Routing Concepts - Computer Action Teamweb.cecs.pdx.edu/~jrb/tcpip/lectures/pdfs/routther.pdf · 11...
Transcript of Routing Concepts - Computer Action Teamweb.cecs.pdx.edu/~jrb/tcpip/lectures/pdfs/routther.pdf · 11...
1Ji
m B
inkl
ey
Rou
ting
Con
cept
s
TCP/
IP c
lass
2Ji
m B
inkl
ey
Rou
ting
-Con
cept
s
intro
con
cept
s–
topo
logi
es–
type
s/pr
oper
ties
–is
sues
vect
or-d
ista
nce
link-
stat
ese
eR
adia
Per
lman
’sIn
terc
onne
ctio
ns, f
or
mor
e in
form
atio
n
3Ji
m B
inkl
ey
issu
es/p
rope
rties
rout
ing
-fin
ding
a p
ath
from
one
end
to th
e ot
her f
or a
pac
ket
we
need
one
or m
ore
algo
rith
mst
hat a
re
mos
t lik
ely
dist
ribu
ted
amon
gst a
set o
f ho
sts a
nd ro
uter
wha
t are
the
prop
ertie
s of s
aid
algo
rithm
?w
hat i
ssue
s aff
ect i
t?
4Ji
m B
inkl
ey
elem
ents
of a
rout
ing
sche
me
rout
ing
prot
ocol
s tha
t allo
w in
fo to
be
gath
ered
and
dis
tribu
ted
-ro
utin
g ag
ents
co
mm
unic
ate
with
thes
e pr
otoc
ols
rout
ing
algo
rith
ms -
may
be
dist
ribut
ed,
use
prot
ocol
s and
dat
a to
det
erm
ine
and
diss
emin
ate
path
sro
utin
g da
taba
ses (
tabl
es in
rout
ers)
(to b
oard
wal
k, v
ia n
ew je
rsey
, $1
00)
5Ji
m B
inkl
ey
topo
logy
Tane
nbau
mm
entio
ns lo
gica
l abs
urdi
ties
no r
oute
r -e
very
hos
t wire
d to
eve
ry o
ther
ho
st (
mes
h )
N *
N w
ires,
go
ahea
d ad
d a
host
...1
rout
er -
for a
ll ho
sts (
star
)–
1 he
ck o
f a ro
utin
g ta
ble
6Ji
m B
inkl
ey
one
solu
tion
typi
cally
a fl
atte
ned
tree
to g
ive
hier
arch
yat
the
top
a sm
all c
ircle
of c
ore
rout
ers t
hat
know
all
the
rout
esid
ea:
defa
ult r
oute
–if
you
are
not i
n th
e ce
nter
AN
D y
ou d
on’t
know
wha
t to
do w
ith it
, se
nd it
“U
P”to
sm
arte
r ent
ity
7Ji
m B
inkl
ey
rout
ing
hier
arch
y
R
RR
R
net
Leve
l 1
Leve
l 2
defa
ult r
oute
H
core
rout
ers
R
rout
er
8Ji
m B
inkl
ey
conn
ectio
nles
s/co
nnec
ted
netw
ork-
laye
r in
TCP/
IP c
onne
ctio
nles
sO
SI st
ack
has c
onne
cted
+ c
onne
ctio
nles
sco
nnec
tionl
ess -
each
pac
ket r
oute
d vi
a ro
ute
tabl
e, p
aths
may
cha
nge
dyna
mic
ally
conn
ecte
d -r
oute
setu
p at
“co
nnec
t”tim
e in
ci
rcui
t sw
itch,
torn
dow
n at
dis
conn
ect
rout
ing
prob
lem
s stil
l sim
ilar
9Ji
m B
inkl
ey
idea
l rou
ting
algo
rithm
fair
or u
nfai
r (w
hat i
f we
wan
tiso
chro
nous
data
?)
corr
ect -
wha
t if a
lgor
ithm
s too
com
plex
?ro
bust
-ca
n de
al w
ith ro
uter
rebo
ot?
stab
le -
do ro
utin
g ch
ange
s sta
biliz
e in
dis
tribu
ted
syst
em?
effic
ient
-al
l rou
ting
and
no d
ata
not g
ood
topo
logi
cally
flex
ible
mai
ntai
nabl
e -a
dmin
not
too
com
plic
ated
scal
able
to m
any
rout
ers,
man
y ho
sts?
(dis
tribu
ted)
dead
lock
? -l
oops
?se
cure
(+ c
lean
, che
erfu
l, ta
kes o
ut th
e tra
sh, e
tc.)
10Ji
m B
inkl
ey
clas
sic
prob
lem
rout
ing
loop
path
to Z
?
11Ji
m B
inkl
ey
type
s of r
outin
g al
gorit
hms
stat
ic v
ersu
s dyn
amic
stat
ic p
ros:
–si
mpl
e, m
ay b
e ea
sies
t thi
ng to
do
in si
mpl
e to
polo
gy,
espe
cial
ly fo
r lea
f hos
t with
1 ro
uter
onl
y–
you
may
be
smar
ter t
han
the
rout
ers (
wan
t a p
ath
they
w
on’t
give
you
)
stat
ic c
ons:
–ca
n’t r
eact
dyn
amic
ally
to c
rash
ed ro
uter
(stil
l nee
d tw
o ro
uter
s to
reac
t tho
ugh.
..)–
not s
cala
ble
12Ji
m B
inkl
ey
rout
ing
algo
rithm
type
s
cent
raliz
ed v
ersu
s dis
tribu
ted
vers
us e
nd-
node
–ce
nter
is n
eces
sary
, can
’t ha
ve d
efau
lts
ever
ywhe
re–
if en
d no
des h
ave
rout
e in
fo, a
nd b
ig n
et, t
hen
rout
e ta
bles
hug
e -n
eed
to li
mit
size
13Ji
m B
inkl
ey
type
s/to
ols -
sour
ce ro
utin
g
sour
ce-r
outin
gvs
hop-
by-h
op–
end
node
has
exa
ct P
ATH
and
dat
agra
m fo
llow
s tha
t pa
th:
( firs
t to
Joe,
the
n to
Bob
, the
n to
Gra
ndm
a’s )
–IP
opt
ion,
but
rare
ly u
sed
–ch
alle
nge
to se
curit
y: w
hat i
f hos
tile
entit
y co
nvin
ces
you
to ro
ute
all p
acke
ts th
roug
h it?
»m
aybe
it c
an m
asqu
erad
e as
you
afte
r tha
t?–
still
a p
ossi
ble
tool
-us
ed in
BG
P, c
an c
omm
unic
ate
POLI
CIE
S, f
rom
Nov
ell t
o In
tel,
plea
se S
kip
Bel
levu
e–
as sc
alab
le a
s hop
by
hop?
14Ji
m B
inkl
ey
type
s/to
ols -
flood
ing
flood
ing
-ass
ume
N in
terf
aces
–pa
cket
com
es in
N(1
)–
pack
et g
oes o
ut N
(2)..
N(N
)
15Ji
m B
inkl
ey
be c
aref
ul w
ith fl
oodi
ng...
16Ji
m B
inkl
ey
type
s -flo
odin
g
impo
rtant
rout
ing
algo
rithm
“to
ol”
-use
d in
m
any
rout
ing
algo
rithm
s in
som
e se
nse
stro
ng p
ro a
nd c
onpr
o -p
erfe
ct r
outin
g, y
ou fo
llow
the
best
pa
thco
n -“
perf
ect c
onge
stio
n”-y
ou u
se u
p to
o m
uch
band
wid
th
17Ji
m B
inkl
ey
type
s: v
ecto
r-di
stan
ce
vect
or-d
ista
nce
algo
rithm
s:“t
ell t
he n
eigh
bors
abo
ut th
e w
orld
”ve
ctor
is d
estin
atio
n (n
et/h
ost)
dist
ance
is m
etric
(hop
coun
t)if
we
calle
d it
dest
inat
ion-
met
ric, o
ther
peo
ple
wou
ld u
nder
stan
dyo
u flo
od y
our d
estin
atio
n,ho
pcou
ntin
fo to
you
r di
rect
ly c
onne
cted
nei
ghbo
r rou
ters
RIP
is a
n ex
ampl
e
18Ji
m B
inkl
ey
type
s: li
nk-s
tate
link-
stat
e or
shor
test
pat
h fir
st (S
PF)
“tel
l the
wor
ld a
bout
you
r nei
ghbo
rs”
find
out w
ho is
up
loca
lly, a
nd fl
ood
that
in
form
atio
n to
the
entir
e se
t of r
oute
rsth
ey c
an u
se th
e “l
ink-
stat
e”to
bui
ld a
sh
orte
st p
ath
map
to e
very
body
LS is
com
pute
-inte
nsiv
e. V
D is
ban
dwid
th
inte
nsiv
e.
19Ji
m B
inkl
ey
issu
es -
scal
abili
ty?
10’s
of h
osts
and
a fe
w ro
uter
s -st
atic
ro
utin
gw
hat a
bout
put
ting
all o
f tho
se to
aste
rs o
n th
e In
tern
et?
one
hom
e/of
fice,
to b
usin
ess/
ente
rpris
e, to
st
ate,
nat
ion,
pla
net,
sola
r sys
tem
, gal
axy.
..co
mpo
nent
s aff
ecte
d in
clud
e th
e ne
twor
k ad
dres
s and
the
rout
er h
iera
rchy
20Ji
m B
inkl
ey
scal
abili
ty...
ip’s
curr
ent p
robl
ems
–ne
t/hos
ts v
ia c
lass
or e
ven
subn
et d
on’t
mat
ch n
umbe
r of
hos
ts re
ally
util
ized
–to
o m
any
rout
es in
cor
e ta
bles
–ip
add
ress
allo
catio
n fr
om c
lass
Csl
ize
of p
ie m
eans
in
effe
ct m
ajor
ity o
f num
bers
are
was
ted
scal
abili
ty a
ffec
ts a
ddre
sses
and
how
they
are
sl
iced
up;
als
o ro
uter
hie
rarc
hyho
w m
uch
low
-leve
l inf
o (e
.g.,
link-
leve
l det
ails
) ca
n w
e af
ford
to d
isse
min
ate
upw
ards
?
21Ji
m B
inkl
ey
gene
ral s
olut
ion
to p
robl
em e
xist
s
whe
n in
dou
bt, a
dd a
new
pre
fix to
ad
dres
s and
a n
ew S
MA
LLER
cen
ter t
o th
e w
orld
pref
ix m
ust s
umm
ariz
e in
tern
al st
ruct
ure
divi
de w
orld
into
ce
nter
: (la
yer 1
) bou
ndar
y ro
uter
sdo
mai
ns: (
laye
r 2) i
nsid
e ro
uter
sbo
unda
ry ro
uter
s hav
e su
mm
ary
rout
es in
them
, no
t all.
22Ji
m B
inkl
ey
add
a pr
efix
...
dom
ain
rout
ers a
s 1st
ass
umpt
ion
-ass
ume
they
kno
w a
ll th
e ro
utes
. if
that
isn’
t sca
labl
e, th
en a
dd n
ew
hier
arch
y an
d in
trodu
ce n
ew la
yer o
f st
ruct
ure
IP is
mov
ing
tow
ards
this
(CID
R)
phon
e co
mpa
nies
hav
e pr
efix
es (n
ot
enou
gh...
nob
ody
is p
erfe
ct)
23Ji
m B
inkl
ey
hier
arch
y pi
ctur
e
boun
dary
rout
er1 2
3
core
(4)
[ net
regi
on =
1..4
,su
bnet
in re
gion
,ho
st ]
Add
ress
To 3
.x.y
, via
4.1
.1
24Ji
m B
inkl
ey
issu
es -
cong
estio
ndo
es n
ot re
fer t
o br
onch
ial c
ondi
tion
conn
ectio
nles
s rou
ters
hav
e on
ly so
man
y bu
ffer
s, to
o m
any
pack
ets,
they
dro
p th
emth
ings
get
wor
se a
t the
“fr
eew
ay e
xcha
nges
”do
es ro
utin
g pr
otoc
ol a
dd c
onge
stio
n bu
rden
?ho
w d
o w
e pr
even
t/det
ect c
onge
stio
n?ob
viou
sally
circ
uit-s
witc
hes d
on’t
have
this
pr
oble
m o
nce
circ
uit i
s set
, but
they
was
te
band
wid
th
25Ji
m B
inkl
ey
cong
estio
n?pr
even
t con
gest
ion:
–ad
d ca
rryi
ng c
apac
ity–
shut
up, e
spec
ially
if h
igh-
volu
me
src
how
do
we
notif
y ne
twor
k ab
out i
t?–
TCP
dete
cts c
onge
stio
n w
hen
send
er n
otes
that
AC
KS
are
mis
sing
, slo
w, o
r dup
licat
ed,
send
er sl
ows r
ate
of
send
ing
–so
me
sche
mes
hav
e ro
uter
s for
war
d or
pas
s bac
k co
nges
tion
bits
26Ji
m B
inkl
ey
cong
estio
n
IP se
nds b
ack
ICM
P so
urce
que
nch
mes
sage
to se
nder
–pr
o: y
ou se
nt it
the
right
way
–co
n: y
ou p
oure
d ga
s on
the
fire
ISO
CN
LP se
ts fl
ag in
net
wor
k he
ader
–pr
o: d
oesn
’t ad
d da
ta to
net
–co
n: c
onge
stio
n no
tific
atio
n is
sent
to th
e D
ESTI
NA
TIO
N (o
h, g
oody
)
27Ji
m B
inkl
ey
cong
estio
n co
nt.
TCP
solu
tion
is n
ot b
ad B
UT
–w
hat a
bout
pro
toco
ls th
at u
se In
tern
et th
at
don’
t im
plem
ent o
r can
’t se
nsib
ly im
plem
ent
it? »N
FS o
r Nov
ell c
ould
but
don
’t, d
rive
TCP
out
»au
dio/
vide
o tra
nsm
issi
on is
stea
dy-s
tate
dat
a flo
w
cong
estio
n de
tect
ion
is a
n op
en q
uest
ion
28Ji
m B
inkl
ey
issu
es -
link
cost
s
we
need
a m
etri
c, w
hich
one
?–
cost
? n
ot a
ppro
pria
te w
ithin
ent
erpr
ise
but
betw
een;
e.g
., w
hich
long
-dis
tanc
e co
mpa
ny?
–ho
p co
unt -
how
man
y ro
uter
s do
we
trave
rse
–av
aila
ble
band
wid
th -
go le
ast c
onge
sted
rout
e–
spee
d of
und
erly
ing
netw
ork,
use
ATM
as
oppo
sed
to 1
200
baud
mod
em?
–tim
e: sh
orte
st p
ath
in te
rms o
f tim
e
29Ji
m B
inkl
ey
issu
es -
link
cost
sif
link
cost
s cha
nge,
that
info
rmat
ion
mus
t co
nver
ge o
f cou
rse
answ
er n
ow is
that
link
cos
t is u
sual
ly h
op c
ount
on
ly (1
met
ric)
ques
tion:
wou
ld m
ore
com
plex
alg
orith
ms (
if po
ssib
le) t
hat d
ynam
ical
ly a
ccou
nt fo
r lin
k co
sts
do q
ualit
ativ
e be
tter j
ob th
an c
urre
nt si
mpl
e al
gorit
hms o
r jus
t use
ban
dwid
th?
30Ji
m B
inkl
ey
type
of s
ervi
ce
my
pack
ets b
efor
e yo
ur p
acke
ts!
mig
ht w
ant t
o pr
iorit
ize
certa
in tr
affic
cl
asse
sm
ight
wan
t to
optim
ize
on m
ultip
le m
etric
spo
licy-
base
d ro
utin
g (p
bco
nstra
ins)
-ou
tlaw
cer
tain
link
s or r
oute
rs–
sour
ce a
nd st
atic
rout
ing
can
be u
sefu
l her
e
31Ji
m B
inkl
ey
issu
es -
som
em
isc.
one
slo
ad-s
plitt
ing
-if w
e ha
ve tw
o sa
me-
leve
l rou
ters
, ca
n w
e sp
lit th
e lo
ad b
etw
een
them
addr
ess m
atch
ing
-rou
ter n
eeds
to d
o th
is fa
st o
r m
ay ru
n ou
t of b
uffe
r spa
cem
igra
ting
rout
ing
algo
rithm
s -yo
u ha
ve R
IP a
nd
now
you
wan
t to
switc
h to
OSP
F–
can
you
run
both
?, s
witc
hing
one
by
one
is d
isru
ptiv
e
parti
tion
repa
ir -i
f tw
o pa
ths t
o on
e ne
t, an
d on
e go
es d
own,
can
rout
ers f
ix it
?
32Ji
m B
inkl
ey
vect
or-d
ista
nce
algo
rithm
exam
ples
: R
IP,
BG
Pal
gorit
hmic
ele
men
ts:
–se
nd: e
very
N se
cond
s out
all
conn
ecte
d in
terf
aces
br
oadc
ast 2
-tupl
es:
(to n
etw
ork
X,
hop
coun
t Y) .
..–
recv
: if n
ewtu
ple,
add
to ro
utin
g ta
ble
if be
ttert
uple
, cha
nge
exis
ting
if “
dead
”tu
ple,
rem
ove
–tim
eout
: if n
o re
fres
h, ti
meo
ut e
ntry
in N
* Y
seco
nds
»br
oadc
ast m
ay b
e lo
st, t
here
fore
tim
eout
is sl
ower
33Ji
m B
inkl
ey
vect
or-d
ista
nce
assu
me
3 ro
uter
s, an
d th
at d
irect
ly
conn
ecte
d ne
ts a
re in
rout
ing
tabl
es to
star
t w
ith.
How
doe
s fol
low
ing
conv
erge
?
r1
r
2
r3
n1
n2
n
3
n4
r1 ta
ble:
(n1
, 1)
(n2,
1)
34Ji
m B
inkl
ey
slow
con
verg
ence
/cou
nt to
infin
ity
vect
or-d
ista
nce
like
this
has
def
ects
chan
ges c
an b
e se
nt w
hen
they
occ
ur, b
ut
mus
trec
ompu
tea
bit s
o co
nver
genc
e ta
kes
time
(mad
e w
orse
by
poss
ible
loop
s)
coun
t to
infin
ity p
robl
em c
an o
ccur
too
-ro
utin
g lo
op u
ntil
hopc
ount
reac
hes
impo
ssib
le v
alue
35Ji
m B
inkl
ey
coun
t to
infin
ityA
BC
C c
rash
es,
B k
now
s C c
rash
ed b
ut h
asn’
t tol
d A
,bu
t unf
ortu
nate
ly A
talk
s to
B fi
rst
B is
told
by
A:
I can
get
to C
in tw
o ho
ps (a
nd n
ote
it do
esn’
t men
tion
to B
that
the
path
isth
ruB
)B
says
AH
A!,
that
mea
ns I
can
get t
o C
in th
ree
hops
and
repo
rts th
at to
AA
says
AH
A!,
it’s n
ow fo
ur h
ops t
o B
and
tells
Bet
c...
RIP
max
hop
cou
nt (i
nfin
ity) i
s 16
36Ji
m B
inkl
ey
split
-hor
izon
fixup
(vec
tor-
dist
ance
)
A te
lls B
that
its d
ista
nce
to C
is in
finity
–(b
ecau
se B
is th
e di
rect
ion
A g
ets t
he in
fo
from
)w
hen
link
goes
aw
ay, B
will
kno
w th
at
ther
e is
no
path
to C
, and
tell
Ado
esn’
t wor
k in
all
case
s
37Ji
m B
inkl
ey
link-
stat
e al
gorit
hm“t
ell t
he w
orld
abo
ut y
our n
eigh
bors
”lin
k-st
ate
requ
ires e
ach
parti
cipa
ting
rout
er to
ke
ep m
ap o
f com
plet
e to
polo
gyin
3 p
arts
–1.
det
erm
ine
neig
hbor
con
nect
ivity
–2.
send
(“flo
od”)
link
-sta
te p
acke
t tha
t sta
tes w
hich
link
ne
ighb
ors a
re u
p–
3. u
seD
ijkst
rash
orte
st-p
ath
first
to c
ompu
te b
est p
ath
to th
at n
etw
ork
38Ji
m B
inkl
ey
link-
stat
e#de
term
ine
link-
stat
e
“pin
g”ne
ighb
ors t
o de
term
ine
if th
ey a
re u
p or
they
may
bro
adca
st (m
ultic
ast)
thei
rex
ista
nce
“i m
ultic
ast,
ther
efor
e i a
m...
”C
AB
39Ji
m B
inkl
ey
link-
stat
e#se
nd L
SP
each
par
ticip
atin
g ro
uter
“flo
ods”
(ver
y ca
refu
lly) r
outin
g do
mai
n w
ith L
SPls
p
40Ji
m B
inkl
ey
link-
stat
e#co
mpu
te sh
orte
st p
ath
each
par
ticip
atin
g ro
uter
take
sLSP
s, st
ores
th
em, a
nd c
ompu
tes s
horte
st p
ath
to se
nder
src
dest
41Ji
m B
inkl
ey
link-
stat
e: p
ros/
cons
pros –co
nver
ges f
aste
r, no
cou
nt to
infin
ity p
robl
em +
rout
er
can
forw
ard
LSP
imm
edia
tely
, mus
trec
ompu
teD
V–
mor
e fu
nctio
nalit
y; e
.g.,
each
rou
ter
has m
ap o
f net
, ca
n m
ake
netw
ork
debu
ggin
g ea
sier
cons
–m
ore
com
pute
than
vd(d
oes t
his m
atte
r?)
toss
ups
–ba
ndw
idth
?vd
broa
dcas
ts su
mm
ary
vers
ion
of ro
ute
tabl
e,ls
rout
ers s
end
LSP
arou
nd n
et