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COS 338

Day 16

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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

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3Figure 8-20: Layer 3 Switches and Routers

in Site Internets

To

Other

Sites

Border

Router Layer 3

Switch

Layer 3

Switch

Ethernet

Workgroup

Switch

Ethernet

Workgroup

Switch

Layer 3 switches are routers.

However, they are faster than

traditional software-based

routers because they doprocessing in hardware.

Switches are faster than routers,

so marketers invented Layer 3 switch.

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4Figure 8-20: Layer 3 Switches and Routers

in Site Internets, Continued

To

Other

Sites

Border

Router Layer 3

Switch

Layer 3

Switch

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.

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5Figure 8-20: Layer 3 Switches and Routers

in Site Internets, Continued

To

Other

Sites

Border

Router Layer 3

Switch

Layer 3

Switch

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.

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6Figure 8-20: Layer 3 Switches and Routers

in Site Internets, Continued

To

Other

Sites

Router Layer 3

Switch

Layer 3

Switch

Ethernet

Workgroup

Switch

Ethernet

WorkgroupSwitch

Like traditional routers, L3 switches

require considerable management labor.

Therefore, they usually do not

replace workgroups switchesat the bottom of the hierarchy.

User

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Topics Covered

IP

Hierarchical IP addresses

Network, subnet, and host parts Parts vary in length, but the total is always 32

bits

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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 ofmatch and metric values

Send the packet out the indicated interface to theindicated destination host or next-hop router

Multiprotocol routers are not limited to routing IPpackets

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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 insteadof IP addresses

Reduces work compared to normal routing andtherefore costs less

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Topics Covered

Domain Name System (DNS)

Not just to look up a destination hosts 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

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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

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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

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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