An alternative to Fast Ethernet that provides Mbps communications based on technology developed by Hewlett-Packard. VG-AnyLan is based on the. Download scientific diagram | A typical network connguration in VG-Any LAN from publication: VGAnet: A Real-Time Transport Protocol Suite for VG-Any. The data delivery protocol stack consists of the data link layer protocol, VG- Any LAN, as well as RDTP. The architecture of VGAnet Suite is.

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Skip to main content. 100bg-any In Sign Up. They do not solve the unbounded jitters for a continuous stream and skew between two synchronized streams problems introduced by the underlying LAN. They also do not provide any QoS guarantees to the applications. They do not include bandwidth reservation mechanisms nor any other mechanisms to bound jitters of streamed packets.

Hub Host 1 Host Host N Figure 1: The architecture of this network is switched and centered around an intelligent hub instead of a network switch. The VG-Any LAN technology uses the demand priority 10vg-any to manage the network access of each end node attached to the hub.

With the demand priority protocol, an end node issues 1000vg-any request to its local hub when it has a frame to transmit.

The hub checks for requests from its attached end nodes and indicates to one end node that it may transmit a frame. The hub simply waits until it observes a request and then serves it; the 10v0g-any does not actively pool the 100vg-zny nodes to see if they might have a frame to send. The hub does not operate in the store-and-forward lwn, but passes the Ethernet frames immediately. Round-robin node selection ensures a fair access for all nodes to the hub.

The paper is outlined as follows: Section 2 discusses related work in the area of real- time communication system. Section 3 outlines the overall architecture of the VGAnet Suite. In Section 6, we describe our experiments and measurements of the protocols. Finally, in Section 7, we conclude with a brief summary. However, so far, there 100vb-any been very few designs and implementations utilizing the VG-Any LAN networking service and almost all of these protocols do not deal with the inter-stream synchro- nization skew problem.

ST-II is a connection-oriented internetwork protocol which has been proposed to handle the requirements of real-time clients [3].


The protocol utilizes the FlowSpec to specify the application’s QoS requirement. RSVP has been designed as a protocol for exchanging reservation messages [4]. It provides receiver-initiated 100vg-sny reservations of bandwidth to accommodate heterogeneity among receivers as well as dynamic membership changes, but plays no other role in providing network services. The Tenet Real-Time Protocol Suite is a set of network protocols providing real-time guar- antees in heterogeneous packet-switching internetworks [5].

Furthermore, RTIP, the network layer protocol of the Tenet Suite, contains a rate control module and a scheduling module to ensure a connection’s performance guarantees. In contrast to the VGAnet Suite based on an intelligent hub, these two modules of the Tenet Suite had to be implemented in each switch along the path, while the VGAnet Suite implemented them within end nodes. The supporting protocols in the VGAnet Suite include: Real-Time Connection Management Protocol RCMP is responsible for admission control on the bandwidth reservation, connection setup and resource allocation, as well as connection teardown and resource deallocation.


By appropriate network access scheduling between sending streams, bandwidth utilization of each stream is guaranteed and prevents streams from exceeding their negotiated bandwidth allocation. In addition, LRMP handles the task of admission control test on the delay jitter and synchronization skew. Architecture of VGAnet Suite: First, we will describe the bandwidth allocation in the VG-Any LAN to provide bandwidth guarantees for each stream. Figure 3 illustrates how the higher level protocol 100vg-nay can use the high and normal priorities.

Data applications on existing protocol stacks, e. The two priorities are absolute – a hub will always serve 10vg-any high priority data frame transmission before a normal priority one, even if the high priority requests are always from the same source. In the VGAnet Suite scheme, real-time connection setup and bandwidth allocation are performed before the data transmission.

RCMP messages performed to release the allocated network resource. The real-time connection is teardown after successfully releasing bandwidth reservation. In current design, BACE is located in one dedicated node. The real-time multimedia applications operate using the client-server paradigm. End nodes involved in the real-time communication operate as either a server node passive node or a client node active node.

The server node passively waits for the connection requests from the client node. It is the client node 010vg-any actively sends the connect request message to the server to establish a real-time connection. RCMP assumes a reliable message delivery system; it does not provide any error recovery in the face lsn lost or corrupted control messages.

Connection establishment is performed in a double round trip. Three 100vb-any scenarios for establishing a real-time connect in RCMP protocol. Therefore, here we only discuss the high priority connection laj and teardown. Figure 4 shows the message ows in the connection establishment phase in three possible scenarios.

Admission control on the bandwidth is performed using a simple criterion. The QoS parameters are listed in Table 2.

In 100vg-ang, Smax is related to the timeout parameter T. Hence, the larger the parameter Smax is, the larger the parameter T is. The admission control criterion of bandwidth is described in equation 1. The message ows in the connection teardown phase.

Finally, either the client or the server can request the release of an established real-time connection. Figure 5 shows the message ows in the connection teardown phase. RDTP provides unreliable, connection-oriented, guaranteed-performance, in- order packet delivery service. 100gg-any and la, the usual error correction and packet loss solution used in a reliable protocol such as TCP, are not appropriate for those real-time applications with stringent delay bounds and for most continuous-media applications.

Reliability can be provided by layers on top of RDTP when needed. RDTP does not implement any kind of ow or congestion control 100vg-ahy. Furthermore, RDTP does not address the issue of packet reordering. Therefore, all packets in the same connection will follow the same path. All packets will be delivered in order. RDTP provides a checksum for its header, and optionally checksum for user data. One of the major functions provided by RDTP is fragmentation and reassembly. The receiving end node uses the bit message sequence number, bit packet sequence number, and bit last packet number to reassemble the received message.

The periodic timer wakes up the scheduler. The scheduler generates byte-counting tokens and assigns the 100vg-nay to one of the senders according to the round-robin scheduling algorithm. The scheduler puts itself to sleep after making the token allocation decision.



Each sending stream must capture and destroy N tokens to send a N -bytes data frame. The number of byte-counting tokens in each time slot, that is, the token generation rate, is calculated as follows: This property means that the sender may accumulate the tokens to send large bursts later. The scheduler executes the following tasks in a loop manner: Everytime a sending stream wants to send a data frame, it must check if there are enough tokens for the data frame.

If the answer is positive, the data frame is transmitted and the number of tokens is decreased by the size of the transmitted data frame. Otherwise, the application waits until it accumulates enough tokens to send the data frame.

Consider the example in Table 3. There are 3 active sending streams in the node. The time frame of a round is 30ms, it contains 3 time slots of 10ms, which is the period of the periodic timer used to wake up the scheduler.

Each time slot is 10ms. First, there is only one connection with CID Figure 7 shows how the token number of each connection will be updated with the establishments of new connections in an end node using the example in Table 3.

Figure 8 shows how the scheduling task is performed in LRMP for this example. Note that a new connection is always placed at the end of the dispatch table in the token scheduling.

VG-AnyLAN Basics

Scheduling of three 100gv-any sending streams within one end node. The scheduler performs two tasks in a loop: This is very useful in the skew admission control test which will be discussed later. Round-robin scheduling ensures that each sending stream has a chance to get the tokens every round time frame. In addition, regulating the token generation rate prevents the send streams from exceeding their bandwidth reservations.

Note that the scheduler in LRMP only lzn the generation rate of tokens.

VGAnet: A real-time transport protocol suite for VG-Any LAN | Klara Nahrstedt –

The sending streams need to get not only the tokens to send data, but also the CPU time to execute the transmission actions. A customized CPU scheduling according to the token scheduling will help to get a better resource control in lann networking activities. It is a future work to extend the current design of the VGAnet Suite. In the connection setup phase of a new 100vvg-any, the admission control test on Jmax will be per- formed for each connection, including the existing ones and the new one, to make sure the delay jitter requirement of each connection will not be violated with the establishment of the new connection.

Admission control on Jmax 100gv-any performed using the following criterion: Figure 9 shows the derivation of the admission control test formula using an example. Without an appropriate CPU scheduling, the sending stream is not guaranteed to have the CPU time to send data during its time slot.

Assume that there are two admitted connections and the third connection to be admitted.