Requirements for DRNI on layer 3
gateway devices
802.1 AX-REV, 201203 IEEE 802 plenary
Lu Huang (huanglu@chinamobile.com)
Agenda
Use case
Requirement
Proposal
Use cases
• Use case 1: Mobile backhaul
-
In LTE mobile backaul, one optional solution is deploying
routers and layer 2 network(PTN). For the interconnection
between routers and PTN, DRNI is an appropriate mechanism
-
Router is the Layer 3 gateway of eNodeBs. In this case, DRNI
is used on layer 3 gateway devices
-
Furthermore, In the best case convergence time should be
less than 200ms, in the worst case it should be less than
500ms
DRNI
• Use case 2: Layer 2 network in cloud
computation IDC
- In cloud computation IDC, we use layer 2 network to
meet the requirement of cloud computation. We want
to use DRNI instead of spanning tree (Of course,
SPB or Trill are also optional, maybe in the future)
DRNI
- Core switch is the layer 3 gateway of servers. In this
case, DRNI is used on layer 3 gateway devices
DRNI
- Furthermore, convergence time should be less than
500ms
1) We want to use DRNI on layer 3 gateway devices
2) We require fast convergence in DRNI for protection
Agenda
Use case
Requirement
Proposal
Requirement(1)
Unique MAC for DRNI
•
Layer 3 network
GW1
GW2
LA1
LA2
L2SW1
For hosts there should be only one gateway, so
GW1 and GW2 should share the same MAC and
IP address for LA1 (the distributed link
aggregation group)
•
When hosts request GW’s ARP, GW1 and GW2
should answer the same ARP ( GW_IP, unique MAC)
•
When GW1 and GW2 request hosts’ ARP, they should
use the same sender ARP info ( GW_IP, unique MAC)
•
Because GW1 and GW2 will use LA1’s MAC as
their ARP MAC, so DRNI should make sure that
L2SW2
Layer 2 network
nodes in the same DAS share an unique
MAC which could be used by upper layer
protocol (e.g. ARP)
L2SW
Host
ARP Request
ARP Reply
•
We can config the same IP on LA1 of GW1 and
GW2. It doesn’t depend on DRNI protocol
Requirement(2)
L3 entries Backup mechanism
•
To obtain fast protection switch, GW1 and GW2 should
share the same L3 entries (e.g. ARP entries). When GW1
or link between GW1 and L2SW1 break down, GW2
could forward all flows immediately
•
Real-time backup
Layer 3 network
GW1
GW2
L2SW1
L2SW2
•
When GW1 receives ARP request or ARP reply packet from
host, it should duplicate one and send to GW2
•
When GW2 receives ARP request or ARP reply packet from
host, it should duplicate one and send to GW1
•
GW1 and GW2 could limit the duplication based on the
ETH_TYPE of packets ( for ARP, it’s 0x0806)
Layer 2 network
Host
ARP Request or Replay
This mechanism could not used in the below scenario
Layer 3 network
GW1
GW2
L2SW1
•
Batch backup
•
When GW1 reboots, batch backup(with GW2) can help GW1
recover forwarding all flows as soon as possible. Otherwise
GW1 wil take even a few seconds to relearn ARP entries and
introduce a long interruption
•
How to fulfill batch backup is under research ( through ICCP,
LACP or ARP )
•
Of course, if we define a protocol for batch backup, it also could
be used for real-time backup
L2SW2
Layer 2 network
Host
Batch backup message
Agenda
Use case
Requirement
Proposal
Proposal
• When using DRNI on layer 3 gateway devices, DRNI should
support the following features
- Nodes in the same DAS share an unique MAC for LA group
- A node could duplicate some certain packets to the other nodes in
the same DAS based on ETH_TYPE of packets
- Nodes in the same DAS could fulfill batch backup of certain entries
(e.g. ARP entries) with each other
Thank you
Q&A