Errata for HTTP: The Definitive Guide

Caches may be configured to serve stale (expired) objects, in order to improve performance. If an origin server wishes caches to strictly adhere to expiration information, it can attach a Cache-Control: must-revalidate header to the original response. Cache-Control: must-revalidate The Cache-Control: must-revalidate response header tells caches they cannot serve a stale copy of this object without first revalidating with the origin server. Caches are still free to serve fresh copies. If the origin server is unavailable when a cache attempts a must-revalidate freshness check, the cache must return a 504 Gateway Timeout error.

as follows: HTTP/1.1 offers several ways to limit the caching of objects, or the serving of cached objects, to maintain freshness. The no-store and no-cache headers prevent caches from serving unverified cached objects: Cache-Control: no-store Cache-Control: no-cache Pragma: no-cache A response that is marked "no-store" forbids a cache from making a copy of the response. A cache would typically forward a no-store response to the client, and then delete the object, as would a non-caching proxy server. A response that is marked "no-cache" CAN actually be stored in the local cache storage. It just cannot be served from the cache to the client without first revalidating the freshness with the origin server. A better name for this header might be "do-not-serve-from-cache-without-revalidation". The Pragma: no-cache header is included in HTTP/1.1 for backward compatibility with HTTP/1.0+. HTTP 1.1 applications should use Cache-Control: no-cache, except when dealing with HTTP 1.0 applications, which understand only Pragma: no-cache. <FOOTNOTE> Pragma: no-cache is technically valid only for HTTP requests, yet it is widely used as an extension header for both HTTP requests and responses.</FOOTNOTE>

"No-Store and No-Cache Response Headers"

/<p> should be </p>

These "expandomatic" features come in a two flavors: NOW READS: These "expandomatic" features come in two flavors:

<status> should be <status-code> because in the next paragraph to describe the part, it is referred to as 'status-code' not 'status'.

Note from the Author or Editor:
This text: <version> <status> <reason-phrase> should be changed to read: <version> <status-code> <reason-phrase> in order to be consistent with subsequent text.

an HTTP version tells the server NOW READS: an HTTP version which tells the server

Let's talk in more detail about the some of the basic NOW READS: Let's talk in more detail about some of the basic

that the server can used to identify the client NOW READS: that the server can use to identify the client

In Figure 4-3b, the 2nd level from the top should be "TLS or SSL", not "TSL or SSL".

Note from the Author or Editor:
The second box from the top in Figure 4-3b should say "TLS" not "TSL"

"Frequently, the disabled acknowledgement algorithms introduce significant delays." should read: Frequently, the delayed acknowledgement algorithms introduce significant delays."

Note from the Author or Editor:
The 5th pp of p.83 has a typo. The phrase "Frequently, the disabled acknowledgement" should read "Frequently, the delayed acknowledgement"

The third line of paragraph six has the following: "Second, Nagle's algorithm interacts poorly with disabled acknowledgments.." "disabled" should be replaced with "delayed"

Note from the Author or Editor:
In pp 6 of p. 84, need to change: "poorly with disabled" to "poorly with delayed"

uncommon is real deployments NOW READS: uncommon in real deployments

The phrase "or even tens or thousands of simultaneous connections" should be "or even tens of thousands of simultaneous connections".

"that he second" NOW READS: "that the second"

There are some cases where we want don't want exact hostnames should be: There are some cases where we don't want exact hostnames

Note from the Author or Editor:
In last pp of p.154, replace "we want don't" with "we don't"

when the server is deleted NOW READS: when the object on the server is deleted

If-None-March: NOW READS: If-None-Match:

Duplicated period "cache.." HAS BEEN CHANGED to "cache."

of even of short-lifetime objects. should be: of even short-lifetime objects.

some large cache providers have been know should be: some large cache providers have been known

allows servers to control the how much NOW READS: allows servers to control how much

"Symbolic link cycles usually are the result of an accidental mistake by the server administrator, ..." NOW READS: "Symbolic link cycles usually are the result of an unintentional error by the server administrator, ..."

Normal SLL connection should be: Normal SSL connection

"indentifying" NOW READS: "identifying"

A robot is making should be: A robot that is making

resource could by dynamically should be: resource could be dynamically

Each robots record starts with one or more User-Agent lines... should be: Each robot's record starts with one or more User-Agent lines...

NOW READS: www.robotstxt.org

The comma after "But" should be removed

The comma after "But" should be removed (same error as on p247)

"Each matching cookie much include any Domain,..." NOW READS: "Each matching cookie must include any Domain,..."

Need a (d) in front of the last box in the figure.

"...documents in an friendly..." NOW READS: "...documents in a friendly..."

the digest provided a correct match for the password.

Plaintext P --> Ciphertext C Ciphertext C --> Plaintext P

2^128 = 262 x 10^36 NOW READS: 2^128 = 340 x 10^36

The second paragraph (pt 6) and third paragraph contain exactly the same information, very trivially reworded. For clarity, one or the other should be deleted.

even thought the should be: even though the

Note from the Author or Editor:
In 4th sentence of 1st pp of p.363, "even thought" should be replaced with "even though".

varaint should be: variant

Note from the Author or Editor:
In last pp of p. 402, the typo "varaint" should be replaced with "variant"

does should be: do

and how to replicating content across NOW READS: and how to replicate content across

"Its" NOW READS: "It's"

"unique" NOW READS: "uniquely"

incoming messages must somehow be somehow among the servers should be: incoming messages must somehow be distributed amongst the servers

Note from the Author or Editor:
Last sentence of pp 3 on p. 449 needs to replace "somehow be somehow" with "somehow be distributed"

combination with some of the other redirection technique. should be: combination with one or more of the other redirection techniques.

Note from the Author or Editor:
Accept the reader's suggestion.

likewise, HTTP traffic NOW READS: Likewise, HTTP traffic

Dynamic Host Discovery Protocol AFAIK this does not exist as described, and should be: Dynamic Host Configuration Protocol

Note from the Author or Editor:
In bulleted list in pp 2, "Dynamic Host Discovery Protocol" should read "Dynamic Host Configuration Protocol".