F5 101 - ADF Exam Flashcards
Describe the format of an HTTP Request.
Below is the request line format - italics are comments:
Method URL Version
GET /Protocols/rfc2616/rfc2616-sec3.html HTTP1/1.1\r\n
The Server Hostname
Host: www.w3.org\r\n
The user-agent; information on client’s browser
User-Agent: Mozilla/5.0\r\n
Accept-Encoding
Accept: text/html\r\n
Accept-language: en-US\r\n
The following indicates a persistent connection:
Connection: keep-alive\r\n
The following is a blank line which indicates that all metadata is sent, followed by an optional body:
\r\n
Describe the format of an HTTP Request
Below is the status line (Version, Status Code and Reason Phrase)
HTTP/1.1 200 OK \r\n
The date and time on the server
Date: Tues,04 Feb, 2014 10:33:40 GMT \r\n
Information on the HTTP server
Server: Apache/2 \r\n
The length of the content sent (minus any headers)
Content-Length: 35041 \r\n
The type of content sent
Content-Type: text/html \r\n
A blank line indicating all metadata has been sent, followed by an optional body
\r\n
Why is HTTP considered to a stateless protocol? What can be used to provide a form of state?
- HTTP is considered to be a stateless protocol since the client and the server do not store data in anyway.
- A request is sent and a response is received, this transaction has no impact on future ones.
- Cookies are used to provide a form of state.
What else are request and status lines in HTTP called?
- The Start Line.
What is the portion of an HTTP request/response from the Start Line to the blank line called?
- The HTTP headers.
- The start line and the HTTP headers collectively are known as the head of the requests/responses.
What is the purpose of HTTP Status Codes?
- HTTP Status codes are used to indicate to the client how the server has handled its request.
What are the five types of HTTP Status codes?
- 1xx - Informational
- 2xx - Success
- 3xx - Redirection
- 4xx - Client Error
- 5xx - Server Error
What are some very common HTTP request codes?
- 100 Continue - everything OK so far, continue with request
- 200 OK - The request has succeeded.
- 204 No Content - There is no content for this request, but possibely headers.
- 302 Found - Used to redirect to a different URL, resource relocated temporarily.
- 304 Not Modified - Used for caching, client can continue using cached version.
- 400 Bad Request - Server couldn’t understand request due to bad syntax.
- 401 Unauthorized - Semantically this response means “unauthenticated”
- 403 Forbidden - Client’s identity is known to server and no access is granted.
Describe the format of the TCP header
- Source Port
- Destination Port
- Sequence Number
- Acknowledgement Number
- Data Offset
- Reserved
- URG
- ACK
- PSH
- RST
- SYN
- FIN
- Window
- Check Sum
- Urgent Pointer
- Options
- Padding
- Data
Describe Distance-Vector Protocols
- Distance-vector protocols will only send full routing tables between neighboring routers and use simple metrics like hop count to determine best routes.
Describe Path-vector protocols
- Path vector protocols use dynamically updated path information.
- Each entry in the Path-Vector Protocol contains the:
- Destination network
- The next-hop router
- The path to the next-hop router
- These route updates are stored in a Routing Information Base (RIB).
- While a routing table will only store the best route for each destination, a RIB can contain multiple paths to a destination.
Describe Link-state protocols.
- Link-state protocols build up a map of the entire network on each router by obtaining information, via link-state advertisements (LSAs) from every other router on the network.
- Whenever there is a change updates are flooded so that recalculations of each route can be made by each router.
- To speed up and limit flooding by this process, hierarchical routing is used, dividing the network into smaller regions and each router only needs to know how to get to other networks in that region.
Describe Routing Information Protocol (RIP).
- This is a distance-vector protocol which uses hop-count as a metric.
- Most recent version is RIPv2 which carries subnet information.
- This is required to support CIDR and VLSM
- The maximum hop count is 16.
Describe Intermediate-System - Intermediate-System (IS-IS)
- This is a link-state protocol
- Creates a full network topology on every router.
- Uses Dijkstra’s algorithm to calculate the best next hop.
- Commonly used by ISPs.
Describe the purpose of signing.
- A digital signature is a mathematical scheme for demonstrating the authenticity of a digital message or document.
- Gives the receiver reason to believe the message was created by a known sender and the sender cannot deny having sent the message
- Non-repudiation and authentication
- Signing also is used to provide integrity (the message wasn’t altered in transit)
- Non-repudiation: signer cannot successfully claim they didn’t sign a message and that their private key remains secret.