Internet DRAFT - draft-baker-ipv6-ospf-dst-flowlabel-routing
draft-baker-ipv6-ospf-dst-flowlabel-routing
Network Working Group F.J. Baker
Internet-Draft Cisco Systems
Intended status: Standards Track August 28, 2013
Expires: March 01, 2014
Using OSPFv3 with Token-based Access Control
draft-baker-ipv6-ospf-dst-flowlabel-routing-03
Abstract
This note describes the changes necessary for OSPF to route IPv6
traffic specified prefix if and only if the packet contains an
authorization token.
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 March 01, 2014.
Copyright Notice
Copyright (c) 2013 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
Baker Expires March 01, 2014 [Page 1]
Internet-Draft OSPF Source/Destination Routing August 2013
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Theory of Routing . . . . . . . . . . . . . . . . . . . . . . 2
2.1. Dealing with ambiguity . . . . . . . . . . . . . . . . . 3
2.2. Interactions with other constraints . . . . . . . . . . . 3
3. Extensions necessary for IPv6 Authenticated Routing in OSPF . 4
3.1. Authorization Token TLV . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
This specification builds on OSPF for IPv6 [RFC5340] and its
extensible LSA, defined in OSPFv3 LSA Extendibility
[I-D.acee-ospfv3-lsa-extend]. This note defines the TLV for an IPv6
[RFC2460] Flow Label, to define routes from to a destination prefix
qualified by an authorization token.
The approach may be combined with other qualifying attributes, such
as routing "to that destination AND from a specified source". The
obvious application is data center inter-tenant routing using a form
of token-based access control. If the sender doesn't know the value
to insert in the flow label or hop-by-hop option (the receiver's
tenant ID), he in effect has no route to that destination.
1.1. 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 [RFC2119].
2. Theory of Routing
Both IS-IS and OSPF perform their calculations by building a lattice
of routers and links from the router performing the calculation to
each router, and then use routes (sequences in the lattice) to get to
destinations that those routes advertise connectivity to. Following
the SPF algorithm, calculation starts by selecting a starting point
(typically the router doing the calculation), and successively adding
{link, router} pairs until one has calculated a route to every router
in the network. As each router is added, including the original
Baker Expires March 01, 2014 [Page 2]
Internet-Draft OSPF Source/Destination Routing August 2013
router, destinations that it is directly connected to are turned into
routes in the route table: "to get to 2001:db8::/32, route traffic to
{interface, list of next hop routers}". For immediate neighbors to
the originating router, of course, there is no next hop router;
traffic is handled locally.
In this context, the route is qualified by an authorization token,
carried in the flow label or a hop-by-hop option; It is installed
into the FIB with the destination prefix, and the FIB applies the
route if and only if the token in the packet matches the token in the
route. Of course, there may be multiple LSPs in the RIB with the
same destination and differing authorization tokens; these may also
have the same or differing next hop lists. The intended forwarding
action is to forward matching traffic to one of the next hop routers
associated with this destination and authorization tokens, or to
discard non-matching traffic as "destination unreachable".
LSAs that lack an authorization token TLV match any token that may be
present, by definition.
2.1. Dealing with ambiguity
In any routing protocol, there is the possibility of ambiguity. For
example, one router might advertise a fairly general prefix - a
default route, a discard prefix (which consumes all traffic that is
not directed to an instantiated subnet), or simply an aggregated
prefix while another router advertises a more specific one. In
source/destination routing, potentially ambiguous cases include cases
in which the link state database contains two routes A->B' and A'->B,
in which A' is a more specific prefix within the prefix A and B' is a
more specific prefix within the prefix B. Traditionally, we have
dealt with ambiguous destination routes using a "longest match first"
rule. If the same datagram matches more than one destination prefix
advertised within an area, we follow the route with the longest
matching prefix.
In this case, we follow a similar but slightly different rule; the
FIB lookup MUST yield the route with the longest matching destination
prefix that also matches the authorization token. A FIB route with
no such token matches any authorization token.
2.2. Interactions with other constraints
In the event that there are other constraints on routing, such as
proposed in [I-D.baker-ipv6-ospf-dst-src-routing], the effect is a
logical AND. The FIB lookup must yield the route with the longest
matching destination prefix that also matches each of the
constraints.
Baker Expires March 01, 2014 [Page 3]
Internet-Draft OSPF Source/Destination Routing August 2013
3. Extensions necessary for IPv6 Authenticated Routing in OSPF
Section 2 of [RFC5340] defines the "IPv6 Reachability TLV", and
carries in it destination prefix advertisements. It has the
capability of extension, using TLVs.
In this model, the flow label is used to prove that the datagram's
sender has specific knowledge of its intended receiver. No proof is
requested; this is left for higher layer exchanges such as IPSec or
TLS. However, if the information is distributed privately, such as
through DHCP/DHCPv6, the network can presume that a system that marks
traffic with the right flow label has a good chance of being
authorized to communicate with its peer.
The key consideration, in this context, is that the flow label is a
20 bit number. As such, an advertised route requiring a given flow
label value is calling for an exact match of all 20 bits of the label
value.
3.1. Authorization Token TLV
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 | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ | 20 bit Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Source Prefix Sub-TLV
Source Prefix Type: assigned by IANA
TLV Length: Length of the TLV in octets
Flow Label: Flow Label value (20 bits)
4. IANA Considerations
The source prefix type mentioned in Section 3 must be defined.
5. Security Considerations
Network layer Token-based Access Control is part of a security
solution. It is not, in itself, a complete solution. It acts as a
pervasive network layer firewall, preventing unauthorized traffic
from arriving at a destination. However, as in any network, a host
is its own last bastion of defense; it needs IPsec or TLS-style
Baker Expires March 01, 2014 [Page 4]
Internet-Draft OSPF Source/Destination Routing August 2013
authorization and authorization of its peers, and must refuse traffic
that contains the authorization token but is in fact malicious.
6. Acknowledgements
7. References
7.1. Normative References
[I-D.acee-ospfv3-lsa-extend]
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
LSA Extendibility", draft-acee-ospfv3-lsa-extend-00 (work
in progress), May 2013.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S.E. and R.M. Hinden, "Internet Protocol, Version
6 (IPv6) Specification", RFC 2460, December 1998.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
7.2. Informative References
[I-D.baker-ipv6-ospf-dst-src-routing]
Baker, F., "IPv6 Source/Destination Routing using OSPFv3",
draft-baker-ipv6-ospf-dst-src-routing-02 (work in
progress), May 2013.
Appendix A. Change Log
Initial Version: February 2013
updated Version: August 2013
Author's Address
Fred Baker
Cisco Systems
Santa Barbara, California 93117
USA
Email: fred@cisco.com
Baker Expires March 01, 2014 [Page 5]
