Internet DRAFT - draft-huang-bier-te-encapsulation-extension
draft-huang-bier-te-encapsulation-extension
INTERNET-DRAFT R. Huang
Intended Status: Standards Track N. Xia
Expires: April 26, 2018 N. Wei
Huawei
October 27, 2017
Encapsulation and Extension for BIER-TE
draft-huang-bier-te-encapsulation-extension-00
Abstract
This document proposes to extend the BIER packet format and some
BIER-TE forwarding rules specified in BIER traffic engineering
architecture.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. BIER-TE Extension . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Set Identifier . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Packet Travel Rule . . . . . . . . . . . . . . . . . . . . 3
2.3. The Bit Index Forwarding Table (BIFT) . . . . . . . . . . . 4
3. BIER-TE Encapsulation . . . . . . . . . . . . . . . . . . . . . 4
3.1 Header . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Header Extension . . . . . . . . . . . . . . . . . . . . . 5
4. BIER-TE Forwarding Example . . . . . . . . . . . . . . . . . . 5
5 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
7 References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1 Normative References . . . . . . . . . . . . . . . . . . . 7
7.2 Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1 Introduction
[I-D.eckert-bier-te-arch] specifies BIER-TE: Traffic Engineering for
Bit Index Explicit Replication (BIER). It shares part of the
architecture with basic BIER as described in [I-D.ietf-bier-
architecture], but uses every BitPosition of the BitString of a BIER-
TE packet indicates one or more adjacencies instead of a BFER as in
BIER.
BIER-TE proposes to share the packet format with BIER. Since it
consumes much more BitPositions than BIER, it has scalability issue.
For example, the maximum BitString length (BSL) that one BIER-TE
packet can carry is 256, which means that one BIER-TE packet cannot
pass over 256 numbered adjacencies. This is not a problem in BIER as
for BIER all the BitPositions are either BFIRs or BFERs.
To alleviate this issue, one direct way is to allow one packet can
travel over more than one Set Indentifier (SI) area. Based on it,
this document proposes an encapsulation to solve this issue by
extending the BIER packet format specified in [I-D.ietf-bier-mpls-
encapsulation] and some BIER-TE forwarding rules in [I-D.eckert-bier-
te-arch].
1.1 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 RFC 2119 [RFC2119].
2. BIER-TE Extension
2.1. Set Identifier
As described in [I-D.ietf-bier-architecture], Set Identifier (SI) is
used to indicate the set of BFERs that one BIER packet can reach. In
this document, SI is the segment area index. The number of
adjacencies assigned BitPosition inside one segment area is not
larger than the value of BSL.
2.2. Packet Travel Rule
As described in [I-D.eckert-bier-te-arch], packets that need to be
sent to BFER in different SI require different BIER packets. If a
packet travel from one BFIR to the BFERs with different SIs, the path
for that packet can only be scheduled for those adjacencies belonging
to the same SI carried by the packet, or some adjacencies may be
assigned with multiple BitPosition as described in [I-D.xiong-bier-
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te-forwarding].
In this document, a packet is allowed to travel to multiple areas
with different SIs. To do that, multiple bitstrings belonging to
different SIs may be carried in the packet header. Considering the
overhead of the BIER-TE header, the total length of all the
bitstrings that a packet can carry is the maximum BSL 4096. For
example, if the BSL is 256, then a packet can pass over at most 16
segment areas. If the topology of the network is well planned, this
design is sufficient for use.
If all of the BitPosition in one of the Bitstrings are set to 0, it
means that the packet will not travel to this area any more. The BFR
could remove that BitString when forwarding the packet to the
adjacencies.
2.3. The Bit Index Forwarding Table (BIFT)
The BIFT is used as described in [I-D.eckert-bier-te-arch], which is
indexed by SI:BitPosition.
3. BIER-TE Encapsulation
3.1 Header
The BIER-TE encapsulation is illustrated as following. It reuses the
format defined in [I-D.ietf-bier-mpls-encapsulation].
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|E| DSCP | Proto | BFIR-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BitString (first 32 bits) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ BitString (last 32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Field (variable) |
B: This 1-bit field identifies a BIER head(0) or a BIER-TE
head(1).
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E: This 1-bit field identifies weather there is a extension field
following the head.
3.2. Header Extension
The header extension is illustrated as following.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| The information of BitPostions |
~ in one specific segment area ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... |
This header extension uses TSV structure. The information of the
BitPositions in one specific segment area (SI) is only carried in one
TSV.
Type: 16 bits It defines the type of the extension. In this
document, the type of TBD is specified.
Length: 16 bits It indicates the total octets of the information
of BitPostions in one specific segment area.
Information of BitPostions in one specific segment area: This
contains the information of the BitString in the specific segment
area other than the previous header. In this document, the details
of this field doesn't specified. It could be several BitStrings
belonging to different segment areas populated together or It
could be another BIER header nested in this extension. In the
latter case, it will be easier for BFRs to pop the unused header.
4. BIER-TE Forwarding Example
Here, the same example from [I-D.eckert-bier-te-arch] is used as
following. Assume the BSL is 8 (The BSL of 8 is used only in this
example). pXX-Y indicate the BitPosition-SI assigned by the BIER-TE
controller host to adjacencies in the BIER-TE topology.
[Bier-Te Controller Host]
/ |
v v v
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|p5-2 p1-1 |
+- BFIR2 --+ |
| | p2-1 p3-1| LAN2
| +-- BFR3 --+ |
| | | p4-1 p6-1 |
Src -+ +-- BFER1 --+
| |p7-1 p5-1| |
| +-- BFR4 --+ +-- Rcv1
| | | |
| |
|p6-2 p8-1|
+- BFIR1 --+ |
| +-- BFR5 --+ p3-2 p4-2 |
LAN1 |p1-2 p2-2 +-- BFER2 --+
| +-- Rcv2
|
LAN3
IP |..... BIER-TE network......| IP
Traffic needs to flow from BFIR2 towards Rcv1, Rcv2. The controller
determines it wants to pass across the following paths:
-> BFER1 ---------------> Rcv1
BFIR2 -> BFR3
-> BFR4 -> BFR5 -> BFER2 -> Rcv2
The BitString is set up in BFIR2 with 2 sets of BitStrings: S1:(p2,
p4, p5, p6); S2:(p1, p3, p4). BFIR2 forwards based on that BitString.
BFR4 has the following BIFT:
p8-1: forward_connected(BFIR1) P1-2: forward_connected(BFR5)
BFR5 sees the sets of BitStrings: S1: (0...0); S2:(p3, p4). It
pops the BitString of S1 and forward the packet out to BFER2.
Other forwarding rules are similar to those specified in [I-
D.eckert-bier-te-arch].
5 Security Considerations
TBD
6 IANA Considerations
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TBD.
7 References
7.1 Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[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-08
(work in progress), September 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-10 (work in progress), October 2017.
7.2 Informative References
[I-D.zcxh-bier-te-forwarding] Zhu, Y., Chen, H., Xiong, Q., and F.
Hu, "BIER-TE Forwarding", draft-zcxh-bier-te-forwarding-00
(work in progress), October 2017.
Authors' Addresses
Rachel Huang
Huawei
101 Software Avenue, Yuhua District
Nanjing 210012
China
EMail: rachel.huang@huawei.com
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Nu Xia
Huawei
101 Software Avenue, Yuhua District
Nanjing 210012
China
EMail: xianu@huawei.com
Naiwen Wei
Huawei
China
EMail: weinaiwen@huawei.com
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