LOKALNE SIECI

KOMPUTEROWE

Specyficzne rozwiązania dla sieci LAN

(100VGAnyLAN, IsoEthernet)

100VG-AnyLAN

100VG-AnyLAN was developed by HP as an alternative to CSMA/CD
for newer time-sensitive applications, such as multimedia.
The access method is based on

Demand Prioryty Access Method

and was designed for Ethernet and 16-Mbps Token Ring.
100VG-AnyLAN supports the following cable types:
• 4-pair Category 3 UTP
• 2-pair Category 4 or 5 UTP
• Fiber optic

IEEE 802.12 100VG-AnyLAN standard specifies

the link-distance limitations

,

hub-configuration limitations, and maximum network-distance limitations.
Link distances from node to hub are 100 meters (Category 3 UTP)
or 150 meters (Category 5 UTP).

100VG-AnyLAN hubs are arranged hierarchically.
Each hub has at least one

uplink port

, and every other port can be a

downlink port

.

Uplink port

Downlink port

100VG-AnyLAN

100VG-AnyLAN Operation

Half Duplex Operation

Full Duplex Operation
(e.g. Ring Network)

25 Mb/s per pair
gives 100 Mb/s

25 Mb/s per pair
gives only 50 Mb/s

100VG-AnyLAN - Demand Priority Link Protocol

Demand Priority uses a small number of control signals:
- four control signals sent from Hub to End Node,
- four control signals sent from End Node to Hub.
In a 4-pair UTP link, the control signals are implemented as low

frequency tones.

Each of two pairs transmits one of two possible low frequency

tones,

giving four control signals in each direction.

The link has 3 states:
1. Hub is sending a frame at 100 Mb/s to End Node
2. End Node is sending a frame at 100 Mb/s to Hub
3. Hub and End Node are exchanging control signals.

1. 25 Mb/s data
on 4 pairs

2. 25 Mb/s data
on 4 pairs

3. Control signal tones
in both directions

100VG-AnyLAN - Demand Priority Link Protocol

A. Link Protocol Sequence of the End Node

transmitting frame

1. End Node
sends Request

2. Hub clears
link

3. Frame
transmitted at
25 Mbps per pair

4. Control
signals resume

(1) When End Node has a frame to send, it sends up a control signal REQ-H

(High Priority Request)

or REQ-N (Normal Priority Request) to the Hub.
(2) When the Hub decides to select this particular End Node, it stops actively

sending the control signal

on 2 pairs, in effect it clears the link to the End Node.
(3) When the End Node senses that there is no signal on the link, it realises

that it has been selected

to transmit by the Hub. It can transmit immediately on 4 pairs.
(4) When the frame is finished, the Hub will send IDLE,
and the End Node will send REQ-H or REQ-N (depending on the priority

level of further frames

to be transmitted) or IDLE (if there are no such frames).

100VG-AnyLAN - Demand Priority Link Protocol

B. Link Protocol Sequence of the End Node

receiving frame

1. Hub and End
Node exchange
control signals

2. Hub sends
INCOMING

3. End Node
clears link

4. Frame
transmitted
at 25 Mbps per pair

(1) The Hub and End Node are exchanging control signals.
(2) The Hub is expecting to receive a frame from some other

End Node.

It sends INCOMING to the End Node.
(3) A short time later, the End Node clears the link.
(4) The link is now clear, so the Hub is able to start sending the

frame on all 4 pairs.

100 VG Any LAN – Round Robin

Demand Priority uses a 2-priority

Round Robin.

The Hub services High Priority Requests before

any Normal Priority Requests are serviced: 1, 3, 2, 4

Hub A

Node 1

Node 2

Node 3

Node 4

REQ_H

REQ_N

REQ_H

REQ_N

Round Robin

100 VG Any LAN - Cascading of Hubs



The each Demand Priority Hubs have a port acting as

a Cascade port,

which

is connected to the Hub in the next level up.



Each of the Hubs are identical.



A Hub knows that it is

the Root Hub

by the fact that it has no communication

through its Cascade Port.

If all of the Nodes have frames to transmit at the same priority level,
then the order of transmitting frames is the same sequence:
Node 1, then Node 2, Node 3, then Node 4, … up Node 10.

Root Hub

Hub A

Hub D

Hub B

Hub C

Hub E

Hub F

Node3

Node4

Node1

0

Node1

Node2

Node5 Node6

Node7

Node8

Node9

Cascade port

Level III

Level II

Level I

What is Isochronous Ethernet (IsoEthernet)?



When an IsoEthernet-equipped sends Ethernet data traffic,

data goes from the IsoHub/Switch to Ethernet hub
and is handled like all other Ethernet transmissions.


When an IsoEthernet-equipment sends isochronous traffic (e.g. voice, video),

IsoHub/Switch sends data to either a PBX
or to a Time-division Multiplexer (TDM) via E-1 or ISDN PRI/PRA trunk.
The bandwidth, required for a specific video/audio call is allocated end-to-end.

IsoEthernet provides a way to bring both

Ethernet and ISDN

services.

IsoEthernet is an enhancement of Ethernet (10Base-T) that includes:
- 6.144 Mbps isochronous data service
- 10 Mbps Ethernet packet service.

Isochronous Ethernet complies to a lot of standards from ITU and IEEE:



ITU-T recommendation H.320 service over N-ISDN networks



ITU-T recommendation H.322 (H32Z.1) modified H.320 for LANs

which provide the same QOS as that of N-ISDN


ITU-T recommendation H.221 protocol layer, does multiplexing and demultiplexing



ITU-T recommendation G.711/G.722/G.728 audio compression algorithm



ITU-T recommendation H.261 video compression algorithm



ITU-T recommendation H.230/231 and H.242/243 in-band signalling

for exchanging commands and capabilities


ITU-T recommendation T.120 protocols which include support

for file transfers, conference control, etc.


ITU Q.93.i network layer ITU Q.921 data link layer



IEEE 802.9 Integrated Services LAN committee specification IEEE 802.9a

defined the physical Layer of Isochronous Ethernet


IEEE 802.3 Carrier Sense Multiple Access Collision Detection (CSMA/CD) specification



ITU LAPD ISDN-D channel specification

The standards family for IsoEthernet

A multimedia service using IsoEthernet

as the integrated services LAN.



A typical IsoEthernet configuration includes a set of Multimedia End Stations (MM ES)

connected to an Access Unit (AU) in a star configuration.


The network side of the AU offers connections to both ISDN and 10Base-T LAN.



Each end station can simultaneously access:

- ISDN (up to 6.144 Mbps for isochronous traffic using)
- 10Base-T LAN (10 Mbps packet traffic) services

ISD

N

LAN

IsoEthernet AU

MM ES

MM ES MM ES

…

PRI

10Base-T

IsoEthernet Interface (16,144 Mbps)

Voice, video and data services

MM ES – Multimedia End Station

IsoEthemet network configuration

ISD

N

LAN

LAN

Isochronous traffic

Synchr./Asynchr. traffic

MM ES

MM ES

MM ES

…

Is

o

E

th

e

rn

e

t

A

U

Is

o

E

th

e

rn

e

t

A

U

MM ES

MM ES

MM ES

…

IsoEthernet

interface

IsoEthernet

interface

MAN, WAN

MAN, WAN

Multimedia End Station and Acces Unit architecture

Video

Audio

Data

IsoEthernet

interface

to IsoEthernet AU

Management

Operational system

H.261/ H.320, T120, …

MM ES

AU

Port #1

Port #N

Packet

switch

Isochr.

switch /

mux.

…

ISDN

LAN

Control

MM ES

MM ES

PMA H-Mux

D, M channel

P channel

C channels

H.261 - video compression algorithm
H.320 - service over N-ISDN networks
T.120 - support for file transfer,
conference control, etc.

IsoEthernet – OSI Model

Physical Layer:

-

HMUX (Hybrid Multiplexing) data from P, C, D and

M – channels,

- PS (Physical Signalling) to 4B/5B coding data,
- PMD (Physical Medium Dependent).

Physical Layer

Link Layer

Management

Sub-Layer Plane

(M-channel)

Management

Layer Plane

Ethernet

P- channel

D – channel /

LAPD

C - channels

HMUX

PS

PMD

…
…

Start P B

B

P

D

D

M

M

…
…

Start P B

B

P

D

D

M

M

…
…

Start P B

B

P

D

D

M

M

0

125

25

0

Time
[s]

Bytes

1

2

3

4

251 252 253 254 255 256

IsoEthernet Frame

Start of Frame Channel:

It carries the start of TDM frame synchronization pattern, which allows the

remote station to detect

the beginning of the TDM frame. It also allows Phase Lock Loops (PLLs) at

the remote end

to synchronize to the incoming frame.

P-channel:

A half or full-duplex 10 Mbps 10BASE-T transport channel for packet traffic.
It obeys the CSMA/CD protocol and is compatible to regular Ethernet.

C-channel:

A full-duplex isochronous circuit-switched channel which offers a multiple of 64 kbps (B-channel) service.
B-channels are provisioned in the same manner as N-ISDN B-channels.

D-channel:

A full-duplex 64 kbps packet channel which is used for transporting call

control and supplementary

Services such as conferencing, call hold, transfer for the C-channel.

M-channel:

A full-duplex 96 kbps channel which transports physical layer control

and status informations

to the remote end of the link.

IsoEthernet – type of channels

The multiple channels are provided through the use of Time Division Multiplexing (TDM).
The information stream is comprised of a continuous sequence of 125 sec (8 KHz)

TDM frames. Each frame consists of up to 256 bytes of information.

10BASE-

T

mode

Muliservice mode

All – isochronous

mode

B /

frame

Data rate

B /

frame

Data rate

P -
channel

10 Mbps

156,5

10 Mbps

-

-

C -
channels

-

96

6,144

Mbps

248

15,872

Mbps

D -
channel

-

1

64 kbps

1

64 kbps

M -
channel

-

1,5

96 kbps

1,5

96 kbps

Overhead

-

1

80 kbps

5,5

352 kbps

Total

-

256

16,384

Mbps

256

16,384

Mbps

Modes of Operation

10BASE-T mode:

The Isochronous Ethernet is fully compatible to to 10Base-T Ethernet. No

TDM frame, no channels.

Multi-service mode:

Both packet and isochronous services are provided. A single 10 Mbps P-channel is dedicated
to the packet traffic, a 6.144 Mbps C-channel (96 B-channels), handles the isochronous services.
A 64 kbps D-channel is used for signalling and a 96 kbps M-channel for maintenance.
Each TDM frame starts with the Start of Frame Channel, which operates at 64 kbps.

All-isochronous mode:

The complete bandwidth is used for circuit-switched isochronous services.
A 15,872 Mbps C-channel (248 B-channels), 64 kbps D-channel, 96 kbps M-channel
and 64 kbps Start of Frame Channel. This mode utilizes the 8 KHz based TDM frame format.