JACS is based on BLAN ‘Blockchain Local Area Network’ as the transport mechanism for the native JACS traffic between the different JACS sites and locations (i.e. Adopters’ sites, JACS public cloud…)
BLAN is the result of integrating blockchain with VxLAN.
What is VxLAN?
As its name indicates, Virtual eXtensible Local Area Network VxLAN is designed to provide the same Ethernet Layer 2 network services as VLAN does, but with greater extensibility and flexibility. Compared to VLAN, VxLAN offers the following benefits:
• Flexible placement of multitenant segments throughout a data center, private or public cloud: It provides a solution to extend Layer 2 segments over the underlying shared network infrastructure so that tenant workload can be placed across physical pods in the data center.
• Higher scalability to address more Layer 2 segments: VLANs use a 12-bit VLAN ID to address Layer 2 segments, which results in limiting scalability of only 4094 VLANs. VxLAN uses a 24-bit segment ID known as the VxLAN Network Identifier (VNID), which enables up to 16 million VxLAN segments to coexist in the same administrative domain.
• Better utilization of available network paths in the underlying infrastructure: VLAN uses the Spanning Tree Protocol (STP) for loop prevention, which ends up not using half of the network links by blocking redundant paths. In contrast, VxLAN packets are transferred through the underlying network based on its Layer 3 header and can take complete advantage of Layer 3 routing, equal-cost multipath (ECMP) routing, and link aggregation protocols to use all available paths.
VxLAN modes of operation
From the various industry implementations of VxLAN, we can categorize the VxLAN modes of operations into two main categories:
• Control-Plane-Less-VxLAN
• Control-Plane-VxLAN
The differences are mainly in the underlay transport network multicast capability, how to deal with BUM (Broadcast, Unknown Unicast & Multicast) traffic as well as the method of discovery & distribution of MAC addresses.
Control-Plane-Less-VxLAN
For the Control-Plane-less mode of operation of VXLAN, we have two main sub-modes:
• Control-Plane-Less-Multicast-VXLAN
• Control-Plane-Less-Unicast-VXLAN
Control-Plane-Less-Multicast-VXLAN
As its name implies; there is NO control or signaling established prior to the VxLAN operation.
This mode is according to the original VxLAN draft as per RFC7348.
It requires the underlay transport network to fully support the IP Multicast & every VTEP (VxLAN Tunnel End Point) node to join the proper Multicast domain.
In this mode; the BUM (Broadcast, Unknown Unicast & Multicast) traffic is always carried over Multicast.
It’s all about the ‘Data-Plane’ learning (or flow-based learning) that’s based on the ‘Flood & learn’ technique; where the remote VTEPs would know about a MAC address because of the conversational MAC address learning approach:
• The destination (receiving) VTEP learns the inner Source MAC of any received VXLAN IP packet (for example a Broadcasted ARP request message carried over Multicast). The source MAC address is then mapped to the Source (Originating) VTEP that originated the VxLAN packet.
• The Originating VTEP will learn the remote MAC address to VTEP mapping once it receives the VxLAN encapsulated ‘Unicast’ ARP reply message from the receiving VTEP.
• All subsequent traffic to a known MAC address is Unicast IP encapsulated VxLAN.
Control-Plane-Less-Unicast-VXLAN
Exactly like the Control-Plane-Less-Multicast-VxLAN; there is NO control or signaling established prior to the VxLAN operation, instead a list of all available & participating VTEPs are configured on each VTEP per supported VxLAN.
In this mode; the underlay transport network doesn’t need to support IP Multicast.
For the BUM traffic; instead of being ‘Multicasted’ over the underlay transport network as in the previous mode of operation; the ‘head-end replication’ is used here where the originating VTEP has to replicate the VxLAN packet & sends a copy to every other VTEP participating in this same VxLAN.
The list of VTEPs must be configured (changed & updated) manually on each & every VTEP in the domain.
The ‘Data-Plane’ learning technique is also here in this mode of operation.
To be cont’d
