# Patent

## Title
System and method for data center security enhancements leveraging server SOCs or server fabrics

## Abstract

A data center security system and method are provided that leverage server systems on a chip (SOCs) and/or server fabrics. In more detail, server interconnect fabrics may be leveraged and extended to dramatically improve security within a data center.

## Background
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
This application is a Continuation of U.S. application Ser. No. 14/725,543, filed May 29, 2015, which is a Continuation of U.S. application Ser. No. 13/475,713, filed May 18, 2012, which is a Continuation-In-Part of U.S. application Ser. No. 12/794,996, filed Jun. 7, 2010, which claims priority to U.S. Provisional Application 61/256723, filed Oct. 30, 2009. U.S. application Ser. No. 13/475,713 also claims priority to U.S. Provisional Application 61/489,569, filed May 24, 2011. Each of the above-referenced application is incorporated herein by reference in their respective entireties.


FIELD
The disclosure relates generally to security aspects for data centers and in particular to data center security enhancements leveraging server systems on a chip (SOCs) or server switch fabrics.
BACKGROUND
FIGS. 1A and 1B show a classic data center network aggregation as is currently well known. FIG. 1A shows a diagrammatical view of a typical network data center architecture 100 wherein top level switches 101a-n are at the tops of racks 102a-n filled with blade servers 107a-n interspersed with local routers 103a-f. Additional storage routers and core switches. 105a-b and additional rack units 108a-n contain additional servers 104e-k and routers 106a-g FIG. 1b shows an exemplary physical view 110 of a system with peripheral servers 111a-bn arranged around edge router systems 112a-h, which are placed around centrally located core switching systems 113. Typically such an aggregation 110 has 1-Gb Ethernet from the rack servers to their top of rack switches, and often 10 Gb Ethernet ports to the edge and core routers. These typical data centers do not have good security.
The idea of network security is well known. The terms used in field of network security may include deep packet inspection (DPI) and intrusion prevention systems (IPS) which are also known as Intrusion Detection and Prevention Systems (IDPS) and are network security appliances that monitor network and/or system activities for malicious activity. The main functions of intrusion prevention systems are to identify malicious activity, log information about said activity, attempt to block/stop activity, and report activity. The network security may also utilize an intrusion detection system (IDS), which is a device or software application that monitors network and/or system activities for malicious activities or policy violations and produces reports to a Management Station.
FIG. 2 shows a typical implementation of an IDS and IPS within a corporate network. In the typical implementation, the IDS is focused on detection, monitoring, and reporting of potential intrusions. As such, the IDS is implemented out-of-line of the core network flow and is not invasive (located outside of the firewall and attached to a DMZ switch as shown in FIG. 2). The IPS adds the capability to prevent and block potential intrusion or undesired network flows and the IPS is implemented in-line of the core network flow.
Thus, it is desirable to provide a data center security system and method that leverage server systems on a chip (SOCs) and/or server fabrics, and it is to this end that the disclosure is directed.



BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B illustrate a typical data center system;
FIG. 2 shows a typical implementation of an IDS and IPS within a corporate network;
FIG. 3 illustrates a high-level topology of a network aggregating system that may be leveraged for increased security in a data center;
FIG. 4 illustrates a block diagram of an exemplary switch of the network aggregation system that may be leveraged for increased security in a data center;
FIG. 5 illustrates a network aggregation system with a network switch and enhanced security;
FIG. 6 illustrates a four-node server fabric with a network switch and enhanced security; and
FIG. 7 illustrates a small three-node server fabric with a network switch and enhanced security.



DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS
The disclosure is particularly applicable to a CalxedaTM server system on a chip and CalxedaTM switch fabrics as illustrated and described below with the security aspects and it is in this context that the disclosure will be described. However, the principles described below can be applied to other server-on-a-chip systems.
A server-on-a-chip (SOC) with packet switch functionality is focused on network aggregation. It contains a layer 2 packet switch, with routing based on source/destination MAC addresses. It further supports virtual local area network (VLAN), with configurable VLAN filtering on domain incoming packets to minimize unnecessary traffic in a domain. The embedded MACs within the SOC do have complete VLAN support providing VLAN capability to the overall SOC without the embedded switch explicitly having VLAN support.
FIG. 3 shows a high-level topology 800 of the network system that illustrates XAUI (a well-known interface standard) connected SoC nodes connected by the switching fabric. Two 10 Gb Ethernet ports Eth0 801a and Eth1 801b come from the top of the tree. Ovals 802a-n are CalxedaTM nodes that comprise at least one computational processors and an embedded switch. Each node may have five XAUI links connected to the internal switch. The switching layers use all five XAUI links for switching. Level 0 leaf nodes 802d, e (i.e., N0n nodes, or Nxy, where x=level and y=item number) only use one XAUI link to attach to the interconnect, leaving four high-speed ports that can be used as XAUI, 10 Gb Ethernet, PCIe, SATA, etc., for attachment to I/O. The vast majority of trees and fat trees have active nodes only as leaf nodes, and the other nodes are pure switching nodes. This approach makes routing much more straightforward. Topology 800 has the flexibility to permit every node to be a combination computational and switch node, or just a switch node. Most tree-type implementations have I/O on the leaf nodes, but topology 800 let the I/O be on any node. In general, placing the Ethernet at the top of the tree (the Ethernet ports) minimizes the average number of hops to the Ethernet.
The system and method also supports a routing using a tree-like or graph topology that supports multiple links per node, where each link is designated as an Up, Down, or Lateral link, or both, within the topology. In addition, each node in the system may be a combination computational/switch node, or just a switch node, and input/outpout (I/O) can reside on any node as described below in more detail. The system may also provide a system with a segmented Ethernet Media Access Control (MAC) architecture which may have a method of re-purposing MAC IP addresses for inside MACs and outside MACs, and leveraging what would normally be the physical signaling for the MAC to feed into the switch. The system may also provide a method of non-spoofing communication, as well as a method of fault-resilient broadcasting, which may have a method of unicast misrouting for fault resilience.
A data center with the CalxedaTM server system on a chip may be implemented using the set of fabric connected nodes with Ethernet uplinks as shown in FIG. 3. Each node may be one or more Calxeda server boxes each of which has at least one CalxedaTM server system on a chip.
The system may also provide a rigorous security between the management processor cores, such that management processors can “trust” one another. In the example node 900 shown in FIG. 4 (which is described below in more detail), there is a management processor core within each SoC (block 906, FIG. 4). The software running on the management processor is trusted because a) the vendor (in this case CalxedaTM) has developed and verified the code, b) non-vendor code is not allowed to run on the processor. Maintaining a Trust relationship between the management processors allow them to communicate commands (e.g. reboot another node) or request sensitive information from another node without worrying that a user could spoof the request and gain access to information or control of the system.
Typically the management processor, block 906, is running an embedded OS, while the multiple processor cores represented by block 905 are more typically running a standard operating system, such as Linux. The management processor would typically use one of the Ethernet MACs, in this case block 907, while the main processors, block 905, would utilize the remaining Ethernet MACs, in this case blocks 902 and 903.
Each routing header unit 901, that may be implemented as a processing unit or processor, prepends routing headers to layer 2 Ethernet frames to form a routing frame going into the fabric switch, and removes the routing headers as they leave the switch and enter standard Ethernet MACs. The routing frame is composed of the routing frame header plus the core part of the Ethernet frame, and is structured as shown in Table 1, below:







TABLE 1







Routing Header Prepended to Layer 2 Frame








Routing Frame



Header
Ethernet Frame Packet















RF Header
MAC
MAC
Ethertype/
Payload
CRC32



destination
Source
Length
(data and






padding)









The routing frame header (RF Header) typically consists of the fields shown in Table 2, below:







TABLE 2







Routing Header Fields










Width



Field
(Bits)
Notes












Domain ID
5
Domain ID associated with this packet. 0 indi-




cates that no domain has been specified.


Mgmt
1
Specifies that the packet is allowed on the


Domain

private management domain.


Source Node
12
Source node ID


Source Port
2
0 = MAC0, 1 = MAC1, 2 = MAC_management




processor, 3 = MAC_OUT


Dest Node
12
Destination node ID


Dest Port
2
0 = MAC0, 1 = MAC1, 2 = MAC_management




processor, 3 = MAC_OUT


RF Type
2
Routing Frame Type (0 = Unicast, 1 =




Multicast, 2 = Neighbor




Multicast, 3 = Link Directed)


TTL
6
Time to Live—# of hops that this frame has




existed. Switch will drop packet if the TTL




threshold is exceeded (and notify management




processor of exception).


Broadcast
5
Broadcast ID for this source node for this


ID

broadcast packet.


Checksum

Checksum of the frame header fields.


Total
46
+checksum









The Routing Header processor 901 contains a MAC Lookup CAM (Content Addressable Memory) (MCAM), macAddrLookup, that maps from 6 byte MAC addresses to 12-bit Node IDs, as shown in Table 3, below.







TABLE 3







MAC Address CAM (MCAM)












MAC Lookup CAM Input

MAC Lookup CAM Output













Node Local
MAC Address
Node ID
Port ID







1 bit
6 bytes
12 bits
2 bits










The approach to security domain management in the system and method disclosed here is as follows: Support multiple domain IDs within the fabric. Allow each of the MACs within a node (management processor, MAC0, MAC1, Gateway) to be assigned to a domain ID individually (and tagged with domain 0 if not set). Allow each of the MACs within a node to have a bit indicating access to the management domain. The domain IDs associated with a MAC could only be assigned by the management processor, and could not be altered by the A9. For frames generated by MACs (both inside and outside), the routing frame processor would tag the routing frame with the domain ID and management domain state associated with that MAC. Domains would provide the effect of tunnels or VLANs, in that they keep packets (both unicast and multicast) within that domain, allowing MACs outside that domain to be able to neither sniff or spoof those packets. Additionally, this approach would employ a five-bit domain ID. It would add options to control domain processing, such as, for example, a switch with a boolean per MAC that defines whether packets are delivered with non-defined (i.e., zero) domain ID, or a switch that has a boolean per MAC that defines whether packets are delivered with defined (non-zero) but non-matching domain IDs. A further option in the switch could turn off node encoded MAC addresses per MAC (eliminating another style of potential attack vector). Each of these options described in this paragraph are options that are implemented in the fabric switch, controlled by bits in the control status registers (CSRs) of the fabric switch. Software initializes the CSRs to the desired set of options.
To keep management processor to management processor communication secure, the management domain bit on all management processor MACs could be marked. Generally, the management processor should route on domain 1 (by convention). Such a technique allows all the management processor's to tunnel packets on the management domain so that they cannot be inspected or spoofed by any other devices (inside or outside the fabric), on other VLANs or domains. Further, to provide a secure management LAN, a gateway MAC that has the management domain bit set could be assigned, keeping management packets private to the management processor domain. Additionally, the switch fabric could support “multi-tenant” within itself, by associating each gateway MAC with a separate domain. For example, each gateway MAC could connect to an individual port on an outside router, allowing that port to be optionally associated with a VLAN. As the packets come into the gateway, they are tagged with the domain ID, keeping that traffic private to the MACs associated with that domain across the fabric.
Unicast routing is responsible for routing non-multicast (i.e. unicast) packets to the next node. This is done by utilizing a software computed unicastRoute[ ] next node routing table that provides a vector of available links to get to the destination node.
Server Interconnect Fabric Security
The above server fabric and switch fabric can benefit by enhanced security and a number of techniques to leverage and extend upon server interconnect fabrics that have some or all of the characteristics described above to dramatically improve security within a data center are described. The different embodiments implement “packet processing” which may include a wide range of packet processing including, but not limited to: IDS functionality, IPS functionality, sFlow monitoring (wherein sFlow is a specification for monitoring computer networks set forth in an sFlow specification that is RFC 3176) Packet routing or bridging between networks, Deep packet inspection, Packet logging, Transparent VPN encapsulation, Packet encryption/decryption and/or Packet compression/decompression.
Multi-Tenant Fabric Use Case
In a first embodiment, the server fabric domains are used to enhance security in fabric multi-tenant use case. In particular, there are data centers that host applications and data for multiple clients and networked servers within a single rack may host multiple clients. In the case of servers and nodes connected via interconnect fabrics, one example of which is described above, multiple clients may exist on separate nodes (such as the nodes shown in FIGS. 3 and 4 above) within a single fabric which is a multi-tenant fabric use case.
There are a couple of network security goals in this multi-tenant fabric use case:

    
    
        Client A should have no possible way to inspect data from Client B, including Client B's network traffic.
        Client A should have no possible way to spoof data to Client B's network. This case specifically covers the case where network packets cannot be hand crafted to look like they came from a Client B node, and routed to a Client B node.
    
    


To illustrate this embodiment, FIG. 5 illustrates a network aggregation system with a network switch and enhanced security. As shown in FIG. 5, a number of server nodes, 802a-n, are connected by a server interconnect fabric, there are two gateway nodes, N30 and N31, that serve as Ethernet gateways to the outside Ethernet network and there are two gateway Ethernet ports, 801a and 801b that are connected to a network switch 804, typically a top of rack switch, connecting to two ports on the switch, Port A and Port B.
When Client A's network traffic comes from Port A on the switch and Client B′s network traffic comes from Port B on the switch, a common way for a network engineer to manage this multi client use would be to have a VLAN assigned to Client A and a different VLAN assigned to Client B. To guarantee isolation of Client A's traffic from Client B′s traffic on the fabric, the following techniques (alone or in combination) can be used:

    
    
        Map Client A's VLAN to Port A and Map Client B's VLAN to Port B.
        Assign Fabric Domain A to Gateway Eth0 801a and assign Fabric Domain B to Gateway Eth1 801b. 
    
    


Initialize every node in the fabric such that the node's MACs will only accept packets from that particular client's fabric domain. As an example, all the nodes in the cluster assigned to Client A will have the MAC fabric ports within that node to be assigned to only accept Domain A packets, and drop other domain packets.
Using this technique, there will be no packet visibility between the clients, and no packets (unicast or multicast) can be transferred directly between them on the fabric, which improves the security of the system by leveraging the server fabric.
Securing Inter-Management Processor Traffic within the Fabric
In a second embodiment, the inter-management processor (906 in FIG. 4) traffic with the fabric is secured. In particular, the management processors within a server fabric (at each node as shown in FIG. 4) need a secure way to communicate between themselves with no possibility of sniffing or spoofing by the application processors within the fabric. The following techniques (alone or in combination) can be used to secure inter-management traffic:
Either set the management domain bit within the Routing Header (see above) Processor for the management processor and/or assign that MAC the Fabric Domain of 0.
Configure the fabric such that the Ethernet MAC for the management processor only accepts routing headers marked with the management domain bit, or having Fabric Domain of 0.
Configure the fabric such that the Ethernet MACs for the application processors do not have the management domain bit set, and have a non-zero Fabric Domain.
Creating Secure Private Management LAN
In a third embodiment, the fabric may be used to create a secure private management local area network (LAN.) Traditional rack-oriented servers may have an embedded BMC (baseboard management controller) and the BMC will have two paths for network connectivity including a shared management LAN with BMC traffic being routed out the main network port of the server and a Private management LAN with BMC traffic being routed out a private network port of the server.
To illustrate this embodiment, FIG. 6 illustrates a four-node server fabric with a network switch and enhanced security with the goal of creating a private management LAN for the server fabric. The following technique (alone or in combination) can be used to secure the management traffic out of Eth1 801b: 
Set the management domain bit within the Routing Header Processor for the management processor and assign that MAC the Fabric Domain of 0.
Configure the fabric such that the Ethernet MAC for the management processor only accepts routing headers marked with the management domain bit, or having Fabric Domain of 0.
Configure the fabric such that the Routing Header Processor for the outgoing MAC, block 910D of FIG. 4, of N31, Eth1 is configured to tag and only accept Fabric Domain of 0.
Configure the fabric such that the Ethernet MACs for the application processors do not have the management domain bit set, and have a non-zero Fabric Domain
In this way, the management processors can securely communicate using the Management Domain, and management traffic will be secured on Eth1.
Using Constrained Routing Tables to Enhance Security in Multi-Tenant Fabrics
In a fourth embodiment, constrained routing tables are used to enhance security in multi-tenant fabric. To illustrate this embodiment, FIG. 6 illustrates a four-node server fabric (nodes 0, 1, 2 and 3 in FIG. 6) with a network switch and enhanced security. The link numbers are depicted in the figure, as an example, packets leaving Node 0 to Node 1 would leave on link 2 (L2 as shown in FIG. 7). A typical unicast routing table for this fabric for Node 1 would look like the following:







TABLE 4







Node 0 Full Fabric Routing Table










Destination Node
Outgoing Link







0
—



1
L2



2
L0



3
L1










In the case in a multi-tenant fabric where Nodes 0 and 1 are being used by Customer A and Nodes 2 and 3 are being used by Customer B, routing can actually be denied from one customer to another by not having the routes such as in the below constrained routing table.







TABLE 5







Node 0 Constrained Routing Table










Destination Node
Outgoing Link







0
—



1
L2



2
—



3
—










Packet Processing Using OS Routing on Gateway Node
In a fifth embodiment, the fabric can perform packet processing using operating system (OS) routing on a gateway node. This embodiment is illustrated in FIG. 7 that shows a small three-node server fabric. The following technique can be used to create an IPS using the gateway node, node 0:
Assign the incoming Ethernet gateway traffic to the Eth0 MAC (block 902 of FIG. 4) and it can be designated as the Outside MAC.
Assign the fabric-side Ethernet traffic to the Eth1 MAC (block 903 of FIG. 4) and it can be designates as the Inside MAC.
Use Linux (or other OS equivalent) routing features to route traffic between the Inside MAC and the Outside MAC.
Linux (or other OS equivalent) IPS (e.g. Snort) or IDS software can then be run on the application processors (block 905 of FIG. 4) to inspect or block traffic between the fabric and the outside Ethernet.
Packet Processing on Arbitrary Nodes Using Non-Symmetric MCAMs
The sixth embodiment is directed to packet processing on arbitrary nodes using non-symmetric MCAMs. This embodiment is illustrated in FIG. 7 that shows the small three-node server fabric. The following technique can be used to create an IPS using an arbitrary node as the IPS (in this example node 2):
Initialize the MCAM on Node 0, the gateway node, such that all fabric MAC addresses map to Node 2







TABLE 6







Asymmetric MCAM for Node 0 for Node 2 IPS/IDS










MAC Address
Node







Node 0 MAC
2



Node 1 MAC
2



Node 2 MAC
2










Initialize the MCAM on Node 2 to map the MAC addresses to the correct nodes.







TABLE 7







Asymmetric MCAM for Node 2 for Node 2 IPS/IDS










MAC Address
Node







Node 0 MAC
0



Node 1 MAC
1



Node 2 MAC
2










Packets coming into the gateway node hit the fabric switch on node 0.
The destination MAC address on the packet gets translated by the Node 0 MCAM to a destination node, in this case Node 2 (for all fabric MAC addresses).
Packet gets routed to Node 2 and delivered to the application processor MAC on Node 2.
IPS/IDS software runs on node 2, then assuming the packet is not blocked forwards the packet back into the fabric for delivery.
The destination MAC address on the packet gets translated by the Node 2 MCAM to a destination node, in this case the correct destination node within the fabric, and gets delivered to the targeted destination node.
Packet Processing Using Local Management Processor
The seventh embodiment relates to packet processing using local management processor(s), which can be illustrated by the small three-node server fabric depicted in FIG. 7. The following technique can be used to create an IDS or other packet inspection and logging using the local management processor on each node:

    
    
        Configure the fabric Promiscuous Vector to replicate packets to the management processor MAC (block 906 of FIG. 4). The Promiscuous Vector defines a list of ports to which the incoming packet should be replicated. This allows the management processor to declare to the switch that it should get a copy of the incoming packets, without knowledge or intervention of the source or destination of the packet transfer.
    
    


Packets entering or leaving Eth0 and Eth1 MACs (blocks 902 and 903 of FIG. 4) will be replicated to management processor MAC, block 906.
The management processor can then run IDS or other packet inspection or logging software not only unobtrusively to the OS and applications on the application processor, but without the OS or applications processor being aware of the management processor packet processing.
Security Enhancement of Having Non-Whitelisted Destination Macs Dropped at the Ingress Node
The eighth embodiment is directed to a security enhancement of having Non-whitelisted destination MACs dropped at the ingress node which can be illustrated using the switch fabric in FIG. 7 to be able to enforce white-listing of destination MAC addresses (meaning that the network manager will have a list of known MAC addresses within the fabric or within the broadcast domain, and packets ingressing into the fabric that are not on the destination MAC whitelist will be immediately dropped.) The following technique can be used to create MAC address whitelists:
The Network administrator collects all the MAC addresses within the broadcast domain, both inside and outside the fabric.
All the MCAMs are initialized with the complete list of (MAC Address, Node ID, Port ID) mappings.
For those MAC addresses that are outside the fabric, the MCAM mapping is to (Gateway Node ID, Outlink Port).
The primary and secondary gateway node ID mappings in each switch are disabled.
This results in packets entering the fabric that don't match the MAC address whitelist to be routed to the gateway node, but by invalidating the gateway node entries, the packets are dropped.
This results in packets being dropped immediately at the ingress point that don't match the MAC address whitelist.
Additional Security Aspects
The security may also include secure fabric local Network Attached Storage (NAS) through private internal domains. There are domains do not have to go all the way to an uplink. Thus, the system can establish a domain between one server node and a node acting as a NAS server.
The system may also provide port scan and port sweep monitoring. A port sweep is the act of systematically scanning the ports on one or more computers by security attackers to find weakened access points to break into computer systems. A port scan is a series of messages sent by someone attempting to break into a computer to learn which computer network services, each associated with a port number, the computer provides. The port scan and port sweep are generally hard to detect at the IPS/IPD level because that are a large number of data flows to watch (and with port sweep many systems) and tracking of the accesses over time. Since the switch system described above has all traffic going into the cluster, the system can monitor for port scan/port sweep better than external appliances.
The system also may allow for the monitoring for a typical network traffic to/from a node. Since the system can monitor all rates over time, the system can monitor traffic to/from a node and isolate it, or flag it, if it exceeds (customer settable) tolerances.
The system may also provide isolation of traffic. In particular, in addition to operating system (OS) routing to separate multi-tenant traffic, the system can also provide physical isolation by cutting links.
The system may also permit customers to configure the topology of the switch. The configuration of the switch may prevent the sharing of links (avoiding a DOS at a link), or sharing of boards (to avoid fault sharing.)
The system may also use IP reputation processing for security. In particular, the blocking or allowing of access based on source address may be incorporated into any place in the switch that packet processing occurs. Using IP reputation processing, the system can support multiple equivalent servers with one server receiving traffic from trusted systems, one receiving traffic from less trusted systems, and one receiving from untrusted system. This could allow for faster/streamlined processing of trusted traffic, and more security checking of less trusted traffic.
The switch security (and the management processor in particular) may provide encryption services in which the keys never leave the trusted zone.
The switch system may also perform real mapping of external virtual local area networks (VLANs) to domains by having the uplink nodes being in their own domains. To provide the real mapping, the switch uses their downlinks as MACLinks (even though they go to our nodes) and uses routing through the downlinks to pick the desired domain (based on VLAN). For example, if the user wants to map a VLAN 101 packet to Domain 10, the uplink node would have the four other links configured as MACLinks, one of those links would go to another node (whose link is also configured as a MACLink with a Domain of 10, so any packet sent down that link goes into the fabric as Domain 10.)
The use of the Outside Ethernet MAC (904 in FIG. 4) gives the system the ability to filter on VLANs, Source MAC, Destination MAC, etc. with perfect filters and wildcards or hashes within the Outlink. Thus, packets can be dropped before they enter the fabric and that is another way of implementing security enhancement of having Non-Whitelisted Destination MACs dropped at the Ingress Node or dropping of packets based on a source address.
While the foregoing has been with reference to a particular embodiment of the invention, it will be appreciated by those skilled in the art that changes in this embodiment may be made without departing from the principles and spirit of the disclosure, the scope of which is defined by the appended claims.

## Claims

1. A server system-on-a-chip device comprising:
a management processor configured to transmit one or more frames;
a routing header unit connected to the management processor, wherein the routing header unit is configured to set a management domain bit in a routing header of the one or more frames, and wherein the management domain bit comprises an identifier that indicates a particular network domain for which the routing header unit belongs and indicates access to a management domain; and
a fabric switch connected to the routing header unit and to a plurality of external ports, wherein the fabric switch is configured to perform packet processing based, at least in part, on the management domain bit.

2. The device of claim 1, further comprising a media access control (MAC) unit connected to the fabric switch, wherein the MAC unit is configured to only accept frames having the management domain bit.

3. The device of claim 2, wherein the management domain bit further indicates a fabric domain to which the management processor belongs, and wherein the MAC unit is assigned the fabric domain.

4. The device of claim 3, wherein the fabric domain is configured to provide a trusted communication channel between multiple management processors.

5. The device of claim 3, wherein the fabric domain is set to zero.

6. The device of claim 5, further comprising a plurality of application processors and a plurality of MAC units associated with respective application processors, wherein the plurality of MAC units associated with the respective application processors do not have management domain bits set, and wherein the plurality of MAC units associated with the respective application processors have a non-zero fabric domain.

7. The device of claim 5, further comprising another routing header unit associated with an outgoing MAC unit, wherein the other routing header unit is configured to tag and only accept frames having management domain bits that indicate the fabric domain of zero.

8. The device of claim 1, further comprising a plurality of application processors and a plurality of MAC units associated with respective application processors, wherein the plurality of MAC units do not have management domain bits set.

9. The device of claim 1, wherein the routing header unit is configured to prepend routing heads to packets generated by an associated MAC unit, and wherein the routing heads include the management domain identifier associated with the associated MAC unit.

10. The device of claim 1, wherein the fabric switch is further configured to stop a packet that has been assigned a default domain identifier.

11. A method comprising:
interconnecting a plurality of nodes with a plurality of links to form a server fabric, wherein each of the plurality of nodes includes:

a management processor configured to transmit data packets;
a routing header unit connected to the management processor, wherein the routing header unit is configured to set a management domain bit in a routing header for the data packets, and wherein the management domain bit comprises an identifier that indicates a particular network domain for which the routing header unit belongs and indicates access to a management domain; and
a fabric switch connected to the routing header unit and to a plurality of external ports, wherein the fabric switch is configured to perform packet processing based, at least in part, on the management domain bit;
generating data packets at a media access control (MAC) unit associated with the management processor; and
routing, by the fabric switch, the data packets in the server fabric based, at least in part, on the management domain identifier.

12. The method of claim 11, wherein said routing the data packets comprises routing the data packets to another MAC unit, and wherein the other MAC unit is configured to only accept data packets having a header with the management domain bit.

13. The method of claim 12, wherein the management domain bit further indicates a fabric domain to which the management processor belongs, and wherein the MAC unit is assigned the fabric domain.

14. The method of claim 13, wherein the fabric domain is set to zero.

15. The method of claim 14, further comprising tagging and only accepting, by another routing header unit, frames having management domain bits that indicate the fabric domain of zero.

16. The method of claim 11, further comprising prepending, by the routing header unit, routing heads to the data packets, wherein the routing heads include the management domain identifier associated with the MAC unit.

17. The method of claim 11, further comprising stopping, by the fabric switch, a packet that has been assigned a default domain identifier.

18. A system comprising:
a plurality of nodes, wherein each node in the plurality of nodes includes:

a management processor configured to transmit one or more frames;
a routing header unit connected to the management processor, wherein the routing header unit is configured to set a management domain bit in a routing header of the one or more frames, and wherein the management domain bit comprises an identifier that indicates a particular network domain for which the routing header unit belongs and indicates access to a management domain; and
a fabric switch connected to the routing header unit and to a plurality of external ports, wherein the fabric switch is configured to perform packet processing based, at least in part, on the management domain bit; and
a plurality of links that interconnect the plurality of nodes to form a server fabric.

19. The system of claim 18, wherein each node further comprises a media access control (MAC) unit connected to the fabric switch, and wherein the MAC unit is configured to only accept frames having the management domain bit.

20. The system of claim 19, wherein the management domain bit further indicates a fabric domain to which the management processor belongs, and wherein the MAC unit is assigned the fabric domain.