Introduction to Networking (Routing & Switching)

1. Introduction to Networking(Routing & Switching) Nir Ingbar

2. Agenda • OSI 7 Layers model • Layer 1 & 2 • Frame forwarding & filtering • VLAN, dot1Q Trunking • IP • Routing

3. OSI 7 Layers model (1977 by ISO)

4. OSI Model Layer’s definitions • Each OSI layer performs unique and specific task • A layer only has a knowledge of its adjacent layers • A layer uses the services of a layer below • A layer performs functions and provides service to the layer above • A layer service is independent of its implementation Application Presentation Session Transport Network Data Link Physical

5. OSI Model Layers • Physical: Electrically encodes and physically transfers messages between nodes • Data Link: Provides reliable transit of data across a physical link, handling physical addressing, link discipline, error detection, ordered delivery of frames and flow control • Network: Provides connectivity and path selection between two end systems that may be located on geographically diverse sub-networks • Transport: End- to- end control & information exchange with a level of reliability required for the applications

6. OSI Model Layers (cont.) • Session: Manages the connection between cooperating applications • Presentation: Transforms data to and from negotiated standardized formats • Application: Provides the window between the application process and OSI

7. Data encapsulation Data Application Application Data Presentation Presentation SH Data Unit Session Session TH Data Unit Transport Transport NH Data Unit Network Network DLH Data Unit FCS Data Link Data Link Bits Physical Physical * FCS (Frame Check Sequence)

8. Internetworking Devices Application Application Presentation Presentation Session Session Transport Transport Network Network Router Switch/Bridge Data Link Data Link Physical Physical Hub/Repeater

9. Protocol Suite Application Telnet FTP SMTP TFTP BOOTP SNMP Presentation Session TCP UDP Transport IP Network ICMP ARP Data Link Ethernet, Token Ring, FDDI, WAN synchronous Physical

10. Layer 1 & 2

11. Device Types • Hub - multi port repeater, provide connectivity, allowing attached devices a path between which they can communicate, works on layer one • Switch – connecting hosts • Bridge – connecting networks, can’t identify different logical networks

12. Bridge vs. Switch • Bridge usually have two interfaces and can connect to physical networks • Switches usually have more than that • The main difference between a switch and bridge is the number of networks each can connect • Switches are often aimed to connect workstations in a single junction • Both are used inside LAN • Both operates on layers one and two

13. Collision Domain • one of the logical network segments in which the data packets can collide to each other • Collision domains are often referred as ‘Ethernet segments'. • defined as a single CSMA/CD network segment in which there will be a collision if two computers attached to the system both transmit at the same time • A collision occurs when two or more network devices are trying to transmit packets at the exact same time

14. Collision domain - example

15. Collision domain - example

16. Type Of Transmission • Unicast - unicast transmission is the sending of information packets to a single destination • Broadcast - broadcasting refers to transmitting a packet that will be received (conceptually) by every device on the broadcast domain • Multicast - multicast is a network addressing method for the delivery of information to a group of destinations simultaneously • Anycast – like multicast but only one address of a set of addresses is chosen at any given time to receive information from any given sender

17. MAC Address • 48 bits (6 octets) address space representing an unique identifier to most network adapters or network interface cards (NIC) • The first three octets identify the organization that issued the identifier and are known as the Organizationally Unique Identifier (OUI) • 00-16-D3-C4-55-6A

18. Broadcast Domain • represents the systems to which a given broadcast will travel • broadcasts do not pass routers by default • If one station will broadcast, all the stations in this domain will get the message • If a station wants to send a message out of the LAN, it will have to know it’s Default Gateway

19. Broadcast domain – simple example

20. Collision domain- problem

21. One switch can be a Single Point Of Failure • Adding an additional Switch can create broadcast storm.

22. Solution: STP – Spanning tree Protocol • On running this algorithm the LAN is reduced to an acyclic tree • The main idea of the Spanning Tree is for the bridges to select the ports over which they will forward frames

23. L2 B1 B3 B4 L1 L2 X B1 L5 X B5 B2 B3 B4 B5 L1 L3 L4 L5 B2 With Spanning Tree L3 L4 Actual Network Spanning Tree Protocol Spanning tree is designed to prevent loops in bridged/switched Ethernet network based on the root bridge concept, which is selected via programmable parameters

24. Frame forwarding & filtering

25. Frame forwarding & filtering • The initial MAC address is empty

26. Frame forwarding & filtering (cont.) • Station A sends a frame to station C • The switch caches the MAC address of station A to port E0 by learning the source address of data frames • The frame from station A to station C is flooded out to all ports except port E0

27. Frame forwarding & filtering (cont.) • Station D sends a frame to station C • The switch caches the MAC address of station D to port E3 by learning the source address of data frames • The frame from station D to station C is flooded out to all ports except port E3

28. Frame forwarding & filtering (cont.) • Station A sends a frame to station C • The destination is known; the frame is not flooded

29. VLAN, dot1Q Trunking

30. VLAN, dot1Q Trunking 802.1Q Frame • FCS (Frame Check Sequence) is recalculated

31. Importance of native VLANs • VLAN 1 untagged traffic (native VLAN) • An 802.1Q trunk and its associated trunk ports have a native VLAN value. 802.1Q does not tag frames for native VLAN. Therefore, ordinary stations will be able to read the native untagged frames, but will not be able to read any other frame because the frames are tagged

32. IP

33. Internet Protocol - IP • Network Layer • Provides network layer services to TCP/IP protocol suite • Responsible for forwarding packets through network based on IP addresses • “Best effort” delivery • Connectionless • Unacknowledged • Relies on a transport protocol to guaranty delivery

34. IPv4 Addressing • Address format: XXX.XXX.XXX.XXX (0≤XXX≤255) • Addresses are 32 bits long (4,294,967,296 IP addresses) • Internet Assigned Numbers Authority (IANA) assigns IP addresses for the Internet • Divided into five classes three of which are available to end-user networks • Consists Network and Host identification fields

35. Available IP Addresses • Class D is reserved for multicast groups • Class E is reserved for future use

36. Private Networks • RFC 1918 addresses • Not routed by Internet routers (filtered by Edge Routers) • RFC 2026—Link Local Addresses 169.254.0.1–169.254.255.255 • Auto-assigned IP address to local host if DHCP server cannot be contacted • Not routed by any router

37. Other Reserved Addresses • 127.0.0.1–127.255.255.255 • Reserved for testing and loopback routines for IP Applications • ping 127.0.0.1—verifies the local host has properly loaded the IP protocol • 224.0.0.1–224.0.0.255—Class D multicast (IANA) • Reserved for well known services and network topology mechanisms

38. Subnetting IP/VLSM/Classless • Allows to divide a single IP network into smaller divisions – Subnets • Done by borrowing bits from the host portion of the address • Subnet bits are defined by the Subnet Mask IP Address 134.125.172.17 1 0 0 0 0 1 1 0 0 1 1 1 1 1 0 1 1 0 1 0 1 1 0 0 0 0 0 1 0 0 0 1 Subnet Mask 255.255.240.0 Or /20 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 Subnet Host

39. SummaryHost-to-Host Packet Delivery (1 of 22)

40. Host-to-Host Packet Delivery (2 of 22)

41. Host-to-Host Packet Delivery (3 of 22)

42. Host-to-Host Packet Delivery (4 of 22)

43. Host-to-Host Packet Delivery (5 of 22)

44. Host-to-Host Packet Delivery (6 of 22)

45. Host-to-Host Packet Delivery (7 of 22)

46. Host-to-Host Packet Delivery (8 of 22)

47. Host-to-Host Packet Delivery (9 of 22)

48. Host-to-Host Packet Delivery (10 of 22)

49. Host-to-Host Packet Delivery (11 of 22)

50. Host-to-Host Packet Delivery (12 of 22)