Organizaciya TCP/IP po posledovatel'nym liniyam
Protokol TCP/IP ne obyazatel'no trebuet nalichiya ether
net'noj seti. Vpolne dopustimy i drugie fizicheskie nositeli,
naprimer:
Posledovatel'nye linii s podklyucheniem cherez porty RS-232,
Skorostnye linii s podklyucheniem cherez parallel'nye porty,
ili skorostnye sinhronnye porty (naprimer 485, V.435).
|ti vozmozhnosti obespechivayutsya specializirovannymi realizaciyami
protokola IP:
dlya podklyucheniya cherez RS-232
SLIP - Serial Line IP - samaya pervaya realizaciya TCP/IP "dlya
bednyh", shiroko ispol'zuetsya do sih por.
CSLIP - Compressed SLIP - modifikaciya protokola SLIP.
Szhatiyu podvergayutsya zagolovki IP-paketov. VNIMANIE: no
ne sami dannye! V standartnom IP-pakete IP-zagolovki so
sluzhebnoj informaciej zanimayut poryadka 40 bajt. V
CSLIP'e eti zagolovki uzhimayutsya do 3 bajt. Pri peresyl-
ke bol'shogo chisla melkih paketov poluchaetsya sushchestven-
nyj vyigrysh v skorosti. Esli pakety krupnye, to vyigry-
sha ne budet nikakogo.
PPP - Point-to-Point Protocol
Eshche odna, sovremennaya realizaciya TCP "dlya bednyh". YAv-
lyaetsya standartnym dlya SVR4. Bolee universalen. Pozvo-
lyaet takzhe organizovat' peredachu po posledovatel'noj
linii protokola IPX. Podderzhivaet rezhimy emulyacii slip
i cslip - dlya sovmestimosti.
dlya podklyucheniya cherez Centronix-parallel'nyj port
PLIP - Parallel Line IP - nekotorye skazhut - ekzotika.
Nichut' ne byvalo. Ves'ma rasprostranennaya veshch'. Vot
kogda TCP/IP po SCSI-shine - eto da, eto - ekzotika.
Kstati, RFC 1149 opisyvaet peredachu paketov IP golubinoj
pochtoj.
TCP/IP po sputnikovoj svyazi.
Teoreticheskih trudnostej organizaciya svyazi TCP/IP cherez
sputnikovuyu antennu net - vse vyglyadit takzhe, kak pri modemnoj
svyazi po telefonu. Tehnologiya primerno sleduyushchaya: s antenny
vyhodit vysokochastotnyj signal, signal progonyaetsya skvoz'
sputnikovyj modem, iz modema vyhodit potok dannyh po formatu
High Speed Interface - zavesti v komp'yuter ego mozhno cherez
skorostnoj port, naprimer V.435 (logicheski on vedet sebya
priblizitel'no kak obychnyj posledovatel'nyj port), i so storony
hosta - podnimaetsya protokol PPP. Estestvenno, na "tom konce"
predpolagaetsya ta zhe shema podklyucheniya.
+-------------------+ +-----------------+ (
| protokol port| dannye |port sputnikovyj| signal ( ><
|Host PPP V.435|========|V.435 modem | ~~~~~~ (
| -TCP/IP-> | | | ~~~~~~ /\
+-------------------+ +-----------------+ Antenna
Vmesto Hosta so skorostnym portom, modem mozhno podklyuchit' k
specializirovannomu ustrojstvu - "Routeru", vnutri kotorogo
"zashit" protokol TCP/IP (PPP, Ether), i imeyutsya porty Ethernet,
i High Speed Interface. Dostatochno populyarny dlya takih celej
routery "Cisco router", "NetBlaser".
+-------------------+ +-----------------+ (
| protokol port| dannye |port sputnikovyj| signal ( ><
|Router PPP V.435|========|V.435 modem | ~~~~~~ (
| -TCP/IP-> | | | ~~~~~~ /\
+-------+-----------+ +-----------------+ Antenna
|
... -Ethernet------ ...
Skorost', kotoruyu mozhno poluchit'.
Skorost' glavnym obrazom zavisit ot tipa i kachestva linii svya-
zi, ispol'zuemyh modemov, i tipa porta, v kotoryj etot modem
votknut.
Prakticheskie ogranicheniya na skorost':
Skorost' dannyh mezhdu modemami V32bis/V42 po gorodskomu telefo-
nu, ili mezhdugorodnej linii "Iskra" do 16800 bit/sek. Real'no ~
12000 bit/s. Nalichie vstroennogo protokola V42 szhatiya dannyh
pozvolyaet podnyat' real'nuyu (zamerennuyu uzhe ne mezhdu modemami, a
mezhdu portami) skorost' peredachi neszhatyh dannyh v 2-4 raza,
t.e. do 38400-57600 bit/s
Maksimal'naya skorost' priema/peredachi dannyh na
posledovatel'nom portu RS-232 zavisit ot nalichiya v onom
mikroshem UART (Universal Asyncronous Receiver-Transmitter)
16450 - 19200 bit/s.
16550 - 19200 bit/s. (otsutstvie bukovki "A" - fatal'no)
16550A - 38400 bit/s.
16550A do 115200 bit/s. (Esli operacionnaya sistema "tyanet")
(v chastnosti - Solaris, Unixware - net,
FreeBSD, Netblaser, Cisco router - da)
V itoge real'naya skorost' peresylki dannyh:
Telefon/"Iskra", V32bis/V42 - 19200 bit/s.
Vydelennaya 2-h provodka, V32bis/V42 - 38400 bit/s.
Vydelennaya 4-h provodka, RAID,????? - 115200 bit/s.
Fizicheskaya 4-h provodka<=4km, ????? do 1 Mbit/s.
Optovolokno <=?km, ????? ?? 2 Mbit/s.
Antenna. Sputnikovyj modem. Port V.435. PPP 64, 128, 256 Kbit/s
* Konfigurirovanie SLIP/CSLIP * .
Dlya etogo soedinyaem dva host'a nul'modemnym kabelem cherez
posledovatel'nye porty, i zapuskaem fonom programmu slattach,
perevodyashchuyu porty v rezhim peredachi protokola TCP/IP.
Estestvenno, chto SLIP nado zapuskat' s oboih koncov, prichem
"odinakovyj".
SVR4, slip
slattach /dev/comport NASH-IP-ADRES IH-IP-ADRES 19200 &
# perevodit port /dev/comport v rezhim "slip" na skorosti 19200
# i ustanavlivaet IP-adres na slip-interfejs
SVR4, cslip
slattach -c /dev/comport NASH-IP-ADRES IH-IP-ADRES 38400 &
# perevodit port /dev/comport v rezhim "Compressed-slip"
# na skorosti 38400
# i ustanavlivaet IP-adres na C-slip-interfejs
slattach -e /dev/comport NASH-IP-ADRES IH-IP-ADRES 38400 &
# perevodit port v rezhim slip ili cslip,
# avtomaticheski opredelyaya, kakoj imenno protokol zapushchen
# "na tom konce", i ustanavlivaet so svoej storony takoj zhe
Linux, SLIP.
Teper' SLIP v Linux zaryazhaetsya komandoj DIP, s konfiguracionnym fajlom:
/usr/sbin/dip config-file-name
---------------------------------------------------------------
# pryamoj konnekt nul'modemnym kabelem
main:
get $local 193.232.171.22
get $remote 193.232.171.19
port /dev/modem
speed 9600
mode SLIP
exit
---------------------------------------------------------------
# slip s telefonnoj dozvonkoj
---------------------------------------------------------------
main:
get $local uwalt.hacktic.nl
get $remote xs4all.hacktic.nl
port /dev/modem
speed 38400
send ATQ0V1E1X4\r
wait OK 2
dial p555-1234
login:
sleep 2
wait ogin: 20
send MYLOGIN\n
wait ssword: 20
send MYPASSWD\n
# We are now logged in.
wait SOMETEXT 15
get $mtu 296
# Ensure "route add -net default xs4all.hacktic.nl" will be done
default
mode SLIP
---------------------------------------------------------------
Na oboih koncah imet' simmetrichnye fajly i zapustit' dip'y
Linux, CSLIP.
# sperva perevodim port v rezhim "cslip"
slattach -p cslip /dev/modem &
ifconfig cs0 NASH-IP-ADRES pointopoint IH-IP-ADRES
route add IH-IP-ADRES
route add default gw IH-IP-ADRES
Linux, PLIP.
ifconfig plip1 NASH-IP-ADRES pointopoint IH-IP-ADRES
route add IH-IP-ADRES
route add default gw IH-IP-ADRES
Ustanovka SLIP po telefonnoj linii cherez modem.
Nado zastavit' nash modem sozvonit'sya s "tem" modemom.
Posle etogo my poluchaem prozrachnoe soedinenie mezhdu
posledovatel'nymi portami, po kotoromu i "podnimaem"
SLIP, sm. predydushchie punkty.
( stty 19200 ; echo atdp9120123 ) < /dev/modem > /dev/modem
sleep 55
Vydaem na modem komandu atdp - nabrat' telefonnyj nomer, i zhdem
55 sekund. Nadeyus', modemam hvatit etogo vremeni, chtoby "snyu-
hat'sya".
Vosstanovlenie svyazi v sluchae obryva.
Kak uznat', chto svyaz' porvalas'? Ping'anut' "tot" konec linka.
Prezhde, chem nabirat' modemom nomer dlya novoj dozvonki,
neobhodimo "snyat'" slip s nashego posledovatel'nogo porta
(poskol'ku v rezhime slip on funkcioniruet ne kak
posledovatel'nyj port, a kak kanal peredachi TCP/IP). Kak snyat'
slip? Kil'nut' slattach.
while true # V vechnom cikle
do sleep 60 # Podozhdat' minutku
if ping 107.65.8.254 | grep 'is alive' ;
then echo Ok > /dev/null # Esli IH-IP-ADRES otzyvaetsya
else
# Inache zarubaem slattach
slip_pid=`ps -ef | grep slattach | cut -c1-6`
kill -9 $slip_pid
# nabiraem tamoshnij telefonnyj nomer
(stty 19200; echo atdp9120123) < /dev/modem > /dev/modem
sleep 55
# podnimaem slattach
slattach -e /dev/modem 195.8.2.3 107.65.8.254 19200 &
fi
done
/etc/inet/ppphosts - perechislyaet ppp-hosty
Pravila dozvonki i soedineniya s etimi hostami opisyvayutsya
standartnymi opisaniyami iz UUCP
Ubedit'sya, chto podderzhka ppp prisutstvuet v
konfiguracionnom fajle /etc/strcf
Ubedit'sya, chto pri zagruzke zapuskaetsya komanda slink
Neposredstvennoe ppp-soedinenie aktiviziruetsya pri
obrashchenii ("po trebovaniyu").
Podrobnosti iskat' v
man ppp
man pppd
man ppphosts
Vse delaetsya komandoj pppd. V komplekt pppd vhodit
komandochka chat, v argumentah zhe pppd zadayutsya IP-adresa,
telefonnye nomera, inicializaciya modema, chat-ovyj dialog s
mashinoj provajdera.
Primer: (Pochti iz zhizni) yavno zadaem nash IP=123.456.789.12
pppd connect 'chat -v ABORT "NO DIALTONE" ABORT BUSY "" ATZ OK \
atdp9386933 Username: ppmoshkow Passwd: mypasswd mode ;' \
crtscts defaultroute modem noipdefault -detach mru 1500 \
123.456.789.12:194.85.105.1 /dev/modem 38400
Primer: vzyat' adresa zadannye serverom
pppd connect 'chat -v ABORT "NO DIALTONE" ABORT BUSY "" ATZ OK \
atdp9386933 Username: ppmoshkow Passwd: mypasswd mode ;' \
crtscts defaultroute modem noipdefault -detach mru 1500 \
0.0.0.0: /dev/modem 38400
Postavit' dopoolnitel'nyj paket iz MS Plus - "Network dialup
script editor"
Podklyuchit' cherez nego skript:
---------------------------------------------------------------
proc main
waitfor "login:" until 5
transmit $USERID, raw
transmit "^M"
waitfor "Password:"
transmit "password^M"
waitfor "modem" until 5
endproc
---------------------------------------------------------------
V zvonil'noj forme vpisat' logname, password ne vpisyvat', ibo
vse ravno on zabyvaetsya pri kazhdom perezapuske.
Na rabochih stanciyah pod HP-UX/10.20 rodnogo ppp NET. Tol'ko slip.
Mozhno sftpit' free-varnyj paket iij-ppp
http://www.verinet.com/~barthold/ftp/iij-ppp0.94beta2.hpux10.tar.gz
Dokumentaciya po konfiguracii i installyacii prilagaetsya k paketu.
Na serverah i rabochih stanciyah SLIP nazvan "ppl" i vklyuchen v
standartnyj paket "LAN/9000 Link" product.
Last-modified: Thu, 09 Jul 1998 12:44:55 GMT