID as
defined in [I-D.ietf-spring-segment-routing].
o Note that with SR-MPLS ([I-D.ietf-spring-segment-routing-mpls]),
an AdjSID is typically preceded by a PrefixSID. This is unlikely
in SRv6 as most likely an End.X SID is globally routed address of
N.
o If a node N has 30 outgoing interfaces to 30 neighbors, usually
the operator would explicitly instantiate 30 End.X SID's at N: one
per layer-3 adjacency to a neighbor. Potentially, more End.X
could be explicitly defined (groups of layer-3 adjacencies to the
same neighbor or to different neighbors).
o If node N has a bundle outgoing interface I to a neighbor Q made
of 10 member links, N may allocate up to 11 End.X local SID's for
that bundle: one for the bundle itself and then up to one for each
member link. This is the equivalent of the L2-Link Adj SID in SR-
MPLS ([I-D.ietf-isis-l2bundles]).
5. SR Nodes
There are different types of nodes that may be involved in segment
routing networks: source nodes that originate packets with an SRH,
transit nodes that forward packets having an SRH and segment endpoint
nodes that MUST process the SRH.
5.1. Source SR Node
A Source SR Node can be any node originating an IPv6 packet with its
IPv6 and Segment Routing Headers. This include either:
A host originating an IPv6 packet.
An SR domain ingress router encapsulating a received IPv6 packet
into an outer IPv6 header followed by an SRH.
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The mechanism through which a Segment List is derived is outside of
the scope of this document. As an example, the Segment List may be
obtained through:
Local path computation.
Local configuration.
Interaction with a centralized controller delivering the path.
Any other mechanism.
The following are the steps of the creation of the SRH:
Next Header and Hdr Ext Len fields are set according to [RFC2460].
Routing Type field is set as TBD (to be allocated by IANA,
suggested value 4).
The DA of the packet is set with the value of the first segment.
).
The first element of the segment list is the last segment (the
final DA of the packet). The second element is the penultimate
segment and so on.
In other words, the Segment List is encoded in the reverse order
of the path.
The Segments Left field is set to n-1 where n is the number of
elements in the Segment List.
The Last_Entry field is set to n-1 where n is the number of
elements in the Segment List.
The packet is sent out towards the packet's DA (the first
segment).
HMAC TLV may be set according to Section 6.
If the segment list contains a single segment and there is no need
for information in flag or TLV, then the SRH MAY be omitted.
5.2. Transit Node
According to [RFC2460], the only node who is allowed to inspect the
Routing Extension Header (and therefore the SRH), is the node
corresponding to the DA of the packet. Any other transit node MUST
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NOT inspect the underneath routing header and MUST forward the packet
towards the DA and according to the IPv6 routing table.
In the example case described in Section 2.3.2, when SR capable nodes
are connected through an overlay spanning multiple third-party
infrastructure, it is safe to send SRH packets (i.e.: packet having a
Segment Routing Header) between each other overlay/SR-capable nodes
as long as the segment list does not include any of the transit
provider nodes. In addition, as a generic security measure, any
service provider will block any packet destined to one of its
internal routers, especially if these packets have an extended header
in it.
5.3. SR Segment Endpoint Node
The SR segment endpoint node is the node whose MyLocalSID table
contains an entry for the DA of the packet.
The segment endpoint node executes the function bound to the SID as
per the matched MyLocalSID entry (Section 4).
6. Security Considerations
This section analyzes the security threat model, the security issues
and proposed solutions related to the new Segment Routing Header.
The Segment Routing Header (SRH) is simply another type of the
routing header as described in RFC 2460 [RFC2460] and is:
o Added by an SR edge router when entering the segment routing
domain or by the originating host itself. The source host can
even be outside the SR domain;
o inspected and acted upon when reaching the destination address of
the IP header per RFC 2460 [RFC2460].
Per RFC2460 [RFC2460], routers on the path that simply forward an
IPv6 packet (i.e. the IPv6 destination address is none of theirs)
will never inspect and process the content of the SRH. Routers whose
one interface IPv6 address equals the destination address field of
the IPv6 packet MUST parse the SRH and, if supported and if the local
configuration allows it, MUST act accordingly to the SRH content.
According to RFC2460 [RFC2460], the default behavior of a non SR-
capable router upon receipt of an IPv6 packet with SRH destined to an
address of its, is to:
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o ignore the SRH completely if the Segment Left field is 0 and
proceed to process the next header in the IPv6 packet;
o discard the IPv6 packet if Segment Left field is greater than 0,
it MAY send a Parameter Problem ICMP message back to the Source
Address.
6.1. Threat model
6.1.1. Source routing threats
Using an SRH is similar to source routing, therefore it has some
well-known security issues as described in RFC4942 [RFC4942] section
2.1.1 and RFC5095 [RFC5095]:
o amplification attacks: where a packet could be forged in such a
way to cause looping among a set of SR-enabled routers causing
unnecessary traffic, hence a Denial of Service (DoS) against
bandwidth;
o reflection attack: where a hacker could force an intermediate node
to appear as the immediate attacker, hence hiding the real
attacker from naive forensic;
o bypass attack: where an intermediate node could be used as a
stepping stone (for example in a De-Militarized Zone) to attack
another host (for example in the datacenter or any back-end
server).
6.1.2. Applicability of RFC 5095 to SRH
First of all, the reader must remember this specific part of section
1 of RFC5095 [RFC5095], "A side effect is that this also eliminates
benign RH0 use-cases; however, such applications may be facilitated
by future Routing Header specifications.". In short, it is not
forbidden to create new secure type of Routing Header; for example,
RFC 6554 (RPL) [RFC6554] also creates a new Routing Header type for a
specific application confined in a single network.
In the segment routing architecture described in
[I-D.ietf-spring-segment-routing] there are basically two kinds of
nodes (routers and hosts):
o nodes within the SR domain, which is within one single
administrative domain, i.e., where all nodes are trusted anyway
else the damage caused by those nodes could be worse than
amplification attacks: traffic interception, man-in-the-middle
attacks, more server DoS by dropping packets, and so on.
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o nodes outside of the SR domain, which is outside of the
administrative segment routing domain hence they cannot be trusted
because there is no physical security for those nodes, i.e., they
can be replaced by hostile nodes or can be coerced in wrong
behaviors.
The main use case for SR consists of the single administrative domain
where only trusted nodes with SR enabled and configured participate
in SR: this is the same model as in RFC6554 [RFC6554]. All non-
trusted nodes do not participate as either SR processing is not
enabled by default or because they only process SRH from nodes within
their domain.
Moreover, all SR nodes ignore SRH created by outsiders based on
topology information (received on a peering or internal interface) or
on presence and validity of the HMAC field. Therefore, if
intermediate nodes ONLY act on valid and authorized SRH (such as
within a single administrative domain), then there is no security
threat similar to RH-0. Hence, the RFC 5095 [RFC5095] attacks are
not applicable.
6.1.3. Service stealing threat
Segment routing is used for added value services, there is also a
need to prevent non-participating nodes to use those services; this
is called 'service stealing prevention'.
6.1.4. Topology disclosure
The SRH may also contains IPv6 addresses of some intermediate SR-
nodes in the path towards the destination, this obviously reveals
those addresses to the potentially hostile attackers if those
attackers are able to intercept packets containing SRH. On the other
hand, if the attacker can do a traceroute whose probes will be
forwarded along the SR path, then there is little learned by
intercepting the SRH itself.
6.1.5. ICMP Generation
Per section 4.4 of RFC2460 [RFC2460], when destination nodes (i.e.
where the destination address is one of theirs) receive a Routing
Header with unsupported Routing Type, the required behavior is:
o If Segments Left is zero, the node must ignore the Routing header
and proceed to process the next header in the packet.
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o If Segments Left is non-zero, the node must discard the packet and
send an ICMP Parameter Problem, Code 0, message to the packet's
Source Address, pointing to the unrecognized Routing Type.
This required behavior could be used by an attacker to force the
generation of ICMP message by any node. The attacker could send
packets with SRH (with Segment Left set to 0) destined to a node not
supporting SRH. Per RFC2460 [RFC2460], the destination node could
generate an ICMP message, causing a local CPU utilization and if the
source of the offending packet with SRH was spoofed could lead to a
reflection attack without any amplification.
It must be noted that this is a required behavior for any unsupported
Routing Type and not limited to SRH packets. So, it is not specific
to SRH and the usual rate limiting for ICMP generation is required
anyway for any IPv6 implementation and has been implemented and
deployed for many years.
6.2. Security fields in SRH
This section summarizes the use of specific fields in the SRH. They
are based on a key-hashed message authentication code (HMAC).
The security-related fields in the SRH are instantiated by the HMAC
TLV, containing:
o HMAC Key-id, 32 bits wide;
o HMAC, 256 bits wide (optional, exists only if HMAC Key-id is not
0).
The HMAC field is the output of the HMAC computation (per RFC 2104
[RFC2104]) using a pre-shared key identified by HMAC Key-id and of
the text which consists of the concatenation of:
o the source IPv6 address;
o Last Entry field;
o an octet of bit flags;
o HMAC Key-id;
o all addresses in the Segment List.
The purpose of the HMAC TLV is to verify the validity, the integrity
and the authorization of the SRH itself. If an outsider of the SR
domain does not have access to a current pre-shared secret, then it
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cannot compute the right HMAC field and the first SR router on the
path processing the SRH and configured to check the validity of the
HMAC will simply reject the packet.
The HMAC TLV is located at the end of the SRH simply because only the
router on the ingress of the SR domain needs to process it, then all
other SR nodes can ignore it (based on local policy) because they
trust the upstream router. This is to speed up forwarding operations
because SR routers which do not validate the SRH do not need to parse
the SRH until the end.
The HMAC Key-id field allows for the simultaneous existence of
several hash algorithms (SHA-256, SHA3-256 ... or future ones) as
well as pre-shared keys. The HMAC Key-id field is opaque, i.e., it
has neither syntax nor semantic except as an index to the right
combination of pre-shared key and hash algorithm and except that a
value of 0 means that there is no HMAC field. Having an HMAC Key-id
field allows for pre-shared key roll-over when two pre-shared keys
are supported for a while when all SR nodes converged to a fresher
pre-shared key. It could also allow for interoperation among
different SR domains if allowed by local policy and assuming a
collision-free HMAC Key Id allocation.
When a specific SRH is linked to a time-related service (such as
turbo-QoS for a 1-hour period) where the DA, Segment ID (SID) are
identical, then it is important to refresh the shared-secret
frequently as the HMAC validity period expires only when the HMAC
Key-id and its associated shared-secret expires.
6.2.1. Selecting a hash algorithm
The HMAC field in the HMAC TLV is 256 bit wide. Therefore, the HMAC
MUST be based on a hash function whose output is at least 256 bits.
If the output of the hash function is 256, then this output is simply
inserted in the HMAC field. If the output of the hash function is
larger than 256 bits, then the output value is truncated to 256 by
taking the least-significant 256 bits and inserting them in the HMAC
field.
SRH implementations can support multiple hash functions but MUST
implement SHA-2 [FIPS180-4] in its SHA-256 variant.
NOTE: SHA-1 is currently used by some early implementations used for
quick interoperations testing, the 160-bit hash value must then be
right-hand padded with 96 bits set to 0. The authors understand that
this is not secure but is ok for limited tests.
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6.2.2. Performance impact of HMAC
While adding an HMAC to each and every SR packet increases the
security, it has a performance impact. Nevertheless, it must be
noted that:
o the HMAC field is used only when SRH is added by a device (such as
a home set-up box) which is outside of the segment routing domain.
If the SRH is added by a router in the trusted segment routing
domain, then, there is no need for an HMAC field, hence no
performance impact.
o when present, the HMAC field MUST only be checked and validated by
the first router of the segment routing domain, this router is
named 'validating SR router'. Downstream routers may not inspect
the HMAC field.
o this validating router can also have a cache of <IPv6 header +
SRH, HMAC field value> to improve the performance. It is not the
same use case as in IPsec where HMAC value was unique per packet,
in SRH, the HMAC value is unique per flow.
o Last point, hash functions such as SHA-2 have been optimized for
security and performance and there are multiple implementations
with good performance.
With the above points in mind, the performance impact of using HMAC
is minimized.
6.2.3. Pre-shared key management
The field HMAC Key-id allows for:
o key roll-over: when there is a need to change the key (the hash
pre-shared secret), then multiple pre-shared keys can be used
simultaneously. The validating routing can have a table of <HMAC
Key-id, pre-shared secret> for the currently active and future
keys.
o different algorithms: by extending the previous table to <HMAC
Key-id, hash function, pre-shared secret>, the validating router
can also support simultaneously several hash algorithms (see
section Section 6.2.1)
The pre-shared secret distribution can be done:
o in the configuration of the validating routers, either by static
configuration or any SDN oriented approach;
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o dynamically using a trusted key distribution such as [RFC6407]
The intent of this document is NOT to define yet-another-key-
distribution-protocol.
6.3. Deployment Models
6.3.1. Nodes within the SR domain
An SR domain is defined as a set of interconnected routers where all
routers at the perimeter are configured to add and act on SRH. Some
routers inside the SR domain can also act on SRH or simply forward
IPv6 packets.
The routers inside an SR domain can be trusted to generate SRH and to
process SRH received on interfaces that are part of the SR domain.
These nodes MUST drop all SRH packets received on an interface that
is not part of the SR domain and containing an SRH whose HMAC field
cannot be validated by local policies. This includes obviously
packet with an SRH generated by a non-cooperative SR domain.
If the validation fails, then these packets MUST be dropped, ICMP
error messages (parameter problem) SHOULD be generated (but rate
limited) and SHOULD be logged.
6.3.2. Nodes outside of the SR domain
Nodes outside of the SR domain cannot be trusted for physical
security; hence, they need to request by some trusted means (outside
of the scope of this document) a complete SRH for each new connection
(i.e. new destination address). The received SRH MUST include an
HMAC TLV which is computed correctly (see Section 6.2).
When an outside node sends a packet with an SRH and towards an SR
domain ingress node, the packet MUST contain the HMAC TLV (with a
Key-id and HMAC fields) and the the destination address MUST be an
address of an SR domain ingress node .
The ingress SR router, i.e., the router with an interface address
equals to the destination address, MUST verify the HMAC TLV.
If the validation is successful, then the packet is simply forwarded
as usual for an SR packet. As long as the packet travels within the
SR domain, no further HMAC check needs to be done. Subsequent
routers in the SR domain MAY verify the HMAC TLV when they process
the SRH (i.e. when they are the destination).
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If the validation fails, then this packet MUST be dropped, an ICMP
error message (parameter problem) SHOULD be generated (but rate
limited) and SHOULD be logged.
6.3.3. SR path exposure
As the intermediate SR nodes addresses appears in the SRH, if this
SRH is visible to an outsider then he/she could reuse this knowledge
to launch an attack on the intermediate SR nodes or get some insider
knowledge on the topology. This is especially applicable when the
path between the source node and the first SR domain ingress router
is on the public Internet.
The first remark is to state that 'security by obscurity' is never
enough; in other words, the security policy of the SR domain MUST
assume that the internal topology and addressing is known by the
attacker. A simple traceroute will also give the same information
(with even more information as all intermediate nodes between SID
will also be exposed). IPsec Encapsulating Security Payload
[RFC4303] cannot be use to protect the SRH as per RFC4303 the ESP
header must appear after any routing header (including SRH).
To prevent a user to leverage the gained knowledge by intercepting
SRH, it it recommended to apply an infrastructure Access Control List
(iACL) at the edge of the SR domain. This iACL will drop all packets
from outside the SR-domain whose destination is any address of any
router inside the domain. This security policy should be tuned for
local operations.
6.3.4. Impact of BCP-38
BCP-38 [RFC2827], also known as "Network Ingress Filtering", checks
whether the source address of packets received on an interface is
valid for this interface. The use of loose source routing such as
SRH forces packets to follow a path which differs from the expected
routing. Therefore, if BCP-38 was implemented in all routers inside
the SR domain, then SR packets could be received by an interface
which is not expected one and the packets could be dropped.
As an SR domain is usually a subset of one administrative domain, and
as BCP-38 is only deployed at the ingress routers of this
administrative domain and as packets arriving at those ingress
routers have been normally forwarded using the normal routing
information, then there is no reason why this ingress router should
drop the SRH packet based on BCP-38. Routers inside the domain
commonly do not apply BCP-38; so, this is not a problem.
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7. IANA Considerations
This document makes the following registrations in the Internet
Protocol Version 6 (IPv6) Parameters "Routing Type" registry
maintained by IANA:
Suggested Description Reference
Value
----------------------------------------------------------
4 Segment Routing Header (SRH) This document
This document request IANA to create and maintain a new Registry:
"Segment Routing Header TLVs"
7.1. Segment Routing Header TLVs Register
This document requests the creation of a new IANA managed registry to
identify SRH TLVs. The registration procedure is "Expert Review" as
defined in [RFC8126]. Suggested registry name is "Segment Routing
Header TLVs". A TLV is identified through an unsigned 8 bit
codepoint value. The following codepoints are defined in this
document:
Suggested Description Reference
Value
-----------------------------------------------------
1 Ingress Node TLV This document
2 Egress Node TLV This document
3 Opaque Container TLV This document
4 Padding TLV This document
5 HMAC TLV This document
6 NSH Carrier TLV This document
8. Manageability Considerations
TBD
9. Contributors
Dave Barach, John Brzozowski, Pierre Francois, Nagendra Kumar, Mark
Townsley, Christian Martin, Roberta Maglione, James Connolly, Aloys
Augustin contributed to the content of this document.
10. Acknowledgements
The authors would like to thank Ole Troan, Bob Hinden, Fred Baker,
Brian Carpenter, Alexandru Petrescu and Punit Kumar Jaiswal for their
comments to this document.
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11. References
11.1. Normative References
[FIPS180-4]
National Institute of Standards and Technology, "FIPS
180-4 Secure Hash Standard (SHS)", March 2012,
<http://csrc.nist.gov/publications/fips/fips180-4/
fips-180-4.pdf>.
[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>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<http://www.rfc-editor.org/info/rfc4303>.
[RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
of Type 0 Routing Headers in IPv6", RFC 5095,
DOI 10.17487/RFC5095, December 2007,
<http://www.rfc-editor.org/info/rfc5095>.
[RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
of Interpretation", RFC 6407, DOI 10.17487/RFC6407,
October 2011, <http://www.rfc-editor.org/info/rfc6407>.
11.2. Informative References
[I-D.bashandy-isis-srv6-extensions]
Bashandy, A., Filsfils, C., Ginsberg, L., and B. Decraene,
"IS-IS Extensions to Support Segment Routing over IPv6
Dataplane", draft-bashandy-isis-srv6-extensions-00 (work
in progress), March 2017.
[I-D.dawra-bgp-srv6-vpn]
(Unknown), (., Dawra, G., Filsfils, C., Dukes, D.,
Brissette, P., Camarillo, P., Leddy, J.,
daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d.,
Steinberg, D., Raszuk, R., Decraene, B., and S.
Matsushima, "BGP Signaling of IPv6-Segment-Routing-based
VPN Networks", draft-dawra-bgp-srv6-vpn-00 (work in
progress), March 2017.
Previdi, et al. Expires January 21, 2018 [Page 29]
Internet-Draft IPv6 Segment Routing Header (SRH) July 2017
[I-D.filsfils-spring-srv6-network-programming]
Filsfils, C., Leddy, J., daniel.voyer@bell.ca, d.,
daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
Matsushima, S., Lebrun, D., Decraene, B., Peirens, B.,
Salsano, S., Naik, G., Elmalky, H., Jonnalagadda, P.,
Sharif, M., Ayyangar, A., Mynam, S., Henderickx, W.,
Bashandy, A., Raza, K., Dukes, D., Clad, F., and P.
Camarillo, "SRv6 Network Programming", draft-filsfils-
spring-srv6-network-programming-01 (work in progress),
June 2017.
[I-D.ietf-isis-l2bundles]
Ginsberg, L., Bashandy, A., Filsfils, C., Nanduri, M., and
E. Aries, "Advertising L2 Bundle Member Link Attributes in
IS-IS", draft-ietf-isis-l2bundles-07 (work in progress),
May 2017.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and j. jefftant@gmail.com,
"IS-IS Extensions for Segment Routing", draft-ietf-isis-
segment-routing-extensions-13 (work in progress), June
2017.
[I-D.ietf-ospf-ospfv3-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
Extensions for Segment Routing", draft-ietf-ospf-ospfv3-
segment-routing-extensions-09 (work in progress), March
2017.
[I-D.ietf-sfc-nsh]
Quinn, P., Elzur, U., and C. Pignataro, "Network Service
Header (NSH)", draft-ietf-sfc-nsh-16 (work in progress),
July 2017.
[I-D.ietf-spring-ipv6-use-cases]
Brzozowski, J., Leddy, J., Filsfils, C., Maglione, R., and
M. Townsley, "IPv6 SPRING Use Cases", draft-ietf-spring-
ipv6-use-cases-11 (work in progress), June 2017.
[I-D.ietf-spring-resiliency-use-cases]
Filsfils, C., Previdi, S., Decraene, B., and R. Shakir,
"Resiliency use cases in SPRING networks", draft-ietf-
spring-resiliency-use-cases-11 (work in progress), May
2017.
Previdi, et al. Expires January 21, 2018 [Page 30]
Internet-Draft IPv6 Segment Routing Header (SRH) July 2017
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-12 (work in progress), June 2017.
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-10
(work in progress), June 2017.
[I-D.previdi-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Mattes, P., Rosen, E., and S.
Lin, "Advertising Segment Routing Policies in BGP", draft-
previdi-idr-segment-routing-te-policy-07 (work in
progress), June 2017.
[RFC1940] Estrin, D., Li, T., Rekhter, Y., Varadhan, K., and D.
Zappala, "Source Demand Routing: Packet Format and
Forwarding Specification (Version 1)", RFC 1940,
DOI 10.17487/RFC1940, May 1996,
<http://www.rfc-editor.org/info/rfc1940>.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<http://www.rfc-editor.org/info/rfc2104>.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
May 2000, <http://www.rfc-editor.org/info/rfc2827>.
[RFC4942] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/
Co-existence Security Considerations", RFC 4942,
DOI 10.17487/RFC4942, September 2007,
<http://www.rfc-editor.org/info/rfc4942>.
[RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
Routing Header for Source Routes with the Routing Protocol
for Low-Power and Lossy Networks (RPL)", RFC 6554,
DOI 10.17487/RFC6554, March 2012,
<http://www.rfc-editor.org/info/rfc6554>.
Previdi, et al. Expires January 21, 2018 [Page 31]
Internet-Draft IPv6 Segment Routing Header (SRH) July 2017
[RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
Litkowski, S., Horneffer, M., and R. Shakir, "Source
Packet Routing in Networking (SPRING) Problem Statement
and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
2016, <http://www.rfc-editor.org/info/rfc7855>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<http://www.rfc-editor.org/info/rfc8126>.
Authors' Addresses
Stefano Previdi (editor)
Cisco Systems, Inc.
Italy
Email: stefano@previdi.net
Clarence Filsfils
Cisco Systems, Inc.
Brussels
BE
Email: cfilsfil@cisco.com
Kamran Raza
Cisco Systems, Inc.
Email: skraza@cisco.com
"Darren Dukes
Cisco Systems, Inc.
Email: ddukes@cisco.com
John Leddy
Comcast
4100 East Dry Creek Road
Centennial, CO 80122
US
Email: John_Leddy@comcast.com
Previdi, et al. Expires January 21, 2018 [Page 32]
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Brian Field
Comcast
4100 East Dry Creek Road
Centennial, CO 80122
US
Email: Brian_Field@cable.comcast.com
Daniel Voyer
Bell Canada
Email: daniel.voyer@bell.ca
Daniel Bernier
Bell Canada
Email: daniel.bernier@bell.ca
Satoru Matsushima
Softbank
Email: satoru.matsushima@g.softbank.co.jp
Ida Leung
Rogers Communications
8200 Dixie Road
Brampton, ON L6T 0C1
CA
Email: Ida.Leung@rci.rogers.com
Jen Linkova
Google
1600 Amphitheatre Parkway
Mountain View, CA 94043
US
Email: furry@google.com
Previdi, et al. Expires January 21, 2018 [Page 33]
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Ebben Aries
Facebook
US
Email: exa@fb.com
Tomoya Kosugi
NTT
3-9-11, Midori-Cho Musashino-Shi,
Tokyo 180-8585
JP
Email: kosugi.tomoya@lab.ntt.co.jp
Eric Vyncke
Cisco Systems, Inc.
De Kleetlaann 6A
Diegem 1831
Belgium
Email: evyncke@cisco.com
David Lebrun
Universite Catholique de Louvain
Place Ste Barbe, 2
Louvain-la-Neuve, 1348
Belgium
Email: david.lebrun@uclouvain.be
Dirk Steinberg
Steinberg Consulting
Email: dws@dirksteinberg.de
Robert Raszuk
Bloomberg
Email: robert@raszuk.net
Previdi, et al. Expires January 21, 2018 [Page 34]
