Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Reexamination Certificate
1999-06-10
2004-03-09
Marcelo, Melvin (Department: 2663)
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
C370S232000
Reexamination Certificate
active
06704280
ABSTRACT:
BACKGROUND
1. Field
The invention relates to the field of communications. More specifically, the invention relates to a switching device and method for policing the flow of information over a network.
2. General Background
Computer networks provide a mechanism for transferring information between various locations. One type of computer network, referred to as an Ethernet, is a packet-based local area network (LAN) using Carrier Sense Multiple Access with Collision Detect (CSMA/CD) access protocol. Typically, Ethernet is configured in accordance with Open System Interconnection (OSI) and the Institute of Electrical and Electronic Engineers (IEEE) 802.3 standard.
As shown in
FIG. 1
, an embodiment of the seven-layer OSI reference model
100
for a conventional Switched Ethernet is shown. Switched Ethernet comprises a physical layer
110
, a data link layer
120
, a network layer
130
, a transport layer
140
, a session layer
150
, a presentation layer
160
and an application layer
170
. More specifically, physical layer
110
is concerned with the transmission of bits across a medium (e.g., twisted pair, coaxial, optical fiber, etc.) while data link layer
120
is concerned with the point-to-point connection between two devices (e.g., switches, computers, etc.). As shown, data link layer
120
is separated into two sublayers, one of which is a media access control (MAC) sublayer
121
. MAC sublayer
121
not only arbitrates for access to the medium using its unique MAC address, but also produces data frames for subsequent transmission as a stream of bits over the medium.
Referring still to
FIG. 1
, network layer
130
is concerned with the transmission of data across multiple links or multiple networks connected by switches. For conventional Switched Ethernet, a policing function
180
is employed within network layer
130
or a higher level layer (e.g., transport). Policing function
180
enforces “traffic contracts” established by differentiated services for example (described below).
As set forth in an Internet Draft of the Internet Engineering Task Force (IETF) entitled “Differentiated Services” published on or around February 1999, differentiated services provides an architecture from which Internet Service Providers (ISPs) can offer a range of network services at different pricing to each customer. More specifically, a customer selects a particular level of service at a predetermined price. Upon selecting a service level, the customer has entered into a traffic contract with the ISP. The “traffic contract” involves the ISP agreeing to support a particular transmission bit rate associated with the chosen service level (referred to as the “negotiated bit rate”) in exchange for monetary compensation. Residing in network layer (OSI layer
3
)
130
for example, policing function
180
attempts to enforce the traffic contract. However, the latency realized in routing data from physical and data link layers
110
and
120
to network layer
130
prevents strict enforcement of the traffic contract.
As shown in
FIG. 2
, an illustrative embodiment of a conventional Switched Ethernet
200
is shown. Switched Ethernet
200
comprises a switch
210
that includes a finite amount of buffer memory
215
. In this embodiment, switch
210
operates as a multiport device having N addressable ports
220
1
-
220
N
(“N” is a positive whole number). A plurality of computers
230
are coupled to a portion of addressable ports
220
1
-
220
N
via a plurality of links
240
. This supports simultaneous, half or full-duplex transmissions of frames between computers
230
and addressable ports
220
1
-
220
N
of switch
210
. A “frame” includes one or more packets of data, address and/or control information arranged in a predetermined format. In addition, switch
210
is coupled to a link
250
.
It has been appreciated that Switched Ethernet may be implemented with different varieties of links. For example, link
250
may be a 100BASE-T link that offers a faster transmission rate than links
240
(e.g., 10BASE-T links). In certain situations, where switching device
210
is not able to handle burst transmissions from devices coupled to link
250
, network performance may worsen. Of course, this performance degradation could be reduced by adding substantial buffer memory to switch
210
at a substantial increased cost.
Recently, in accordance with IEEE 802.3x, additional features have been added to handle the above-described performance issues for full-duplex Switched Ethernet. For example, once buffer memory
215
is full, switch
210
is capable of throttling the transmission of incoming frames from a computer (e.g., computer
230
1
) by sending a particular type of Media Access Control (MAC) control frame
260
back to computer
230
1
. This type of MAC control frame
260
is referred to as a PAUSE frame. Once computer
230
1
decodes and recognizes incoming information as a PAUSE frame, computer
230
1
pauses the transmission of frames for the specified time period. Once the time period has expired, computer
230
1
continues to transmit frames. However, a PAUSE frame
260
is used solely and exclusively to handle overflow conditions of buffer memory
215
.
Hence, it would be desirable to develop a switching device and method to utilize data link layer functionality for enforcement of traffic contracts.
SUMMARY
The present invention relates to a switching device and method for policing a flow of information over a network. The policing function is situated at the data link layer and capable of receiving a transmission rate from a traffic contract at a higher level. The close proximity of the policing function to the physical medium enables stricter enforcement of traffic contracts.
For full-duplex communications, the policing function uses a PAUSE frame to throttle input. A PAUSE frame is issued when an accumulated count value has exceeded an interval bit rate based on the transmission rate set by a traffic contract. Multiple PAUSE frames may be used to halt transmissions beyond the maximum delay time provided by a single PAUSE frame. For half-duplex communications, the policing function relies on collision-based backpressure and carrier sense backpressure techniques.
REFERENCES:
patent: 5666353 (1997-09-01), Klausmeier et al.
patent: 5898673 (1999-04-01), Riggan et al.
patent: 5905870 (1999-05-01), Mangin et al.
patent: 6018517 (2000-01-01), Bengio et al.
patent: 6072989 (2000-06-01), Witters et al.
patent: 2002/0004379 (2002-01-01), Gruhl et al.
patent: 2002/0133589 (2002-09-01), Gubbi et al.
patent: WO 98 37730 (1998-08-01), None
Varadarajan, S., et al.: “EtheReal: a host-transparent real-time Fast Ethernet switch” Proceedings Sixth International Conference on Network Protocols )Cat. No. 98TB100256), Austin, TX, Oct. 13-16, 1998, pp. 12-21, XP002160322; 1998, Los Alamitos, CA, IEEE Comput. Soc. ISBN: 0-8186-8988-9.
MacLeod, B.: “Gigabit Ethernet Full-Duplex Repeaters”; Annual Review of Communications, 1997, XP000720916, p. 505.
Engel, R., et al: “Exploring the Performance Impact of QOS Support in TCP/IP Protocol Stacks” Proceedings IEEE Infocom; The Conference on Computer Communications, New York, NY; IEEE, Mar. 29, 1998, pp. 883-892; XP000852074; ISBN: 0-7803-4384-0.
Kalkunte Mohan V.
Mangin James L.
Munshi Sanjay
Blakely , Sokoloff, Taylor & Zafman LLP
Marcelo Melvin
LandOfFree
Switching device and method for traffic policing over a 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 Switching device and method for traffic policing over a network, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Switching device and method for traffic policing over a network will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3253139