BIER WG C. Wang
Internet-Draft Z. Zhang
Intended status: Standards Track ZTE Corporation
Expires: September 16, 2016 A. Qu
March 15, 2016
BIER Ethernet
draft-wang-bier-ethernet-01
Abstract
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. When a multicast
data packet enters the BIER domain, the BFIR determines the BFERs to
which the packet needs to be sent. Then the BFIR encapsulates the
packet in a BIER header and forwards the packet according to the
BIFTs. Currently, there is a BIER-MPLS solution to transmit
multicast traffic using MPLS label indication. Alternatively, this
document tries to propose a solution named BIER Ethernet to support
BIER forwarding in Ethernet network.
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 September 16, 2016.
Copyright Notice
Copyright (c) 2016 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Convention and Terminology . . . . . . . . . . . . . . . . . . 4
3. BIER Ethernet Header . . . . . . . . . . . . . . . . . . . . . 5
4. Imposing and processing the BIER Ethernet header . . . . . . . 8
5. Control Plane Considerations about BIER Ethernet . . . . . . . 9
6. BIER Ethernet Considerations . . . . . . . . . . . . . . . . . 11
6.1. BIER Ethernet for Traffic Enginerring . . . . . . . . . . 11
6.2. BIER Ethernet for Multicast VPN . . . . . . . . . . . . . 11
7. Assignment Considerations . . . . . . . . . . . . . . . . . . 12
7.1. IEEE Registration Authority Considerations . . . . . . . . 12
7.2. IANA Considerations . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
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 encapsulates a BIER header to the
packet. The BIER header contains a BitString in which each bit
represents exactly one BFER to forward the packet to.
Specifically, after encapsulating a BIER header to the original
multicast data packet, the BFIR and the intermediate BFRs as well as
the BFERs require to carry out the BIER forwarding procedures to the
BIER-encapsulated packet according to the information in the BIER
header. As described in [I-D.ietf-bier-architecture], each BFR
firstly should determine the packet's Subdomain-ID, BitStringLength
and Set ID information to locate the exact "Bit Index Forwading
Table" (BIFT), and then do the subsequent procedures in terms of
BitString and the found BIFT.
However the existing draft requires MPLS label preceding the BIER
header and using Bottom label to carry BIER forwarding information is
not clean cut deign.
Hence we should design BIER header that holds all BIER forwarding
related information, and just let MPLS as an independent layer
protocol to help BIER forwarding as it does for IPv4/IPv6/IPmcast
traffic.
Additionally, the BIER forwarding capability will be also introduced
in enterprise/data center, such feature may be newly implemented in
switch ASICs, with clean cut design using BIER-ethernet draft, the
implementation will be more clean as well.
So this document tries to propose this kind of BIER header which
contains significant BIER information directly such as Subdomain-ID,
BitStringLength and Set ID as well as BitString. It is applicable
when a given BIER domain is an Ethernet network.
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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].
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3. BIER Ethernet Header
The BIER Ethernet header is shown in Figure 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1 0 1| Ver | Len | Entropy |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subdomain-ID | Set ID | BSL | TTL | TOS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|OAM| Reserved | Proto | BFIR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BIER Ethernet Header
First nibble: The first 4 bits of the header are set to 0101; this
ensures that the BIER header will not be confused with an IP header
or with the header of a pseudowire packet.
Ver: this 4-bit field identifies the version of the BIER header.
Len: This 4-bit field encodes the length of BIER Ethenet header.
Entropy: This 20-bit field specifies an "entropy" value that can be
used for load balancing purposes. The BIER forwarding process may do
equal cost load balancing, but the load balancing procedure MUST
choose the same path for any two packets have the same entropy value.
Subdomain-ID: unique value identifying the BIER Subdomain within
the BIER domain, as described in section 1 of
[I-D.ietf-bier-architecture].
Set ID: indicates the packet's Set Identifier.
BSL: indicates the packet's BitStringLength.
TTL: Time to Live
TOS: Type of Service. It can be used to differentiate services to
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different BIER packets.
BitString: together with the packet's Set ID, identifies the
destination BFERs for this packet.
OAM: These two bits are used for the passive performance
measurement marking method.
Reserved: These 10 bits are currently unused. They SHOULD be set
to zero upon transmission, and MUST be ignored upon reception.
Proto:This 4-bit field identifies the type of the payload. (The
"payload" is the packet or frame immediately following the BIER
header.)
BFIR-id: By default, this is the BFR-id of the BFIR, in the
Subdomain to which the packet has been assigned. The BFR-id is
encoded in the 16-bit field as an unsigned integer in the range
[1,65535].
Furthermore, BIER Ethernet encapsulated packet has the following
format. The original multicast data packet is encapsulated with two
headers (starting from the outermost header): Outer Ethernet Header +
BIER Ethernet Header. Figure 2 is an example of an outer Ethernet
Header. The outer VLAN tag is optional. In some situations, there
may be some other encapsulation headers before the multicast data
packet and after the BIER Ethernet header.
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
Outer Ethernet Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Destination MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Destination MAC Address | Outer Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Outer Source MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|OptnlEthtype = C-Tag 802.1Q | Outer.VLAN Tag Information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ethertype = TBD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Outer Ethernet Header
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Ethertype: requires a new Ethertype for BIER Ethernet header.
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4. Imposing and processing the BIER Ethernet header
When a BFIR receives a multicast packet from outside the BIER domain,
the BFIR carries out the following procedure:
1.By consulting the "multicast flow overlay", the BFIR determines the
set of BFERs that must receive the packet.
2.By consulting the "BIER layer", the BFIR determines the packet's
Subdomain, BitStringLength, Set Identifier and BitString information.
The BFERs have the same Set Identifier can be encoded into the same
BitString.
3.Using information provided by the routing underlay associated with
the packet's BIER information, the BFIR determines the next hop for
each (Set Identifier, the BitString) combination, and copies packet
to each Set Identifier.
4.Before transmitting the packet to the next hop, the BFIR updates
the BitString information and encapsulates the BIER Ethernet header
to the multicast packet.
When an intermediate BFR receives a BIER Ethernet encapsulated
packet, it acquires Subdomain-ID, BitStringLength as well as Set
Identifier information directly from the BIER Ethernet header to
determine the BIFT, and then forwards the received BIER packet
according to the procedures described in
[I-D.ietf-bier-architecture].
When a BFR receives a BIER Ethernet encapsulated packet whose
Subdomain ID, Set Identifier and BitString identify the BFR itself,
then the BFR is also a BFER for that packet. As a BFER, it must
decapsulate the BIER Ethernet header, and pass the original multicast
packet out.
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5. Control Plane Considerations about BIER Ethernet
As described in the BIER OSPF extensions
[I-D.ietf-bier-ospf-bier-extensions] and BIER ISIS extensions
[I-D.ietf-bier-isis-extensions], they already define BIER Info Sub-
TLV as the following format in Figure 3(take the ospf extensions for
example).
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-domain-ID | MT-ID | BFR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
Figure 3: BIER Info Sub-TLV
To implement BIER Ethernet, the control plane, except the
advertisements of BIER Info Sub-TLV, should have advertisements about
BitStringLengths information the sending BFR supports. A reference
format of BSL Sub-sub-TLV is illustrated in Figure 4 (take the ospf
extensions for example as well).
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|BSL Identifier | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: BSL Sub-sub-TLV
Type: value of 1 indicating BSL Sub-sub-TLV for BIER Ethernet
encapsulation.
Len: This 8-bit field encodes the length of this sub-sub-TLV.
BSL Identifier: indicating the BSL the sending BFR supporting.
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The sending BFR may support one or several BSLs, as following:
00000001: represents BSL 64 bits;
00000010: represents BSL 128 bits;
00000100: represents BSL 256 bits;
00001000: represents BSL 512 bits;
00010000: represents BSL 1024 bits;
00100000: represents BSL 2048 bits;
01000000: represents BSL 4096 bits;
Each bit represents one BSL. When there are two or more bits set,
that means the sending BFR supports more than one BSL. For example,
if the BSL Identifier is 00010101, it means the sending BFR supports
1024 bits, 256 bits and 64 bits.
Additionally, the similar BSL Sub-sub-TLV extension can be introduced
in ISIS extension and IDR extension for implementing BIER Ethernet.
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6. BIER Ethernet Considerations
6.1. BIER Ethernet for Traffic Enginerring
Specifically, BIER-TE encapsulation format may be the same as BIER
encapsulation. However,how to interpret the BitString is totally
different. Hence, BIER-Ethernet encapsulation MUST need one
identifier to be assigned to identify the BIER header is for BIER
forwarding or BIER-TE forwarding. For example, one bit in Reserved
field can be reserved for this purpose.
6.2. BIER Ethernet for Multicast VPN
In MVPN, the P-tunnels are used for carrying multicast traffic across
backbone. BIER tunnel Type is newly defined in [I-D.ietf-bier-mvpn].
The BIER Encapsulation used for multicast tunnel is independant of
the (upstream assigned) MPLS label. Hence, BIER-Ethernet can also be
used as P-Tunnel. In other words, there may need a new Tunnel Type
to identify BIER-Ethernet Tunnel type, or a new flag to distinguish
BIER-MPLS tunnel and BIER-Ethernet Tunnel.
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7. Assignment Considerations
7.1. IEEE Registration Authority Considerations
This document requests the IEEE Registration Authority to assign a
new Ethertype for BIER Ethernet Header.
7.2. IANA Considerations
This document requires new IANA allocation for BSL Sub-sub-TLV
extension in different routing protocol.
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8. Acknowledgements
The authors would like to thank IJsbrand Wijnands,Tony Przygienda and
Andrew Qu for their ideas and contribution to this document.
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9. References
9.1. 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>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<http://www.rfc-editor.org/info/rfc4915>.
9.2. Informative References
[I-D.ietf-bier-architecture]
Wijnands, I., Rosen, E., Dolganow, A., P, T., and S.
Aldrin, "Multicast using Bit Index Explicit Replication",
draft-ietf-bier-architecture-03 (work in progress),
January 2016.
[I-D.ietf-bier-isis-extensions]
Ginsberg, L., P, T., Aldrin, S., and J. Zhang, "BIER
support via ISIS", draft-ietf-bier-isis-extensions-01
(work in progress), October 2015.
[I-D.ietf-bier-mpls-encapsulation]
Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J., and
S. Aldrin, "Encapsulation for Bit Index Explicit
Replication in MPLS Networks",
draft-ietf-bier-mpls-encapsulation-03 (work in progress),
February 2016.
[I-D.ietf-bier-mvpn]
Rosen, E., Sivakumar, M., Aldrin, S., Dolganow, A., and T.
P, "Multicast VPN Using BIER", draft-ietf-bier-mvpn-02
(work in progress), December 2015.
[I-D.ietf-bier-ospf-bier-extensions]
Psenak, P., Kumar, N., Wijnands, I., Dolganow, A., P, T.,
Zhang, J., and S. Aldrin, "OSPF Extensions For BIER",
draft-ietf-bier-ospf-bier-extensions-01 (work in
progress), October 2015.
[I-D.ietf-ospf-prefix-link-attr]
Psenak, P., Gredler, H., rjs@rob.sh, r., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
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Advertisement", draft-ietf-ospf-prefix-link-attr-13 (work
in progress), August 2015.
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Authors' Addresses
Cui(Linda) Wang
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China
Email: wang.cui1@zte.com.cn
Zheng(Sandy) Zhang
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China
Email: zhang.zheng@zte.com.cn
Andrew Qu
2860 Junction Ave
San JoseGBP[not] CA 95134
Email: laodulaodu@gmail.com
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