rfc1237.ps

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

b(among)h(routing)f(domains)g(\(inter)o(-domain)h(IS-IS\).)0
1329 y(ES-IS,)17 b(international)e(standard)h(ISO9542)f([13])h(approved)g(in)
g(1987,)g(is)g(available)f(in)h(vendor)g(products)f(and)h(is)0
1385 y(planned)h(for)g(the)g(next)g(release)h(of)f(Berkeley)h(UNIX)f(\(UNIX)h
(is)e(a)i(trademark)f(of)g(A)-5 b(T&T\).)17 b(It)g(is)g(also)g(cited)f(in)0
1442 y(GOSIP)11 b(V)-5 b(ersion)11 b(2)f([4],)h(which)f(became)h(ef)o
(fective)h(in)e(April)g(1991)g(for)h(all)f(applicable)g(federal)h
(procurements,)g(and)0 1498 y(mandatory)g(beginning)f(eighteen)h(months)f
(later)h(in)g(1992.)0 1605 y(Intra-domain)g(IS-IS)i(advanced)e(to)g(draft)h
(international)e(standard)h(\(DIS\))i(status)d(within)g(ISO)i(in)f(November)n
(,)h(1990)0 1661 y(as)i(DIS10589)f([17].)23 b(It)14 b(is)f(reasonable)h(to)f
(expect)h(that)f(\256nal)g(text)g(for)h(the)g(intra-domain)e(IS-IS)j
(standard)e(will)g(be)0 1717 y(available)e(by)g(mid-1991.)0
1824 y(There)19 b(are)g(two)f(candidate)g(proposals)g(which)g(address)g(OSI)h
(inter)o(-domain)e(routing,)j(ECMA)e(TR/50)g([3])h(and)0 1880
y(Border)g(Router)f(Protocol)f(\(BRP\))j([19],)g(a)e(direct)g(derivative)f
(of)h(the)g(IETF)g(Border)h(Gateway)f(Protocol)g([18)o(].)0
1937 y(ECMA)f(TR/50)f(has)h(been)g(proposed)f(as)h(base)g(text)f(in)g(the)h
(ISO/IEC)g(JTC1)g(SC6/WG2)g(committee,)g(which)g(is)0 1993
y(responsible)12 b(for)i(the)f(Network)g(layer)g(of)g(the)g(ISO)h(Reference)h
(Model)e([11].)22 b(X3S3.3,)15 b(the)e(ANSI)g(counterpart)g(to)0
2050 y(WG2,)e(has)g(incorporated)g(features)h(of)f(TR/50)f(into)g(BRP)j(and)d
(submitted)g(this)g(as)h(alternate)g(base)g(text)f(at)h(the)g(WG2)0
2106 y(meeting)g(in)h(October)n(,)h(1990.)19 b(Currently)m(,)13
b(it)f(is)f(out)h(for)g(ISO)h(Member)f(Body)g(comment.)19 b(The)12
b(proposed)g(protocol)0 2162 y(is)f(referred)i(to)e(as)g(the)g(Inter)o
(-domain)g(Routing)g(Protocol)g(\(IDRP\))i([20].)0 2269 y(This)f(paper)i
(examines)f(the)g(technical)g(implications)e(of)i(NSAP)h(assignment)d(under)j
(the)f(assumption)e(that)h(ES-IS,)0 2325 y(intra-domain)e(IS-IS,)k(and)d
(IDRP)h(routing)f(are)h(deployed)f(to)g(support)f(CLNP)-5 b(.)0
2678 y(Colella,)12 b(Gardner)n(,)g(&)f(Callon)1243 b([Page)12
b(6])p eop
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bop 0 50 a Fi(RFC)13 b(1237)281 b(Guidelines)10 b(for)i(OSI)g(NSAP)g
(Allocation)e(in)h(the)g(Internet)293 b(July)11 b(1991)0 195
y Fh(3.2)50 b(Overview)12 b(of)g(DIS10589)0 332 y Fi(The)k(IS-IS)h
(intra-domain)e(routing)g(protocol,)i(DIS10589,)g(developed)f(in)f(ISO,)i
(provides)e(routing)g(for)h(OSI)h(en-)0 389 y(vironments.)26
b(In)15 b(particular)n(,)i(DIS10589)e(is)f(designed)h(to)f(work)h(in)g
(conjunction)e(with)i(CLNP)g(and)g(ES-IS.)i(This)0 445 y(section)11
b(brie\257y)g(describes)h(the)f(manner)g(in)g(which)g(DIS10589)g(operates.)0
551 y(In)i(DIS10589,)g(the)f(internetwork)g(is)g(partitioned)f(into)h
(routing)f(domains.)19 b(A)13 b(routing)e(domain)h(is)g(a)g(collection)g(of)0
608 y(ESs)f(and)g(ISs)g(that)g(operate)g(common)f(routing)g(protocols)g(and)h
(are)h(under)f(the)g(control)f(of)h(a)h(single)e(administration.)0
664 y(T)m(ypically)m(,)g(a)g(routing)f(domain)f(may)i(consist)f(of)h(a)g
(corporate)g(network,)h(a)f(university)e(campus)i(network,)g(a)g(regional)0
721 y(network,)17 b(or)f(a)g(similar)f(contiguous)f(network)i(under)g
(control)f(of)h(a)g(single)f(administrative)f(or)o(ganization.)30
b(The)0 777 y(boundaries)10 b(of)h(routing)f(domains)g(are)h(de\256ned)h(by)e
(network)h(management)f(by)g(setting)g(some)g(links)g(to)g(be)h(exterior)n(,)
0 834 y(or)j(inter)o(-domain,)g(links.)22 b(If)15 b(a)f(link)f(is)g(marked)g
(as)h(exterior)n(,)h(no)f(DIS10589)f(routing)g(messages)g(are)i(sent)e(on)h
(that)0 890 y(link.)0 996 y(Currently)m(,)19 b(ISO)e(does)g(not)f(have)i(a)f
(standard)f(for)i(inter)o(-domain)e(routing)f(\(i.e.,)20 b(for)d(routing)f
(between)h(separate)0 1053 y(autonomous)12 b(routing)g(domains\).)23
b(In)14 b(the)f(interim,)h(DIS10589)f(uses)g(manual)g(con\256guration.)24
b(An)13 b(inter)o(-domain)0 1109 y(link)e(is)g(statically)g(con\256gured)h
(with)f(the)g(set)h(of)g Fb(addr)n(ess)f(pr)n(e\256xes)h Fi(reachable)h(via)e
(that)g(link,)h(and)f(with)g(the)h(method)0 1166 y(by)e(which)g(they)g(can)g
(be)h(reached)g(\(such)f(as)g(the)g(DTE)g(address)g(to)g(be)g(dialed)g(to)g
(reach)h(that)f(address,)h(or)f(the)g(fact)h(that)0 1222 y(the)g(DTE)g
(address)h(should)e(be)h(extracted)h(from)f(the)h(OSI)g(NSAP)g(address\).)0
1328 y(DIS10589)k(routing)e(makes)i(use)f(of)h(two-level)g(hierarchical)g
(routing.)29 b(A)16 b(routing)f(domain)f(is)i(subdivided)e(into)0
1385 y(areas)e(\(also)e(known)g(as)h(level)g(1)g(subdomains\).)k(Level)10
b(1)h(ISs)g(know)g(the)f(topology)f(in)i(their)f(area,)j(including)c(all)i
(ISs)0 1441 y(and)j(ESs)g(in)f(their)h(area.)26 b(However)n(,)15
b(level)f(1)g(ISs)g(do)g(not)f(know)g(the)h(identity)f(of)h(ISs)g(or)g
(destinations)e(outside)h(of)0 1498 y(their)e(area.)18 b(Level)11
b(1)f(ISs)i(forward)f(all)g(traf)o(\256c)h(for)f(destinations)f(outside)g(of)
h(their)f(area)i(to)f(a)g(level)g(2)g(IS)h(within)d(their)0
1554 y(area.)0 1660 y(Similarly)m(,)i(level)g(2)h(ISs)g(know)f(the)g(level)h
(2)f(topology)f(and)i(know)f(which)g(addresses)h(are)g(reachable)h(via)e
(each)h(level)0 1717 y(2)h(IS.)i(The)f(set)f(of)h(all)f(level)g(2)h(ISs)g(in)
f(a)h(routing)e(domain)h(are)h(known)f(as)h(the)f(level)g(2)h(subdomain,)f
(which)g(can)h(be)0 1773 y(thought)e(of)h(as)h(a)f(backbone)h(for)g
(interconnecting)e(the)h(areas.)24 b(Level)13 b(2)g(ISs)h(do)f(not)g(need)h
(to)f(know)f(the)i(topology)0 1830 y(within)9 b(any)h(level)g(1)g(area,)i
(except)e(to)g(the)g(extent)f(that)h(a)h(level)e(2)h(IS)h(may)f(also)g(be)g
(a)g(level)g(1)g(IS)h(within)e(a)h(single)g(area.)0 1886 y(Only)15
b(level)h(2)f(ISs)h(can)g(exchange)h(data)e(packets)h(or)g(routing)f
(information)f(directly)h(with)g(external)h(ISs)g(located)0
1943 y(outside)10 b(of)i(their)f(routing)f(domain.)0 2049 y(As)17
b(illustrated)f(in)h(Figure)h(1,)h(ISO)f(addresses)g(are)g(subdivided)e(into)
g(the)h(Initial)g(Domain)f(Part)i(\(IDP\))h(and)e(the)0 2105
y(Domain)c(Speci\256c)i(Part)f(\(DSP\),)i(as)e(speci\256ed)g(in)f
(ISO8348/Addendum)f(2,)j(the)f(OSI)g(network)g(layer)g(addressing)0
2162 y(standard)f([14])h(\(also)f(RFC)i(941)e([6]\).)23 b(The)14
b(IDP)g(is)f(the)g(part)g(which)g(is)g(standardized)h(by)f(ISO,)h(and)f
(speci\256es)h(the)0 2218 y(format)d(and)g(authority)f(responsible)g(for)i
(assigning)d(the)i(rest)h(of)f(the)g(address.)17 b(The)11 b(DSP)h(is)e
(assigned)h(by)g(whatever)0 2275 y(addressing)e(authority)h(is)f(speci\256ed)
i(by)e(the)h(IDP)h(\(see)g(Appendix)e(A)h(for)h(more)f(discussion)e(on)i(the)
g(top)f(level)h(NSAP)0 2331 y(addressing)j(authorities\).)25
b(The)14 b(DSP)h(is)e(further)i(subdivided,)f(by)f(DIS10589,)i(into)f(a)g
(High)g(Order)g(Part)h(of)f(DSP)0 2388 y(\(HO-DSP\),)j(a)e(system)f
(identi\256er)h(\(ID\),)i(and)e(an)g(NSAP)h(selector)f(\(SEL\).)h(The)f
(HO-DSP)h(may)f(use)g(any)g(format)0 2444 y(desired)h(by)g(the)g(authority)f
(which)h(is)f(identi\256ed)h(by)g(the)g(IDP)-5 b(.)17 b(T)m(ogether)n(,)g
(the)f(combination)f(of)h([IDP)-5 b(,HO-DSP])0 2501 y(identify)13
b(an)i(area)g(within)e(a)i(routing)e(domain)h(and,)h(implicitly)m(,)e(the)h
(routing)g(domain)f(containing)g(the)h(area.)27 b(The)0 2678
y(Colella,)12 b(Gardner)n(,)g(&)f(Callon)1243 b([Page)12 b(7])p
eop
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bop 0 50 a Fi(RFC)13 b(1237)281 b(Guidelines)10 b(for)i(OSI)g(NSAP)g
(Allocation)e(in)h(the)g(Internet)293 b(July)11 b(1991)0 195
y(combination)f(of)h([IDP)-5 b(,HO-DSP])14 b(is)d(therefore)h(referred)h(to)e
(as)g(the)g Fb(ar)n(ea)h(addr)n(ess)p Fi(.)p 420 297 300 2
v 420 353 2 56 v 533 340 a(IDP)p 718 353 V 420 355 300 2 v
720 297 750 2 v 720 353 2 57 v 447 w(DSP)p 1468 353 V 720 355
750 2 v 420 361 150 2 v 420 417 2 56 v 458 404 a(AFI)p 568
417 V 420 419 150 2 v 570 361 V 570 417 2 56 v 82 w(IDI)p 718
417 V 570 419 150 2 v 720 361 420 2 v 720 417 2 57 v 172 w(HO-DSP)p
1138 417 V 720 419 420 2 v 1140 361 225 2 v 1140 417 2 56 v
216 w(ID)p 1363 417 V 1140 419 225 2 v 1365 361 106 2 v 1365
417 2 57 v 101 w(SEL)p 1468 417 V 1365 419 106 2 v 549 519
a(IDP)142 b(Initial)10 b(Domain)h(Part)549 575 y(AFI)142 b(Authority)10
b(and)h(Format)g(Identi\256er)549 632 y(IDI)152 b(Initial)10
b(Domain)h(Identi\256er)549 688 y(DSP)132 b(Domain)10 b(Speci\256c)j(Part)549
745 y(HO-DSP)51 b(High-order)11 b(DSP)549 801 y(ID)167 b(System)11
b(Identi\256er)549 858 y(SEL)134 b(NSAP)12 b(Selector)523 951
y(Figure)f(1:)16 b(OSI)c(Hierarchical)g(Address)f(Structure.)0
1103 y(The)16 b(ID)g(\256eld)g(may)f(be)h(from)f(one)h(to)f(eight)g(octets)h
(in)f(length,)h(but)f(must)g(have)h(a)g(single)f(known)g(length)g(in)g(any)0
1160 y(particular)g(routing)e(domain.)26 b(Each)14 b(router)h(is)f
(con\256gured)h(to)f(know)g(what)h(length)e(is)h(used)h(in)f(its)g(domain.)25
b(The)0 1216 y(SEL)13 b(\256eld)g(is)g(always)g(one)g(octet)f(in)h(length.)21
b(Each)13 b(router)g(is)f(therefore)i(able)f(to)g(identify)f(the)h(ID)g(and)g
(SEL)g(\256elds)0 1273 y(as)i(a)g(known)f(number)g(of)h(trailing)e(octets)h
(of)h(the)f(NSAP)i(address.)26 b(The)15 b(area)h(address)e(can)i(be)e
(identi\256ed)g(as)h(the)0 1329 y(remainder)d(of)f(the)g(address)h(\(after)g
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y(Usually)m(,)18 b(all)e(nodes)h(in)f(an)h(area)h(have)f(the)g(same)f(area)i
(address.)33 b(However)n(,)19 b(sometimes)d(an)g(area)i(might)e(have)0
1492 y(multiple)10 b(addresses.)17 b(Motivations)9 b(for)i(allowing)g(this)f
(are)i(several:)68 1625 y Fc(\017)23 b Fi(It)10 b(might)f(be)i(desirable)g
(to)f(change)h(the)f(address)h(of)g(an)g(area.)17 b(The)11
b(most)e(graceful)j(way)e(of)h(changing)f(an)h(area)114 1681
y(from)f(having)g(address)h(A)g(to)g(having)f(address)h(B)g(is)f(to)h
(\256rst)g(allow)f(it)g(to)h(have)g(both)f(addresses)h(A)f(and)h(B,)h(and)114
1738 y(then)i(after)h(all)f(nodes)g(in)g(the)g(area)h(have)g(been)g
(modi\256ed)e(to)h(recognize)h(both)f(addresses,)h(one)g(by)f(one)g(the)114
1794 y(ESs)d(can)h(be)f(modi\256ed)g(to)g(for)o(get)h(address)f(A.)68
1882 y Fc(\017)23 b Fi(It)11 b(might)f(be)i(desirable)f(to)g(mer)o(ge)h
(areas)h(A)e(and)h(B)g(into)e(one)i(area.)18 b(The)12 b(method)e(for)i
(accomplishing)e(this)h(is)114 1938 y(to,)h(one)g(by)g(one,)h(add)g
(knowledge)e(of)i(address)f(B)h(into)e(the)h(A)g(partition,)g(and)g
(similarly)f(add)h(knowledge)g(of)114 1995 y(address)f(A)g(into)g(the)g(B)h
(partition.)68 2082 y Fc(\017)23 b Fi(It)7 b(might)g(be)h(desirable)f(to)h
(partition)e(an)i(area)h(C)g(into)e(two)g(areas,)j(A)e(and)f(B)i(\(where)f(A)
g(might)f(equal)g(C,)i(in)e(which)114 2138 y(case)14 b(this)e(example)i
(becomes)f(one)g(of)h(removing)f(a)g(portion)g(of)h(an)f(area\).)25
b(This)13 b(would)f(be)i(accomplished)114 2195 y(by)f(\256rst)h(introducing)e
(knowledge)i(of)f(address)h(A)g(into)f(the)h(appropriate)f(ESs)h(\(those)g
(destined)f(to)g(become)114 2251 y(area)h(A\),)h(and)e(knowledge)g(of)h
(address)g(B)g(into)e(the)i(appropriate)f(nodes,)i(and)e(then)g(one)h(by)f
(one)h(removing)114 2308 y(knowledge)c(of)i(address)f(C.)0
2441 y(Since)g(the)g(addressing)f(explicitly)f(identi\256es)h(the)h(area,)h
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(going)0 2497 y(to)h(destinations)f(outside)g(of)i(their)f(area,)i(which)e
(need)h(to)f(be)g(forwarded)h(to)f(level)h(2)f(ISs.)20 b(Thus,)13
b(in)f(DIS10589)g(the)0 2554 y(two)f(types)g(of)g(ISs)h(route)f(as)h
(follows:)0 2678 y(Colella,)g(Gardner)n(,)g(&)f(Callon)1243
b([Page)12 b(8])p eop
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bop 0 50 a Fi(RFC)13 b(1237)281 b(Guidelines)10 b(for)i(OSI)g(NSAP)g
(Allocation)e(in)h(the)g(Internet)293 b(July)11 b(1991)68 195
y Fc(\017)23 b Fi(Level)9 b(1)g(intermediate)g(systems)f(\261)h(these)g
(nodes)g(route)g(based)g(on)g(the)g(ID)h(portion)e(of)h(the)g(ISO)h(address.)
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b(If)11 b(so,)g(they)f(route)g(towards)g(the)g(destination.)15
b(If)c(not,)f(they)g(route)g(to)g(the)114 364 y(nearest)h(level)h(2)f(IS.)68
458 y Fc(\017)23 b Fi(Level)10 b(2)g(intermediate)g(systems)f(\261)i(these)f
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114 571 y(without)d(regard)j(to)e(the)h(internal)f(structure)h(of)f(an)h
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628 y(boundary)f(that)g(have)h(advertised)f(external)h(address)f(pre\256xes)i
(into)d(the)i(level)f(2)h(subdomain.)19 b(A)12 b(level)h(2)f(IS)114
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(become)g(a)0 897 y(neighbor)e(with)g(an)g(IS)h(whose)g(area)g(addresses)g
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b(if)e(a)h(level)f(1)0 953 y(IS)i(has)e(area)i(addresses)f(A,)h(B,)f(and)g
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