Explain how a T-1 Works

How does a T-1 connect to the internet?

Local Central Office

What are the important Headers for UDP (5)?

Source Port

Destination Port

Checksum

User Data

Length

What are the Headers to know for TCP (7)?

Source Port

Destination Port

Sequence Number

Acknowledgment Number

Window Size

Checksum

Data

What is the important fields of IP (8)?

Version

Type

Length

Time to Live

Check

Source Address

Destination Address

Data

List the important headers of Frame Relay(7)?

DLCI

CMD

FECN

BECN

DE

Data

Check

What are the Headers for MPLS (6)?

L2 Header

shim

IP Header

User Data

ATM

What are the headers for Shim (3)?

MPLS Label

Class of Service

TTL

What are the Headers for ATM (7)?

Virtual Path Identifier (VPI)

Virtual Channel Identifier (VCI)

Payload Type Identifier (PTI)

Cell Loss Priority (CLP)

Header Error Check (HEC)

Data

What are the headings for AAL5?

VPI (virtual path)

VCI (virtual channel)

PTI (Payload Type Identifier)

CLP (cell lost priority)

HEC (Header error Check)

GFC(UNI Cell, not NNI cell)

What are the steps for MPLS Operation?

1. Build routing tables

2. Packet enters at the ingress edge and label insertion

3. Label switched path creation and packet forwarding

4. Egress edge strips the label and forwards it to the destination

What is the port # for HTTP?

80

Describe the TCP process (6ish steps):

1) Application sends a file or email to the operating system

2) The OS gives to TCP. Data Block put in buffer by TCP and chopped up into 1500 bite segments (packets, frames)

3) Put in Header Info

4) Put it in Queue

5) Send it over layer 2 & 1

6) IF gets response, than asks if has big enough windows in TCP-IP that can send 20 packets. The other buffer responds affirmative, or negotionates packet size.

7) Then they set up a timer system. After the reciever gets it, steps 5-1 happen backwards.

Describe the 3 way handshake process

Step 1) Sending TCP puts starting sequence number and ack number.

Step 2)  Receiving routers takes and uses for responding seq number but adds one for ack number

Step 3) old IP packet sequence number becomes new ack number

When would you use a Routed Network?

When you want a private connection

What is the T-1 framing structure?

24 frames

125 milisecons

each byte repsresents 64 kb,

193rd Bit of each frame used for frame synchronization.

(Extended Super Framing)

Describe the information contained in the RIP routing table?

 Destination IP address- tells how many routers

HOP Count- tells fewest hops it will take,

maximum # of hops (RIP Metric)- This is 15

Explain what the RIP Metric is and what it means?

RIP Metric is hop count or router count (go the smallest every time not the fastest path but fewer hops). Maximum 15

Describe the information contained in the OSPF routing table:

Cost factor.- the smallest that gives you the least number after adding out each path 

Timer-  uses a 90sec timer for routers …

Designation IP ADdress, IP address of next hop router, ID of routing table source Neighbor. 

4 parts of the table to know: Destination Address of Next Router, Cost Factor, Time between updates, and what interface is used to reach that destination (ex: Serial 0/1)

What are the 6 elements of the OSPF metric

Link state (0-10)

Link Cost

Link Speed

delay

throughput

reliability

How is a route cost calculated with OSPF?

Cost is sum of 6 components (LINK STATE (0-10) LINK COST, LINK SPEED, DELAY, THROUGHPUT, RELIABILITY)

 for each link added up for each path, sum of number of the path is then put in table. Lowest cost factor = path

Describe the pieces of frame relay you have to buy (5):

Have to buy a access and a destination T-1.

Have to buy a port entry and exit frame relay switch.

Then you pay a frame relay charge, and full 1.5 meg charge if have it. 

When would you use frame relay?

Use frame relay if you have 4 or more locations across long distances (multi-state)

What medium does frame relay use to transfer information?

Uses T-1 or subchannels of T-1 as a connection vehicle, there from 64 kbps up to 1.5 mpbs

Explain FECN

In a Frame Relay network, FECN (forward explicit congestion notification) is a header bit transmitted by the source terminal requesting the destination terminal slow down its request for data. 

Explain BECN

BECN (Backward Explicit Congestion Notification) is a header bit transmitted by the destination terminal requesting that the source terminal send data more slowly.

What does PVC stand for?

Permanent Virtual Circuit

A permanent association btw DTE established by config. it uses a fixed logical channel to maintain permanent association b/w two DTE's. all data b/w two points follows predetermined physical path.

Switched Virtual Circuit

A virtual circuit connection established across a network on an as needed basis and lasting only for the duration of the transfer. 

 Why would you use SVC over PVC?

What is Piggy Backing?

you can put 2 IP packets in a single frame relay frame

 What are the steps needed to establish an ATM connection with SVC?

How are the steps needed to establish an ATM connection with SVC differ from a PVC connection?

you only dynamically set it up when you want a temporary connection. Requires receiving router.

  A ____ way connection is established with ATM.

One

  Name the devices of the MPLS Network (3):

1) Label

2) Label Edge Routers- apply the labels to the packets across the MPLS network

  At edge of network you put a Router

3) Label Switch Routers – device that switches labeled packets according to pre-computed tables.

Explain the MPLS process: (it is LONG)

MPLS sends special :”first/dialing” IP address using the Reservation Protocol saying I want to send to this IP address- uses resercation protocol or LDP. And the edge will essentially dynamically tell all routers along the way and tell quality and speed, then come back and say OK send.  So sends ack says ok I have a path set up. MPLS addressing the edge router takes the layer two of that packet and takes a layer two and layer 3 and shoves it down and creates a shim and puts in the label and the TTL (and a couple other fields (pg. 11) of notes (CoS and S). If it brings ATM it does a special thing, instead of pry apart layer 2 and 3 just puts the MPLS label and then routers through the network.

  What are the two features associated with MPLS?

Traffic Engineering- allows rerouting of traffic

VPN's - Virtual Private Networks

What are the differences between TCP, IP, Frame Relay, UDP and ATM

TCP- have a source address and a destination address

Frame Relay- only have destination, bursting data

ATM- only put destination address, not source

MPLS- put whole IP address and layer 2.

UDP- Does not have sequencing or ack. Numbers.

 IP- address is essentially layer 3 that carries all things (MPLS etc.). IP version 4 or 6, is stated in header.

Explain how PVC operates.

Permanent is a circuit and it changes DLCI across. (for any WAN have to call telephone company and say set me up circuit for this IP address, and they will say when you want to use that use this frame address called DLCI and then in your edge router put dest IP address and associated DLCI, and when packet comes can just send it over t-1 to edge relay network that is waiting for it and it has a frame relay frame inside that has the IP and do a table look up for the DLCI)

ARP request for ATM address to the destiniation

ATM address response from the destination

call path set up with QoS to the destination

request response from the destination

further QoS agreement if needed

ATM switch assign a VPI and VCI that it send to the source

source start cell transmission

If the destination also wants to send cells to the source, the same process will have to be done the other way.

Explain how SVC operates:

all telephone company and say set me up with ability to make connection, and I will  not tell you when I will make connection and to who.  So doesn’t know who you want to connect to.  So what you have to do is send message saying where I want to go to (and only commonly know IP addresses).  So say I wanna set up a circuit to the IP address I want to send to (like giving them the telephone number).

What are port numbers?

say to IP layer which program gets it. Delivering packets to TCP layer 4 is worthless unless indicate to program where packet goes. Where it goes is in source port. The program that gets it is in Destination port. 

How do you identify source or destination ports?

The program for source port has these numbers. Numbers from 0-1023 are preestablished, but the ones beyond are assigned by two TCP’s talking to each other. 

ex. Source port “hey, I am tcp and I am sending this stuff”

With a T-1 private line or sub channel of one:

How do you get from your office to the frame relay ed?

Where might Edge frame relay be setting?

Use a T1  Switch

Carrier POP office

What are the 5 costs to frame relay (list charges too)?

Local T-1 Cost - $500

FR Port Cost- $300

FR CIR Cost - $1,000

FR Port Cost - $300

Local T-1 Cost - $500

=$2,600/Mo

Explain how PVC is setup and operates:

-Want frame relay service between site 1 and site 2. indicate IP number you want to use- put in edge router.

-When want to use circuit, put in frame relay Data Link Control Indicator (DLCI).

- DLCI number you use Hop by hop gets changed so only locally relevant.

-pay 24/7 for this service.  

Explain how SVC is set up:

- like dialing up a phone call.

- have to order circuit on demand- says you have ability to dial up call.

- going to send LIM requesting DLCI for IP address (don’t know addresses to use in Frame Relay) to edge router, the router sets up a connection trough here, and give up DLCI number to use. 

-ARP with IP address, get back a DLCI, put in routers address and associated with. 

What are the differences between TCP, IP, and UDP with Congestion

UDP says don’t tell me –

IP says- throw it way if want to

TCP says- did you get it… no, I’ll send it again….

IF going to slow down traffic, going to do with TCP. TCP does this by reducing window size.

FECN- Forward Error network notification

BECN- Backward error network notification

Frame Relay and IP are inter connected…

State the difference b/w the connections of Asynchronous Transfer Mode and Frame Relay.

Frame Relay is 2 way connection

ATM is one Way

… if want to respond have to establish a second connection

Connections are guarantee

ATM supports multiple service types and is applicable to LAN & WAN, but what happens if loose a cell or bit damaged?

have to resend 30 to make up packet.

If window of 20, have 20x30 that need to resend. Big deal when best effort. 

53 bites, tend to  break IP into 30 ATM cells

(a lost cell is a problem also to IP and Frame Relay)

PC NIC

HUB Module

Switch Module

Enterprise Edge Router

RBOC/Carrier Edge Switch

For ATM, indicate how you would set up path across circuit/network or get VPI and VCI. 

–use IP to tell destination, get ATM. ATM to set up Circuit, get back VP and VC. Use VC for every circuit you send.

(Slide 50- Class 7 Review)

What Type of ATM transmission is the underlying part of telephone network emulating circuits (hint AAL#)?

AAL1

What are the number of cells in Ethernet? IP over ATM?

Ethernet (1500 Bytes) =   32 Cells

FDDI (4470 Bytes) =   96 Cells

IP over ATM–1577 (9180 Bytes) = 192 Cells

Where are the Switches located on MPLS, ATM, and Frame Relay?

Switch on MPLS labels

  vs. ATM switches on VP/VC

  vs. Frame relay switches on DLCI

Name a Protocol that distributes labels across a path

Label Distribution Protocol

MPLS adds a simple label which is called a What? What is it?

shim header

The shim header is 32 bits and is located in front of the IP packet)

Label Field- where does it come from and who puts label in this packet going across network?

Carrier Point of Presence Office

With MPLS, where are a Switch Router and Edge Router located?

Switch router- in the middle of the network

Edge router- at the edge

Briefly Explain Sonnet Framing

Sonnet frame is a big frame with dispersed area, has 3 bytes of header

 next line 3 bytes

Where do you get WAN?

At Carrier POP

What is attached to metropolitan ring?

Carrier POP

 How to get to Distance network?

Carrier POP

 How to get to internet from office?

at carrier POP

When considering OSPF, what’s at border?

Border call

Explain how to Calculate the OSPF:

When the routers exchange info, not just on the whole paths, but about every link (from one router to another), and build network saying “I am here and can get to that destination different ways” and all other destinations (big tree structure of paths). And it prices out each link of each path (only have to do first time through or when new links or paths are offered) price it out with 6 components (and use scale 0-10, even fewer in most cases), good is small (fast speed is 1, slow is 10, high cost is 1, cheap cost is 10).  So at each point, have number at each link.

What fields are part of what headers?

(Think of how it operates, and what fields are needed)

No Clue!

Identify parts of RIP table

Know RIP Protocol  

Know what it looks like

  & be able to give one

Know OSPF

What are the components of IGRP Best path Calculation?

Path = Function of (Unloaded Path Bandwidth, Chanel Un-Occupancy,  Delay)

Indicate purpose of the following ATM transmissions

AAL1-

AAL5- 

AAL1- underlying part of telephone network emulating circuits

AAL 5   Variable Bit Rate-  Signaling, Packet Data and MPEG2 Video

What are the 3 types of Signaling