Desktop Connectivity with Badge Ring
Token Arena is additionally a LAN technology that provides aggregate media admission to abounding connected
stations. Rather than administration a accepted bus or “wire” as Ethernet does, Badge Arena stations are
arranged in a ring, in a daisy-chain fashion. A badge is anesthetized from base to base about the
ring, giving the accepted badge holder permission to abode a anatomy assimilate the ring. Once the
frame is sent, it is anesthetized about the arena until it is accustomed afresh by the source. The sending
station is amenable for removing the anatomy from the arena and for introducing a new badge to
the abutting adjoining station.
Notice that alone one base can abode at a accustomed time—the one with the token. This
restriction prevents a Badge Arena arrangement from anytime acceptable a blow domain. Stations can
expect to accept the badge at approved intervals as it circulates the ring. This affection makes Token
Ring deterministic and advantageous for adjournment acute protocols. Frames can be beatific to a broadcast
Table 3-4 Gigabit Ethernet Cabling and Distance Limitations
GE Blazon Wiring Blazon Pairs Cable Length
1000BaseCX Shielded Twisted Pair (STP) 1 25 m
1000BaseT EIA/TIA Category 5 UTP 4 100 m
1000BaseSX Multimode cilia (MMF) with 62.5 micron core;
850 nm laser
1 275 m
MMF with 50 micron core; 1300 nm laser 1 550 m
1000BaseLX/LH MMF with 62.5 micron core; 1300 nm laser 1 550 m
Single-mode cilia (SMF) with 50 micron core;
1300 nm laser
1 550 m
SMF with 9 micron core; 1300 nm laser 1 10 km
1000BaseZX SMF with 9 micron core; 1550 nm laser 1 70 km
SMF with 8 micron core; 1550 nm laser 1 100 km
Desktop Connectivity with Badge Arena 75
MAC address, like Ethernet, causing all stations on the arena to listen. Therefore, a badge arena is
a advertisement domain.
A Badge Arena arrangement offers a bandwidth of 4 Mbps or 16 Mbps. At the college rate, stations
are accustomed to acquaint a new badge as anon as they accomplishment transmitting a frame. This early
token absolution increases ability by absolution added than one base abode a anatomy during the
original token’s annular trip. One base is adopted to be the arena monitor, to accommodate recovery
from delinquent frames or tokens. The arena adviser will abolish frames that accept circled the ring
once, if no added base removes them.
Traditional Badge Arena networks use multistation admission units (MSAUs) to accommodate connectivity
between end user stations. MSAUs accept several ports that a base can affix to, with either
a B adapter for Blazon 2 cabling or an RJ-45 adapter for Category 5 UTP cabling. Internally,
the MSAU provides station-to-station access to anatomy a arena segment. The Ring-In and
Ring-Out connectors of a MSAU can be chained to added MSAUs to anatomy a complete ring
topology.
Token Arena Bridging
To anatomy beyond networks, Badge Rings are commutual with bridges. Although a transparent
bridge (or one that assiduously frames based alone on MAC addresses) can be used, IBM
designed and alien Badge Arena differently. Source-route bridges are acclimated to forward
frames amid rings, based on a agreed path. The antecedent base includes the exact
ring-and-bridge aisle aural the anatomy so that specific bridges will advanced the anatomy to the
appropriate rings. Rings charge be abnormally numbered and articular with the campus network,
with a cardinal amid 1 and 4095. Bridges, however, do not accept to be different beyond the
network, as continued as two bridges with the aforementioned cardinal do not affix to the aforementioned ring. Bridges
are numbered 1 through 15.
The accomplish to actuate the aisle a anatomy should booty are as follows:
Step 1 The antecedent base aboriginal sends a analysis anatomy to see if the destination
is on the bounded ring. If the destination responds, the antecedent knows
that it is local. If there is no response, the antecedent base will send
an all routes charlatan (ARE) frame, which will account all bridges to
forward the anatomy to all rings.
Step 2 Aural the anatomy is a acquisition advice acreage (RIF). The RIF
carries a almanac of bridges and rings traversed alternating the way. As
the anatomy is forwarded, anniversary arch will adjoin its arch number
and the abutting arena cardinal to the RIF in the frame.
Step 3 The destination will again acknowledgment to anniversary ARE anatomy it receives, so
that the antecedent will accept a acceptance of every accessible path
to the destination.
76 Chapter 3: Basic About-face and Anchorage Configuration
For approaching transmissions, the antecedent can accept the aisle it thinks is best (quickest response,
least cardinal of arch hops, better best manual assemblage (MTU), aggregate of
factors, and so forth). These frames will accommodate the exact aisle adapted by the antecedent station, in
the anatomy of a RIF.
In assertive scenarios, amalgam bridging can be provided. Sometimes, both source-route bridging
(SRB) and cellophane bridging charge occur. Here, source-route cellophane bridging (SRT)
forwards a anatomy according to a RIF, if present, or according to MAC abode tables if it finds
no RIF.
As in Ethernet switching, Badge Rings can additionally be anecdotal by adding a arena beyond several
switch ports. While this affection increases the accessible bandwidth on a arena segment, it requires
more all-embracing forwarding decisions. Badge arena switching, or added appropriately termed sourceroute
switching, assiduously frames according to a aggregate of MAC addresses and RIF
contents.
Source-route switching differs from added forms of bridging in that it alone looks at the RIF and
never updates or adds to the RIF. Instead, the about-face learns avenue descriptors, or the ring/bridge
combinations that specify the next-hop destinations from admission frames. The source-route
switch again assembly the avenue descriptors and MAC addresses (if needed) with outbound
ports abutting to the destination. When consecutive frames are accustomed on added ports, the route
descriptor is bound indexed to lookup the outbound port.
In this fashion, source-route switching supports alongside source-route paths to destinations. The
number of MAC addresses to be abstruse is lessened, because avenue descriptors point to the nexthop
ports. The absolute operation of source-route switching is abundant like basic LANs with
Ethernet. For this reason, added altercation of source-route switching is presented in
Chapter 4, “VLANs and Trunking.”
Table 3-5 summarizes the attributes of anniversary blazon of Badge Arena connectivity and segmentation
method.
Table 3-5 Badge Arena Segmentation Methods
Method
Forwarding
Decision
Frame
Modification Arena Numbering
Transparent bridging MAC abode N/A
Source-route bridging RIF RIF Arena numbers charge be unique
among arch ports.
Source-route transparent
bridging
MAC abode or RIF RIF Arena numbers charge be unique
among arch ports.
Source-route switching Avenue descriptor Arena numbers can be same
across about-face ports (single ring
can be anecdotal on several
ports).