Node insertion and removal in a loop network

Details Node insertion and removal in a loop network Node insertion and removal in a loop network

1998-10-22

2001-04-10

Olms, Douglas (Department: 2661)

Multiplex communications

Network configuration determination

In a bus system

C370S254000

Reexamination Certificate

active

06215775

ABSTRACT:

TECHNICAL FIELD
The present invention relates to electronic network communications systems, and more specifically to insertion and removal of a node in a loop network.
BACKGROUND INFORMATION
Electronic data systems are frequently interconnected using network communication systems. Area-wide networks and channels are two approaches that have been developed for computer network architectures. Traditional networks (e.g., LAN's and WAN's) offer a great deal of flexibility and relatively large distance capabilities. Channels, such as the Enterprise System Connection (ESCON) and the Small Computer System Interface (SCSI), have been developed for high performance and reliability. Channels typically use dedicated short-distance connections between computers or between computers and peripherals.
Features of both channels and networks have been incorporated into a new network standard known as “Fibre Channel”. Fibre Channel systems combine the speed and reliability of channels with the flexibility and connectivity of networks. Fibre Channel products currently can run at very high data rates, such as 266 Mbps or 1062 Mbps. These speeds are sufficient to handle quite demanding applications, such as uncompressed, full motion, high-quality video. ANSI specifications, such as X3.230-1994, define the Fibre Channel network. This specification distributes Fibre Channel functions among five layers. The five functional layers of the Fibre Channel are: FC-0—the physical media layer; FC-1—the coding and encoding layer; FC-2—the actual transport mechanism, including the framing protocol and flow control between nodes; FC-3—the common services layer; and FC-4—the upper layer protocol.
There are generally three ways to deploy a Fibre Channel network: simple point-to-point connections; arbitrated loops; and switched fabrics. The simplest topology is the point-to-point configuration, which simply connects any two Fibre Channel systems directly. Arbitrated loops are Fibre Channel ring connections that provide shared access to bandwidth via arbitration. Switched Fibre Channel networks, called “fabrics”, are a form of cross-point switching.
Conventional Fibre Channel Arbitrated Loop (“FC-AL”) protocols provide for loop functionality in the interconnection of devices or loop segments through node ports. However, direct interconnection of node ports is problematic in that a failure at one node port in a loop typically causes the failure of the entire loop. This difficulty is overcome in conventional Fibre Channel technology through the use of hubs. Hubs include a number of hub ports interconnected in a loop topology. Node ports are connected to hub ports, forming a star topology with the hub at the center. Hub ports which are not connected to node ports or which are connected to failed node ports are bypassed. In this way, the loop is maintained despite removal or failure of node ports.
More particularly, an FC-AL network is typically composed of two or more node ports linked together in a loop configuration forming a single data path. Such a configuration of a node port-to-node port loop is shown in FIG.
1
. In
FIG. 1
, six node ports
102
,
104
,
106
,
108
,
110
,
112
are linked together by data channels
114
,
116
,
118
,
120
,
122
,
124
. In this way, a loop is created with a datapath from node port
102
to node port
104
through data channel
114
then from node port
104
to node port
106
through data channel
116
, and so on to node port
102
through data channel
124
.
When there is a failure at any point in the loop, the loop datapath is broken and all communication on the loop halts. For example, if node port
104
fails, data no longer passes through node port
104
. A failure may also occur in a data channel between node ports, such as by a physical break in the wire or electromagnetic interference causing significant data corruption or loss at that point. At this point, loop
100
has been broken. Data no longer flows in a circular path and the node ports are no longer connected to one another. The loop has, in effect, become a unidirectional linked list of node ports.
A conventional technique to avoid broken datapaths in a node port-to-node port loop introduces a hub within a loop. A hub creates a physical configuration of node ports in a star pattern, but the virtual operation of the node ports continues in a loop pattern. The connection process (i.e., sending data between node ports) and interaction with the hubs is effectively transparent to the node ports connected to the hub, which perceive the relationship as a standard Fibre Channel arbitrated loop configuration.
FIG. 2
illustrates an arbitrated loop
200
with a centrally connected hub. Similar to loop
100
illustrated in
FIG. 1
, loop
200
includes six node ports
202
,
204
,
206
,
208
,
210
,
212
, each attached to a hub
214
. Hub
214
includes six hub ports
216
,
218
,
220
,
222
,
224
,
226
where each hub port is connected to another hub port in a loop topology by a sequence of internal hub links. In this way, node ports
202
-
212
are each connected to a corresponding hub port
216
-
226
. Thus, node ports
202
-
212
operate as though connected in a loop fashion as illustrated in FIG.
1
. Data typically flows into a hub port from an upstream hub port, into the attached node port, back from the node port to the hub port, and out of the hub port to a downstream hub port.
When a node port or a data channel fails or is disconnected, the loop is maintained by bypassing the failed node port. In a conventional hub, when a hub port no longer receives data from a node port, the hub port goes into a bypass mode. In bypass mode, rather than passing data received on the data channel from the node port, the hub port passes data received along the internal hub link from the previous, upstream hub port. Thus, nodes are removed and inserted in the loop by changing the corresponding hub port in and out of bypass mode.
The content of a datastream of an FC-AL network is defined by FC-AL protocols. Characters are constantly moving through the loop from one port to the next. These characters may be actual data or loop control signals. Loop control signals are always present in the datastream except when a data frame is being sent from a source node port to a destination node port. Under FC-AL protocols, the loop control signals are ordered sets, including primitive signals and primitive sequences. Ordered sets typically begin with a special character indicating the beginning of an ordered set, such as K28.5. A data frame is an uninterrupted stream of data preceded by a special ordered set called a Start Of Frame (“SOF”) and succeeded by a special ordered set called an End Of Frame (“EOF”).
A datastream of encoded characters ideally always has a valid “running disparity”. The encoded characters are defined according to a conventional
8
B/
10
B encoding scheme, defined in Fibre Channel protocols. The running disparity at the end of a character in the datastream is the difference between the number of 1's and 0's in the bit encoding of the character. A character with more 1's than 0's has a positive running disparity. A character with more 0's than 1's has a negative running disparity. A character with an equal number of 1's and 0's has a neutral running disparity. An encoder transmits a positive, negative, or neutral disparity encoded character. A neutral character does not affect the running disparity of the datastream. A positive character changes the running disparity from negative to positive and a negative character changes the running disparity from positive to negative.
Each word has an overall running disparity as well. The running disparity for a word determines the effect that word has on the running disparity of the datastream. As with characters, a word with a positive running disparity changes the running disparity to positive at the end of the word. Similarly, a word with a negative disparity changes the running disparity to negative and a word with a

Affiliated with

Also associated with

Rating

Node insertion and removal in a loop network does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Node insertion and removal in a loop network, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Node insertion and removal in a loop network will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2515609