NVO3 Weiguo Hao
Lucy Yong
Yizhou Li
Internet Draft Huawei
Feng Wang
H3C
W.Shao
Tencent
Vic Liu
China Mobile
Intended status: Informational June 30, 2014
Expires: December 2014
NVO3 Anycast Layer 3 Gateway
draft-hao-nvo3-anycast-gw-00.txt
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Abstract
This draft describes centralized anycast layer 3 gateway solution
for NVO3 networks interworking with external networks. Comparing to
traditional VRRP based active-standby layer 3 gateway solution, this
solution can achieve better load balancing and scalability.
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Table of Contents
1. Introduction ................................................ 3
2. Conventions used in this document............................ 4
3. Anycast Layer 3 Gateway...................................... 5
4. ARP Handling ................................................ 6
5. Resilience on Gateway Node Failure........................... 6
6. Anycast GW and VRRP GW Comparison............................ 6
6.1. VRRP based layer 3 gateway solution..................... 6
6.2. Comparison ............................................. 7
7. Security Considerations...................................... 7
8. IANA Considerations ......................................... 7
8.1. Normative References.................................... 8
8.2. Informative References.................................. 8
9. Acknowledgments ............................................. 8
1. Introduction
NVO3 overlay networks provide network connectivity to a set of
Tenant Systems (TSs) [NVO3FRWK]. A data center(DC) may support many
tenant networks.[NVO3PS] It is very often that some Tenant Systems
need to communicate with external networks. An external network may
be another overlay network in DC or a VPN in WAN or Internet. In
this case, a gateway (GW) is required where inter-network policies
are placed and enforced.
Figure 1 illustrates a popular DC infrastructure where two DC GWs
are used at DC boarder. All tenant system traffic going in/out DC
and between overlay VNs will pass through the DC GWs. For a large DC
and supporting many tenant networks, such GWs can be the pain point
for the scalability. Although VRRP [RFC2338] [RFC3768] [RFC5798] may
be used at the GWs to provide link/node redundancy, it does not
resolve the scalability issue. Distributed GW may be implemented on
NVEs [NVO3ARCH], which may reduce the traffic passing through these
GWs; however all the traffic going in/out DC still have to go
through these GWs.
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,---------.
,' `.
( IP/MPLS WAN )
`. ,'
* -+------+' *
* *
* *
--------- ---------
| GW1 | | GW2 |
| | ************ | |
--------- ---------
* *
* *
* *
* *
* *
--------- --------- --------- ---------
| TOR1 | ******** | TOR2 | ********| TOR3 |********| TOR4 |
| | | | | | | |
--------- --------- --------- ---------
| | | |
| | | |
--------- --------- --------- ---------
| NVE1 | | NVE2 | | NVE3 | | NVE4 |
| | | | | | | |
--------- --------- --------- ---------
| | | | | | | |
____ ____ ____ ____ ____ ____ ____ ____
|T | |T | |T | |T | |T | |T | |T | |T |
|S1| |S2| |S3| |S4| |S5| |S6| |S7| |S8|
---- ---- ---- ---- ---- ---- ---- ----
1. Figure1 Centralized layer 3 gateway in NVO3 network
This draft proposes anycast layer 3 gateway solution for DC GWs that
address the scalability concern. To differentiate it from
distributed GWs in NVO3, the DC GW is referred to as centralized GW.
A centralized GW is a gateway network device that has embedded NVE
capability, i.e. ability to maintain the inner/outer mapping and
terminates overlay tunnels.
2. Conventions used in this document
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].The acronyms and terminology in [RFC6325] is used herein
with the following additions:
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Network Virtualization Edge (NVE)- An NVE is the network entity that
sits at the edge of an underlay network and implements network
virtualization functions.
Tenant System - A physical or virtual system that can play the role
of a host, or a forwarding element such as a router, switch,firewall,
etc. It belongs to a single tenant and connects to one or more VNs
of that tenant.
VN - A VN is a logical abstraction of a physical network that
provides L2 network services to a set of Tenant Systems.
3. Anycast Layer 3 Gateway
Anycast Layer 3 Gateway means that multiple GW network devices
support GW functions between overlay VNs and external networks and
have the same GW IP and MAC address for each overlay VN, these
gateways share same gateway IP and MAC address for each VN, the GW
IP and MAC address is called gateway anycast IP and MAC address. To
ensure NVO3 traffic load balancing from ingress NVEs to these
gateways, these gateways also share same outer IP address, this
address is called as device underlying anycast IP address in the
document.
Gateway anycast IP address is used as the default gateway's IP
address for all TSs in the corresponding VN. As different VNs are
allowed to have overlapping MAC address space, different anycast
gateway IP addresses can map to the same anycast MAC. That is to say,
each VN should have a unique anycast gateway IP address, however the
gateway MAC address for VNs may map to the same anycast MAC. It is
recommended to configure only one anycast MAC as all VNs gateway MAC
address on each gateway device for simplicity purpose.
When sending traffic toward a VN gateway on GW devices, ingress NVEs
use the device underlying anycast IP address as outer IP destination
address on NVO3 packets. The VN may be an L2 VN or L3 VN.
Each GW network device announces device underlying anycast IP
address in underlying IGP network. If these gateways have same
routing cost to an ingress NVE, the underlying equal-cost multi-path
(ECMP) approach will distribute the NVO3 traffic from the ingress
NVE to one of GW devices.
When sending traffic toward a tenant system in a VN, a VN GW on a GW
device obtains the mapping of the tenant system and attached NVE
from a table lookup. If the VN is an L3 VN, the GW device
encapsulates the packet with the NVE IP address as outer destination
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IP address and its device underlying anycast IP address as the outer
source IP address. If the VN is an L2 VN, the GW device inserts
inner MAC header with its anycast MAC address as the source MAC
address and tenant MAC address as the destination MAC address; then
encapsulates the packet with the NVE IP address as outer destination
IP address and its underlying anycast IP address as the outer source
IP address.
NVA [NVO3ARCH] maintains TS/NVE mappings per a VN and pushes the
mappings to the NVEs and GW network devices. To support anycast L3
GW, NVA has the mapping of VN GW anycast IP and device underlying
anycast IP for an L3 VN; or the mapping of VN GW anycast MAC and
device underlying anycast IP for an L2 VN.
4. ARP Handling
To avoid ARP request flooding in each VN, NVEs can make use of the
mapping information from a Network Virtualization Authority (NVA) to
response the ARP request.
For L3 VN, upon receiving an ARP request with a VN GW anycast IP
address, local NVE intercepts it, and uses itself MAC address in the
reply.
For L2 VN, upon receiving an ARP request with a VN GW anycast IP
address, local NVE snoop it, and uses VN GW anycast MAC address in
the reply. Note that NVEs may locally maintain the mapping of VN GW
anycast IP and MAC address, or obtain from NVA.
5. Resilience on Gateway Node Failure
Anycast L3 gateway solution is resilient on a GW network device
failure. If a GW network device fails, IGP updates link status and
the host routes, the NVO3 encapsulated traffic with device
underlying anycast IP will only reach the remaining GW network
devices.
6. Anycast GW and VRRP GW Comparison
6.1. VRRP based layer 3 gateway solution
The Virtual Router Redundancy Protocol (VRRP) [RFC2338] [RFC3768]
[RFC5798] is designed to eliminate the single point of gateway
failure. VRRP is an election protocol that dynamically assigns
responsibility for a virtual router to one of the VRRP routers on a
layer 2 VN. Any of the virtual router's IP addresses on a LAN can
then be used as the default first hop router by end-hosts. The layer
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3 gateway of VRRP master is responsible for forwarding packets
destined to the virtual router. If VRRP master fails, VRRP backup
will take over.
VRRP based solution has the following issues:
1. Inefficient network bandwidth usage. Only the VRRP master gateway
forwards the traffic. VRRP slave is idle most of the time.
2. VRRP session number per VN. VRRP session among physical layer 3
gateways should be established per layer 2 VN. Large number of
layer 2 VN will cause heavy CPU workload for each layer 3 gateway.
6.2. Comparison
+----------------------------+------------------------+--------------------------------+
| Dimension | VRRP | Anycast gatway solution |
+----------------------------+------------------------+--------------------------------+
| Network bandwidth usage | Low | High |
+----------------------------+------------------------+--------------------------------+
| Keep alive workload | VRRP Session per VN | No |
+----------------------------+------------------------+--------------------------------+
| Network resilience | VRRP Switchover | Underlying network convergence |
+----------------------------+------------------------+--------------------------------+
7. Security Considerations
NA
8. IANA Considerations
NA
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8.1. Normative References
[1] [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC2119, March 1997.
8.2. Informative References
[1] [NVO3ARCH] Black, D, Narten, T., et al, " An Architecture for
Overlay Networks (NVO3)", draft-ietf-nvo3-arch-01, work in
progress.
[2] [NVO3FRWK] LASSERRE, M., Motin, T., et al, "Framework for DC
Network Virtualization", draft-ietf-nvo3-framework-03, work in
progress.
[3] [RFC 2338] S. Knight, et al, ''Virtual Router Redundancy
Protocol'',RFC 2338, April 1998
[4] [RFC 3768] R. Hinden, Ed., "Virtual Router Redundancy Protocol
(VRRP)", RFC 3768, April 2004
[5] [RFC 5798] S. Nadas,Ed., ''Virtual Router Redundancy Protocol
(VRRP) Version 3 for IPv4 and IPv6'', RFC 5798, March 2010
9. Acknowledgments
The authors wish to acknowledge the important contributions of Zhang
Chengsong.
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Authors' Addresses
Weiguo Hao
Huawei Technologies
101 Software Avenue,
Nanjing 210012
China
Phone: +86-25-56623144
Email: haoweiguo@huawei.com
Lucy Yong
Phone: +1-918-808-1918
Email: lucy.yong@huawei.com
Yizhou Li
Huawei Technologies
101 Software Avenue,
Nanjing 210012
China
Phone: +86-25-56625375
Email: liyizhou@huawei.com
Feng wang
H3C Technologies
Email: imfeng@h3c.com
Wade Shao
Tencent
Email: wadeshao@tencent.com
Vic Liu
China Mobile
32 Xuanwumen West Ave, Beijing, China
Email: liuzhiheng@chinamobile.com
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