BIER Use Case in VxLAN
draft-wang-bier-vxlan-use-case-00
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| Authors | Cui Wang , Zheng Zhang , fangwei hu | ||
| Last updated | 2015-10-12 | ||
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draft-wang-bier-vxlan-use-case-00
BIER WG C. Wang
Internet-Draft Z. Zhang
Intended status: Standards Track F. Hu
Expires: April 13, 2016 ZTE Corporation
October 11, 2015
BIER Use Case in VxLAN
draft-wang-bier-vxlan-use-case-00
Abstract
Bit Index Explicit Replication (BIER) is an architecture that
provides optimal multicast forwarding through a "BIER domain" without
requiring intermediate routers to maintain any multicast related per-
flow state. BIER also does not require any explicit tree-building
protocol for its operation. A multicast data packet enters a BIER
domain at a "Bit-Forwarding Ingress Router" (BFIR), and leaves the
BIER domain at one or more "Bit-Forwarding Egress Routers" (BFERs).
The BFIR router adds a BIER header to the packet. The BIER header
contains a bit-string in which each bit represents exactly one BFER
to forward the packet to. The set of BFERs to which the multicast
packet needs to be forwarded is expressed by setting the bits that
correspond to those routers in the BIER header.
This document tries to describe the drawbacks of how BUM services are
deployed in current data centers, and proposes how to take full
advantage of BIER to implement BUM services in data centers.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 13, 2016.
Copyright Notice
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Copyright (c) 2015 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Convention and Terminology . . . . . . . . . . . . . . . . . . 5
3. BIER in data centers . . . . . . . . . . . . . . . . . . . . . 6
4. BIER IS-IS extension for VXLAN-specific information . . . . . 7
5. BIER OSPF extension for VXLAN-specific information . . . . . . 9
6. BIER BGP extension for VXLAN-specific information . . . . . . 10
7. Considerations on BIER in data centers . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
This document is motivated by [I-D.ietf-bier-use-cases].
In current data center virtualization, virtual eXtensible Local Area
Network (VXLAN) [RFC7348] is a kind of network virtualization overlay
technology which is overlaid between NVEs and is intended for multi-
tenancy data center networks, whose reference architecture is
illustrated as per Figure 1.
+--------+ +--------+
| Tenant +--+ +----| Tenant |
| System | | (') | System |
+--------+ | ................ ( ) +--------+
| +-+--+ . . +--+-+ (_)
| | NVE|--. .--| NVE| |
+--| | . . | |---+
+-+--+ . . +--+-+
/ . .
/ . L3 Overlay . +--+-++--------+
+--------+ / . Network . | NVE|| Tenant |
| Tenant +--+ . .--| || System |
| System | . . +--+-++--------+
+--------+ ................
Figure 1: NVO3 Architecture
And there are two kinds of most common methods about how to forward
BUM packets in this virtualization overlay network. One is using PIM
as underlay multicast routing protocol to build explicit multicast
distribution tree, such as PIM-SM[RFC4601] or PIM-BIDIR
[RFC5015]multicast routing protocol. Then, when BUM packets arrive
at NVE, it requires NVE to have a mapping between the VXLAN Virtual
Network Instances (VNI) and the IP multicast group. According to the
mapping, NVE can encapsulate BUM packets in a multicast packet which
group address is the mapping IP multicast group address and steer
them through explicit multicast distribution tree to the destination
NVEs. This method has two serious drawbacks. It need the underlay
network supports complicated multicast routing protocol and maintains
multicast related per-flow state in every transit nodes. What!_s
more, how to configure the ratio of the mapping between VNI and IP
multicast group is also an issue. If the ratio is 1:1, there should
be 16M multicast groups in the underlay network at maximum to map to
the 16 M VNIs, which is really a significant challenge for the data
center devices. If the ratio is n:1, it would result in inefficiency
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bandwidth utilization which is not optimal in data center networks.
The other method is using ingress replication to require each NVE to
create a mapping between the VXLAN Virtual Network Instances (VNI)
and the remote NVEs!_ addresses which belong to the same virtual
network. When NVE receives BUM traffic from the attached tenant, NVE
can encapsulate these BUM packets in unicast packets and replicate
them and tunnel them to different remote NVEs respectively. Although
this method can eliminate the burden of running multicast protocol in
the underlay network, it has a significant disadvantage: large waste
of bandwidth, especially in big-sized data center where there are
many receivers.
Bit Index Explicit Replication (BIER) [I-D.ietf-bier-architecture] is
an architecture that provides optimal multicast forwarding through a
"BIER domain" without requiring intermediate routers to maintain any
multicast related per-flow state. BIER also does not require any
explicit tree-building protocol for its operation. A multicast data
packet enters a BIER domain at a "Bit-Forwarding Ingress Router"
(BFIR), and leaves the BIER domain at one or more "Bit-Forwarding
Egress Routers" (BFERs). The BFIR router adds a BIER header to the
packet. The BIER header contains a bit-string in which each bit
represents exactly one BFER to forward the packet to. The set of
BFERs to which the multicast packet needs to be forwarded is
expressed by setting the bits that correspond to those routers in the
BIER header.
The following section tries to proposes how to take full advantage of
BIER to implement BUM services in data centers.
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2. Convention and 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 [RFC2119].
The terms about BIER are defined in [I-D.ietf-bier-architecture].
The terms about NVO3 are defined in [RFC7365].
Here tries to list the most common terminology mentioned in this
draft.
BIER: Bit Index Explicit Replication(Bit Index Explicit Replication
(The overall architecture of forwarding multicast using a Bit
Position).
NVE: Network Virtualization Edge, which is the entity that implements
the overlay functionality. An NVE resides at the boundary between a
Tenant System and the overlay network.
VXLAN: Virtual eXtensible Local Area Network
VNI: VXLAN Network Identifier
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3. BIER in data centers
This section tries to describe how to use BIER as an optimal scheme
to forward the broadcast, unknown and multicast (BUM) packets when
they arrive at the NVE.
The principle of using BIER to forward BUM traffic is that: it
requires each NVE to have a mapping between the VXLAN Virtual Network
Instances (VNI) and the bit-string in which each bit represents
exactly one remote NVE to forward the packet to. On other words,
this requires the underlay network to support BIER which already be
elaborated in [I-D.ietf-bier-architecture].
Already mentioned above, BIER requires no explicit tree-building
protocols and maintains no multicast related per-flow state on the
end nodes and intermediate nodes, just extends the IGP protocol or
BGP protocol to advertise BIER-specific information to form BIER
forwarding table in the BIER forwarding routers, such as NVEs and
intermediate nodes in the data centers.
More importantly, as for how each NVE knows the other remote NVEs
that belong to the same virtual network can also be discovered by
additional BIER extensions. The following sections describe how to
extend IGP protocol and BGP protocol to advertise VXLAN-specific
information to tell each NVE where the other NVEs are in the same
virtual network. As a result of this advertisement, each NVE creates
the mapping between the VXLAN Virtual Network Instances (VNI) and the
bit-string in which each bit represents exactly one remote NVE to
forward the packet to.
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4. BIER IS-IS extension for VXLAN-specific information
Specifically, in [I-D.ietf-bier-isis-extensions], there defines a new
BIER Info sub-TLV which is illustrated in Figure 2. Here, extending
a VXLAN-specific sub-sub-TLV to current BIER Info sub-TLV for IS-IS,
a reference format is illustrated in Figure 3.
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 | subdomain-id | BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: IS-IS BIER Info sub-TLV extensions for BIER-specific
information
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VXLAN Network Identifier | Res |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: IS-IS VXLAN sub-sub-TLV extensions for VXLAN-specific
information
Type:
indicates VXLAN sub-sub-TLV
Length: 1 cotet.
VXLAN Network Idenfifier:
indicates a virtual subnet
Then NVEs and intermediate nodes flood this VXLAN-specific sub-sub-
TLV together with BIER Info sub-TLV through IS-IS in overlay network.
When one NVE receives this IS-IS advertisement, this NVE builds a
mapping between the receiving VNI in the VXLAN-specific sub-sub-TLV
and the bit-string which represents the sending NVE and can extract
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from the BIER Info sub-TLV. Once this NVE receives some other IS-IS
advertisements which include the same VXLAN-specific sub-sub-TLV, it
updates the bit-string in the mapping and adds the corresponding
sending NVEs to the updated bit-string.
After finishing the above IS-IS flooding, each NVE knows where are
the remote NVEs in the same virtual network. When receiving BUM
traffic from the attached tenant, each NVE knows exactly how to
forward this traffic to.
This can be used in both IPv4 network and IPv6 network.
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5. BIER OSPF extension for VXLAN-specific information
Specifically, in [I-D.ietf-bier-ospf-bier-extensions], there defines
a new BIER Info sub-TLV as well. Here, extending a VXLAN-specific
sub-sub-TLV to current BIER Info sub-TLV for OSPF, a reference format
is also illustrated in Figure 3.
Then NVEs and intermediate nodes flood this VXLAN-specific sub-sub-
TLV together with BIER Info sub-TLV through OSPF in overlay network.
When one NVE receives this OSPF advertisement, this NVE builds a
mapping between the receiving VNI in the VXLAN-specific sub-sub-TLV
and the bit-string which represents the sending NVE and can extract
from the BIER Info sub-TLV. Once this NVE receives some other OSPF
advertisements which include the same VXLAN-specific sub-sub-TLV, it
updates the bit-string in the mapping and adds the corresponding
sending NVEs to the updated bit-string.
After finishing the above OSPF flooding, each NVE knows where are the
remote NVEs in the same virtual network. When receiving BUM traffic
from the attached tenant, each NVE knows exactly how to forward this
traffic to.
This can be used in both IPv4 network and IPv6 network.
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6. BIER BGP extension for VXLAN-specific information
Specifically, in [I-D.ietf-bier-idr-extensions], there defines a new
BGP path attribute referred to as the BIER attribute. Here,
extending a VXLAN-specific sub-TLV to current BIER attribute TLV for
BGP, a reference format is also illustrated in Figure 3.
Then NVEs and intermediate nodes flood this VXLAN-specific sub-TLV
together with BIER attribute TLV through BGP in overlay network.
When one NVE receives this BGP attribute, this NVE builds a mapping
between the receiving VNI in the VXLAN-specific sub-TLV and the bit-
string which represents the sending NVE and can extract from the BIER
attribute TLV. Once this NVE receives some other BIER attribute TLV
which include the same VXLAN-specific sub-TLV, it updates the bit-
string in the mapping and adds the corresponding sending NVEs to the
updated bit-string.
After finishing the above BGP advertisement, each NVE knows where are
the remote NVEs in the same virtual network. When receiving BUM
traffic from the attached tenant, each NVE knows exactly how to
forward this traffic to.
This can be used in both IPv4 network and IPv6 network.
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7. Considerations on BIER in data centers
TBD
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8. Security Considerations
It will be considered in a future revision.
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9. IANA Considerations
There need a new Type for VXLAN sub-sub-TLV.
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10. References
10.1. Normative References
[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>.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, DOI 10.17487/
RFC4601, August 2006,
<http://www.rfc-editor.org/info/rfc4601>.
[RFC5015] Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
"Bidirectional Protocol Independent Multicast (BIDIR-
PIM)", RFC 5015, DOI 10.17487/RFC5015, October 2007,
<http://www.rfc-editor.org/info/rfc5015>.
[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3
Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
<http://www.rfc-editor.org/info/rfc7348>.
[RFC7365] Lasserre, M., Balus, F., Morin, T., Bitar, N., and Y.
Rekhter, "Framework for Data Center (DC) Network
Virtualization", RFC 7365, DOI 10.17487/RFC7365,
October 2014, <http://www.rfc-editor.org/info/rfc7365>.
10.2. Informative References
[I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., Przygienda, T., and
S. Aldrin, "Multicast using Bit Index Explicit
Replication", draft-ietf-bier-architecture-02 (work in
progress), July 2015.
[I-D.ietf-bier-idr-extensions]
Xu, X., Chen, M., Patel, K., Wijnands, I., and T.
Przygienda, "BGP Extensions for BIER",
draft-ietf-bier-idr-extensions-00 (work in progress),
September 2015.
[I-D.ietf-bier-isis-extensions]
Ginsberg, L., Aldrin, S., Zhang, J., and T. Przygienda,
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"BIER support via ISIS",
draft-ietf-bier-isis-extensions-00 (work in progress),
April 2015.
[I-D.ietf-bier-ospf-bier-extensions]
Psenak, P., Kumar, N., Wijnands, I., Dolganow, A.,
Przygienda, T., Zhang, J., and S. Aldrin, "OSPF Extensions
For BIER", draft-ietf-bier-ospf-bier-extensions-00 (work
in progress), April 2015.
[I-D.ietf-bier-use-cases]
Kumar, N., Asati, R., Chen, M., Xu, X., Dolganow, A.,
Przygienda, T., arkadiy.gulko@thomsonreuters.com, a.,
Robinson, D., and V. Arya, "BIER Use Cases",
draft-ietf-bier-use-cases-01 (work in progress),
August 2015.
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Authors' Addresses
Cui Wang
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China
Email: wang.cui1@zte.com.cn
Zheng Zhang
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China
Email: zhang.zheng@zte.com.cn
Fangwei Hu
ZTE Corporation
Email: hu.fangwei@zte.com.cn
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