1. Компютърни Мрежи и GNU/Linux Боян Кроснов boyan@krosnov.org http://boyan.krosnov.org/ Мариян Маринов mm@yuhu.biz SiteGround LLC

2. 2 Лекцията Преговор Linux Networking Stack Команди – IP ARP протокол Команди – ARP Sniffers TCP и UDP протоколи Команди – TCP и UDP

3. 3 Преговор

4. 4 Слоести мрежови модели

5. 5

6. 6 Протоколи

7. 7 Мрежова топология

8. 8 Команди lspci ip link ethtool, mii-tool ifconfig; /proc/net/dev vconfig; /proc/net/vlan

9. 9 Demo setup

10. 10

11. 11 NIC

12. 12 Linux kernel networking stack

13. 13 Linux kernel

14. 14 Команди - IP ipcalc ip addr; ifconfig ip route; route ping; fping traceroute; mtr /etc/network/interfaces (Debian) /etc/sysconfig/network-scripts (Redhat)

16. ARP Protocol RFC826: Ethernet Address Resolution Protocol: Or Converting Network Protocol Addresses to 48.bit Ethernet Address for Transmission on Ethernet Hardware. D. Plummer. November 1982. (Format: TXT=21556 bytes) (Also STD0037) (Status: STANDARD)

17. Команди - ARP ip neigh, arp arping

18. ARP Table gw:~# arp -n Address HWtypeHWaddress Flags MaskIface 192.168.0.5 ether00:0B:DB:4A:BD:8ACeth1 192.168.0.10ether00:0E:A6:6A:B1:12Ceth1 192.168.0.150ether00:14:BF:2C:94:5ACeth1 172.16.0.199ether00:13:02:4F:78:16Ceth1 192.168.0.124ether00:1C:BF:0F:24:F9Ceth1 172.16.0.22 (incomplete) eth1 85.14.21.165ether00:17:0F:AD:E1:C0Ceth0 85.14.21.44 ether00:19:66:34:B1:24CMeth0

19. MAC address table Switch# show mac-address-table vlan 254... vlan mac address type learn age ports ------+----------------+--------+-----+----------+----------------- * 254 0004.6a00.326c dynamic Yes 5 Gi1/29 * 254 0003.f402.60e5 dynamic Yes 0 Gi1/3 * 254 0004.6a00.35c0 dynamic Yes 5 Gi1/3 * 254 0004.6a00.31dc dynamic Yes 5 Gi1/3 * 254 0040.c7f6.11e3 dynamic Yes 0 Gi1/3 * 254 0004.6a00.3004 dynamic Yes 5 Gi1/3 * 254 0004.6a00.350c dynamic Yes 5 Gi1/3 * 254 0004.6a00.3720 dynamic Yes 5 Gi1/3...

20. 20 Sniffers Wireshark, tshark tcpdump

21. 21 Демонстрация

22. 22 Q&A

23. 23 TCP и UDP протоколи UDP (RFC768 J.Postel 1980) – ports TCP (RFC793 J.Postel 1981) – Session establishment and tear-down – Window procedure – Slow start and congestion avoidance (VJ 1988) Berkeley sockets (1983) – The Berkeley socket API forms the de facto standard abstraction for network sockets. Most other programing languages use an interface similar to the C API. // wikipedia

24. 24 Протоколи

25. UDP header 0 7 8 15 16 23 24 31 +--------+--------+--------+--------+ | Source | Destination | | Port | Port | +--------+--------+--------+--------+ | | | | Length | Checksum | +--------+--------+--------+--------+ | | data octets... +----------------... User Datagram Header Format

26. TCP Header 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port | Destination Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Acknowledgment Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data | |U|A|P|R|S|F| | | Offset| Reserved |R|C|S|S|Y|I| Window | | | |G|K|H|T|N|N| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Checksum | Urgent Pointer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ TCP Header Format

27. 27 Linux kernel networking stack

28. 28 TCP и UDP команди telnet tcptraceroute netstat, fuser, lsof hping nc - TCP/IP swiss army knife /etc/inetd.conf

29. 29 Q&A

30. Extra slides

31. iptables Netfilter firewall connection tracking filter, nat, mangle, raw

32. Linux router ip route zebra/quagga XORP, Vyatta

33. Linux bridge (switch) brctl ebtables

34. IP Fragmentation, MTU, PMTU-D MTU concept TCP MSS DF (Don't Fragment) bit ICMP type 3 (destination unreachable), code 4 (fragmentation needed but don't-fragment bit set)