Network Working Group B. Sarikaya
Internet-Draft F. Xia
Expires: November 16, 2015 Huawei USA
S. Fan
China Telecom
May 15, 2015
DHCP Options for Configuring Tenant Identifier and Multicast Addresses
in Overlay Networks
draft-sarikaya-nvo3-dhc-vxlan-multicast-03.txt
Abstract
This document defines DHCPv4 and DHCPv6 options for assigning VXLAN
Network Identifier and multicast addresses for overlay networks such
as the Virtual eXtensible Local Area Network (VXLAN). New DHCP
options are defined which allow a Network Virtualization Edge to
request any source multicast address and tenant identifier for the
newly created virtual machine.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview of the protocol . . . . . . . . . . . . . . . . . . 4
4. DHCPv6 Options . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. VXLAN Network Identifier Option . . . . . . . . . . . . . 6
4.2. DHCPv6 VXLAN Multicast Address Option . . . . . . . . . . 6
5. DHCPv4 Options . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. VXLAN Network Identifier Option . . . . . . . . . . . . . 7
5.2. VXLAN Multicast Address Option . . . . . . . . . . . . . 8
6. Client Operation . . . . . . . . . . . . . . . . . . . . . . 9
7. Server Operation . . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. IANA considerations . . . . . . . . . . . . . . . . . . . . . 10
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
11.1. Normative References . . . . . . . . . . . . . . . . . . 11
11.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Data center networks are being increasingly used by telecom operators
as well as by enterprises. Usually these networks are organized as
one large Layer 2 network in a single building. In some cases such a
network is extended geographically using Virtual Local Area Network
(VLAN) technologies still as an even larger Layer 2 network
connecting the virtual machines (VM), each with its own MAC address.
Another important requirement was growing demand for multitenancy,
i.e. multiple tenants each with their own isolated network domain.
In a data center hosting multiple tenants, each tenant may
independently assign MAC addresses and VLAN IDs and this may lead to
potential duplication. At the same time, it is usually the Layer 3
network between the VMs run on different servers, whether these VMs
located inside the same DCs or different DCs. That is, the Layer3
switches inside DC and the Internet between DCs will isolate the
Layer2 network. By the way, as the granularity is based on VM and
the end-points may be deployed in different DCs, the existed VLAN ID
will be a big barrier as the max number is 4096.
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What we need is IP tunneling scheme based overlay network. In this
document we assume the Virtual eXtensible Local Area Network (VXLAN)
based overlay is used but the solution is valid for other overlay
networks such as NVGRE and others.
VXLAN overlays a Layer 2 network over a Layer 3 network. Each
overlay is identified by the VXLAN Network Identifier (VNI). This
allows up to 16M VXLAN segments to coexist within the same
administrative domain [RFC7348]. In VXLAN, each MAC frame is
transmitted after encapsulation, i.e. an outer Ethernet header, an
IPv4/IPv6 header, UDP header and VXLAN header are added. Outer
Ethernet header indicates an IPv4 or IPv6 payload. VXLAN header
contains 24-bit VNI.
It should be noted that in this document, VTEP plays the role of the
Network Virtualization Edge (NVE) according to NVO3 architecture for
overlay networks like VXLAN or NVGRE defined in [I-D.ietf-nvo3-arch].
NVE interfaces the tenant system underneath with the L3 network
called the Virtual Network (VN).
In order to deliver tenant traffic, NVE needs to know the VXLAN
Network Identifier (VNI) assigned to this tenant. In this document,
we use Dynamic Host Configuration Protocol (DHCP) for this purpose.
NVE needs VNI to encapsulate the packets that its virtual machines
generate. Since multi-tenancy requires independent address space for
each tenant. The address configuration mechanism, e.g. DHCP server
needs to keep track of VNI values assigned when assigning addresses
to the virtual machines (VM). It is possible for a VM to be
configured the same IPv4/IPv6 address as another VM belonging to a
different tenant.
As stated in NVO3 architecture document [I-D.ietf-nvo3-arch] for
tenant multicast (or broadcast) traffic, an NVE MUST maintain a per-
VN table of mappings and other information on how to deliver
multicast (or broadcast) traffic. Since we assume that the
underlying network supports IP multicast, the NVE could use IP
multicast to deliver tenant traffic. In such a case, the NVE would
need to know what IP underlay multicast address to use for a given
VN. By the way, the underlying network maybe can NOT support IP
multicast, in that case the VTEP should act as the node run multicast
protocol itself, for instance, PIM. But it will be beyond the scope
of this document.
In this document, we develop a protocol to assign multicast addresses
to the VXLAN tunnel end points or NVEs using Dynamic Host
Configuration Protocol (DHCP). Multicast communication in the
overlay network is used for sending broadcast MAC frames, e.g. the
Address Resolution Protocol (ARP) broadcast frame. Multicast
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communication can also be used to transmit multicast frames and
unknown MAC destination frames.
2. 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
terminology in this document is based on the definitions in
[RFC7348], [I-D.ietf-nvo3-arch] and [I-D.ietf-nvo3-nve-nva-cp-req].
3. Overview of the protocol
Multicast addresses to be assigned by the DHCP server are
administratively scoped multicast addresses, in IPv4 [RFC2365] and in
IPv6 [RFC4291]. The steps involved in the protocol are explained
below for IPv4:
Creation of a VM
In this step, NVE receives a request from the Network
Virtualization Authority (NVA)[I-D.ietf-nvo3-nve-nva-cp-req] to
create a Virtual Machine with a tenant identifier, e.g. VXLAN
Network Identifier or VNI.
DHCP Operation
NVE starts DHCP state machine by sending DHCPDISCOVER message to
the default router, e.g. the Top of Rack (ToR) switch or the
aggregation switch. ToR switch, aggregation switch could be DHCP
server or most possibly DHCP relay with DHCP server located
upstream. NVE MUST include Multicast Address options defined in
this document. NVE sends the parameter request list option with
the newly defined VXLAN Network Identifiers(VNI) DHCP Option to
request a value for VXLAN Network Identifier. DHCP server replies
with DHCPOFFER message. DHCP server sends VNI DHCP Option and
administratively scoped IPv4 multicast address. NVE checks this
message and if it sees the options it requested, DHCP server is
confirmed to support the multicast address options. DHCPREQUEST
message from NVE and DHCPACK message from DHCP server complete
DHCP message exchange. Different VXLAN Network Identifiers (VNI)
need different multicast groups (for load balancing). At the same
time, different VNIs need different address spaces for VM, that
is, two VMs belong to different VNIs probably have the same IP
address.
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NVE as Multicast Source
After receiving the required information, the NVE as multicast
source communicates with the edge router in order to build the
multicast tree.
NVE as Listener
After receiving the required information, the NVE as listener
communicates with the edge router by sending IGMP Report to join
the multicast group.
IPv6 operation is slightly different:
Creation of a VM
In this step, NVE receives a request from the NVA to create a
Virtual Machine with a tenant identifier or VNI.
DHCP Operation
NVE starts DHCP state machine by sending DHCPv6 Solicit message to
the default router, e.g. the Top of Rack (ToR) switch or
aggregation switch. ToR switch/aggregation switch could be DHCP
server or most possibly DHCP relay with DHCP server located
upstream. NVE MUST include the Option Request Option with
OPTION_VNI defined in this document to request a value for the
tenant id or VXLAN Network Identifier. NVE MUST include DHCPv6
VXLAN Multicast Address Option or OPTION_MA to request the
multicast address. DHCP server replies with DHCPv6 Advertise
message. NVE checks this message and if it sees the options it
requested, DHCP server is confirmed to support multicast address
options. DHCPv6 Request message from NVE and DHCPv6 Reply message
from DHCPv6 server complete DHCP message exchange.
NVE as Multicast Source
After receiving the required information, the NVE as multicast
source communicates with the edge router in order to build the
multicast tree.
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NVE as Listener
After receiving the required information, the NVE as listener
communicates with the edge router by sending MLD Report to join
the multicast group.
4. DHCPv6 Options
4.1. VXLAN Network Identifier Option
A DHCP VNI Option is defined 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_VNI | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VXLAN Network Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_VNI (TBD).
option-len 7.
VXLAN Network Identifier 3.
4.2. DHCPv6 VXLAN Multicast Address Option
The option allows the NVE to send solicited-node multicast address to
DHCP server and receive administratively scoped IPv6 multicast
address.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_MA | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 multicast address |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| reserved | Solicited Node Multicast Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_MA (TBD).
option-len 24.
IPv6 multicast address An IPv6 address.
reserved must be set to zero
Solicited Node Multicast Address as in RFC 4861.
5. DHCPv4 Options
5.1. VXLAN Network Identifier Option
The option allows the NVE to send the VNI to DHCP server.
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0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| a1 | a2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| a3 |
+-+-+-+-+-+-+-+-+
Option-code
VXLAN Network Identifier Option (TBD)
Option-len
3.
a1-a4
NVE as DHCP Client receives VNI value in a1-a3.
5.2. VXLAN Multicast Address Option
The option allows the NVE to receive administratively scoped IPv4
multicast address.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| a1 | a2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| a3 | a4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code
VXLAN Multicast Address Option (TBD)
Option-len
4.
a1-a4
VTEP as DHCP Client sets a1-a4 to zero, DHCP server sets a1-a4 to the multicast address.
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6. Client Operation
In DHCPv4, the client, VTEP MUST set 'htype' and 'chaddr' fields to
specify the client link-layer address type and the link-layer
address. The client must set the hardware type, 'htype' to 1 for
Ethernet [RFC1700] and 'chaddr' is set to the MAC address of the
virtual machine.
The client MUST request VXLAN Network Identifier Option in parameter
request list to receive the VXLAN network identifier value assigned
to the virtual machine by DHCP server.
In DHCPv6, the client MUST use OPTION_CLIENT_LINKLAYER_ADDR defined
in [RFC6939] to send the MAC address. In this option, link-layer
type MUST be set to 1 for Ethernet and link-layer address MUST be set
to the MAC address of VM. Note that in [RFC6939],
OPTION_CLIENT_LINKLAYER_ADDR is defined to be used in Relay-Forward
DHCP message. In this document this option MUST be sent in DHCPv6
Solicit message.
The client MUST request IPv6 VXLAN Network Identifier Option
OPTION_VNI in Option Request Option (ORO) to request the VXLAN
network identifier value assigned to the virtual machine by DHCP
server.
The Client MUST set IPv6 multicast address in DHCPv6 VXLAN Multicast
Address Option, OPTION_MA to zero.
The client MUST set Solicited Node Multicast Address to zero if the
neighbor discovery message is sent to all-nodes multicast address.
The client MUST set Solicited Node Multicast Address to the low-order
24 bits of an address of the destination if the neighbor discovery
message is sent to the solicited-node multicast address.
7. Server Operation
DHCPv4 server looks for VXLAN Network Identifier Option code in
parameter request list option in DHCPDISCOVER message from the
Client. DHCP server MUST add VXLAN Network Identifier Option in DHCP
OFFER message with VNI value assigned in a1-a3.
If DHCPv4 server is configured to support VXLAN multicast address
assignments, it SHOULD look for VXLAN Multicast Address Option in
DHCPDISCOVER message. The server MUST return in VXLAN Multicast
Address Option's a1-a4 an organization-local scope IPv4 multicast
address (239.192.0.0/14) [RFC2365]. The server MUST use the VNI
value for obtaining the organization-local scope IPv4 multicast
address. VNI value is directly copied to 239.192.0.0/14 if the first
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6 bits are zero, i.e. no overflow ranges need to be used. Otherwise,
either of 239.0.0.0/10, 239.64.0.0/10 and 239.128.0.0/10 overflow
ranges SHOULD be used. Note that these ranges can accomodate the VNI
in its entirety.
DHCPv4 server MUST know and consider VXLAN Network Identifier (VNI)
value before assigning VXLAN Multicast Address Option. The server
gets VNI value by means out of scope in this document.
DHCPv6 server looks for VXLAN Network Identifier Option or OPTION_VNI
value in Option Request Option of DHCPv6 Solicit message. DHCPv6
server MUST add VXLAN Network Identifier Option in DHCPv6 Advertise
message with VNI value in VXLAN Identifier field.
If DHCPv6 server is configured to support VXLAN multicast address
assignments it SHOULD look for DHCPv6 VXLAN Multicast Address Option
in DHCPv6 Solicit message. The server MUST return in IPv6 multicast
address field an Admin-Local scope IPv6 multicast address (FF04/16)
by copying the VNI of the virtual machine to the least significant 24
bits of the group ID field and setting all other bits to zero if
Solicited Node Multicast Address field received from the client was
set to zero in DHCPv6 Advertise message. Otherwise the Solicited
Node Multicast Address field is copied to bits 47-24 of the group ID
field and all leading bits are set to zero.
DHCPv6 server MUST know and consider VXLAN Network Identifier (VNI)
value before assigning VXLAN Multicast Address Option. The server
gets VNI value by means out of scope in this document.
8. Security Considerations
The security considerations in [RFC2131], [RFC2132] and [RFC3315]
apply. Special considerations in [RFC7348] are also applicable.
9. IANA considerations
IANA is requested to assign the OPTION_VNI and OPTION_MA and VXLAN
Network Identifier and VXLAN Multicast Address Option Codes in the
registry maintained for DHCPv4 and DHCPv6.
10. Acknowledgements
The authors are grateful to Bernie Volz and Ted Lemon for providing
comments that helped us improve the document.
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11. References
11.1. Normative References
[RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700,
October 1994.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3956] Savola, P. and B. Haberman, "Embedding the Rendezvous
Point (RP) Address in an IPv6 Multicast Address", RFC
3956, November 2004.
[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
RFC 2365, July 1998.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC6939] Halwasia, G., Bhandari, S., and W. Dec, "Client Link-Layer
Address Option in DHCPv6", RFC 6939, May 2013.
[I-D.ietf-nvo3-arch]
Black, D., Hudson, J., Kreeger, L., Lasserre, M., and T.
Narten, "An Architecture for Overlay Networks (NVO3)",
draft-ietf-nvo3-arch-03 (work in progress), March 2015.
[I-D.ietf-nvo3-nve-nva-cp-req]
Kreeger, L., Dutt, D., Narten, T., and D. Black, "Network
Virtualization NVE to NVA Control Protocol Requirements",
draft-ietf-nvo3-nve-nva-cp-req-03 (work in progress),
October 2014.
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11.2. Informative References
[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, August 2014.
[I-D.sridharan-virtualization-nvgre]
Garg, P. and Y. Wang, "NVGRE: Network Virtualization using
Generic Routing Encapsulation", draft-sridharan-
virtualization-nvgre-08 (work in progress), April 2015.
Authors' Addresses
Behcet Sarikaya
Huawei USA
1700 Alma Dr. Suite 500
Plano, TX 75075
Phone: +1 972-509-5599
Email: sarikaya@ieee.org
Frank Xia
Huawei USA
Nanjing, China
Phone: +1 972-509-5599
Email: xiayangsong@huawei.com
Shi Fan
China Telecom
Room 708, No.118, Xizhimennei Street
Beijing , P.R. China 100035
Phone: +86-10-58552140
Email: shifan@ctbri.com.cn
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