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Data collection models, 568
Data Collection Modules (DCMs), 655
Datagrams, 553
Data Link Layer (OSI reference model), 18
Data Link Layer (TCP/IP protocol suite), 28–29
defined, 27
LLC sublayer, 29
Mac sublayer, 28–29
Data replication/disk mirroring, 399
Data Service Units (DSUs), 40–41
Dead host detection, 507
DECbit, 499
Decentralized model, 22
Dedicated VPNs, 352, 356
Default routes, 166
Demand circuits, 185–86
acknowledgments/retransmissions, 185–86
defined, 185
flow control, 186
presumption of reachability, 185
triggered updates, 185
Demilitarized Zone (DMZ), 37
Democratic model, 518
Denial of Service (DOS), 307
Dense distribution model, 255
Dense-mode PIM (PIM-DM), 276–78
conditions for use, 276–77
defined, 276
illustrated, 277
operations, 277–78
PIM-SM vs., 280
See also PIM
Dense Wave Division Multiplexing (DWDM), 400
Deployment, 14
Design. See Network design
Designated forwarder
defined, 267
DVMRP, 271
OSPF, 201–2
Designated Router (DR), 201–2
election of, 202
LSA generation by, 275
misconception, 201
purpose, 201
Desktop management, 431–32
Detailed Requirements Specification, 7–8
Deterministic flow hashing, 515, 516
Dial on Demand Routing (DDR), 420
Dial VPNs, 351, 353–55
client-initiated, 354–55
defined, 351
NAS-initiated, 355
operation, 355
service providers and, 354
See also Virtual Private Networks (VPNs)
Differentiated Services (DS), 563–64, 617–23
advantage, 618
architecture, 619
boundary nodes, 620–22
byte format, 619
CBR with, 626
design considerations, 620–23
domains, 620
goal, 618
interior nodes, 622–23
with IPSec, 626
PHB, 619–20
RSVP with, 624–25
service marking, 618–19
source domains, 623
specifications, 617
summary, 629
traffic conditioner, 621–22
Diffie-Helman (D-H) model, 321
Diffusing Update Algorithm (DUAL), 164–65
Dig, 693–94
Digital signatures, 324, 372–73
Directed broadcast, 64–65
Direct interface routing, 166
Directory-Enabled Network (DEN), 131
Directory Service Markup Language (DSML), 126
Directory services, 122–31
benefits, 122
client/server model, 124
defined, 122
DEN and, 131
LDAP and, 126–31
name services and, 123
networked file systems and, 123
RDBMSs and, 123–24
relational databases and, 123
uses, 123
when not to use, 124–25
X.500 standard, 125–26
Disaster recovery
data replication/disk mirroring, 399
defined, 394
electronic vaulting, 398
models, 398–401
outsourced, 401
SANs/OSNs, 400
server mirroring/clustering, 399
tape/CD site backup, 398
Disaster Recovery (DR) plan
approach, 397–98
defined, 397
development, 395–401
Disk compression, 542–43
Disk mirroring, 458–59
Distance-Vector Multicast Routing Protocol. See DVMRP
Distance-vector routing algorithms, 161–65
convergence, 172
defined, 161
flooded updates, 163
hybrid, 164–65
link-state routing vs., 162–65
RIP routing enhancements, 186–87
See also Routing protocols
Distributed hashing techniques, 518–19
Distributed load-sharing algorithms, 505–6
Distributed model, 23–24
CORBA, 23, 24
defined, 22
IIOP, 24
Documentation, 13–14
Domain names, 108–10
format, 109–10
FQDNs, 110
hierarchy, 109
registration, 110
SLDs, 110
TDLs, 108, 109, 110
Domain Name System (DNS), 107–21
access, 107
administrator, 113
caching, 117, 120
components, 110–14
defined, 36, 107
Domain Name Space, 111
dynamic, 119
extensions, 108
implementing, 117–19
inverse query operation, 116–17
ISP maintained primary and locally maintained secondary service, 118–19
ISP maintained primary/secondary service, 117–18
load sharing, 507–9
load-sharing proxies, 454
locally maintained primary/secondary service, 118
mapping names to addresses, 116
name resolvers, 113–14
name servers, 112–13
operations, 114–17
performance, 120–21
queries, 113
query operation, 114–15
resilience, 119
Resource Records (RR), 111–12
running over UDP or TCP, 110
SOHO configurations and, 121
split, 119
structure, 108
vulnerabilities, 310–11
Domains
DS, 620
source, 623
tree hierarchy, 112
zone relationship, 113
Downstream interfaces, 266
Downtime cost, 394–95
example, 396
financial models, 395
Dual-Modular Redundancy (DMR), 436
Dual port transceivers, 430–31
DVMRP, 264–72
building multicast trees, 268–71
defined, 264
designated forwarder, 271
design issues, 272
field definitions, 265–66
functioning of, 265
grafting, 271
interoperability, 283
message format, 265–66
multicast network running, 270
operation, 266–72
pruning, 269–70
routers, 268, 371
routing process, 267–68
terminology, 266–67
timers, 267
tunneling, 271–72
versions, 272
See also Multicast routing
Dynamic Address Translation (DAT), 134
Dynamic DNS, 119
Dynamic Host Configuration Protocol (DHCP), 95–102
address allocation, 96
allocating new network address, 97
BOOTP concurrent use, 102
client/server interaction, 98–100
defined, 95
features, 95
field definitions, 97–98
lease renewal, 100–101
message format, 96–97
operations, 97–101
running over UDP, 101
Safe Failover Protocol, 102
Dynamic router discovery, 174
Dynamic routing entries, 166
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