TCP/IP Tutorial and Technical Overview - IBM Redbooks

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SNMP agent implementations provide no means for a user to make new objects available. The SNMP DPI addresses this issue by providing a lightweight mechanism that permits users to dynamically add, delete, or replace application-specific or user-specific management variables in the local MIB without requiring recompilation of the SNMP agent. This is achieved by writing a subagent that communicates with the agent through the SNMP distributed programming interface (DPI), described in RFC 1592. The SNMP DPI allows a process to register the existence of a MIB object with the SNMP agent. When requests for this object are received by the SNMP agent, it will pass the query on to the process acting as a subagent. This subagent then returns an appropriate answer to the SNMP agent, which then packages an SNMP response packet and sends it to the remote network management station that initiated the request. The DPI communication between the SNMP agent and the subagent is transparent to the remote network management stations. This communication can occur over a variety of transports, including stream, datagram, and UNIX sockets. Using the SNMP DPI, a subagent can: ► Create and delete subtrees in the application-specific or user-specific MIB ► Create a register request packet to inform the SNMP agent of the MIB supported by the subagent ► Create response packet to answer requests received from the SNMP agent ► Create a TRAP request packet to be delivered by the SNMP agent to remote management stations 420 TCP/IP Tutorial and Technical Overview
The interaction between a subagent and the SNMP agent is illustrated in Figure 11-5. SNMP Agent SNMP DPI Figure 11-5 SNMP DPI overview Open Response Register Response Get/Getnext/Set Response Trap ARE_YOU_THERE Response Unregister Response Close DPI Interface Client or SNMP subagent An SNMP subagent, running as a separate process (potentially on another machine), can set up a connection with the agent. The subagent has an option to communicate with the SNMP agent through UDP, TCP sockets, or other mechanisms. After the connection is established, the subagent issues a DPI OPEN and one or more REGISTER requests to register one or more MIB subtrees with the SNMP agent. The SNMP agent responds to DPI OPEN and REGISTER requests with a RESPONSE packet, indicating success or failure. As the SNMP agent receives queries from remote management stations, any requests for an object in a subtree registered by a subagent are forwarded through the DPI to that subagent. These requests are in the form of GET, GENEXT, or SET. Chapter 11. Application structure and programming interfaces 421
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TCP/IP Tutorial and Technical Overv
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Note: Before using this information
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2.7 Frame relay . . . . . . . . . .
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5.4.2 RIP-2 limitations . . . . . .
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8.4 RFCs relevant to this chapter .
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12.4.7 LDAP and DCE . . . . . . . .
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16.1 Web browsers . . . . . . . . .
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21.1 IPTV overview . . . . . . . .
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24.6.1 Introduction . . . . . . . .
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Trademarks The following terms are
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► TCP/IP and System p: http://www
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Thanks to the following people for
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xxiv TCP/IP Tutorial and Technical
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Finally, other standard protocols e
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1.1 TCP/IP architectural model 1.1.
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To be able to identify a host withi
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est-effort service. As a result, ap
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The client/server model TCP is a pe
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Gateway Interconnects networks at h
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1.2.1 ARPANET the last release of t
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Integrated Digital Network Exchange
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1.2.4 Internet2 coordination. RIPE
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1.2.5 The Open Systems Interconnect
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The process of standardization is s
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Protocol status can be any of the f
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1.4 Future of the Internet Trying t
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28 TCP/IP Tutorial and Technical Ov
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2.1 Ethernet and IEEE 802 local are
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► Introduced in 1985, RFC 948 - T
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The mapping of 32-bit Internet addr
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There are a large number of propose
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2.5 Integrated Services Digital Net
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► The value hex 81 (binary 100000
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process the incoming packet (refer
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frame size, retransmission timer, a
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2.8.1 Physical layer PPP presents a
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Basic InATMARP operates essentially
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The client handles the table update
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To be exact, the TCP/IP PDU is enca
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The address resolution in an ATM ne
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LANs. Each separate LE layer needs
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services of a classic LAN; thus, th
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2.11.3 MPOA functional components T
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Destination resolution The action o
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3.1 Internet Protocol (IP) 3.1.1 IP
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There are five classes of IP addres
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3.1.2 IP subnets Special use IP add
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Therefore, it is normal to use a co
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Because of the all bits 0 and all b
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► Hosts or networks for which the
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► The default route that contains
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To differentiate between subnets, t
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3.1.4 Methods of delivery: Unicast,
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Anycasting Sometimes, the same IP s
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212.0.0 - 213.255.255 RIPE NCC 214.
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Originally, NAT was suggested as a
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packet, the destination address is
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As shown in Figure 3-14, Network Ad
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class of the network number (thus t
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3.1.9 IP datagram Therefore, a larg
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► Service Type: The service type
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► Destination IP Address: The 32-
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Fragmentation When an IP datagram t
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Pointer This field points to the op
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► Because IP routers are not requ
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3.2.1 ICMP messages ICMP messages a
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5 Source route failed 6 Destination
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Figure 3-34 ICMP: Router Solicitati
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Timestamp Request (13) and Timestam
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Record routes Record the route per
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An exception to the rule is the asy
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ARP packet reception When a host re
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different physical device, it will
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BOOTP is a draft standard protocol.
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Length Hardware address length in b
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3. The value of the hops field is i
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3.7.1 The DHCP message format The f
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Options The first four bytes of the
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3. The client receives one or more
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Figure 3-46 shows the DHCP process
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administration workload and removes
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► RFC 2474 - Definition of the Di
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4.1 Ports and sockets 4.1.1 Ports T
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► An association is the 5-tuple t
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The UDP datagram has an 8-byte head
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4.3.1 TCP concept Communication, or
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The window principle A simple trans
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Imagine some special cases: ► Pac
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TCP segment format Figure 4-10 show
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158 TCP/IP Tutorial and Technical O
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SACK option Selective Acknowledgmen
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A problem now arises, because the s
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► TIME-WAIT: FINs have been recei
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sender, while the advertised window
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most one segment each round-trip ti
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2. Each time another duplicate ACK
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Figure 5-1 shows an environment whe
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Figure 5-2 on page 173 depicts the
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► To provide more efficient resou
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Figure 5-3 Shortest-Path First (SPF
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5.2.5 Hybrid routing ► Unless the
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The RIP packet format is shown in F
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Figure 5-5 illustrates the distance
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can be considerable. Figure 5-7 ill
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The limitation to this rule is that
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► Support for multicasting: RIP-2
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5.4.2 RIP-2 limitations Authenticat
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The use of the command field and th
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5.6 Open Shortest Path First (OSPF)
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Intra-area, area border, and AS bou
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► Hello and dead intervals: The r
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neighbors. This store and forward a
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All OSPF packets share the common h
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Step 1: Database exchange process T
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Area 1 Area 0 Figure 5-18 OSPF virt
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In this example, the ASBR is redist
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In this figure, the ASBR is adverti
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EIGRP processes the information in
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5.9.1 BGP concepts and terminology
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► Routes and paths: A route assoc
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► Full mesh of BGP sessions withi
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RFC 4271 recommends a 90 second hol
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Each path attribute is placed into
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► LOCAL_PREF (local preference):
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5.9.6 BGP aggregation ► Redistrib
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ecause AS 2 does not know this aggr
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Figure 5-29 also illustrates the in
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► Ease of implementation: Distanc
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6.1 Multicast addressing Multicast
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address. In this situation, multica
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The fields in the IGMP message cont
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In Figure 6-4 on page 245, the Type
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To join a group, the host sends an
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amount of processing involved in re
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6.4 Multicast forwarding algorithms
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The disadvantage to the center-base
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When the routers exchange their rou
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6.5.3 DVMRP tunnels Some IP routers
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6.6.2 MOSPF and multiple OSPF areas
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6.7.1 PIM dense mode The PIM-DM pro
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Building the PIM-SM multicast deliv
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RP selection An RP is selected as p
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See Figure 6-14 for an overview of
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6.9.1 MBONE routing MBONE will most
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of multicast systems has accelerate
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7.1 Mobile IP overview Mobile IP en
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Figure 7-1 shows a mobile IP operat
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The prefix lengths extension can fo
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D Decapsulation by mobile node. The
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7.2.1 Tunneling The home agent exam
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When a mobile node moves from its h
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8.1 Why QoS? In the Internet and in
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8.2.1 Service classes The Integrate
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a specific bandwidth, a maximum pac
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obeying a token bucket (r,b) and be
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If the path message reaches the fir
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Figure 8-6 shows the reservation pr
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Path and reservation states can als
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RSVP message format An RSVP message
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Style The Style object defines the
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The RSVP Resv messages looks simila
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Integrated Services, described in 8
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different priorities, the DS field
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Figure 8-15 shows the use of bounda
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The traffic conditioner is mainly u
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Figure 8-18 shows the traffic condi
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Intserv model end-to-end across a n
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2. HostA generates a RSVP PATH mess
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Figure 8-21 shows the cooperation o
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► RFC 2212 - Specification of Gua
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9.1 IPv6 introduction 9.1.1 IP grow
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Eventually, the specification for I
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vers Figure 9-3 IPv6 packet contain
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Where: Type The type of the option.
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source routing, which operates in a
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► It improves multicast scalabili
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Global unicast address format IPv6
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Scope 4-bit value indicating the sc
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9.2.4 Flow labels Figure 9-10 Traff
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9.2.6 Packet sizes If the algorithm
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9.3 Internet Control Message Protoc
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Address resolution Figure 9-15 show
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The response to the neighbor solici
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IP Header Option 2 Figure 9-18 Rout
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(for example, a new workstation tha
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outer A has forwarded the packet to
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The stateless autoconfiguration pro
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Note the following fields in the IP
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The following extensions are specif
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Some example searches expressed inf
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12.4.6 LDAP URLs agree on a common
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LDAP interface for the GDA One way
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key piece to building intelligent n
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► RFC 4505 - Anonymous Simple Aut
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13.1 Telnet Telnet is a standard pr
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► The NVT provides a local echo f
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Number Name State RFC STD 12 Output
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The Interpret As Command (IAC) char
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Send Reply Meaning The terminal typ
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locks following the command. Howeve
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Principle of operation REXECD is a
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13.3.1 DCE directory service When w
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In order to find a resource in anot
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Login facility Provides the environ
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4. Now the user needs the authoriza
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e defined as single threading. A th
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environment. It also provides a way
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13.4.1 File naming DFS follows the
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typically provided by an operating
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14.1 File Transfer Protocol (FTP) F
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► Navigate and manipulate the dir
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14.1.3 The active data transfer Whe
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command would receive an error when
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long, with the first two digits hav
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This command instructs the FTP serv
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ADAT Passes Base64-encoded security
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14.2.1 TFTP usage TFTP file transfe
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14.2.4 Data modes The TFTP header c
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Both the user ID needed to gain acc
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-B buffer_size Specifies the size o
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chmod mode path Changes the permiss
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Where: options System-specific opti
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14.4.2 File integrity REMOVE Delete
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public file handles and the LOOKUP,
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several directories away. WebNFS ca
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Figure 14-11 on page 547 shows an e
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Datagram Service Just as the Sessio
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1 2 3 4 5 6 7 SMB/CIFS Client Figur
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15.1 Simple Mail Transfer Protocol
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RFC Description 3030 This introduce
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user%remote-host@gateway-host For a
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Figure 15-1 The SMTP model SMTP mai
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Figure 15-2 illustrates the normal
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TEST.MY.CORP. Instead, it must firs
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15.2 Sendmail Using the Domain Name
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the queue file, attempts to send an
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MIME is a draft standard that inclu
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3. The priority considered when des
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mandatory ones, and some have both.
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videos. Only part of the data is sh
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One such addition defined in RFC 37
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Quoted-Printable encoding uses the
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Base64 value ASCII char Base64 valu
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► Message relaying programs frequ
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3. After the client sends the QUIT
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15.5.2 IMAP4 states The disconnecte
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15.5.3 IMAP4 commands and response
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- EXPUNGE: Permanently removes all
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other sessions. This allows a clien
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► RFC 3030 - SMTP Service Extensi
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“Ports” on page 144 for more in
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16.2 Web servers Web browsers are r
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16.3.2 HTTP operation desirable fas
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esponse chain. Therefore, if the se
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- Upgrade - Via Request A request m
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► Successful (2xx) This class of
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Content negotiation In order to fin
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computer, an AIX 5L or UNIX machine
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alternative dynamic portion each ti
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HTTP-Based Client Java Application
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Given these circumstances, this cha
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Group name Description of objects w
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As an example, consider the object
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This if further illustrated in Figu
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getBulkRequest Performs the same fu
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Messages sent between SNMP agents a
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To illustrate the process of queryi
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17.1.6 SNMP traps In this illustrat
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► User-based Security Model (USM)
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► A single authentication protoco
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InformRequest An InformRequest is g
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SnmpAuthMsg This field is used as a
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Data origin authentication Provided
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Local Socket The local IP address a
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► RFC 1213 - Management Informati
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advance, we now have fourth generat
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► The Extended Hypertext Markup L
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User Agent Profile Manager Used mai
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Here, we give a brief description o
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18.6 WAP push architecture The desi
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► Client control As owner of the
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18.6.4 Service indication The servi
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18.7 The Wireless Application Envir
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► WAP-specific data, such as the
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The primitive types and their abbre
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implementing an end-to-end connecti
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and allows WPT-TCP to send acknowle
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datagrams. For that functionality,
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Example of a WSP-WTP sequence flow
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exchange of information and control
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peer layer). The dashed line repres
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The peer who starts the negotiation
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2. The server uses the S-Connect.re
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Normal session establishment Figure
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Normal method invocation Figure 18-
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Wireless client HTTP WTLS WP-TCP Fi
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WTLS layer goals The primary goal i
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CipherSpec Specifies the bulk data
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WIM is used to store permanent priv
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► WAP-229_001-HTTP-20011031-a - W
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The following terminology is used w
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Changes to presence information are
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19.2 Presence Information Data Form
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19.3 Presence protocols The Extensi
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19.3.1 Binding to TCP client-to-ser
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networks in such a manner, organiza
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20.1 Voice over IP (VoIP) introduct
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20.1.2 VoIP functional components F
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is a set of international CODEC sta
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Operational support system OSS prov
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► The proxy server provides appli
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Figure 20-2 An example of SIP reque
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► Stream Control Transmission Pro
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MDCX “ModifyConnection” changes
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Terminals Terminals are the LAN cli
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RTP RTCP audio G.711, G.723.1, etc.
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► RFC 3266 - Support for IPv6 in
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21.1 IPTV overview IPTV is an IP ne
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► Communication context This is s
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21.2 Functional components Figure 2
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21.2.4 IP (TV) transport IPTV requi
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► Congestion control SCTP maintai
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Type Description s Session name i*
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RTP header format The header of an
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1 1016 25 CelB 2 G726-32 26 JPEG 3
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Application RTP 12 1 10 2 9 3 8 4 7
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Receiver report An RTCP receiver re
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Length Contains the packet length.
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It allows weighted prediction, enab
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21.4 RFCs relevant to this chapter
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22.1 Security exposures and solutio
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Problem/exposure Remedy How to ensu
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Application proxy Access control En
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Encryption and decryption: Cryptogr
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eighth bit serving as parity bit. F
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cleartext clea cle Cleartext Alice'
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e and d are called the public and p
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A hash function that takes a key as
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Examples of hash functions The most
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Digital Signature Standard (DSS) As
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public key and identification, a di
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22.3 Firewalls In September 1998, t
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time. The network administrator mus
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Service level filtering Because mos
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etween the secure and the non-secur
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In normal mode, the FTP client firs
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circuit-level gateway (see Figure 2
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Generally, a packet-filtering firew
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Internal DNS and Mail server Secure
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22.4.1 Concepts IPSec adds integrit
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Tunneling Tunneling or encapsulatio
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AH format The AH format is describe
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AH in transport mode In this mode,
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connectionless, in that they operat
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Padding Most encryption algorithms
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The tunnel mode is used whenever ei
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When designing a VPN, limit the num
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Figure 22-33 illustrates the simple
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Figure 22-36 shows in detail how th
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Before describing the details of th
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Permanent identifiers The IKE proto
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Note: For ISAKMP phase 1 messages,
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authority using a protocol such as
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IKE phase 2: Setting up protocol Se
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Hash A Hash payload must immediatel
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Generating the keys (phase 2) Using
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22.5 SOCKS intranet is considered t
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22.5.1 SOCKS Version 5 (SOCKSv5) SO
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Where: VER Indicates the version of
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X'03' Network unreachable X'04' Hos
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X Window System’s clients. SSH fo
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22.7.2 SSL protocol Authentication
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CipherSpec message after processing
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The client then sends a finished me
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In this chapter, we begin by defini
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usiness partner's and supplier's VP
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name the principal. Both the realm
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The authentication process consists
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After the server has validated a cl
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► Authorization and accounting in
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modem connection is made, the NAS p
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22.14.1 Terminology Before describi
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PPP Data Figure 22-54 L2TP packet c
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complementary use of IPSec, an L2TP
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The diagram shows the following tra
Page 910 and 911:
Key management on such a large scal
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► RFC 2405 - The ESP DES-CBC Ciph
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23.1 Port based network access cont
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23.3 Port based network access cont
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Figure 23-3 illustrates the control
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802.1x authentication process The a
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Figure 23-6 and Figure 23-7 show sn
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Request and response type Value TLS
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Figure 23-15 EAP-Success packet EAP
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Figure 23-21 shows the sniffer trac
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► Multicast propagation If authen
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The Internet business has grown so
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Generic techniques to enhance scala
Page 938 and 939:
24.5 Virtualization Virtualization
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Network virtualization Network virt
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24.6.2 VRRP definitions 24.6.3 VRRP
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24.6.4 Sample configuration Figure
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The fields of the VRRP header are d
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24.8.1 Network Address Translation
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24.9 RFCs relevant to this chapter
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A.1 MPLS: An introduction The idea
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MPLS also provides the ability to a
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Layer 2 Header MPLS Header Figure A
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Label switched path (LSP) An LSP re
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► The packet does not contain a l
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7. R22 reviews the level-2 label ap
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A.2.5 Label distribution protocols
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Emulated Ethernet MUX MPLS Figure A
Page 968 and 969:
► The effort can provide a single
Page 970 and 971:
A generalized label only carries a
Page 972 and 973:
Fault management The LMP fault mana
Page 974 and 975:
Note: GMPLS allows SP to dynamicall
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Furthermore, because the labels can
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A.5 RFCs relevant to this chapter T
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DLCI Data Link Connection Identifie
Page 982 and 983:
MTU Maximum Transmission Unit MVS M
Page 984 and 985:
VRML Virtual Reality Modeling Langu
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► TCP/IP and System i http://www.
Page 988 and 989:
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DHCP interoperability 140 forwardin
Page 992 and 993:
fingerprint 785 firewall 12, 776, 8
Page 994 and 995:
Security Parameter Index (SPI) 810
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latency 61 Layer 2 Forwarding (L2F)
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RFC 1483 53 RFC 1492 873 RFC 1510 8
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subnet number 73 subnets 72 subnett
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TCP/IP Tutorial and Technical Overv
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