Internet DRAFT - draft-xu-homenet-traffic-class
draft-xu-homenet-traffic-class
Network Working Group M. Xu
Internet-Draft S. Yang
Expires: October 23, 2014 J. Wu
Tsinghua University
F. Baker
Cisco Systems
April 21, 2014
Traffic Class Routing Protocol in Home Networks
draft-xu-homenet-traffic-class-02
Abstract
Home IT staff is generally unfamiliar with network operations, making
it desirable to provide a configuration-free mode of operation.
Policy-based routing (in the sense of configuring one router to
redirect traffic to another based on access control) and multi-
topology routing both require configuration, making them undesirable.
In this document, we propose a configuration-free mechanism, in which
packets will be routed towards the corresponding upstream ISPs based
on both destination and source addresses.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Router Behavior . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Egress Router Behavior . . . . . . . . . . . . . . . . . 5
4.2. Interior Router Behavior . . . . . . . . . . . . . . . . 5
5. TC-LSA Format . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Routing Table Structure . . . . . . . . . . . . . . . . . . . 8
7. Calculation of the Routing Table . . . . . . . . . . . . . . 8
8. Matching Rule . . . . . . . . . . . . . . . . . . . . . . . . 9
9. Forwarding Table Structure . . . . . . . . . . . . . . . . . 9
10. Implementation . . . . . . . . . . . . . . . . . . . . . . . 10
11. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 10
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
14.1. Normative References . . . . . . . . . . . . . . . . . . 11
14.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Home networks are growing both in device count and in complexity.
Today they generally contain both wired and wireless components, and
may require routing to place audio/visual entertainment traffic one
one path, office services on another, and wireless LANs (both IEEE-
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style and 4G/LTE-style) on a third. Traditionally, we have
simplified networks using a single exit router and a default route.
Today, we might have multiple routers to wired upstream networks, and
by separate paths LTE services, "Smart Grid" services, or health
network services. Increasingly, such networks are multihomed, and
multihomed using diverse access network technologies.
Traditionally, routing protocols make routing decisions solely based
on destination IP addresses, packets towards the same destination
will be delivered to the same next hop no matter where they come
from. These protocols work well with simple home networks that have
only one egress router. However, in the multi-homing scenario,
packets may be dropped if forwarded only based on destination
addresses [RFC3704].
Although many patch-like solutions, like policy-based routing (PBR),
multi-topology routing (MTR) and layer-3 VPN can solve the problem,
they complex the configurations in home networks, and are not
suitable for home IT staffs. We need a configuration-free solution
to help operators set up their home networks in the multi-homing
scenario.
In this document, we propose a configuration-free mechanism - traffic
class routing, based on OSPFv3, such that home networks can route
packets towards the corresponding upstream ISPs, according to both
destination and source addresses.
2. Terminology
Terminology used in this document:
o Traffic Class (TC): Identified by (destination prefix, source
prefix), all packets falling in the domain belong to the traffic
class.
o TC-Route: Identified by (destination prefix, source prefix,
value), where value is the administrative value applied to the
traffic class (destination prefix, source prefix).
o TC-LSA: Link state advertisement that communicates the
reachability for a traffic classes.
3. Overview
In a home network, traditionally, egress routers obtain delegated
prefixes from upstream ISPs using DHCPv6 with prefix options
[RFC3633]. The egress routers will then assign longer sub-prefixes
to the other links in the home network. Each router inside the home
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network will act as standard OSPFv3 router, and forward packets based
on their destination addresses.
With traffic class routing, after obtaining delegated prefixes and
assigning sub-prefixes, egress routers will populate traffic classes
(with extended LSAs), rather than destination address only, into the
home network. Each router inside the home network will flood these
traffic classes information. When calculating the path towards a
destination address, routers will take the traffic classes into
considerations. Intrinsically, in traditional routing model, the
object being routed to is a destination prefix; in our routing model,
the object being routed might be a destination prefix given that the
packet sports a certain source prefix.
Each traffic class is associated with a cost, which is a single
dimensionless metric.
For example, a site is connected to the Internet through two ISPs,
ISP1 and ISP2. ISP1 delegates prefix P1 to the site, and ISP2
delegates prefix P2 to the site. After being delegated with P1, the
egress router E1 of the site will advertise a traffic class - {::/0,
P1}, into the site. After being delegated with P2, the egress router
E2 of the site will advertise a traffic class - {::/0, P2}, into the
site. Receiving these advertisements, interior router I1 will
compute two paths towards ::/0, one through router E1 for traffic
from P1, the other through E2 for traffic from P2.
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+---------------+ +-----------------+
| | | |
| ISP1: P1 | | ISP2: P2 |
| | | |
+--------+------+ +-----+-----------+
| |
+--+---+ +--+---+
|Router| |Router|
| BR1 | | BR2 |
+---+--+ +---+--+
------+---------- -----------+-----
| |
+---+--+ +---+--+
|Router| |Router|
| E1 | | E2 |
+------+ +------+ +------+
-+-------+Router+---------+-
| I1 |
+--+---+
+--+---+ Address A in P1
| Host |
+------+ Address B in P2
Figure 1: Multi-homing Scenario in Home Networks
4. Router Behavior
All routers behave like traditional OSPFv3 routers, however, the
following behaviors are different with traditional OSPFv3 routers.
4.1. Egress Router Behavior
After obtaining delegated prefixes using DHCPv6 with prefix options,
an egress router should originate TC-LSAs, i.e., extended LSAs with
source prefixes appended. Egress routers then will advertise these
TC-LSAs into the home network.
Note that an egress router behaves like an interior router if it
receives a TC-LSA from other egress routers.
4.2. Interior Router Behavior
Receiving TC-LSAs from egress routers, an interior router should
store the TC-LSAs into its LSDB, and flood it to other routers.
After calculating a path to an egress router advertising
reachability, i.e., a destination prefix, the interior router should
decide which traffic class can follow this path towards the egress
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router. If a traffic class can travel through two different paths,
then interior router should compare their costs, and select the path
with the lowest cost. The cost for a traffic class is the sum of the
advertised metric of the traffic class plus the cost towards the
egress router.
Interior routers contains a routing table that contains all necessary
information to forward an IP packet following the path of a traffic
class. After computing the path towards a traffic class, interior
routers should update the entry in the routing table if necessary,
e.g., change the next hop towards the traffic class. The routing
table structure will be described in Section 6. Calculation of
routing table will be illustrated in Section 7.
At last, interior routers should update the Forwarding Information
Base (FIB), which will be discussed in the next version of this
document.
5. TC-LSA Format
TC-LSA adds TLV extensions, which contains source prefix information,
based on original OSPFv3 LSA. We follow the TLV format in
[I-D.baker-ipv6-ospf-dst-src-routing] and extended LSA format in
[I-D.acee-ospfv3-lsa-extend].
Each extended LSA includes the traditional LSA part in [RFC5340], and
one or more TLVs defined in [I-D.baker-ipv6-ospf-dst-src-routing].
Because home network is not so large, we do not need to extend all
LSAs. The extended LSAs are as follows:
o E-Intra-Area-Prefix-LSA: The extended LSA has type 0xA029.
The format of E-Intra-Area-Prefix-LSA in multi-homing 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Age |0|0|1| LSA Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LS Checksum | LSA Length |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| # Prefixes | Referenced LS Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Referenced Link State ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Referenced Advertising Router |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PrefixLength | PrefixOptions | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PrefixLength | PrefixOptions | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPrefixLength | SPrefixOptions| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address Prefix |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPrefixLength | SPrefixOptions| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address Prefix |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Multi-homing Scenario in Home Networks
All LSA header fields are the same as defined in [RFC5340], except
the following:
o LSA type: The LSA type value is 0xA029, according to
[I-D.acee-ospfv3-lsa-extend];
o LSA length: The length of the whole LSA header, including the
TLVs;
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o TLV type: The type of IPv6 source prefix TLV, assigned by IANA;
o TLV length: The value is 20 as defined in
[I-D.baker-ipv6-ospf-dst-src-routing];
o SPrefixLength, SPrefixOptions, Source Address Prefix:
Representation of the IPv6 address prefix, which is delegated from
the upstream ISP providers;
For simplicity, each extended LSA should only carry one source
prefix, suppose there are n destination prefix d1, d2, ..., dn, and
the source prefix is s, then the LSA carries n TC-route announcement,
(d1, s, v1), (d1, s, v2), ..., (dn, s, vn), where vi is the metric
associated with destination prefix di.
6. Routing Table Structure
For traditional routing, the routing table structure contains all
needed information to forward IP packets to the right destination.
For example, destination prefixes are commonly structured into a
prefix trie, where each trie nodes contain the necessary information.
Routers can lookup and update the prefix trie.
With traffic classes, the routing table structure must contain all
needed information to forward IP packets following the right traffic
class, i.e., towards the related destination and from the related
source. For each routing table entry, there are two additional
fields other than the fields mentioned in [RFC5340]:
o Source IP Address: The IP address of the source in traffic class.
o Source Address Mask: If the source is a subnet, then it is
referred to as the subnet mask.
The routing table must provide interface for update and lookup in it.
For example, traffic classes can be structured into a two dimensional
(or two level) trie, where each trie node in the first dimension
points to a sub-trie in the second dimension. The trie nodes in the
second dimension contain the necessary information to forward IP
packets following the right traffic class.
7. Calculation of the Routing Table
The fundamental algorithm in OSPFv3 doesn't change. The algorithm
uses the SPF approach to calculate a path to the router advertising
reachability, and then uses the reachability advertisement to decide
what traffic should follow that route. What we are changing is the
reachability advertisement, in traiditional OSPFv3, the
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advertisements, which is one or several kinds of LSAs, represent
destination prefixes; in this document, the advertisements, which is
one or several kinds of TC-LSAs, represent traffic classes.
Note that we do not have to change router-LSA and network-LSA in
[RFC5340]. Thus, the first stage of Section 4.8.1 in [RFC5340]
remains the same in this document. However, the second stage of
Section 4.8.1 in [RFC5340] should change by a little bit. Instead of
examining the list of the intra-area-prefix-LSAs, the list of
extended intra-area-prefix-LSAs is examined. The cost of any
advertised traffic class is the sum of the class' advertised metric
plus the cost of the transit vertex (either router or transit
network) indentified by extended intra-area-prefix-LSAs' referenced
LS type, referenced link state ID, and referenced advertising router
field.
8. Matching Rule
We also adopt the LMF (longest match first) rule when a packet
matches multiple routing entries. However, traffic class has two
dimensions, there might exist ambiguity. For example, if there
exists two routing entries, (d1, s1, nexthop1), (d2, s2, nexthop2),
where d1 is longer than d2 and s2 is longer than s1, then none entry
is longer than the other in both dimensions. In this situation, we
must insert an additional entry into the routing table, e.g., (d1,
s2, nexthop1) in the above example. The entry directs to nexthop1
rather than nexthop2, because we must guarantee reachability
according to the destination prefix.
9. Forwarding Table Structure
As the format of routing table entries changes from (destination
prefix, nexthop) to (destination prefix, source prefix, nexthop), The
Forwarding Information Base (FIB), based on which routers forward IP
packets, should be redesigned. There can be different possible FIB
structures, e.g., TCAM-based structure, linear table structure, trie-
based structure, etc. we use a trie-based solution in this document.
In traditional routing, the destination prefixes are constructed
using a prefix trie. However, in traffic class routing, the
forwarding decision is based on both the destination and source
prefixes. To store them, we design a new structure, based on
patricia-trie to meet the needs.
In traffic class routing, the router forwards IP packets following
the right traffic class based on destination and source prefixes.
Routers construct a two dimensional (or two level) patricia-trie,
where each trie node in the first dimension points to a sub-trie (the
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sub-trie can be empty). When a packet arrives, the packet should
match a trie node (destination prefix) in the first dimension using
the destination address. Following the sub-trie under the node, the
packet should match another trie node (source prefix) in the second
dimension, i.e., the sub-trie.
10. Implementation
We implemented the routing protocol in Quagga, an open-source routing
software. In Quagga, we modified the LSA format to support E-Intra-
Area-Prefix-LSA, the routing table format, and the routing table
calculation algorithm.
To implement the FIB structure, we modified Click, which is a modular
software router. The FIB structure could support lookup and update.
When the routing table changes, routers can update the FIB through
pre-defined interfaces.
11. Compatibility
Routers can also announce the traditional destination-based LSAs,
e.g., Intra-Area-Prefix-LSA, at the same time. When a router
receives traditional destination-based LSAs, it has two choices. In
the first choice, the destination-based LSAs are treated as TC-LSAs
where the source prefix equal the wildcard, and routers keep all
routes in a common routing table. When a packet arrives, routers
need to lookup in the routing table according to the matching rule.
In the second choice, routers have to keep two routing tables, one
for destination prefix only, and the other for traffic classes. When
a packet arrives, routers first lookup in the routing table storing
traffic classes; If none entry matches, then routers lookup in the
routing table storing destination prefixes.
12. IANA Considerations
The newly LSA types and TLVs should be assigned by IANA, please refer
to [I-D.baker-ipv6-ospf-dst-src-routing] and
[I-D.acee-ospfv3-lsa-extend].
13. Acknowledgments
Zheng Liu and Gautier Bayzelon provided useful input into this
document.
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14. References
14.1. Normative References
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, March 2004.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
14.2. Informative References
[I-D.ietf-homenet-arch]
Chown, T., Arkko, J., Brandt, A., Troan, O., and J. Weil,
"Home Networking Architecture for IPv6", draft-ietf-
homenet-arch-07 (work in progress), February 2013.
[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.
[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.
[I-D.baker-fun-routing-class]
Baker, F., "Routing a Traffic Class", draft-baker-fun-
routing-class-00 (work in progress), July 2011.
Authors' Addresses
Mingwei Xu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R. China
Phone: +86-10-6278-5822
Email: xmw@csnet1.cs.tsinghua.edu.cn
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Shu Yang
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R. China
Phone: +86-10-6278-5822
Email: yangshu@csnet1.cs.tsinghua.edu.cn
Jianping Wu
Tsinghua University
Department of Computer Science, Tsinghua University
Beijing 100084
P.R. China
Phone: +86-10-6278-5983
Email: jianping@cernet.edu.cn
Fred Baker
Cisco Systems
Santa Barbara, California 93117
USA
Email: fred@cisco.com
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