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S 2160 11680 P 0 12 F 24 12 F B (Encapsulation) S E 2520 11920 P 0 12 F 24 12 F (The) S 60 J ( process) S 60 J ( of) S 60 J ( mapping) S 60 J ( a) S 60 J ( Clear) S 60 J ( Datagram) S 60 J ( to) S 60 J ( the) S 60 J ( Encapsulation) S 60 J ( Space,) S 60 J ( prepending) S 60 J ( an) S 2520 12160 P (Encapsulation) S 60 J ( Header) S 60 J ( to) S 60 J ( the) S 60 J ( Clear) S 60 J ( Datagram) S 60 J ( and) S 60 J ( routing) S 60 J ( the) S 60 J ( Encapsulated) S 60 J ( Datagram) S 2520 12400 P (to) S 60 J ( a) S 60 J ( Decapsulator.) S 2160 12880 P 0 12 F 24 12 F B (Encapsulation) S 60 J ( Header) S E 2520 13120 P 0 12 F 24 12 F (The) S 60 J ( header) S 60 J ( for) S 60 J ( the) S 60 J ( Encapsulation) S 60 J ( Protocol) S 60 J ( prepended) S 60 J ( to) S 60 J ( the) S 60 J ( Clear) S 60 J ( Datagram) S 60 J ( during) S 2520 13360 P (Encapsulation.) 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S 2160 4320 P 0 12 F 24 12 F B (Encapsulator) S E 2520 4560 P 0 12 F 24 12 F (The) S 60 J ( entity) S 60 J ( responsible) S 60 J ( for) S 60 J ( mapping) S 60 J ( a) S 60 J ( given) S 60 J ( User) S 60 J ( Space) S 60 J ( datagram) S 60 J ( to) S 60 J ( the) S 60 J ( Encapsulation) S 2520 4800 P (Space,) S 60 J ( encapsulating) S 60 J ( the) S 60 J ( datagram,) S 60 J ( and) S 60 J ( forwarding) S 60 J ( the) S 60 J ( Encapsulated) S 60 J ( Datagram) S 60 J ( to) S 60 J ( a) S 2520 5040 P (Decapsulator.) S 60 J ( ) S 60 J ( An) S 60 J ( Encapsulator) S 60 J ( may) S 60 J ( be) S 60 J ( a) S 60 J ( host) S 60 J ( or) S 60 J ( a) S 60 J ( gateway.) S 2160 5520 P 0 12 F 24 12 F B (Flow) S E 2520 5760 P 0 12 F 24 12 F (Also) S 60 J ( called) S 60 J ( a) S 60 J ( "tunnel.") S 60 J ( ) S 60 J ( A) S 60 J ( flow) S 60 J ( is) S 60 J ( the) S 60 J ( end-to-end) S 60 J ( path) S 60 J ( in) S 60 J ( the) S 60 J ( Encapsulation) S 60 J ( Space) S 60 J ( over) S 2520 6000 P (which) S 60 J ( Encapsulated) S 60 J ( Datagrams) S 60 J ( travel.) S 60 J ( ) S 60 J ( There) S 60 J ( may) S 60 J ( be) S 60 J ( several) S 2520 6240 P (Encapsulator/Decapsulator) S 60 J ( pairs) S 60 J ( along) S 60 J ( a) S 60 J ( given) S 60 J ( flow.) S 60 J ( ) S 60 J ( Note) S 60 J ( that) S 60 J ( a) S 60 J ( Flow) S 60 J ( does) S 60 J ( not) S 2520 6480 P (denote) S 60 J ( what) S 60 J ( User) S 60 J ( Space) S 60 J ( gateways) S 60 J ( are) S 60 J ( traversed) S 60 J ( along) S 60 J ( the) S 60 J ( path.) 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S 1440 14640 P (Woodburn) S 60 J ( &) S 60 J ( Mills) S 10153 14640 P (Page) S 60 J ( ) S (2) S 0 12 F PE 1440 1680 P 24 12 F (RFC) S 60 J ( 1241) S 5035 1680 P (Internet) S 60 J ( Encapsulation) S 9860 1680 P (July) S 60 J ( 1991) S 1440 2160 P (There) S 155 J ( are) S 156 J ( several) S 155 J ( means) S 156 J ( of) S 155 J ( accomplishing) S 155 J ( tunneling.) S 155 J ( ) S 155 J ( In) S 155 J ( the) S 155 J ( past,) S 155 J ( tunneling) S 155 J ( has) S 155 J ( been) S 1440 2400 P (accomplished) S 97 J ( through) S 98 J ( source) S 97 J ( routing) S 98 J ( options) S 98 J ( in) S 98 J ( the) S 98 J ( IP) S 98 J ( header) S 98 J ( which) S 98 J ( allow) S 98 J ( gateways) S 98 J ( along) S 98 J ( a) S 1440 2640 P (given) S 98 J ( path) S 99 J ( to) S 98 J ( be) S 99 J ( enumerated.) 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S 108 J ( ) S 107 J ( Current) S 107 J ( routing) S 1440 3360 P (implementations) S 111 J ( generally) S 112 J ( don't) S 111 J ( support) S 112 J ( source) S 112 J ( routes) S 112 J ( in) S 112 J ( their) S 112 J ( routing) S 112 J ( tables) S 112 J ( as) S 112 J ( a) S 112 J ( means) S 112 J ( of) S 1440 3600 P (reaching) S 60 J ( an) S 60 J ( IP) S 60 J ( address,) S 60 J ( nor) S 60 J ( do) S 60 J ( current) S 60 J ( routing) S 60 J ( protocols.) S 1440 4080 P (Another) S 80 J ( means) S 81 J ( of) S 80 J ( tunneling) S 81 J ( would) S 80 J ( be) S 81 J ( to) S 80 J ( develop) S 81 J ( a) S 81 J ( new) S 81 J ( IP) S 81 J ( option.) S 81 J ( ) S 81 J ( This) S 81 J ( option) S 81 J ( field) S 81 J ( would) S 81 J ( be) S 1440 4320 P (part) S 85 J ( of) S 86 J ( a) S 85 J ( separate) S 85 J ( IP) S 85 J ( header) S 85 J ( that) S 85 J ( could) S 85 J ( be) S 85 J ( prepended) S 85 J ( to) S 85 J ( an) S 85 J ( IP) S 85 J ( datagram.) S 85 J ( ) S 85 J ( The) S 85 J ( IP) S 85 J ( option) S 85 J ( would) S 1440 4560 P (indicate) S 70 J ( information) S 71 J ( about) S 70 J ( the) S 71 J ( original) S 70 J ( datagram.) S 71 J ( ) S 70 J ( This) S 71 J ( tunneling) S 70 J ( option) S 70 J ( has) S 70 J ( the) S 70 J ( disadvantage) S 70 J ( of) S 1440 4800 P (significantly) S 66 J ( modifying) S 67 J ( existing) S 66 J ( IP) S 67 J ( implementations) S 66 J ( to) S 67 J ( handle) S 66 J ( a) S 67 J ( new) S 66 J ( IP) S 67 J ( option.) S 66 J ( ) S 67 J ( It) S 66 J ( also) S 67 J ( would) S 66 J ( be) S 1440 5040 P (less) S 70 J ( flexible) S 71 J ( in) S 70 J ( permitting) S 71 J ( the) S 70 J ( tunneling) S 71 J ( of) S 70 J ( other) S 71 J ( protocols,) S 70 J ( such) S 71 J ( as) S 70 J ( ISO) S 71 J ( protocols,) S 71 J ( through) S 71 J ( an) S 71 J ( IP) S 1440 5280 P (environment.) S 76 J ( ) S 77 J ( An) S 76 J ( even) S 77 J ( less) S 76 J ( palatable) S 77 J ( alternative) S 76 J ( would) S 76 J ( be) S 76 J ( to) S 76 J ( replace) S 76 J ( IP) S 76 J ( with) S 76 J ( a) S 76 J ( new) S 76 J ( networking) S 1440 5520 P (protocol) S 60 J ( or) S 60 J ( a) S 60 J ( new) S 60 J ( version) S 60 J ( of) S 60 J ( IP) S 60 J ( with) S 60 J ( tunneling) S 60 J ( built) S 60 J ( in) S 60 J ( as) S 60 J ( part) S 60 J ( of) S 60 J ( its) S 60 J ( functionality.) S 1440 6000 P (A) S 71 J ( final) S 71 J ( alternative) S 71 J ( is) S 71 J ( to) S 71 J ( create) S 71 J ( a) S 71 J ( new) S 71 J ( IP) S 71 J ( encapsulation) S 71 J ( protocol) S 71 J ( which) S 71 J ( uses) S 71 J ( the) S 71 J ( current) S 71 J ( IP) S 71 J ( header) S 1440 6240 P (format.) S 84 J ( ) S 85 J ( By) S 84 J ( using) S 85 J ( encapsulation,) S 84 J ( a) S 85 J ( destination) S 84 J ( can) S 85 J ( be) S 84 J ( reached) S 84 J ( transparently) S 84 J ( without) S 84 J ( the) S 84 J ( source) S 1440 6480 P (having) S 134 J ( to) S 135 J ( know) S 134 J ( topology) S 135 J ( specifics.) S 134 J ( ) S 135 J ( Virtual) S 134 J ( networks) S 135 J ( can) S 134 J ( be) S 134 J ( created) S 134 J ( by) S 134 J ( tying) S 134 J ( otherwise) S 1440 6720 P (unconnected) S 60 J ( machines) S 60 J ( together) S 60 J ( with) S 60 J ( flows) S 60 J ( through) S 60 J ( an) S 60 J ( encapsulation) S 60 J ( space.) S 1440 14640 P (Woodburn) S 60 J ( &) S 60 J ( Mills) S 10153 14640 P (Page) S 60 J ( ) S (3) S 0 12 F PE 1440 1680 P 24 12 F (RFC) S 60 J ( 1241) S 5035 1680 P (Internet) S 60 J ( Encapsulation) S 9860 1680 P (July) S 60 J ( 1991) S 1080 1920 P II11080 9201 IX 10080 12960 7281 9360 IS 0 15840 IXII2%%BeginDocument: RFC-FIG1.EPS%!PS-Adobe-2.0 EPSF-1.2%%Title: RFC-FIG1.EPS%%Creator: Freelance Plus 3.01%%CreationDate: 1/16/1991%%Pages: 1%%DocumentFonts: (atend)%%BoundingBox: 0 0 648 468%%EndComments%%BeginProcSet: Freelance Plus/Freelance_Plus dup 100 dict def load begin[ ] {bind} stopped { (patching the bind operator...) = flush/*bind /bind load def /bind { dup xcheck { *bind } if } *bind def } if pop/bdf {bind def} bind def /ldf {load def} bdf/mt /moveto ldf /rt /rmoveto ldf /l2 /lineto ldf /c2 /curveto ldf/sg /setgray ldf /gs /gsave ldf /ef /eofill ldf /rl2 /rlineto ldf/st /stroke ldf /gr /grestore ldf /np /newpath ldf/sv /save ldf /su /statusdict ldf /rs /restore ldf/sw /setlinewidth ldf /sd /setdash ldf /cp /closepath ldf /ed {exch def } bdf/cfnt {findfont exch makefont setfont} bdf/itr {transform round exch round exch itransform} bdf/fres 72 0 matrix currentmatrix dtransformexch dup mul exch dup mul add sqrt def/res fres def /mcm matrix currentmatrix bdf%%EndProcSetend%%EndProlog%%BeginSetupFreelance_Plus beginsave newpath.1 .1 scale/ecm matrix currentmatrix bdf/sem {ecm setmatrix} bdf-720 -720 translate2 setlinecap0 setlinejoin1.42 setmiterlimit%%EndSetup0.000 sg6 swsv np [] 0 sd 1818 3405 itr mt
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