1. COS 338 Day 16

2. 2 DAY 16 Agenda Capstone Proposals Overdue 3 accepted, 3 in mediation Capstone progress reports still overdue I forgot to mark in calendar so I will grant a reprieve Second capstone progress report due Lab 5 write-up Due Today Assignment 5 Due November 7 Today we will finish discussing TCP/IP and then do Lab 6

3. 3 Figure 8-20: Layer 3 Switches and Routers in Site Internets To Other Sites Border Router Layer 3 Switch Layer 3 Switch L3 Ethernet Workgroup Switch Ethernet Workgroup Switch Layer 3 switches are routers. However, they are faster than traditional software-based routers because they do processing in hardware. Switches are faster than routers, so marketers invented “Layer 3 switch.

4. 4 Figure 8-20: Layer 3 Switches and Routers in Site Internets, Continued To Other Sites Border Router Layer 3 Switch Layer 3 Switch L3 Ethernet Workgroup Switch Ethernet Workgroup Switch Layer 3 switches are routers. However, hardware limitations mean that they are limited routers. They are not full multiprotocol routers. They only support TCP/IP and, sometimes, IPX/SPX. This limits their usefulness.

5. 5 Figure 8-20: Layer 3 Switches and Routers in Site Internets, Continued To Other Sites Border Router Layer 3 Switch Layer 3 Switch L3 Ethernet Workgroup Switch Ethernet Workgroup Switch Layer 3 switches are routers. However, hardware limitations mean that they are limited routers. They usually cannot connect to WANs because they usually only implement Ethernet at the data link layer. A router is normally used at the border.

6. 6 Figure 8-20: Layer 3 Switches and Routers in Site Internets, Continued To Other Sites Router Layer 3 Switch Layer 3 Switch L3 Ethernet Workgroup Switch Ethernet Workgroup Switch Like traditional routers, L3 switches require considerable management labor. Therefore, they usually do not replace workgroups switches at the bottom of the hierarchy. User

7. 7 Topics Covered IP Hierarchical IP addresses Network, subnet, and host parts Parts vary in length, but the total is always 32 bits

8. 8 Topics Covered IP Router Operation Compare destination IP address of packet to each row to find all matching rows Find the best-match row based on length of match and metric values Send the packet out the indicated interface to the indicated destination host or next-hop router Multiprotocol routers are not limited to routing IP packets

9. 9 Topics Covered IP Routing Protocols Allow routers to share route information so they can update their routing tables Multiprotocol Label Switching (MPLS) Bases routing decisions on packet labels instead of IP addresses Reduces work compared to normal routing and therefore costs less

10. 10 Topics Covered Domain Name System (DNS) Not just to look up a destination host’s IP address if you only know its host name A general system for naming things on the Internet Firms want second-level domain names (cnn.com) ICMP For supervisory messages at the internet layer Error advisement messages of various types Pinging to see if a host or router is online

11. 11 Topics Covered IPv4 Fields Version Time to live (TTL) Protocol Options (rare and suspicious) Data field IPv6 128-bit address fields to allow many more hosts on the Internet

12. 12 Topics Covered TCP One-bit Flag fields (if value is 1, said to be set) Sequence numbers Acknowledgement numbers and ACK bit FIN versus RST closes Window size field for flow control (Module A) Port numbers Well-known, registered for applications Ephemeral for client connections Socket syntax = IP address : port number

13. 13 Topics Covered UDP Also has source and destination port numbers Otherwise simple because does not do supervisory chores Layer 3 Switches Routers, but fast and inexpensive like switches. But labor cost to manage any router is high Limited in protocol handling, interfaces Very attractive where they can be used