Internet DRAFT - draft-xiong-bier-te-encapsulation
draft-xiong-bier-te-encapsulation
BIER WG Quan. Xiong
Internet-Draft Fangwei. Hu
Intended status: Standards Track Zheng. Zhang
Expires: January 19, 2018 ZTE Corporation
July 18, 2017
BIER-TE Encapsulation
draft-xiong-bier-te-encapsulation-00.txt
Abstract
Traffic Engineering for Bit Index Explicit Replication (BIER-TE)
shares part of architecture , definition and packet format with Bit
Index Explicit Replication (BIER) according to the introduce in
[I-D.eckert-bier-te-arch]. BIER-TE supports the traffic engineering
by explicit hop-by-hop forwarding and loose hop forwarding of
packets.[I-D.ietf-bier-mpls-encapsulation] specifies a BIER
encapsulation that BIER header contains a bitstring in which each bit
represents exactly one egress router in the domain.
This document proposes a set of extensions to BIER encapsulation for
BIER-TE. The extensions define the BIER-TE header which contains
serveral bitstrings and each bit in each bitstring represents one or
more adjacencies in BIER-TE domain. The encapsulation can be used
both in an MPLS network and a non-MPLS 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 January 19, 2018.
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
3. BIER-TE Encapsulation . . . . . . . . . . . . . . . . . . . . 3
3.1. BitString Sub-TLV . . . . . . . . . . . . . . . . . . . . 4
4. Processing Rules with the BIER-TE Encapsulation . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Traffic Engineering for Bit Index Explicit Replication (BIER-TE)
shares part of architecture, definition and packet format with Bit
Index Explicit Replication (BIER) according to the introductions in
[I-D.eckert-bier-te-arch]. But BIER-TE supports the traffic
engineering by explicit hop-by-hop forwarding and loose hop
forwarding of packets. The BIER-TE controller host determines and
assigns the BitPositions to the adjacencies which explicit paths
passing through.
[I-D.ietf-bier-mpls-encapsulation] specifies a BIER encapsulation
that BIER header contains a bitstring in which each bit represents
exactly one egress router in the domain. But in BIER-TE every
BitPosition of the BitString of a BIER-TE packet indicates one or
more adjacencies instead of an egress router as in BIER. That MUST
be a huge number of adjacencies from BFIR to all BFERs and the
BitString in BIER encapsulation is related to SD,BSL and SI
combination. For these distinct SD,BSL and SI combinations, there
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must be more than one BitStrings and the BFR must make many copies of
multicast data packet. Even more, BitPositions of all adjacencies
passing through BFIR to a BFER MAY be carried in different BitStrings
and within the different packets.
Based on the discussion above, this document proposes a set of
extensions to BIER encapsulation for BIER-TE. The extensions define
the BIER-TE header which contains one or more bitstrings and each bit
in each bitstring represents one or more adjacencies in BIER-TE
domain.The encapsulation can be used both in an MPLS network and a
non-MPLS network.
2. 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].
2.1. Terminology
The terminology is defined as [I-D.ietf-bier-architecture],
[I-D.eckert-bier-te-arch] and [I-D.ietf-bier-mpls-encapsulation].
3. BIER-TE Encapsulation
The BIER-TE header is shown in Figure 1. It extends the BIER
encapsulation and adds one or more BitString Sub-TLVs.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BIFT-id | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Nibble | Ver | BSL | Entropy |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|OAM|B|Rsv| DSCP | Proto | BFIR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString Sub-TLVs (variable) |
+- -+
| |
Figure 1:BIER-TE Header Format
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B bit : 1bit, indicates BIER-TE packet when it is set. As the
[I-D.eckert-bier-te-arch] mentioned, when a BFR receives a packet, it
needs to interpret the BitString of a BIER-TE packet differently from
a BIER packet and it is necessary to distinguish BIER from BIER-TE
packets.
BitString Sub-TLV: identifies BitString related information and each
BitString Sub-TLV corresponds to a particular combination of SD, BSL,
SI and bitstring.The format details see section 3.1.
The definition of other fields is the same with
[I-D.ietf-bier-mpls-encapsulation].
3.1. BitString Sub-TLV
This document proposes BitString Sub-TLV for BIER-TE header. The TLV
is optional. The format of the new sub-TLV is shown in Figure 2 and
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubDomainId | SI | BSL | Rsv |N|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (variable) |
+- -+
| |
Figure 2: BitString Sub-TLV Format 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BIFT-id | Rsv |N|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (variable) |
+- -+
| |
Figure 3: BitString Sub-TLV Format 2
The fields in the format are:
SD : 8bits, indicates the Sub-DomainId of the BitString in the range
[0,255].
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SI : 10bits,indicates the Set Identification ofthe BitString in the
range [0,1023].
BSL : 4bits,indicates the length in bits of the BitString. If k is
the length of the BitString, the value of this field is log2(k)-5.
The values are supported as follows:
1: 64 bits
2: 128 bits
3: 256 bits
4: 512 bits
5: 1024 bits
6: 2048 bits
7: 4096 bits
N : 1bit, indicates that there are one or more BitString Sub-TLVs
immediately preceding the TLV when it is set.
BitString: variable, identifies the collection of the adjacencies
from BFIR to all BFERs and each BitString is related to SD,BSL and SI
combination or BIFT-id of the packet.
BIFT-id: 22bits,The BIFT-id represents a particular Bit Index
Forwarding Table (BIFT); see Section 6.4 of
[I-D.ietf-bier-architecture]. Each BIFT corresponds to a particular
combination of SD,BSL and SI.
4. Processing Rules with the BIER-TE Encapsulation
As defined in [I-D.eckert-bier-te-arch], the BIER-TE operations
consists of four layers: the "Multicast Flow Overlay", the "BIER-TE
Controller Host", the "Routing Underlay" and the "BIER-TE forwarding
layer".The BIER-TE Multicast flow processing with BIER-TE
encapsulation is as follows:
1. The BIER-TE Controller assigns the BitPositions for adjacencies
based on the operator policy and populates the BitPositions to the
BIFT of each BFR as mentioned in [I-D.eckert-bier-te-arch].
2. The Multicast Flow Overlay determines the BFIR and a set of BFERs
and sends this information to the BIER-TE controller.
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3. The BIER-TE controller calculates the explicit paths based on
algorithms from BFIR to all BFERs.
4. The BIER-TE controller gets all adjacencies which the paths
passing through and determines the list of bitstrings based on the
SD,BSL and SI combination and BitPositions/adjacencies assignments.
Each bit/BitPosition in each bitstring represents one or more
adjacencies in BIER-TE domain. The BitPositions of the adjacencies
that have the same SD,BSL and SI combination can be encoded into the
same BitString. It then pushes the BitStrings into the BFIR.
5. When a BFIR receives a multicast packet from outside the BIER-TE
domain, the BFIR carries out the following procedure:
a. The BFIR makes a copy of the multicast data packet and
encapsulates the copy in a BIER-TE header as this document
proposes(see Section 3). The BitStrings which received from the
BIER-TE controller are mapped to the field of BitString Sub-TLVs.
b. The BFIR checks the BIER-TE header and get the BitString Sub-TLVs
infomation. Then traverses the Sub-TLVs and related local BIFT which
has the same SD,BSL and SI combination. The packet may then be
transmitted to adjacencies/neighboring BFRs and applies to that copy
with the forwarding procedure of [I-D.eckert-bier-te-arch].
5. Security Considerations
TBD.
6. IANA Considerations
TBD.
7. Acknowledgements
TBD.
8. Normative References
[I-D.eckert-bier-te-arch]
Eckert, T., Cauchie, G., Braun, W., and M. Menth, "Traffic
Engineering for Bit Index Explicit Replication BIER-TE",
draft-eckert-bier-te-arch-05 (work in progress), June
2017.
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[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-07 (work in
progress), June 2017.
[I-D.ietf-bier-mpls-encapsulation]
Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J.,
Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
Explicit Replication in MPLS and non-MPLS Networks",
draft-ietf-bier-mpls-encapsulation-07 (work in progress),
June 2017.
[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>.
Authors' Addresses
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan, Hubei 430223
China
Phone: +86 27 83531060
Email: xiong.quan@zte.com.cn
Fangwei Hu
ZTE Corporation
No.889 Bibo Rd
Shanghai 201203
China
Phone: +86 21 68896273
Email: hu.fangwei@zte.com.cn
Zheng Zhang
ZTE Corporation
No.50 Software Avenue,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Phone: +86 025 88016576
Email: zhang.zheng@zte.com.cn
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